Health and Safety Laboratory

Stray Radiation Measurements at Particle Accelerator Sites

Leonard R. Solon

James E. McLaughlin, Jr. Hanson Blatz

This document is PUBLIjCLY RELEASABLE

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U. S. Atomic Energy Commission New York Operations Office

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DISCLAIMER

This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency Thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.

DISCLAIMER Portions of this document may be illegible in electronic image products. Images are produced from the best available original document.

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ABSTRACT

This p rog res s repor t reviews s t ray radiation measurements made at representa t ive acce le ra tor s i tes by members of the Health and Safety Laboratory. Information is p resen t ­ed on radiation levels encountered, personnel monitoring r eco rds , eco­nomics of radiation protection, and biological effects of ionizing r a d i ­ation with relation to acce le ra tor operation.

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CONTENTS

Introduction - _ - _ - - - - - - - - - - - - _ - 1

Types of Par t i c le Accelera tors - - - - - - - - - 1

Biological Effect of Accelerator Radiations - - - - 9

Instrumentation - - - - - - - - - - - - - - - - 13

Charts - - - - - - - - - - - - - - - - - - - - I9

Individual Surveys - - - - - - - - - - - - - - - 26

Conclusions and Recommendations - - - - - - - - 60

Acknowledgments _ - _ _ - - - - - - - - - - - 61

103

STRAY RADIATION MEASUREMENTS AT PARTICLE ACCELERATOR SITES

Introduction

The stray radiation field from high energy part icle acce le ra to r s is comprised of severa l components, e.g., fast and thermal neutrons, x - and gamma rays , proton r e ­coils, and at siifficiently high energies , heavy par t ic le reco i l s and mesons .

In order to determine permiss ib le occupancy t imes for personnel in this rad ia ­tion field, a measurement i s requi red both of the intensity and the energy of the dif­ferent components constituting the spectrum. Then, from biological or clinical ex­per ience concerning the re la t ive effectiveness, of different radiat ions in producing deleter ious effects, the biological hazard may be inferred.

This outlines very briefly the radiation problem with an acce lera tor in operation. Also of importance a re the radiations encountered when work must be done on the

accelera tor with the beam off. Induced beta and gamma activi t ies can be of suffi­ciently high level to require limiitations on personnel working t ime so that ser ious overexposure is avoided.

This paper is a p rog res s repor t of a continuing p rogram conducted by the Health and Safety Laboratory. As pa r t of this program, radiation surveys , with par t icular emphasis on fast neutron measurements , have been conducted at 15 acce le ra tors during the period from January 1953 to August 1954. Discussed in this repor t a re radiation levels encountered, personnel monitoring r eco rds , economics of radiation protection, and biological effects of ionizing radiation with relat ion to accelera tor operation.

Types of Par t ic le Accelera tors

A par t ic le accelera tor i s any device which makes use of magnetic and/or e lectr ic fields to achieve par t ic les of high energy. For purposes of radiat ion protection m e a s ­u rements , the most important charac te r i s t ics of an acce le ra tor a re the kinds, in­tens i t ies , and energies of the par t ic les produced and whether the radiations a re p r o ­duced continuously or intermittently.

The|4n£iximum energy of the accelerated part icle is not necessar i ly the maximum energy olf the radiations associated with the accelera tor . Certain acce le ra tors , which a re mos t appropriately designated as kevatrons, make use of exoergic nuclear r e ­actions in which a charged par t ic le is accelerated only to an energy sufficient to pen­e t ra te the coulomb b a r r i e r of a target nucleus. Once the accelera ted par t ic le is in­side the target nucleus, a nucleon can be ejected and will c a r r y away with it, in the form of kinetic energy, the energy which bound it to the nucleus . Thus a kevatron accelerat ing deuterons to only 500-kev energy produces 14-Mev neutrons when the deuterons bombard a t r i t ium target .

In this section, a brief descript ion of the types of par t ic le acce le ra tors is given.

Fixed Frequency Cyclotron^ '

In this device (see Figure l ) a charged positive ion, usually a proton, deuteron, or alpha par t ic le , i s accelera ted in a magnetic field and rece ives successive i nc re ­ments of energy as it pa s se s through the instantaneous potential difference of two e lect rodes czJled the dees . The basic cyclotron equation is that which governs the motion of any charged par t ic le in a magnetic field:

J.

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2

• 1

' " • ^ S ^ ^ ^ -' • ' ^ , - ^ -

. ^ ^ . : - ^

^gjj^-i-**.

Figure 1. Massachuse t t s Institute of Technology conventional cyclotron. The 42-in. d iameter pole face of the cyclotron magnet is located over the dee vacuum chamber The tapered cylinder to the right shields the feed l ines from the radiofrequency osci l la tor . Anew targe t is being inser ted in the foreground. (Courtesy of Massachuset ts Institute of Technology.)

H Z v _ m v 2 ^ (1) c ~ r

w h e r e

H i s the m a g n e t i c field s t r e n g t h ( o e r s t e d s ) , Z is the c h a r g e of the p a r t i c l e (esu), V i s the ve loc i ty of the p a r t i c l e ( c m / s e c ) , c i s the ve loc i ty of l ight -which c o n v e r t s Z (esu) to Z (emu) , m i s the m a s s of the p a r t i c l e (g), r i s the r a d i u s of the c i r c u l a r orb i t in which the p a r t i c l e m o v e s (cm) .

Now the angu la r ve loc i t y , oj, in r a d i a n s / s e c o n d i s

v HZ

r m c (2)

which for a cons tan t m a g n e t i c field, c h a r g e , and m a s s is s e e n to be independent of the ve loc i ty and the r a d i u s .

If the potent ia l a c r o s s the d e e s is adjus ted to a f r equency , f, equa l to W/ZTT, then each t i m e the p a r t i c l e a r r i v e s at the space be tween the d e e s i t wi l l be in the c o r r e c t p h a s e to be a c c e l e r a t e d by the p o t e n t i a l d i f ference a c r o s s the dee gap .

The k ine t ic e n e r g y , E , in e r g s of the e m e r g i n g p a r t i c l e d e p e n d s on the ve loc i ty ach ieved on the final h a l f - t u r n which c o r r e s p o n d s to R (cm) , the r a d i u s of the dee .

3

Thus , f rom equat ion (Z), it m a y be seen that

„ 1 / H Z R \ ' ^ „ / N H 2 Z 2 R 2 E =---m or E ( e r g s ) = -—~-

2 \ m c / 2 m c 2

(3 )

T h u s , for a fixed field the u l t i m a t e e n e r g y of the a c c e l e r a t e d p a r t i c l e wi l l v a r y a s the s q u a r e of i t s c h a r g e and i n v e r s e l y a s i t s m a s s .

It i s a l so feas ib le to m a i n t a i n the o s c i l l a t o r f r equency for different ions c o n s t a n t and adjus t the m a g n e t i c f ield.

One s e e s f rom equa t ion (2) that

ZTT f R, or E =J_rnv2 = 2ir2f^R^m. 2

(4)

This p r o p o r t i o n a l i t y be tween the k inet ic e n e r g y of the a c c e l e r a t e d p a r t i c l e and i t s m a s s exp la ins why the e n e r g i e s of a lpha p a r t i c l e s (^He ), d e u t e r o n s ( I H 2 ) , and p r o t o n s ( jH^) , a r e in the r a t i o s of 4:2:1 for any s ingle c y c l o t r o n .

The f r e q u e n c i e s involved can be obta ined by subs t i t u t i on in equat ion (2) and a r e of the o r d e r of 30 m e g a c y c l e s for p r o t o n s in a 2 x 10 o e r s t e d field and half th i s for d e u t e r o n s or a lpha p a r t i c l e s in a s i m i l a r field.

F r e q u e n c y Modula ted C y c l o t r o n or Synchrocyc lo t ron^ ' ' ' ' . In a fixed f re ­quency cyc lo t ron the r e s o n a n c e condit ion (equat ion 2) i s u p s e t when the m a s s , m .

, (1 .2 ,3 ,4)

Figure 2. Columbia University (Nevis Laboratory) synchrocyclotron. The magnet di­ameter of this synchrocyclotron is 164 in. with the accelerator capable of achieving pro­ton energies up to 385 Mev. Massive shielding is required to attenuate stray radiations to permissible levels. The large overhead crane is used to position shielding compo­

nents for different experimental arrangements. (Courtesy of Columbia University.)

4

changes by about 1 percent because of the relat ivist ic increase with velocity. The connection between m, the relat ivist ic m a s s , and mo, the r e s t m a s s , is given by

^o(l - - , ) • 1 / 2 (5)

This relat ivist ic effect is not the only limitation on the energy attainable by a fixed frequency cyclotron. Due to inhomogeneities in the nnagnetic field, t h e b e a m m a y b e lost unless the field is sloped to res to re ions straying from the median plane of the magnet.

In the frequency modulated cyclotron or synchrocyclotron, these limitations a re overcome. The frequency of the rf dee voltage is adjusted to decrease as the part icle increases in m a s s so that the voltage drop ac ross the dees occurs at the cor rec t moment for accelerat ion to take place. The la rges t conventional cyclotron cannot accelerate protons to more than 15 Mev (30 Mev for deuterons or about 50 Mev for alpha par t ic les) while synchrocyclotrons produce protons with energies of hundreds of Mev - - up to 450 Mev for the la rges t (e.g., the synchrocyclotrons at the Carnegie Institute of Technology and the University of Chicago). The beam is pulsed, a typical pulse being of the order of 100 (jisec and repeated 100 t imes per second.

REMOVABLE TANK COVER

ELECTRONIC CIRCUITS-

BUILT-IN 2 KW POWER SUPPLY

CHARGE COLLECTOR

GENERATING VOLTMETER

EOUIPOTENTIAL PLANES

INSULATING COLUMN 18' LG

CORONA COLLECTING SHIELD

EOUIPOTENTIAL SHIELD 68" ID

HIGH VOLTAGE TERMINAL 38" DIA

POSITIVE ION SOURCE

WINDOWS

2 - 5 0 hp 1800 rpm MOTORS

BELT TENSION ADJUSTMENT

LEAD SHIELDING

DRY ICE TRAP

MERCURY DIFFUSION PUMPING SYSTEM

4 0 0 */ in' STEEL PRESSURE TANK

FIELD CONTROL RODS

INSULATING BELT

POSITIVE ION ACCELERATION TUBE

DIFFERENTIAL PUMPING TUBE

MANHOLE

MOVABLE PLATFORM

MAIN VALVE

SYLPHON

ANALYZING MAGNET

9<y PORTAL BEAM AXIS

SLIT SYSTEM

MASS 2 PORTAL

^ k\\\\%i>^~ADJUSTABLE MAGNET BASE

Figure 3. Massachuse t t s Institute of Technology 12-Mev Vande Graaff acce l e ra to r . This acce le ra to r produces highintensi ty beams of protons or deuterons The e lec t rons from the ion source impinging at the top of the p r e s s u r i z e d steel tank contribute significantly to the s t ray radiat ion hazard . (Courtesy of Massachuse t t s Institute of Technology.)

• > .07

5

E l e c t r o s t a t i c G e n e r a t o r (1,5)

In the h igh e n e r g y e l e c t r o s t a t i c g e n e r a t o r or Van de Graaff m a c h i n e ( F i g u r e 3), a m o v i n g be l t conveys c h a r g e to a conduct ing s p h e r e unt i l the s p h e r e i s at e q u i l i b r i u m p o t e n t i a l . Th i s s t a t e i s a c h i e v e d when the c h a r g i n g c u r r e n t conveyed by the mov ing be l t i s b a l a n c e d by r e m o v a l of the c h a r g e by l e a k a g e f r o m the s p h e r e in to the s u r ­round ing gas d i e l e c t r i c . The t ank conta in ing t h i s g a s i s u s u a l l y p r e s s u r i z e d in m o d e r n m a c h i n e s . Ano the r l i m i t a t i o n on the a t t a i n a b l e po t en t i a l d i f fe rence i s the i n s u l a t o r b r e a k d o w n vo l tage of c o m p o n e n t s of the dev ice inc lud ing the e v a c u a t e d tube a long wh ich p o s i t i v e ions or e l e c t r o n s can be a c c e l e r a t e d .

The h ighes t e n e r g y a c h i e v e d by th i s dev ice so far i s about 10 Mev . I ts g r e a t advan tage i s the p r e c i s i o n p o s s i b l e in the e n e r g y of a c c e l e r a t e d p a r t i c l e s .

•\ • * > .

* * \

^ • '

fW

C^tfcl'EiviaiwJ

ih*

Figure 4 (Above). Sloan-Ketter ing Institute beta t ron. E l ec ­t rons of 25-Mev energy are achieved in this betatron. One important application of this acce le ra to r is i ts use for t h e r a ­peutic t r e a t m e n t s . Ei ther x - r a y s or e lec t rons a re utilized for attaining des i red doses at pa r t i cu la r depths in t i s s u e s .

(Courtesy of Sloan-Kettering Insti tute.)

F igure 5 (Right). Sloan-Ketter ing Institute beta t ron. The Sloan-Ketter ing Institute betat ron schematic of the acce l ­e r a to r shown in Figure 4 exhibits the donut and col l imator r ings for narrowing beam to des i r ed a r ea The shielding ma te r i a l is masoni te , a composit ion consist ing of e lements having a low atomic number to minimize the production of s t r a y x - r a y s (bremss t rah lung) . (Courtesy of Sloan-Ketter ing

Inst i tute . )

MASONITE COLLIMATOR-

f

MASONITE LEG

A / f

ff

\

MASONITE /COLLIMATOR RINGS

-EVACUATED TUBE

TRANSMISSION ION CHAMBER

MASONITE SHIELD EVACUATED

GLASS TUBE

MASONITE LEG

6

Betatron(4' ^)

Electrons in the region of 10 to 300 Mev are produced in a type of accelera tor known as the betatron (Figures 4 and 5), This device is essential ly a transfornner, the secondary winding of which is a s t ream of electrons moving in a fixed radius of an evacuated chamber called the "donut."

The magnetic field of the betatron, unlike that of the cyclol^^ron, is made variable by the introduction of an alternating current into the coils of a Suitably designed magnet. Acceleration of the electrons takes place during only one-quarter of the op­erating cycle of the magnetic field power which usually has a frequency of 60 cycles per second. At the end of this period (l/Z40 sec), the magnetic field is electr ical ly interrupted and the high energy electrons are either directed at a target for x - ray production or brought out of the donut to be used as a high energy, high intensity beta source.

Because many (-y ,n) nuclear thresholds fall below the energies of x - rays p r o ­duced by a betatron, the fast neutron production of such a device, especially when op­erated as an x - ray machine, should be considered as par t of the s tray radiation hazard.

Electron Synchrotron(4. 7)

The electron synchrotron (Figure 6) may be used to achieve electron energies up to 300 Mev and possibly up to 1 Bev. Similar to the betatron in general appearance.

Figure 6. Massachuse t t s Institute of Technology 300-Mev synchrotron. This acce le ra tor is shown in relat ion to i ts associa ted l abo ra to r i e s . The pulsed nature of this acce le ra to r and the s t ray radiofrequency associa ted with its operation make it a difficult device to survey for the neutron components of i ts s t ray radia t ions . (Courtesy of Massachuse t t s Institute of Technology.)

09

7

the s y n c h r o t r o n d i f fe rs in tha t it u t i l i z e s a r a d i o f r e q u e n c y a c c e l e r a t i n g po ten t i a l in add i t ion to a changing m a g n e t i c field to a c c e l e r a t e e l e c t r o n s . In fact , one type of e l e c t r o n s y n c h r o t r o n beg ins a s a b e t a t r o n , and a f te r the p a r t i c l e s have r e a c h e d Z Mev in e n e r g y (or a ve loc i t y of 0.98C) add i t iona l e n e r g y i s a c h i e v e d by i n t r o d u c i n g the r a d i o f r e q u e n c y .

F r o m the point of view of s t r a y r a d i a t i o n m e a s u r e m e n t s , the s y n c h r o t r o n and b e t a t r o n p r e s e n t s i m i l a r p r o b l e m s . An add i t iona l con ip l i ca t ion in the f o r m e r a c c e l ­e r a t o r i s r a d i o f r e q u e n c y i n t e r f e r e n c e of s u r v e y i n s t r u m e n t s .

P r o t o n Synchrotron(3> •*> °)

The s y n c h r o t r o n p r i n c i p l e , involving the use of both v a r y i n g m a g n e t i c and rf f i e ld s , is p o s s i b l e for the a c c e l e r a t i o n of p r o t o n s as we l l as e l e c t r o n s ( see F i g u r e 7).

P r o t o n s a r e i n t r o d u c e d into a v a c u u m c h a m b e r of l a r g e d i a m e t e r af ter ach iev ing e n e r g i e s of about 5 or 10 Mev f r o m an a u x i l i a r y a c c e l e r a t o r . A chang ing high f r e ­quency rf field is then u s e d to ach ieve e n e r g i e s in the Bev r eg ion . At the p r e s e n t t i m e , t h r e e s u c h a c c e l e r a t o r s a r e known to be in o p e r a t i o n , two in the USA and one in Eng land :

1) B r o o k h a v e n Na t iona l L a b o r a t o r y - - 3 -Bev p ro ton s y n c h r o t r o n often r e ­f e r r e d to a s the C o s m o t r o n , 60-ft d i a m e t e r o r b i t .

2) U n i v e r s i t y of Ca l i fo rn i a , B e r k e l e y - - 6 -Bev p r o t o n s y n c h r o t r o n known as the B e v a t r o n , 100-ft d i a m e t e r o rb i t .

3) U n i v e r s i t y of B i r m i n g h a m , Eng land - - 1 .3-Bev p r o t o n s y n c h r o t r o n , 30-ft d i a m e t e r o rb i t .

The p r o t o n s y n c h r o t r o n o p e r a t i o n a l cyc l e t a k e s 5 or 6 s e c o n d s at the end of which t i m e a b u r s t of p r o t o n s and s t r a y r a d i a t i o n s e m e r g e s f r o m the a c c e l e r a t o r .

The high e n e r g i e s a c h i e v e d by t h e s e a c c e l e r a t o r s r e s u l t in m a n y d i f fe ren t k inds of p a r t i c l e s of unknown s p e c t r a l d i s t r i b u t i o n . The b io log ica l effects of t h e s e p a r t i c l e s

can only be c o n j e c t u r e d unt i l th i s s p h e r e of i n v e s t i g a t i o n is m o r e tho rough ly e x ­p l o r e d .

It should be m e n t i o n e d that w o r k is we l l unde r way for the d e s i g n of a new type of p r o t o n s y n c h r o t r o n known as the a l t e r n a t i n g g r a d i e n t s y n c h r o t r o n (AGS) which wil l m a k e u s e of the r e c e n t l y d i s ­c o v e r e d " s t r o n g focusing" p r i n c i p l e . It i s an t i c i pa t ed that th i s d e v i c e , to be c o n ­s t r u c t e d a t the B r o o k h a v e n Na t iona l L a b o r a t o r y , wi l l a ch i eve p r o t o n e n e r g i e s up to 25 Bev .

Dr i f t Tube L i n e a r A c c e l e r a t o r ! ^ * ^> ^)

F o r the a c c e l e r a t i o n of heavy p o s i ­t ive ions (p ro tons and p a r t i c l e s of g r e a t e r m a s s ) , a concep tua l ly s i m p l e dev ice is the dr i f t tube a c c e l e r a t o r . In th is dev ice a pos i t ive ion p r o g r e s s e s along tubes of i n c r e a s i n g l eng ths in such a way that the p a r t i c l e a r r i v e s at the end

VAN DE GRAAFF ACCELERATOR

2 8 8 MAGNET BLOCKS

2 0 DIA. DIFFUSION AND BACKING PUMPS

PICK-UP ELECTRODES

Figure 7. Brookhaven National Labora tory proton synchrotron. The Brookhaven proton synchrotron (Cosmotron) is shown schemat ical ly . Along with the 6-Bev Berkeley bevatron, this acce le ra to r r e p ­r e sen t s the frontier of acce le ra to r development, a l thoughacce le ra to rs in the 25-Bev range are well

along in the precons t ruc t ion design stage.

8

of e a c h tube in the c o r r e c t p h a s e to be a c c e l e r a t e d by an i m p r e s s e d rf po ten t i a l dif­f e r e n c e ex i s t ing be tween two adjoining t u b e s .

Two such a c c e l e r a t o r s have been bui l t , one at the U n i v e r s i t y of Ca l i fo rn i a (Berke ley ) and the o ther at the U n i v e r s i t y of Minneso t a . The Ca l i fo rn i a m a c h i n e h a s ach ieved 3-Mev p r o t o n s while the l a r g e r m a c h i n e a t M i n n e s o t a h a s r e a c h e d 40 Mev and h a s a des ign va lue of 68 Mev.

The advantage of th i s type of a c c e l e r a t o r l i es in the v e r y n a r r o w s p e c t r a l and s p a t i a l s p r e a d of the e m e r g i n g i o n s , which i s useful for c e r t a i n types of n u c l e a r i n ­v e s t i g a t i o n s .

Wave Guide L i n e a r A c c e l e r a t o r ( ^ ' 3 , 4)

Ano the r type of dev ice u sed for ach iev ing e l e c t r o n s of v e r y high e n e r g y is the wave guide l i n e a r a c c e l e r a t o r . In th i s dev ice an e l e c t r o n i s i n t r o d u c e d in c o r r e c t p h a s e with a high f r equency e l e c t r i c field t r a v e l i n g along a wave guide .

An e l e c t r o n wil l r e c e i v e a s t e ad i l y i n c r e a s i n g amoun t of e n e r g y unt i l it i s f inally e j ec ted . The only known l i m i t a t i o n on e l e c t r o n e n e r g i e s for th i s type of a c c e l e r a t o r i s p r e s u m a b l y the p r a c t i c a l l eng th of the a c c e l e r a t o r . The l a r g e s t a c c e l e r a t o r of th i s type is at Stanford U n i v e r s i t y and is 220 ft in o v e r - a l l l ength . It h a s a c h i e v e d e n e r g i e s of 650 Mev, but the d e s i g n l i m i t of th is a c c e l e r a t o r i s I Bev .

Figure 8. Brown University Cockcroft-Walton genera tor . This acce le ra tor produces deuterons of 500-kev energy, which are used to bombard a t r i t ium ta rge t . The r e s u l t ­ing interact ion is exoergic producing neutrons of 14 Mev. Stray x - r ay levels from the back-e lec t ron cur ren t of the accelera t ing tube can be significant even without neutron

production. (Courtesy of Brown Universi ty .)

9

K e v a t r o n ( l ' ^)

D e v i c e s mak ing use of t r a n s f o r m e r c a p a c i t a n c e a r r a n g e m e n t s to obta in c h a r g e d p a r t i c l e s of c o m p a r a t i v e l y low e n e r g y (in the kev reg ion) a r e s o m e t i m e s r e f e r r e d to a s k e v a t r o n s ( F i g u r e 8). The c h a r g e d p a r t i c l e s a r e then u s e d to b o m b a r d a su i t ab le t a r g e t which i n t e r a c t s e x o e r g i c a l l y with the b o m b a r d i n g p a r t i c l e .

A v e r y useful type of such dev ice i s one in which d e u t e r o n s of s e v e r a l h u n d r e d - k e v e n e r g y b o m b a r d a t r i t i u m t a r g e t and fu rn i sh a supply of n e a r l y m o n o e n e r g e t i c n e u t r o n s of 14-kev e n e r g y , f ree of g a m m a - r a y con t amina t i on . Such an a c c e l e r a t o r i s s o m e ­t i m e s r e f e r r e d to as a D - T n e u t r o n g e n e r a t o r .

The n u c l e a r i n t e r a c t i o n as exp la ined above i s :

lU^ (d,n) 2He'*.

A f requen t ly u sed k e v a t r o n c i r c u i t i s the vo l tage mul t ip ly ing dev ice of Cockcrof t and Walton. R e f e r e n c e i s s o m e t i m e s m a d e in a c c e l e r a t o r c i r c l e s to a C o c k c r o f t - W a l t o n g e n e r a t o r which , a s exp la ined above , i s a D - T r e a c t i n g s y s t e m for the p r o d u c t i o n of n e u t r o n s in which the d e u t e r o n s a r e fu rn i shed suff ic ient e n e r g y to o v e r c o m e the Coulomb r e p u l s i o n of the t r i t i u m n u c l e u s .

B io log i ca l Effect of A c c e l e r a t o r R a d i a t i o n s

An a p p r a i s a l of the h a z a r d s a s s o c i a t e d wi th a c c e l e r a t o r o p e r a t i o n canno t be m a d e without s o m e a c q u a i n t a n c e wi th the ex ten t of c l i n i ca l e x p e r i e n c e and e x p e r i m e n t a l i n ­f o r m a t i o n in the field of b io log ica l d a m a g e , p a r t i c u l a r l y tha t c a u s e d by fas t n e u t r o n s .

In th i s sunnmary the a u t h o r s have m a d e ex t ens ive u s e of the i n f o r m a t i o n p r e ­sen t ed at the C o n f e r e n c e s on R a d i a t i o n C a t a r a c t s s p o n s o r e d by the Na t iona l R e s e a r c h Counc i l for the Atonnic E n e r g y C o m m i s s i o n and in p a r t i c u l a r the e x c e l l e n t p a p e r p r e ­s e n t e d by H a m ( 9 ) a t t h e F o u r t h C o n f e r e n c e , and subsequen t ly pub l i shed in the A m e r i c a n Med ica l A s s o c i a t i o n A r c h i v e s of Oph tha lmology 50, 618 (1953).

In g e n e r a l , the ava i l ab l e ev idence m a y be g rouped in the following way: a) C a t a r a c t s in p e r s o n s engaged in a c c e l e r a t o r w o r k . b) C a t a r a c t s in p e r s o n s exposed to i r r a d i a t i o n f r o m cha in r e a c t i n g a s s e m b l i e s . c) C a t a r a c t s in h u m a n s as a c o n s e q u e n c e of i r r a d i a t i o n by ion iz ing r a d i a t i o n s

o the r than n e u t r o n s . d) O c c u r r e n c e of o the r b io log ica l effects ( n o n c a t a r a c t ) in h u m a n s by a c c e l e r a t o r

r a d i a t i o n s . e) C a t a r a c t s in n o n h u m a n s a s a c o n s e q u e n c e of i r r a d i a t i o n by fas t n e u t r o n s and

o the r ioniz ing r a d i a t i o n s . f) Effects of r a d i o f r e q u e n c y o s c i l l a t i o n s .

C a t a r a c t s in P e r s o n s Engaged in A c c e l e r a t o r Work

Abe lson and K r u e g e r ( l ' J ) in 1949 r e p o r t e d ten m a l e p h y s i c i s t s wi th s o m e d e g r e e of l ens opaci ty p r e s u m a b l y i n c u r r e d whi le engaged in i n v e s t i g a t i o n s at c y c l o t r o n s i t e s .

Since then Dollfus'•'• ^z h a s r e p o r t e d s e v e n c a s e s of c y c l o t r o n - i n d u c e d l ens o p a c ­i t i e s in F r a n c e , whi le K r a u s e and Bond( l2 ) have r e p o r t e d an add i t iona l five c a s e s of r a d i a t i o n c a t a r a c t , t h r e e of which a r e a s s o c i a t e d wi th c y c l o t r o n o p e r a t i o n , one with Van de Graaff m a c h i n e s , and one with " r a d i o a c t i v e m a t e r i a l s . "

The m o s t s t r i k i n g f e a t u r e of the Abe lson and K r u e g e r c a s e s w a s the un i fo rmly low e s t i m a t e s of t h e i r to ta l e x p o s u r e to n e u t r o n s m a d e by the p e r s o n s c o n c e r n e d .

In a c o n s i d e r a b l e p o r t i o n of the o lde r pub l i shed l i t e r a t u r e , d o s e s a r e e x p r e s s e d in n - u n i t s , a uni t no l o n g e r u s e d in s e r i o u s n e u t r o n d o s i m e t r y . The n - u n i t i s tha t r e a d i n g

: .J^ - 1 2

^iVp^TO^^^^(5r-"??«^/i5*^ ! f

10

obtained with a lOO-r Victoreen thimble chamber exposed to fast neutrons. A gener ­ally accepted conversion is 1 n-unit = 2 or 2.5 rep which, though varying from chamber to chamber , is certainly more precise than the es t imates made by the ten physicis ts .

On a rep basis the neutron es t imates ranged from 10 to 300 rep , with a median dose est imate of 125 rep with exposure t imes varying from 10 to 250 weeks.

Cataracts in Pe r sons Exposed to Irradiat ion from Chain Reacting Assentiblies

Persons in this group may be classified in two categories; those exposed to the radiations from the 1945 nuclear detonations in Japan, and those exposed as a resul t of cr i t ica l assembly accidents.

Fillrnore'-l^^) has reviewed detailed physiological studies of 78 persons exposed to radiations from the Hiroshima weapon who subsequently developed lens opacities. He concludes that 50 percent or more of this group received near whole-body doses of radiation and that radiation ca tarac ts were the only late effects in these persons .

Hennpelmann et all-'-'*) have reviewed acute exposures experienced by nine sc i ­entists at Los Alamos in 1945 and 1946 as a resul t of exposures to fast chain reacting assembl ies . Of these, two died shortly after exposure (9 and 24 days). Of the seven surv ivors , six showed no lens abnormali t ies three to four years after exposure. The est imated dose to the eyes of these six persons ranged from 4 to 21 rep .

The most heavily exposed survivor, who received an est imated 45 rep to the eyes, developed a ca taract in the left eye three years after exposure and a ca tarac t in the right eye five years after exposure.

Cataracts in Humans as a Consequence of I rradiat ion by Ionizing Radiation Other than Neutrons

That opacities resul t from x - ray and radium exposures of the head and eyes in therapy is well known. On the other hand, the prevailing evidence appears to be that relat ively mass ive exposures , considerably in excess of the LD-50 (400 r )andeven600 r of total body x- or gannma radiation, may be below the threshold of the cataractogenic dose.

Mer r i am( l^ ) , for example, repor t s no ca ta rac ts result ing from doses vmder 1500 r and only one out of 22 eyes showed a ca tarac t after t rea tment with doses be­tween 1500 and 2000 r of x - r a y s .

A summary of these findings are exhibited as the f i rs t entry in Table 1. Mer r iam, however, has continued his observations and wri tes in a private communication (February 1956) " . . . additional work on a considerably la rger s e r i e s does include some lower doses and there a re patients with ca tarac ts at these levels . . . they are lower than those as yet reported.and . , . there is a considerable difference between single and multiple exposures in the dose necessa ry to produce a lens opacity."

Hunt(l6) a s s e r t s that the threshold for ca taract production is between 500 and 1000 r for 100- to 200-kvp x - r a y s . Ham,(9) taking into account the wide variation in clinical data, cautions that 500 r of x - o r gamma radiation should be regarded "as potentially dangerous to the human lens."

Occurrence of Other Biological Effects (Noncataract) in Humans by Accelerator Radiations

Aside from the very ser ious radiation exposure to scat tered electrons from a 1,2-Mev electrosta t ic generator experienced by six men at the Massachuset ts General

'-* V13

\l 17^

Radiation

Beta X-Ray X-Ray Radium

X-Ray and Radium

Neutrons

Neut rons , fast

X-Ray, 250 kvp

Neut rons , fast

X-Ray, 250 kvp

Neut rons , fast

Gamma r a y s (Co^^)

Neut rons , fast (fission)

Mixed gamma-neutrons in -y/n dose ra t io of approximate ly 3 0 / l

Gamma Co^O

„Fast neu t rons , 14 Mev

The rma l neutrons

•Second Conference on

Threshold Orgcinism dose

Man Man 1500-2000 r Man Man

Man

Dog

Rabbit

Rabbit - •

Mice

Mice 15 r

M i c e C F # l (female)

M i c e C F # l (femiale)

Rabbit <2 X 10^ n / c m ^

Rhesus monkey

6 X 106 n / c m 2

-

-

Radiation Ca t a r ac t s .

Times weekly MPE for humans Exposures

5 - 7 x

-

-

-

45

-

'V.5 X 1

1.4

-

-

io3

02

250 rep (av)

6050 r (av) 2950 r (av) <1000 r 1000-2000 r 7590 r (av)

60-150 n 810-900 n 62.7-83.7 n (3.1 n fraction) 33-100 n (single dose)

70 n 120 n (40 n fractions) 500 r

60 n 120 n (40 n fraction)

15 r 45 r

240-252 rep 182-215 rep 174 r e p

986-1040 r

-

26 rep 110 r e p 505 r e p

3000 rep 2000 rep 1000 rep 500 r ep

250 r ep 75 r 21 850 r e p 250 r e p 75

7500 2500 825

Table

Number of cases ; percent of sample

4 eyes (0 %) 1 eye (4.5 %} 22 eyes 73 eyes 13 eyes (17.8 %) 25 eyes (34.2 %) 7 eyes (-)

0/10 (0%) (60-75 %)

0/16 (0 %)

3

0 (0 %)

MOO (100 %)

11 (29%) 32 (86 %)

16 (100 %) 139 (~85 %) 21 (^60 %)

136 (M5%)

0 % (36) total

-

-

1

Time of onset

Average for ent i re group of 99 eyes in 3 yea r s and 9 months, with an "inverse ra t io b e ­tween dosage and t ime of onset"

2-5 months

~2 months

" 3 months

28 weeks 33 + weeks

~3 months 3 months 4 months

~4 months

-

-

8 months 9 months 10-1/4 months

14-1/2 months 19-22 months

6 months 12-1/4 months 13-1/2 months

Died in 16 days 9 months 14-1/2 nnonths

R e m a r k s

-

Complete opacit ies of the lens (Vogel grade ++++) one year after i r rad ia t ion (rbe) for min imum dose to produce complete opacities (-y/n = ~6)

"Comparable effectivity" 5x 10l6 n / c m 2 (14 Mev) 9 X lOlO n /cm2 (fission) 500 r (1.2 Mev gamma)

No opacities 30 months after exposure

11-1/2 months after radiat ion

26 months after exposure

16-1/2 months after exposure

19-3/4

References

G.R. M e r r i a m , CRC-2,* Dec. 1950

C. Moses et al, AECU-2527, Mar. 1953

T.C. Evans , CRC-2,* Dec. 1950

G.C. Upton, K.W. Chr i s t enbe r ry , J. Fur th , Am. Med. Assoc . Arch. Ophthalmol. 49, 164 (1953)

H.H. Vogel, J r . , CRC-5, Mar . 1954

ANL-5332, pp. 29 -31 , Oct. 1954

David G. Cogan, John L. Goff, El izabeth Graves -AECU-1743, Jan. 1952

D.V.L. Brown, CRC-5, Mar. 1954

D.V.L. Brown, J .E . P icker ing , CRC-6, Mar. 1955

Ul4

12 13' Hospital{17) in 1945, the available l i te ra ture is all but nonexistent on noncataract physiological effects experienced by acce le ra tor workers .

Of great in te res t in this connection is the work of Ingram et al(l°» 1°) in con­nection with the operation of the synchrocyclotron at the University of Rochester . It was reported that very minute exposures to the s t ray radiat ions of the acce le ra tor produced ein increase in the number of bilobed lymphocytes in the blood of both humansV*"/ and dogs.V*°) The occurrence of these unusual double nuclei was not a c ­companied by a significant change in the hematological picture usually associated with relatively mass ive exposure to ionizing radiation. '

It is perhaps worthy of mention in this regard that at one large Eas t e rn universi ty which the authors visited they were advised that the technician performing routine hematological tes t s had a surpr is ingly good record of determining who was working in the cyclotron a rea on the basis of subjective appearance of the blood ce l l s . Unfortu­nately no quantitative data along these lines were available.

Cataracts in Aninnals as a Consequence of Irradiat ion by Fas t Neutrons and Other Ionizing Radiations

The biological effects of controlled exposures to ionizing radiat ion a re under study at a number of instal lat ions. Ra t s , rabbi ts , xnice, dogs, and, more recently, large simians have been exposed to a grea t variety of electronaagnetic and neutron radiations of different energies (cf. Table 1).

Effects of Radiofrequency Oscil lations

On the basis of existing information, it can be said that the case against fast neutrons is well established and fast neutrons should be regarded as the most likely suspect in cataract-producing potential at accelera tor s i t es .

On the other hand, the possibility has not been ruled out, in the opinion of the w r i t e r s , that the s t ray rf energy associated with accelera tor operation is in itself, or in combination with ionizing radiation, cataractogenic.

Richardson, Duane, and HinesC^O) have reported experimental production of opac­it ies in the eyes of rabbits by exppsure of rabbit eyes to pulsed microwaves of 3-cm wavelengthat a 5-cm distance fjrofti a generator with a 67-watt average output.

Hines and Randalll^l) fu5nish lethality data obtained from i r radia t ion with 10- to 12,25-cm microwaves and point out that shielding of the eyes and tes tes can be ef­fected by covering these s t ruc tures with close fitting screen wi re .

Salisbury, Clark, auid Hinesv^^) speak of 3 watts per cm^ as "known to be dangerous," but add that this energy flux ra te is not likely to be achieved except in the "immediate vicinity of a powerful t ransmi t te r . "

Rapid tes t icular degeneration of r a t s exposed to 12-cm microwaves is reported by Imig, Thomson, and Hines(23) who caution that "because of the unusual susceptibility of tes t icular t i ssue to thermal agents it seems desirable to shield these s t ruc tures . . . during periods of t reatment or exposure."

The relat ionship between the microwave data and the operation of part ic le acce l ­e r a to r s involving the use of rf fields deserves further exploration.

A summary, by no means complete, of some of the work is exhibited in Table 1. For comparison, the compilation of M e r r i a m ' s observations is included as the initial entry.

It must be confessed that the animal experimentation to date, though of unquestion­able value in the understanding of the mechanism of ca ta rac t formation, furnishes little insight into the maximum permiss ib le exposures for humans at high energy a c ­celera tor s i tes . For obvious reasons , most experimental work is confined to relat ively

i 5

massive short t e r m exposures at high dose r a t e s , whereas accelera tor personnel are exposed, in general , to long t e r m exposures at low dose r a t e s .

For persons having responsibi l i t ies in evaluating the adequacy of shielding and establishing good radiation control , the guide lines obtained from the animal ex­per iments appear to indicate the need for conservat i sm and caution pending further work.

Instrumentation

Introduction

In the evaluation of the electromagnetic and neutron dose produced by part icle a c ­ce l e r a to r s , a variety of radiation survey ins t ruments have been used by the Health and Safety Laboratory. These a re ionization chambers for gamma rays ; ionization chambers , proportional counters , and scintillation detectors for neutrons.

Negligible use was made of the valuable photographic film and threshold detection techniques which a re not quite so amenable to the 1 - to 3-day field surveys during which measurements were made.

Ionization Chambers . By measuring either the ra te of change of potential as charge is collected or the potential drop appearing ac ross a known r e s i s to r , one can determine the amount of ionization produced by electromagnetic radiat ion (x- or gamma), beta radiation, or neutrons incident upon the ionization chamber. In a mixed field of gamma rays and neutrons, the result ing ionization cur ren t does not differentiate be ­tween the agencies producing it.

X- or gamnna radiation dose, expressed in roentgens, should properly be m e a s ­ured with an ionization chamber constructed of a mater ia l approximating the sanne ef­fective atomic number as air since the roentgen is defined in t e rms of the interaction of electromagnetic radiat ion with a i r .

One such expression is

/ z a n Z n ^ y / ^

where a = the proportional amount of the nth element, with atomic number Zj., in the com­position.(25) o the r forms for the est imation of Zeff have been given in the l i t e ra ture . (2 6)

On the other hand, this so-cal led "air-wall" chamber cannot measure the dose due to neutrons in roentgens-equivalent-physical (rep)* since the relation of chamber r e ­sponse to energy absorbed in t issue depends on several var iables such as relat ive c ross sections for neutrons, relat ive stopping power of the chamber mater ia l for r e ­coil nuclei, and chamber size.(27) jn other words , the energy absorption difference between air and t issue for electronnagnetic radiation is relat ively small , but the differ­ence between air -and t issue with respect to neutron interact ion is considerable. The t issue dose due to fast neutrons will be generally proport ional to the amount of hydro­gen present .

For neutron energies lower than 0.5 Mev, the nitrogen content is also important. So, ionization chambers designed for the measurement of radiation doses due to

*The t e r m rep is used throughout the r epo r t r a the r than the p r e f e r r ed rad because mos t of the re fe rences cited re fer to the r ep . One r ep is the quantity of any ionizing radiat ion which r e su l t s in energy abso rp ­tion of 93 e r g s / g of t i s sue . The rad i s , simply, that quantity of any ionizing radiat ion which r e su l t s in energy absorption of 100 e r g s / g of t i s sue .

14

neutrons require quantities of hydrogenous and nitrogenous mate r ia l in the same proportions present in the biological t issue of in teres t . Such chambers have been built by Fai l la and Rossi , and will be discussed subsequently.

In order to learn of the component radiations in a mixed field, the surveyor may use two ionization chambers , one whose response is a measure of radiation dose in t issue - - i .e. , one made of hydrogenous and nitrogenous material - - and one whose response to neutrons is deficient - - e.g., one made of carbon. Indications of the r e l a ­tive amounts of neutrons and x - or gamma radiation present can also be obtained by changing the gas filling of the same chamber. This, of course , is not as desirable as having the wall mater ia l also changed correc t ly . In p rac t ice , one usually es t imates the neutron contribution to total dose by means of the more sensitive mechanisms de­scr ibed in the following sections. For example, if a mixed radiation field composed of the maximum permiss ib le gamma- ray level, 300 mrep /week , plus the maximum p e r ­missible fast neutron level, 30 mrep/week , were examined, the neutron contribution to the ionization will be only 10 percent of that of the gamma radiation. If one were not aware of the neutron component, it is possible that the s t ray radiation level would be regarded as only 10 percent more than permiss ib le instead of 100 percent g rea te r .

Proport ional Counters. The p r imary value of the proportional counter l ies in the l inear relation between the pulse si:Se from the counter and the total ionization p r o ­duced in the counter by the charged recoil par t ic le initiating the ionization. The sen­sitivity of the counter to fast neutrons is enhanced considerably by introducing a hydrogenous mater ia l into it. Sinnilarly, the use of such mate r ia l s as boron, which has a high thermal neutron c ross section, inc reases the thermal neutron sensitivity. Since the pulse sizes due to the alpha par t ic les or protons, result ing from neutron interact ions , are much la rger than those ar is ing from the electrons produced by x - or gamma radiation, one can discrintiinate against gamma radiation by electronically r e ­jecting the electron pulses .

By the use of an appropriate hydrogenous gas (e.g., methane) and suitable r e ­flectors and absorbe r s , a counting ra te proportional to the t issue dose ra te can be achieved for a portion of the neutron energy spectrum. A t issue equivalent proportional counter has been devised by Hurst,(28) and a version of this counter is discussed la ter .

Scintillation Counters.(^9) if an organic mate r ia l such as lucite or polyethylene is placed next to a scint i l lator , the incident neutrons can be measured by observation of the visible light which is produced in the scintil lator with a photomultiplier tube. That i s , the products of a neutron react ion in the lucite (pr imari ly protons in the case of fast neutrons) will produce visible light if permit ted to reac t with a scint i l lator . The amount of light, or the number of pulses in a given t ime i s , then, a measure of the in­cident neutron flux. However, the pulses do not appear to be proportional to the proton recoi l energy.(^0)

Threshold Detectors.(-^U A detector which will respond only to neutrons above a cer ta in energy, by any of severa l mechanisms, is known as a threshold detector. For example, a chamber employing mater ia l such as U^^^ or 31^09(31, 32, 33) js useful as a detector of neutrons produced by the fission process with energies above 1,1 and 60 Mev, respect ively. The S^^ isotope has value as a threshold detector by virtue of the (n,p) react ion which occurs above neutron energies of about 1 Mev.V^^)

Nuclear Track Fi lm. Nuclear t rack photographic film can indicate the presence of neutrons by means of the (n,p) reaction occurring in the hydrogenous film. The number of t racks appearing in the developed film will be a measure of the total number of neutrons intercepted by the film. Thus, Kodak NTA film is useful for personnel monitoring purposes for neutrons with energies between about 0.3 and 20 Mev,(34. 35)

S3'l 017

16 15

T y p i c a l I n s t r u m e n t s

D u r i n g 1953 and 1954, r e p r e s e n t a t i v e s u r v e y i n s t r u m e n t s w e r e u s e d e x t e n s i v e l y by the Hea l th and Safety L a b o r a t o r y in connec t ion with s t r a y r a d i a t i o n m e a s u r e m e n t s at a c c e l e r a t o r s i t e s . A br ie f d e s c r i p t i o n of e a c h i n s t r u m e n t , a long with s o m e n o t e s of i n t e r e s t to the s u r v e y o r , i s g iven below. A s e m i l o g c h a r t ind ica t ing the effect ive r a n g e of the v a r i o u s i n s t r u m e n t s and the m o s t i m p o r t a n t n e u t r o n e n e r g i e s f r o m the v iewpoint of the m a x i m u m p e r m i s s i b l e e x p o s u r e i s shown ( F i g u r e 9).

Q O

UjX 2

en CO

S

I lo'

M '1 '1 '

c

-

-

^

BF3 C

"~>-

OUNTE =i

1

1 '1 M '

TISSUE RE

CH4 PROPC

—, —

\SCINT

\

1

SPONSE COUNTER

)RTIONAL COUNTER

' ILLATION COUNTER

Bl'°= FISSION ^

^FISSION -

°,NTA FILM

\

FLAT RESPONSE BF3 COUNTER (LONG )

1 1 1 1 i [ ! 1 1 1 ! 1 1 I

-

1

/

it V

NEUTRON ENERGY (ev)

Figure 9 (Above). Energy range of neutron in s t rumen t s .

F igure 10 (Right). Fas t neutron dos imeter , AEC Model SPC-6A.

F a s t N e u t r o n D o s i m e t e r - - AEC No. S P C - 6 A , Model E - 1 . Th i s s u r v e y m e t e r (p roduced by the R a d i o a c t i v e P r o d u c t s , Inc . ( s ee F i g u r e 10)) u t i l i z e s a p r o p o r t i o n a l c o u n t e r , which h a s been d e s c r i b e d by G.S. H u r s t . ( 2 8 ) Th i s a r g o n - m e t h a n e - f i l l e d p r o p o r t i o n a l coun te r con ta in s two po lye thy lene r a d i a t o r s and an a l u m i n u m a b s o r b e r a r r a n g e d so tha t the count ing r a t e is p r o p o r t i o n a l to a c a l c u l a t e d f i r s t - c o l l i s i o n t i s s u e dose r a t e , when the coun te r is i r r a d i a t e d wi th c o l l i m a t e d n e u t r o n s wi th e n e r g i e s of 0.2 to about 10 Mev. T h r e e r a t e m e t e r s c a l e s p e r m i t m e a s u r e m e n t s up to 5, 50, and 500 m r e p / h r , r e s p e c t i v e l y . By t im ing the a c c u m u l a t i o n of up to 200 coun t s on an i n t e g r a t i n g s c a l e , dose r a t e s a s low a s 0.2 m r e p / h r can be m e a s u r e d in about 16 m i n u t e s . The a d j u s t m e n t of a g a m m a r a d i a t i o n d i s c r i m i n a t o r af fords a c a l i b r a t i o n check . With a 2 5 - m g r a d i u m s o u r c e p l aced 5 c m f r o m the face of the c o u n t e r , the d i s c r i m i n a t o r should be ad jus ted unt i l the m e t e r r e a d s 3.5 to 4.5 m r e p / h r . The d o s i m e t e r i s then sa id to have the c o r r e c t n e u t r o n s e n s i t i v i t y (0.0145 c t s / n / c m ^ ) and i s i n s e n s i t i v e to g a m m a r a d i a t i o n up to 1 r / h r .

S e v e r a l f e a t u r e s have been no t i ced du r ing the field use of t h e s e d o s i m e t e r s : a) The g a m m a r a d i a t i o n d i s c r i m i n a t o r se t t ing h a s changed m a r k e d l y f r o m day to

day on s e v e r a l o c c a s i o n s . It i s be l i eved that a d i s c r i m i n a t o r check be fore e a c h s u r v e y i s a d v i s a b l e ,

b) The n e u t r o n r e s p o n s e a p p e a r s to be l e s s than the n o m i n a l va lue af te r the d o s i m e t e r has been checked with the 2 5 - m g r a d i u m s o u r c e . Th i s led to the u s e of c o r r e c t i o n f a c t o r s as l a r g e as 2 . It i s conce ivab l e that one d o s i m e t e r m a y a p p e a r to be funct ioning w e l l , in sp i te of a def ic ient s e n s i t i v i t y . T h u s ,

H

16 n

'•••y.-a.

f requen t c a l i b r a t i o n wi th a s t a n d a r d n e u t r o n s o u r c e i s a n e c e s s i t y . Such s o u r c e s a r e not a lways ava i l ab le at the v a r i o u s a c c e l e r a t o r s i t e s .

c) This coun te r h a s an a p p r o x i m a t e 2 to 1 d i r e c t i o n a l r e s p o n s e to c o l l i m a t e d n e u t r o n s . In the m e a s u r e m e n t of s t r a y r a d i a t i o n , no p a r t i c u l a r difficulty was e x p e r i e n c e d b e c a u s e of th i s c h a r a c t e r i s t i c .

d) The long t i m e (5 m i n u t e s ) r e q u i r e d to obta in a r e a d i n g in the 5 n a r e p / h r ( r a t e m e t e r ) s c a l e r e n d e r s th is s ca l e i m p r a c t i c a l for s u r v e y w o r k . Low leve l m e a s u r e m e n t s w e r e g e n e r a l l y m a d e by the r a t e - o f - d r i f t m e t h o d p r o v i d e d for in this i n s t r u m e n t .

Sc in t i l l a t ion Counte r , , Model F N - 1 , AEC Model SBX-21A. This s c in t i l l a t i on c o u n t e r (the Nuc leon ic Company of A m e r i c a ( see F i g u r e 11)) e m p l o y s a mo lded , c y l i n d r i c a l luc i te d e t e c t o r conta in ing a d i s p e r s i o n of s i l v e r - a c t i v a t e d z inc su l f ide , and a pho tomul t i p l i e r tube . The s u r v e y i n s t r u m e n t i s a c o u n t - r a t e m e t e r having two s c a l e s which can be c a l i b r a t e d wi th r e s p e c t to P o - B e f luxes f r o m about 5 n / c m ^ - s e c to about 500 or 600 n / c m ' ^ - s e c . The de tec t ing phospho r h a s been d e s c r i b e d by W. Hornyak , (^" )

and the o r ig ina l s u r v e y i n s t r u m e n t bv J. H a n d l o s e r and W.A. Hig inbo tham. (3 7)

„, O r i g i n a l l y , it w a s be l i eved that the p r o t o n s (which i n t e r a c t wi th the ZnS-Ag to give l ight p u l s e s ) w e r e p r o d u c e d in the luc i t e . Subsequen t w o r k by G.R • K e e p i n g °) i n d i c a t e s t ha t a s ign i f ican t p a r t of the d e t e c t o r r e s p o n s e is a t t r i b u t a b l e to p r o ­tons f r o m the s32(n,p)P-^2 r e a c t i o n . In any c a s e , the p r i m a r y value of this i n ­s t r u m e n t l i e s in i t s h igh s e n s i t i v i t y , quick r e s p o n s e and s h o r t w a r m - u p t i m e , and i t s p o r t a b i l i t y , a l l of which m a k e s th is c o u n t e r va luab le as a n e u t r o n d e ­t e c t o r . The s e n s i t i v i t y of the s c i n t i l l a ­t ion c o u n t e r can be i n c r e a s e d s e v e r a l f a c t o r s by us ing the l a r g e r de t ec t ing e l e m e n t s and p h o t o m u l t i p l i e r t ubes now a v a i l a b l e .

At about 0,4 Mev the i n s t r u m e n t "cuts off," the e x a c t poin t being d e t e r ­mined by the p h o t o m u l t i p l i e r tube ga in . T h i s , of c o u r s e , r e d u c e s the va l i d i t y of a P o - B e n e u t r o n c a l i b r a t i o n in s i t ua t ions involving o the r n e u t r o n e n e r g i e s . G a m m a r a d i a t i o n d i s c r i m i n a t i o n is effected by m e a n s of a 1 - m e g o h m p o t e n t i o m e t e r which p e r m i t s addi t ion to the 900 r e g u ­la ted vo l t s f r o m the supply . The i n ­s t r u m e n t i s g e n e r a l l y i n s e n s i t i v e to g a m m a r a d i a t i o n l eve l s up to about

3 r / h r . The s e n s i t i v i t y d e c r e a s e s c o n s i d e r a b l y wi th d e c r e a s i n g n e u t r o n e n e r g y f r o m a va lue of about 1 count pe r 100 inc iden t 15-Mev n e u t r o n s to about 0.02 counts p e r 100 inc iden t 0 .5 -Mev n e u t r o n s .

F a s t N e u t r o n Su rvey M e t e r , AEC Model SBX-20A. Th i s s c i n t i l l a t i o n c o u n t e r (the L e r m a c Inc . , F i g u r e 12) des igned by B.W. Thompson(39) e m p l o y s a m e t a l s p h e r i c a l ( t h e r e f o r e nond i r ec t iona l ) d e t e c t o r , the i n s ide of which i s l ined with po lye thy lene and

.<• -V-xSi.

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Figure 11. Fast neutron scintillation counter, AEC Model SBX-21A.

1)

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Figure IZ. Fas t neutron scinti l lat ion counter, AEC Model SBX-20A.

coa t ed with s i l v e r - a c t i v a t e d z inc su l f ide . P r o t o n s a r e p r o d u c e d in the po lye thy lene du r ing n e u t r o n i r r a d i a t i o n , and l ight r e s u l t s a s the p r o t o n s r e a c t wi th the z inc su l f ide . The n e u t r o n de t ec t ion m e c h a n i s m , then , i s l ike the one u s e d in the Z n S - l u c i t e s c i n t i l l a ­t ion c o u n t e r . H o w e v e r , the c o u n t e r t a k e s advan tage of the dependence of s e n s i t i v i t y upon n e u t r o n e n e r g y by r e c o r d i n g the m e a s u r e m e n t in n e u t r o n e n e r g y flux dens i ty , tha t i s M e v / c m ^ - s e c . T h u s , the m e a n e n e r g y of the n e u t r o n s p e c t r u m m u s t be known in o r d e r to l e a r n the n e u t r o n flux dens i ty ( n / c m ^ - s e c ) . The r e l a t i o n be tween n e u t r o n flux dens i ty , ^ , m e a n e n e r g y , E , and the count ing r a t e , C, i s g iven by

</> = (38)

(1.0 X 10-27)Nj^ AE

w h e r e Nh is the n u m b e r of h y d r o g e n nuc le i p e r cm- ' . A i s the d e t e c t o r a r e a . H o w e v e r , the eva lua t ion of E is not e a s i l y a c c o m p l i s h e d , which l i m i t s the u s e f u l n e s s of the c o u n t e r s o m e w h a t in s t r a y r a d i a t i o n m e a s u r e m e n t s . As wi th the Z n S - l u c i t e c o u n t e r , i t s p r i m a r y u t i l i ty i s a s a fas t n e u t r o n d e t e c t o r .

T h o m p s o n s t a t e s that the a p p r o x i m a t e p r o p o r t i o n a l i t y be tween count ing r a t e and e n e r g y flux d e n s i t y beg ins to b r e a k down a t about 0.5 Mev , depend ing upon the a c t u a l g a m m a d i s c r i m i n a t o r l eve l ,

A s u g g e s t e d p r o c e d u r e for se t t ing the g a m m a d i s c r i m i n a t o r i s to b i a s out 100 m r / h r of r a d i u m g a m m a , but in th i s c a s e the i n s t r u m e n t m a y be too g a m m a s e n s i t i v e .

M e t h a n e - F i l l e d (CH4) P r o p o r t i o n a l C o u n t e r . This c o u n t e r can be u s e d in c o n ­junc t ion with a s c a l i n g uni t . (40) A m e t h a n e p r o p o r t i o n a l c o u n t e r i s g e n e r a l l y c y l i n ­d r i c a l in shape and con ta in s g a s to a p r e s s u r e of about 1 a t m o s p h e r e . A w i r e e l e c t r o d e

18

at high po ten t i a l ( a p p r o x i m a t e l y 2000 vol t s ) i s i n s u l a t e d f r o m the c h a m b e r wa l l , the second e l e c t r o d e . A ca thode - fo l l ower p r e a m p l i f i e r i s often u s e d at the coun te r output and thus p e r m i t s the u s e of long c a b l e s .

When a m e t h a n e c o u n t e r i s u s e d in conjunct ion wi th a s c a l e r hav ing a v a r i a b l e gain p o t e n t i o m e t e r , t h e r e is an u n l i m i t e d n u m b e r of c h a m b e r vo l tage and a m p l i f i e r ga in se t t i ngs at which n e u t r o n s can be de t ec t ed and m e a s u r e d . In g e n e r a l , i t would be d e s i r a b l e to have such a vo l t age and gain se t t ing that an o p t i m u m s e n s i t i v i t y i s o b ­ta ined wi thout having the count ing r a t e inf luenced by e l e c t r o n p u l s e s due to g a m m a r a d i a t i o n . Methane c o u n t e r s do not show a s igni f icant p l a t e a u s ince the p r o t o n r e c o i l e n e r g y v a r i e s un i fo rmly up to the m a x i m u m n e u t r o n e n e r g y . The s ens i t i v i t y of a m e t h a n e c o u n t e r i s g e n e r a l l y of the o r d e r of 0.04 c t s / n / c m ^ , a s o m e w h a t h i g h e r s e n ­s i t iv i ty than the t i s s u e equ iva len t fas t n e u t r o n d o s i m e t e r p r e v i o u s l y d e s c r i b e d . How­e v e r , the coun te r and s c a l e r a r r a n g e m e n t i s r a t h e r c u n n b e r s o m e ,

B o r o n - T r i f l u o r i d e - ( B F i ^ ) - F i l l e d P r o p o r t i o n a l Coun te r (Na tu ra l and E n r i c h e d in B-^Q). B e c a u s e of the r e l a t i v e l y high n u m e r i c a l f luxes of t h e r m a l n e u t r o n s r e q u i r e d to p r o d u c e the m a x i m u m p e r m i s s i b l e dose r a t e (2000 n / c m ^ - s e c for . 0 2 5 - e v n e u t r o n s c o m p a r e d to about 30 n / c m ^ - s e c for P o - B e n e u t r o n s ) , the t h e r m a l n e u t r o n h a z a r d is u s u a l l y u n i m p o r t a n t at m o s t a c c e l e r a t o r s i t e s c o m p a r e d to the fas t . H o w e v e r , B F 3 c o u n t e r s , which a r e e x t r e m e l y eff icient d e t e c t o r s of t h e r m a l n e u t r o n s , m a k e c o n ­

ven ien t s cann ing d e v i c e s in i n h o m o -geneous n e u t r o n f ie lds having c o m p a r a ­t ive ly low f luxes of t h e r m a l n e u t r o n s . The B F 3 c o u n t e r s e n s i t i v i t y d r o p s to a neg l ig ib le va lue (1 p e r c e n t of the m a x i ­m u m ) at n e u t r o n e n e r g i e s of about 1 e l e c t r o n volt , (41)

R e c e n t l y , a B F 3 c o u n t e r - s e a l e r a r ­r a n g e m e n t w a s r e p l a c e d wi th a p o r t a b l e B F 3 c o u n t e r . An S P C - 6 A fas t n e u t r o n d o s i m e t e r w a s modif ied by r e p l a c i n g the H u r s t a r g o n - m e t h a n e - f i l l e d p r o p o r t i o n a l coun te r with a B F 3 c o u n t e r which p e r ­m i t s the m e a s u r e m e n t of t h e r m a l n e u ­t r o n flux d e n s i t i e s be tween 5 and 200 n^j- i /cm^-sec ( F i g u r e 13). A c o u n t e r having a f a i r ly u n i f o r m r e s p o n s e to n e u t r o n f luxes f r o m about t h e r m a l to 3 Mev h a s been c o n s t r u c t e d . The s e n ­s i t iv i ty of such a c o u n t e r known as a H a n s o n - M c K i b b e n "long" coun te r does not v a r y m o r e than 10 p e r c e n t in the i n t e r ­va l 0.01 to 3 Mev.(3*^) H o w e v e r , the s e n s i t i v i t y i s s t i l l h ighly s igni f icant down to t h e r m a l e n e r g i e s . The t h e r m a l c o n ­t r i bu t i on can be r e m o v e d with a su i t ab le cadmiumi sh ie ld .

The F a i l l a - R o s s i T i s s u e E q u i v a l e n t C h a m b e r . An ion iza t ion c h a m b e r of t h i s type w a s obta ined f r o m G. F a i l l a and H.H. R o s s i in 1953 for u s e with a v i b r a t -

Figure 13. An improvised portable ing r e e d e l e c t r o m e t e r ( F i g u r e 14). T i s -BF3 proportional counter. Sue equ iva len t c h a m b e r s a r e d i s c u s s e d

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19

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K „., : -7~ - . : . . . : . "_• - .* ' • . ••-, i n t h e l i t e r a t u r e . ( 2 ' » '*2/ T h e c o n d u c t i n g t i s s u e e q u i v a l e n t p l a s t i c i s c o m p o s e d of 9 .7 p e r c e n t h y d r o g e n , 71 p e r c e n t o x y g e n , 1 5 . 8 p e r c e n t c a r b o n , a n d 3,5 p e r c e n t

.jl I li n i t r o g e n . ( 2 7 ) T h e g a s f i l l i n g i s 6 4 . 4 2 p e r -

) c e n t C H 4 , 3 2 . 3 8 p e r c e n t C02> a n d Is 3 .20 p e r c e n t N2 t o a t o t a l p r e s s u r e of

-•g '':•''"--^.'•'- .^''"i ^ a b o u t 30 c m of m e r c u r y . B e c a u s e of t h e 'iSfy'fi' 'f. r e l a t i v e l y s m a l l d i m e n s i o n of t h i s

S c h a m b e r i n t e r m s of t h e n e u t r o n m e a n # ' 1 ^ ~. Jx. f r e e p a t h , i t s r e s p o n s e i s d u e p r i n c i p a l l y

t o f i r s t - c o l l i s i o n n e u t r o n s . P r e s u m a b l y ,

'4 •••''•, • •'• > ". • . ..a t h e t i s s u e d o s e i n d i c a t e d by t h i s c h a m b e r

i -' :\,.KSi'^ -'• , "^-^ w i l l be t h a t d e l i v e r e d t o a p o i n t a b o u t

.... •^.•,i.s -' ' 'K ' '" '' .'•'.•?i „ •--••-. ' " - 3 6 m m b e l o w t h e s u r f a c e of t h e b o d y

•'• .- • 1".- .•,•;,''.'.;-:vj.'.->•';•,';-"'.•':';'' '-••.$ ( s i n c e t h e c h a m b e r w a l l i s 1 /4 i n . t h i c k ) .

'i\"-X%-' • '• • ^'•''- f-'-^' Uy^^-'''^'Z^'''-//-»hS Of c o u r s e , t h e t i s s u e d o s e i n m i x e d '...; -'f-• •].'C^^"/^" ".'":l;.'}'~,?^}';::i^-- i;-.V''^ r a d i a t i o n f i e l d s w i l l be t h e t o t a l d o s e

c o n t r i b u t e d by a l l e n e r g i e s a n d a l l t y p e s 4 of r a d i a t i o n . O n l y i n d e p e n d e n t m e a s u r e -

yJ m e n t s c a n g i v e t h e s u r v e y o r a n i d e a a s t o t h e c o m p o n e n t s of t h e m i x e d r a d i a t i o n .

R e c e n t l y , a p o r t a b l e v e r s i o n of t h i s F igure 14. A t i ssue equivalent ionization chamber ' ^ •, , i , used with an Applied Phys ics Corporat ion vibrating c h a m b e r h a s b e e n m a d e a v a i l a b l e b y

reed e l ec t rome te r . R a d i a t i o n I n d u s t r i e s ( S P C - l l A ) .

C h a r t s

T h e c h a r t s b e l o w f u r n i s h p e r t i n e n t f e a t u r e s of t h e a c c e l e r a t o r s i t e s a t w h i c h s t r a y r a d i a t i o n s u r v e y s h a v e b e e n m a d e by H e a l t h a n d S a f e t y L a b o r a t o r y g r o u p s .

C h a r t 1 f u r n i s h e s a c o d e l e t t e r f o r e a c h i n s t a l l a t i o n ; t h e n a m e , t y p e , a c c e l e r a t e d p a r t i c l e a n d e n e r g y , d a t e of i n i t i a l o p e r a t i o n , s p h e r e s of i n v e s t i g a t i o n , a n d t h e A E C c o n t r a c t n u m b e r w h e r e a p p l i c a b l e .

C h a r t 2 g i v e s t h e i n i t i a l c o s t o r e s t i m a t e d r e p l a c e m e n t c o s t of t h e a c c e l e r a t o r , a n a p p r o x i m a t e e s t i m a t e of t h e a n n u a l o p e r a t i n g b u d g e t , t h e e s t i m a t e d c a p i t a l c o s t of r a d i a t i o n p r o t e c t i o n , a n e s t i m a t e , w h e r e a v a i l a b l e , of t h e a n n u a l c o s t f o r r a d i a t i o n p r o t e c t i o n , a n d t h e n u m b e r of p e r s o n s a s s o c i a t e d w i t h t h e a c c e l e r a t o r o p e r a t i o n .

C h a r t 3 c o n t a i n s i n f o r m a t i o n a s t o t h e w o r k l o a d of t h e a c c e l e r a t o r , w o r k f a c t o r s of p e r s o n s a t t h e s i t e a n d m a x i m u m r a d i a t i o n l e v e l s e n c o u n t e r e d i n n o r m a l w o r k a r e a s , o c c a s i o n a l l y o c c u p i e d ( o r a c c e s s i b l e ) i n s i d e a r e a s , a n d u n r e g u l a t e d o u t s i d e a r e a s .

C h a r t 4 c o n t a i n s c o s t e s t i m a t e s a n d d e s c r i p t i v e m a t e r i a l o n t h e a c c e l e r a t o r s h i e l d i n g .

C h a r t 5 d e s c r i b e s r e g u l a r p h y s i o l o g i c a l e x a m i n a t i o n s a t t h e s i t e s . C h a r t 6 s u m m a r i z e s t h e f i l m b a d g e r e c o r d s a t s i t e s s u b s c r i b i n g t o t h e B r o o k h a v e n

N a t i o n a l L a b o r a t o r y O f f - s i t e M o n i t o r i n g S e r v i c e . T h e f i l m b a d g e p a c k e t s c o n s i s t of a c o n v e n t i o n a l b e t a - g a m m a s e n s i t i v e f i l m a s w e l l a s o n e w i t h a n u c l e a r t r a c k e m u l s i o n ( N T A ) c a l i b r a t e d a g a i n s t a k n o w n f l u x of p o l o n i u m - b e r y l l i u m n e u t r o n s . T h e c o u n t i n g of p r o t o n r e c o i l s i n t h e e x p o s e d n u c l e a r e m u l s i o n i s t h e n a m e a s u r e of t h e n e u t r o n f l u x to w h i c h a w e a r e r of t h e f i l m p a c k e t h a s b e e n e x p o s e d . T h i s c h a r t f u r n i s h e s a b r e a k d o w n of t h e s e f i l m b a d g e r e c o r d s i n t e r m s of c u r r e n t l y a c c e p t e d m a x i m u m p e r m i s s i b l e w e e k l y d o s e s of g a m m a r a d i a t i o n a n d f a s t n e u t r o n s . U n d e r r e m a r k s a r e l i s t e d n u m b e r s g i v i n g a s t r o n g i n d i c a t i o n t h a t a t m o s t s i t e s s i g n i f i c a n t p e r s o n n e l e x ­p o s u r e s a r e r e c e i v e d b y a s m a l l m i n o r i t y of p e r s o n s .

• » 9

#

A

B

C

D

E

F

G H

I J

K

L

M

N O

Code le t ter

CO-CY

PR-CY

PI-CY

CI-SC

CO-SC

MI-CY

MI-SY MI-EG

MI-VG BR-CW

YA-CY

RO-SC

BA-CW

BA-VGS BA-VGS

Installat ion

Columbia Universi ty Pupin Labora tory

Pr ince ton Universi ty P a l m e r Labora tory

Universi ty of P i t t sburgh S.M. Scaife Labora tory

Carnegie Institute of Technology

Columbia Universi ty Nevis Labora tory

Massachuse t t s Institute of Technology

"

" rt

Brown University

Yale Universi ty Sloane Labora tory

Universi ty of Rochester

Bar to l Resea rch Foundation

ti

"

Acce le ra to r

Cyclotron

Cyclotron

Cyclotron

Synchrocyclotron

Synchrocyclotron

Cyclotron

Synchrotron Elec t ros ta t ic

generator Van de Graaff Cockcroft-Walton

Cyclotron

Synchrocyclotron

Cockcroft-Walton

Van de Graaff Van de Graaff

Chart

Pa r t i c l e and energy (Mev)

8-10 d

18 p

8.5 p 16 d 32 a

440 p

385 p

15 d 7.5 p 30 a

340 e 12 + ions

5 + ions 0.25 d

4 d

250 p

0.10 d

1.8 p,d 5-10 p,d

1*

Date of init ial operation

1934

1935 / 1951 \ \ ( rebui l t ) /

1947

1950

1950

1940

1954

1939

1948

1954

--

General spheres of investigation

Cros s - sec t i on measurements resonance levels sca t te r ing studies Cross - sec t ion measurements sca t ter ing studies energy levels nuclear chemis t ry Scattering studies c r o s s - s e c t i o n measurements solid s ta te , nuclear chemis t ry radiat ion damage, biological studies Meson production and scat ter ing me sic atoms radiat ion damage on c rys ta l s nuclear chemis t ry Meson production and scat ter ing

Phys ics - energy levels scat ter ing c ro s s section

nuclear chemis t ry C o s m i c - r a y r e s e a r c h Nuclear energy levels

Nuclear energy levels Cross sections n,p inelas t ic scat ter ing angular distr ibutions enzyme a Biophysics - virus radiation physics - light nuclei

energy levels Scat ter ing (n,n), )n,p),

(meson-nucleon) -

--

AEC contract no

AT(30

AT(30.

AT(30 te rm

AT(30-

ONR

AT(30

AT(30-

AT(30

AT(30-

AT(30

- l ) -Gen-72

•l)-937

- l)-866 1 inated

-l)-882

-l)-905

-1)-1082

- l ) -568

-l)-875

-1)-1679

*Date of Table, October 1954.

ZL

Let ter

A

B

C

D

E

F

G

H

I

J

K

L

Code designation

CO-CY

PR-CY

PI-CY

CI-SC

CO-SC

MI-CY

MI-SY

MI-EG

MI-VG

BR-CW

YA-CY

RO-SC

Total init ial cos t or rep lacement e s t ima te (^)

75,000 (1934)

250,000 (180,000 - acce l e r a to r alone with basic shield in 1935)

50,000 - 100,000 (1941-1947)

1,500,000 (1948)

2,264,000 acce l e r a to r (1950) 750,000 buildings and land

1,000,000 rep lacement es t imate

1,000,000 rep lacement es t imate

500,000 acce le ra to r

150,000 acce le ra to r

200,000 acce l e r a to r , buildings, and grounds

40,000 - 50,000 acce le ra to r r e ­placement

1,520,000 cyclotron and equipment MOO,000 buildings

Chart 2

Cost es t imates

Annual operating budget ($)

250,000

230,000

170,000

500,000

500,000

100,000

150,000

80,000

40,000

32,000

51,000

500,000

Est imated capital cost of radiation

protection ($)

6,000

60,000 (est imate of shield replacement)

6,000

101,153 initial shield 15,000 additional

67,551 initial shield 57,000 additional

50,000

2,500 initial shield 500 back-s top

275,000 initial shield plus building

600 additional

6,000 initial

Nothing

3,500 additional

6,450 initial 17,000 dike, etc .

Radiation protect ion operating costs ($)

7,000

No es t imate made

No es t imate made

No es t imate made

5,000/year excluding sa l a r i e s

No es t imate made

No es t imate made

No es t imate made

No es t imate made

No es t imate made

No es t imate made

No es t imate made

Number of persons

26

52

85

102

60

5 (>10% time)

40

2-10

6

6

20

40

2-5

Let ter

A

B

C

D

E

F

G

H

I

J

K

L,

Code designation

CO-CY

PR-CY

PI-CY

CI-SC

CO-SC

MI-CY

MI-SY

MI-EG

MI-VG

BR-CW

YA-CY

RO-SC

App roximate number

of persons

26

52

85

102

60

5 >10%

40

10

6

6

20

40

Es t ima ted work load of

acce le ra to r (hr/wk)

90-100

125

No es t imate made

72

75

No es t imate made

140-168

No information available

56

56

<112

168

Chart 3

Radiation level es t imates

Es t imated work factor of persons (fraction of 40 hr)

and persons

>0.2 <0.2

>0.2 <0.2

0.1 -

0.2

0.1 -<0.1

>0.2 <0.2

>0.2 <0.2

>0.2 <0.2

>0.2 <0.2

>0.2

>0.2 <0.2

>0.2

1.0

1.0

(20) (6)

(3) (49)

(85)

(102)

(45) (15)

(3) (2)

(6) (34)

(2) (8)

(2) (4)

(6)

(3) (17)

(40)

Radiation levels; fractions maximum permiss ib le dose

Normal w a r ea s

<0.1

<0.1

1.3

4 .0

15

5.0

No m e a s u r e made

2.0

0

0.5

2.0

2 .0

o r k

ment

Occasionally occupied or

access ib le inside a r ea s

6.0

2 1

53

80

40

2 .6

No measurement made

<0.10

4 .0

10

8.0

4.0

of (fast neutrons) r a t e (40 hr) hourly

Unregulated outside a r e a s

No me a s ur eme nt s made Believed <0.1

No m e a s u r e m e n t s made Believed <0.1

No m e a s u r e m e n t s made

4

No m e a s u r e m e n t s made

No m e a s u r e m e n t s made

No m e a s u r e m e n t s made

No m e a s u r e m e n t s made

No m e a s u r e m e n t s made

0.50

16.50 along walk

10.0 along walk

f ' I > I

^f

Let te r

A

B

C

D

E

F

G

H

I

J

K

L

Code designation

CO-CY

PK-GY

PI-CY

CI-SC

CO-SC

MI-CY

MI-SY

MI-EG

MI-VG

BR-CW

YA-CY

RO-SC

Es t imated init ial cost of radiation protect ion (shield)

($)

6,000

60,000

6,000

101,153

67,551

50,000

2,500

275,000

6,000

0

P a r t of

6,450

including

building

building

Chart 4

Shi elding

Es t imated cost of additional protection

($)

0

0

600-800,

15,000

57,000

0

500

600

0

0

wate

'

r windows

3,500 - 2 additional walls

17,000

Description of existing shielding

3 ft of water in 1/4-in. s teel tanks

3 ft of i ron and limonite concrete

4 ft water plus 14 in. brick, 8 ft water , ear th roof (26 ft)

North - 8 ft magnetite concrete Eas t - 8 ft magnetite concrete at beam level , 8 ft lead South - 4 ft magnetite concrete plus ea r th dike West - 15 ft magnetite concrete loaded with s c r ap s tee l

North - mostly 8 ft i ron Eas t - 6 ft concrete plus ear th South and west - 6 ft concrete plus i ron local shields Roof - 6 ft concrete

4 ft concrete , 3 ft on roof, plus 2 ft concrete locally

3 ft concrete except in beam - 3 ft lead

2 ft concrete walls

3 ft concrete

Remote operation - chain link fence (no shielding per se)

18 in. brick walls

Remote operation - local concrete blocks, chain link fence

ts)

t\)

ru-S^

Let ter

A

B

C

D

E

F

G

H

1

J

K

L

Code designation

CO-CY

PR-CY

PI-CY

CI-SC

CO-SC

MI-CY

MI-SY

MI-EG

MI-VG

BR-CW

YA-CY

RO-SC

Chart 5

Studies of acce le ra to r worke r s

Blood examination

Monthly blood counts for 20 persons ; quar te r ly blood counts for 6; annual blood counts for everyone

Quar te r ly blood counts

Quar te r ly blood counts (weekly blood counts for 6 weeks when exposure exceeds weekly MPE)

Quar t e r ly for r e s e a r c h personnel

Monthly blood counts

Blood counts every 4 months for everyone >20 m r / w e e k

Blood counts every 4 months for everyone >20 m r / w e e k

Blood counts every 4 months for everyone >20 m r / w e e k

Blood counts every 4 months for everyone >20 m r / w e e k

Per iod ic blood counts

Per iod ic blood counts

Per iod ic blood counts

Eye examination

No

No

Semiannual slit lamp

Semiannual slit lannp for personnel from r e s e a r c h

Twice since 1950

Annual slit lamp

Annual slit lamp

Annual slit lamp

Annual slit lamp

No

No

No

2 . ^ Chart 6

Site

Bartol Resea rch Foundation

Brown University

Carnegie Institute of Technology

Columbia University

Massachuset ts Institute of Technology

University of Pi t tsburgh

Princeton University

University of Rochester

Yale University

Accelerator

Van de Graaff Van de Graaff Cockcroft-Walton

Cockcroft-Walton

Synchrocyclotron

Cyclotron

Synchrocyclotron

Cyclotron Synchrotron Van de Graaff Van de Graaff

Cyclotron

FM Cyclotron

Synchr ocyclotr on

Cyclotron

Accelerated particle

ancl energy (Mev)

1.8 d 5 p 0,10 d

0.25 d

440 p

10 d

385 p

15 d 340 e 12 + ions 5 + ions

16 d

18 p

250 p

4 d

Approx. no. of

persons employe cl

at site

12 12

2

6

102

27

60

6 40 10

6

85

52

60

20

No. of persons wearing batlges

12** 12** 2

6

51 w

27

6 11

3 3

10

32

60

11

Dates*

8/2/54-1/2/55 b

6/15/54-1/13/55 b

5 /1 /53-1/6/55 w

11/20/53-1/6/55 w 3 /2 /53 -1/2/55 w

4 / 1 / 5 3 -1/2/55 b

7 /3 /53 -1/6/55 b

3 / 2 / 5 3 -1/2/55 b

6/14/54-1/9/55 b

11/30/53-1/9/55 b

Fast neutrons fraction of MPE

0.5-1.0

5 5 -

-

75

9

170

1 3 1 1

8

8

37

3

1-2 2-3 >3

1 - -1 - -

- -

- - -

3 0 1

- -

49 16 4

- -- . - . - -

- - 1

1 -

- 1 -

- -

0.25-0.

5 5

-

-

253

12

48

46 13

2

-

67

4

24

1

Gamma r fraction

5 0.5-l.C

1 1

-

-

116

_

35

16 4

--

25

4

6

1

adiation of MPE

1-2 2-3

-- -- -

- -

58 19

1 -

28 9

- 1 - -- --

17 8

-

1 -

-

>3

_ --

-

6

-

7

_ 1

--

_

-

-

-

Remarks

2 persons accounted for all 12 exposure s

-

-

10 persons accounted for 50% of exposures

14 persons - all exposures

8 persons - 50% of exposures

2 persons - 83% 8 persons - 100% 2 persons - 100%

-

6 persons - 73%

14 persons - 100%

9 persons - 2 6%

3 persons - 100%

*b signifies a bi-weekly period; w signifies a weekly period. **Same persons at both Van de Graaffs.

26 -^7 Individual Surveys

Stray radiation measurements were made of 15 part icle accelera tor sites at ten installations in the Eas t e rn United States between January 1953 and August 1954. Some of the acce lera tors were visited more than once. Results of the individual s u r ­veys are given below along with the observations and recommendations which were t ransmit ted to the accelera tor operator. In sonne cases , the specific instrument which yielded a measurennent is indicated since measurements made with different in s t ru ­ments do not always agree.

Pupin Physics Laboratory, Columbia

This cyclotron i s , nominally, a 10-Mev deuteron accelera tor having 36-in. magnet pole pieces and is located in the north side of the Pupin Laboratory basement on the campus. It is shielded by stacks of water cans as shown in the floor plan (Figure 15). Radiation surveys were conducted during two modes of operation. Under the one con­dition, the 8-Mev deuteron beam was pulsed 4 jxsec out of each 1024 jisec, the pulses attaining values as high as 700 [la. The second nnode, because of nnore frequent pulses , produced one-third of the possible average beam current . Results of the first or "low level" survey appear in Table 2; Table 3 shows the "high level" survey findings. Recommendations were based on fast neutron measurements . No quantitative thermal neutron studies were made, though exposed film badges indicated the presence of some thermals by virtue of a high degree of blackening under the cadntiium shield in the film badge.

Recommendations: 1) Under the low level operating conditions (Table 2), it was thought that the corr idor a rea in front of the cyclotron vault could be occupied without res t r ic t ion by informed cyclotron personnel . It was pointed out that because of the lack of positive de te r ren t s , such as interlocking devices, exposure to high radiation levels at the vault entrance was possible. 2) During the so-cal led high intensity

CYCLOTRON 128 PROTECTED ON SIDES AND ABOVE

BY WATER TANKS

Figure 15. P lan of the Pupin Phys ics Labora tory , Columbia Universi ty .

m^^^w^

^r 27

Radiation

Location

1

2

6 9

10 13

levels at Pupin Phy January 16, 1953. Cyclotr 12.4- Mev neutrons (max);

attaining beam currents

Description

Vault entrance

Vault entrance

Water shield void Against shield Against shield Near collimator

sics on eye

Table 2

Lab oratory, Columbia Univers operation: 8-Mev j H' on Be to

ity (co-produce

lotron pulsed 4 usee of every 1024 of about 700 jia (0.4 percent of the

Radiation

4.2 mrep/hr 15 mr/hr 1.2 mrep/hr 5 mr/hr 0.42 mrep/hr Nothing detected Nothing detected 0.35 mrep/hr 3 mr/hr

j i s ec time).

Frac

CY),

tion MPE*

11 2.0 3.0 0.7 1.1

--0.9 0.4

operation, it was recommended that no one should pass the fence indicated in the floor plan. Although it was noted that this fence was purely a mechanical device used only at the discret ion of the cyclotron operator , it was felt that this ra ther informal radiation control might be adequate because of the presumably smal l number* of p e r ­sons directly concerned with cyclotron operation. A review of past filnn. badge records disclosed no sustained significant radiation exposures .

Radiation levels at Pupin Physics

Location

4

3

5 7 8

13

14 15 11 16

,

Table 3

Laboratory, Columbia University (CO-CY), January 26, 1953, Cyclotron operation: 1/3 maximum

12-Mev neutrons

Description

Vault entrance

Vault entrance

Against shield Against shield Against shield Near collimator

Behind collimator Outside room 133 Fence Control room

by Be9(d.n)B^".

Radiation

10.7 mrep/hr 160 mr/hr 15,2 mr/hr 250 mr/hr Nothing detected Nothing detected Nothing detected 21 mrep/hr 150 mr/hr Nothing detected Nothing detected Nothing detected Nothing detected

intensity;

F faction MPE

29 21.3 40.5 33.3

---

56 20

----

Pa lmer Physical Laboratory, Princeton

The Princeton University frequency modulated (FM) cyclotron is located in a concrete vault in the basement of the physics building on the campus. The magnet has

•Because of the uncertainties in neutron dosimetry, as well as in biological information, an arbitrary factor of two was introduced in calculating the fraction of the MPE in all the summaries.

L^.j C30

28 ^ ?

Location

1 2 3 4

5 6 7

8

9 10

R a d A p

lation levels at P a l m e r Physics

Tab] e 4

Laboratory , Pr ince ton Universi ty (PR ril 7, 1953. Cyclotron operation: If neutrons; beam cur ren t = 10"°

Descr ipt ion

Near console s ta i r s 3 m e t e r s left of col l imator 1 me te r left of coll imator Behind sca t ter chamber

near entrance (not shown) Behind end of water shield Escape hatch Right of col l imator

Work a r ea

Entrance to No. 8 Balcony over No. 9

amp, -Mev I H ' on polyethylene

-CY), to produce

or about 10 percent of maximum.

Radiation

Nothing detected 0.80 m r e p / h r 0.80 m r e p / h r 20 n f / cm^-sec No the rmals measurab le Nothing detected <50 n j / c m ^ - s e c 540 n^ /cm^-sec <50 n j / c m ^ - s e c 4.60 m r e p / h r 15 n f / cm^-sec No the rma l s measurab le No the rmals measurab le 30 n f / cm2-sec No the rma l s measurab le

Frac t ion MPE

-2.1 2 .1 1.0

---

36.0

12.3 1.0

-2.0

33-in. diameter pole pieces . This cyclotron is generally operated with a pulsed proton beam with an average beam cur ren t between 0.01 and 0.1 jia. Pulses are of a 25-(xsec duration and occur about every 500 (xsec. During the radiation survey, measurements were made with an 0.01-|j.a proton beam current and a polyethylene target (Table 4) and a beryllium target (Table 5).

R a d

Location

2

11

Table

lation levels at P a l m e r Phys ics Labor April 7, 1953. Cyclotron operation:

5

atory , Pr ince ton Universi ty 18

produce neutrons; beam curr

Descr ipt ion

3 m e t e r s left of col l imator

6 m e t e r s left of col l imator near console depress ion

(PR-CY), -Mev protons on beryl l ium to ent = 1 0 - ° amp.

Radiation

4000 n f / c m ^ - s e c

9.2 m r e p / h r

Frac t ion MPE

267

24.5

Reconnmendations: No significant radiation levels were encountered during the use of the polyethylene target except immediately adjacent to the beam coll imator. The shielding and radiation pract ices were quite adequate for the operating and r e sea rch groups at Princeton. It was noted that the Princeton cyclotron group had availed itself of the Brookhaven National Laboratory off-site fast neutron film badge in March 1953. During cyclotron operation with the thick beryll ium target , radiation levels were uni­formly high in the experimental a rea (Locations 2 and 11 in Figure 16). This is an un­usual operating procedure conducted outside regular working hours and is scheduled only when neighboring students ' a reas a re not in use.

31

3je 29

Figure 16. Plan of the Palmer Physics Laboratory, Princeton University.

S.M. Scaife Cyclotron Laboratory, Pi t tsburgh

The Pi t tsburgh cyclotron is a 16-Mev deuteron accelera tor which is located part ly underground near the University campus in Pi t tsburgh. The deuteron beam rota tes counter-clockwise and then interacts with an appropriate target so oriented that the predominant direction of the radiation is into the side of a hill - - essential ly an in­finite ear th shield. That i s , the neutron beam passes from the cyclotron vault through a coll imator in an 8-ft-thick water shield into an underground "cave" (cf. floor plan, Figure 17). At the time of the survey, 10-Mev deuterons were permit ted to in teract with copper to produce 15-Mev neutrons.

Recommendations: F i r s t , the adoption of fast neutron personnel monitoring equip­ment by the Pi t tsburgh cyclotron group. At the t imeof the survey, film badges capable of indicating the amounts of beta and gamma radiation dose were in use. Pi t tsburgh subscribed to the Brookhaven National Laboratory fast neutron film badge service in July 1953.

Secondly, it was recommended that a radiation sign indicating the location of the neutron beam in the "cave" be used. It was pointed out that pencil beams can be peculiarly hazardous because locating them with a survey ntieter is difficult (Figure 18). Fur the rmore , it i s conceivable that a person wearing a film badge could stand in a narrow beam without exposing his film badge.

It was recommended that any maintenance required inside the pump room not be done during cyclotron operation. If this is not feasible, no person should be pernaitted to remain in the pump room during cyclotron operation more them 45 minutes in any given week. Since the cyclotron vault door is not interlocked, the installation of an automatic warning device was suggested.

: : i 32

3/

COUNTERS PARTICLE ANALYZER

Figure 17. P lan of the Sarah Mellon Scaife Cyclotron Laboratory, Pi t tsburgh.

,::;^:;» ,

" * < - j " ^ ' * * - i « f l ^ i

&

If-r-T|^-~jS2SfAtj

t

. \ .^lOSfLr

- , * , >

..:] ' I

*4t ' i r - , ' ' . ' '

w*?'

Figure 18. An experinaental a r e a m the Scaife Laboratory , which is shielded from the cyclotron by a water tank, contains a naagnetic ana­lyzer . A pencil neutron beam emerges f rom this magnet to the right.

3

Table 6

Radiation levels at the Sarah Mellon Scaife Laboratory, University of Pittsburgh (PI-CY), April 15, 1953. Cyclotron operation: 10-Mev jH^ on copper to produce

~15-Mev neutrons; beam current = 10"* amp.

Location

1

2

3

4

5

6

.

-

-

-

•Cyclotron

Description

Contact vault door

3 ft from void

5 ft from vault door

Lab doorway

Head of stairs

In beam

Control room

Pump room downstairs

Paraffin doorway

Paraffin door closed*

operated with paraffin door closed and

Radiation

40 nf /cm^-sec 0.1 lArep/hr

150 nf /cm2-sec 0.84 mrep/hr

35 nf /cm2-sec

30 nf /cm2-sec

0.1 mrep/hr

70 mrep/hr

36 nf /cm^-sec 0.1 mrep/hr

35 mrep/hr

5.2 mrep/hr

Nothing detected

pump room generally not

Fraction MPE

2 .7 0 .3

10.0 2 .2

2 .3

2 .0

0 .3

187

2 .4 0.3

93

14

-

occupied.

Table 7

Radiation levels at the Nuclear Research Center,

Location

1

2

3a

3b

4

5

6

7

-

-

-

April 14, 1953. Cyclotron operation: Be Carnegie Institute of

ryllium target, meson beam current meter reading = 75-80 jia.

Description

Entrance to excluded area

Shield corner

Console - front

Console - behind

3 ft from stairs

Experimental area

Vault door

10 ft from door

Outside double door (Figure 23)

Building (end of proposed fence)

Garage (middle door)

R adiation

1550 nf/cm^-sec 12 mrep/hr

410 nf/cm^-sec 1.95 mrep/hr

180 nf /cm2-sec 0.98 mrep/hr

86 nf/cm^-sec 0.24 mrep/hr

140 nf/cm^-sec

70 ttf/cm^-sec 0.4 mrep/hr

145 nf/cm^-sec 0,24 mrep/hr

60 nf/cm2..sec 0.17 mrep/hr

5 mrep/hr

0.9 mrep/hr

0.33 mrep/hr

Technology (CI-SC), production;

Fraction MPE

103 32

27 5.2

12 2.6

5.7 0.63 .

9.3

4.7 1.1

9.7 0.63

4.0 0.45

13.3

2 .4

0.88

I

32 3J5

Table 8

Radiation levels kt the Nuclear Resea rch Center , Carnegie Institute of Technology (CI-SC), April 16, 1953. Cyclotron operation:

No target; beam current meter reading = 75-80 (la.

Location

1 8 9

10

Description

Entrance to excluded a rea General work a rea Beyond end of shield

Radiation

3 m r e p / h r MO n j / cm -sec 20 n f / cm^-sec 75 n f / cm^-sec

Frac t ion MPE

8.0 0.7 1.3 5.0

VAULT

2

3a 3b

EXPERIMENTAL AREA

Nuclear Research Center, Carnegie Institute of Technology

The 145-in, synchrocyclotron is capable of accelerating protons to energies as high as 440 Mev. It is located in the southeast end of a building in Saxonburg approx­

imately 30 miles from Pit tsburgh. Radi­ation measurements were made during various operating conditions. Tables 7 and 8 give measurements made in 1953 (see floor plan. Figure 19). Tables 9 to 14 are the resul ts of surveys performed in 1954 (see floor plan. Figure 20). It should be noted that this accelera tor is one of the largest synchrocyclotrons in t e rms of the number of persons assoc i ­ated with it, as well as the size of the installation and part icle energies pos ­sible.

Recommendations (1953): The a-doption of the Brookhaven National Labo­ra tory fast neutron personnel monitoring service on a weekly basis was r ecom­mended. This service was actually sub­scribed to in May 1953. It was sug­gested that the commercia l neutron s u r ­vey meter , used by the Nuclear Research Center, be tested routinely with a known flux of neutrons to verify its calibration. On this ear ly occasion the surveyors found that reliance upon only one neutron detector was likely to give a gross ly e r ­roneous estimate of the dose ra te . One of the purposes of this survey was to test the efficiency of additional shielding.

As a resul t of the survey, it was felt that this modified shielding was certainly neces ­sary for safe operation of the accelera tor . In fact, it was suggested that personnel occupancy of cer ta in a reas be res t r ic ted until more shielding was installed.

Finally, it was reconamended that, since some of the Carnegie cyclotron workers spend considerably more than 40 hours per week at their duties, the average hourly maximum permiss ib le dose rate should be scaled downward according to the time

8 EQUIPMENT ROOM

10

Figure 19. Plan of the Nuclear Research Center synchrocyclotron, Carnegie Ins t i ­

tute of Technology, April 1953.

35

Table 9

33

Radiation levels at the Nuclear Research Center synchrocyclotron, January 5, 1954 (evening). Operating condition: Meson target (#1);

normal field, counter-clockwise BMLM 185; BMIC: 183.

Location

105 106 143 144 145 110 113 112 111 146 115 114 117 116 122 123 126 130 129 128a 128 127 124 120a 120 119 502 501 503 504

Corridor (monitor Control room (near

201 218

station) wall)

Behind 218 (farthest wall) 2 1 6

Behind 216 (M4 ft) 213

Behind 213 (M4 ft) 209 225

Work bench behind oil system

Back doorway 123

•Instruments used: methane counter.

magnet

Instrument*

ZnS ZnS ZnS ZnS ZnS ZnS ZnS ZnS ZnS ZnS ZnS ZnS ZnS ZnS ZnS ZnS ZnS ZnS ZnS ZnS ZnS ZnS ZnS ZnS ZnS ZnS ZnS ZnS ZnS ZnS ZnS ZnS ZnS ZnS ZnS ZnS ZnS ZnS ZnS ZnS ZnS ZnS

ZnS CH4

FND #36 FND #43 FND #44

ZnS-lucite scintillation

Neutron flux or dose rate

46 n/cm^-sec 40 n/cm^-sec 40 n/cm^-sec 33 n /cm2-sec 37 n/cm^-sec 58 n/cm^-sec 46 n/cm^-sec 38 n/cm^-sec 33 n/cm^-sec 28 n/cm^-sec 19 n /cm^-sec 28 n /cm2-sec 23 n /cm2-sec 17 n /cm^-sec 44 n/cm^-sec 62 n/cm^-sec 102 n /cm2-sec 49 n /cm2-sec

• 65 n/cm^-sec 40 n/cm^-sec 33 n /cm^-sec 35 n /cm2-sec 46 n / c m ' - s e c 46 n /cm^-sec 35 n/cm2_sec 23 n /cm2-sec

MO n/cm2-sec 17 n/cm^-sec

<10 n/cm^-sec <10 n/cm^-sec <10 n /cm2-sec <10 n/cm^-sec MO n/cm^-sec <10 n/cm^-sec <10 n/cm^-sec <10 n/cm^-sec

13 n/cm2-sec <10 n/cm^-sec

16 n /cm^-sec 19 n /cm^-sec 33 n /cm^-sec 13 n/cm^-sec

16 n/cm^-sec 38 n /cm -sec 0.75 mrep/hr 1.12 mrep/hr 0.97 mrep/hr

counter, Raychronix FND

Fraction MPE

3.1 2 .7 2 .7 2.2 2.5 3 .9 3.1 2 .5 2.2 1.9 1.3 1.9 1.5 1.1 2 ,9 4 .1 6.8 3.3 4 .3 2 .7 2.2 2,3 3,1 3,1 2 ,3 1.5 0 .7 1.1

'\'0.7 M).7 ~0.7

•~0.7 ^0.7 ~0.7 ~0.7 ~0.7

0.9 ~0.7

1.1 1.3 2 .2 0.9

1.1 2 .5 2 .0 3.0 3 .6

#36, #43. #128 and

Table 9 (Continued)

Location

124 126

130 120 146 113** 110** 106**

301** 302** 303** 303**

Along fence** Inside garage** Inside garage"** (west wall)

123**

146**

126a**

*Instruments used: counter.

**Beam cur ren t up.

ZnS-lucite

Ins t rument*

CH4 CH4 ZnS CH4 CH4 C H 4 CH4 CH4 CH4 ZnS ZnS ZnS ZnS ZnS ZnS ZnS ZnS

FND #36 FND #43

ZnS FND #36 FND #43

ZnS FND #36 FND #43

ZnS

scintillation counter ,

Neutron flux or dose rate

30 n / c m ^ - s e c 53 n / c m ^ - s e c 84 n / c m ^ - s e c 33 n / c m 2 - s e c 34 n / c m ^ - s e c 40 n/cmr-sec 37 n / c m ^ - s e c 30 n / c m ^ - s e c 34 n / c m ^ - s e c 42 n / c m ^ - s e c 84 n / c m ^ - s e c 172 n / c m ^ - s e c 120 n / c m ^ - s e c 124 n / c m ^ - s e c 11-80 n / c m ^ - s e c 0

<10 n / c m ^ - s e c 0.93 m r e p / h r 1.47 m r e p / h r 61 n / c m 2 - s e c 0.38 m r e p / h r 0.55 m r e p / h r 33 n / c m ^ - s e c 1.18 m r e p / h r 0.89 m r e p / h r 102 n / c m ^ - s e c

Raychronix FND #36, #43. #1

Frac t ion MPE

2.0 3.5 5.6 2 .2 2 . 3 2 .7 2 .5 2 .0 2 .3 2 .8 5.6

11.5 8.0 8.3

0.73-5.3 -

^0.7 2 .5 3.9 4 .1 1.0 1.5 2.2 3.1 2 .4 6.8

28 and methane

Location

111-112 115 120 123 120a 130 101 102 103 104

129 128a 128

Radiation le January

vels at the

Table

*Juclear 6, 1954 (evening).

normal beam.

Instrument

ZnS ZnS ZnS ZnS ZnS ZnS

FND #128 FND #128 FND #128 FND #128

ZnS ZnS ZnS

BMIC:

10

Resea rch Center syn Op 48

"rating condition: (100 meg); BMLM

Neutron flux or dose ra te

~0 n / c m ^ - s e c ~3 n / c m ^ - s e c ~7 n / c m ^ - s e c 35 n /cm'" -sec 19 n / c m ^ - s e c 21 n/cm'^-sec 4 m r e p / h r 6 m r e p / h r 3 m r e p / h r

-33 n / c m ^ - s e c 21 n / c m ^ - s e c 19 n / c m ^ - s e c

ciirocy No tar : 50.

clotron. get.

Frac t ion MPE

~0.0 ~0.2 ~0.5

2.3 1.3 1.4

10.7 16.0

8.0

-2.2 1.4 1.3

37

3J^ 35

Location

127-124(area) 501 201 213 (center 216

Bench behind 212 Back door* End of cooling tower General area Centrifuge

302-303 Garage Console Bench behind 212^

Bench in back^ Centrifuge*

213* 220*

202-218^ 216*

Control room^ Equipment roona bay

123* 120a* 128*

line)

system

*

*Beam up: Beam monitor -

Table

Instrument

ZnS ZnS ZnS ZnS ZnS ZnS ZnS ZnS ZnS ZnS ZnS ZnS ZnS ZnS

FND #128 ZnS ZnS ZnS ZnS ZnS ZnS ZnS ZnS ZnS ZnS ZnS

48 to 80. Log

10 (Continued)

Neutron flux or dose rate

16-21 n/cnn^-sec <10 n/cm^-sec <10 n/cm^-sec <10 n/cm^-sec <10 n/cm^-sec 16 n /cm2-sec 10-21 cm^-sec 21 n /cm^-sec 10-21 n/cm^-sec 31 n / cm2-sec 10-21 n/cm^-sec not detectable <10 n /cm^-sec 39 n /cm^-sec 0.69 mrep/hr 39 n / cm2-sec 84 n /cm^-sec 16 n / c m 2 . s e c 46 n / cm2-sec 19 n /cm^-sec 21 n /cm2-sec MO n/cm^-sec 17 n/cnn2-sec 72 n/cmr-sec 4 3 n / c m ^ - s e c 4 7 n / c m 2 - s c c

m e t e r - 50 to 80 .

F r a c t i o n M P E

1 . 1 - 1 . 4 <0.7 < 0 . 7 <0 .7 <0.7

1.1 0 . 7 - 1 . 4

1.4 0 . 7 - 1 . 4

2.1 0 . 7 - 1 . 4

M).0 < 0 . 7

2 .6 1.8 2 . 6 5 .6 1.1 3.1 1.3 1.4

•vO.7 1.1 4 . 8 2 .9 3 .1

Table

Rad ia t ion l e v e l s at the N u c l e a r January

L o c a t i o n

1 0 1 - 1 0 2

3 f ee t high 105 106 105a 143 ( c r a c k ) 144 108 145 110 112 113 114

• 116a 115

11

R e s e a r c h Center synchroc 6, 1954 (morning) . Oper n o r m a l field; BMIC:

Ins trument

F N D #36 F N D #128

ZnS ZnS ZnS ZnS ZnS ZnS ZnS ZnS ZnS ZnS • ZnS ZnS ZnS ZnS

30 ating

yclotron. condit ion: Neutron target ;

(10 m e g ) ; BMLM: 310.

Neutron flux or d o s e rate

100 m r e p / h r 100 m r e p / h r

31 n / c m ^ - s e c 21 n / c m ^ - s e c 31 n / c m ^ - s e c 13 n / c m ^ - s e c

<10 n / c m ^ - s e c 21 n/cmr-sec 14 n/cm^-sec 12 n /cm2-sec

MO n/cm^-sec ~10 n/cm^-sec •vlO n/cm^-sec MO n/cm^-sec <10 n/cm^-sec

Fraction MPE

267 267

2 .1 1.4 2 .1 0 .9

<0.7 1.4 0.9 0 .8

~0.7 ~0.7 ~0.7 ~0.7 <0.7

Jc 38

T a b l e 11 ( C o n t i n u e d )

L o c a t i o n

118 120 121 120a 123 122 126 126a 130 129a 129 128a 128 501 502 503 504

505 ( t h r o u g h o u t r o o m ) C o r r i d o r m o n i t o r s t a t i o n C o n t r o l r o o m R o o m #128

201 201a 216

14 f ee t b e h i n d 216 213 ( m i d - p t of w a l l ) 14 feet b e h i n d 212

211 3 fee t b e h i n d 209

205 E q u i p m e n t r o o m (back d o o r ) B e n c h n e a r d o o r E n d of c o o l i n g t o w e r s y s t e m D e s k n e a r b e n c h R i g h t of 302 ( s m a l l d o o r )

303 Along fence G a r a g e b e n c h G a r a g e ( g e n e r a l )

112

126a ( f i r e h o s e )

128a

E q u i p m e n t r o o m B e n c h (beh ind 212)

I n s t r u m e n t

ZnS ZnS ZnS ZnS ZnS ZnS ZnS ZnS ZnS ZnS ZnS ZnS ZnS ZnS ZnS ZnS ZnS ZnS ZnS ZnS ZnS ZnS ZnS ZnS ZnS ZnS ZnS ZnS ZnS ZnS ZnS ZnS ZnS ZnS ZnS ZnS ZnS ZnS ZnS

R e p e a t w i th o t h e r

CH4 ZnS

F N D #36 CH4 ZnS

F N D #36 CH4 ZnS

F N D # 3 6 CH4 ZnS

F N D # 3 6

N e u t r o n flux or d o s e r a t e

MO n / c m ^ - s e c 19 n / c m 2 - s e c 21 n / c m 2 - s e c 42 n / c m 2 - s e c 55 n / c m ^ - s e c 43 n / c m ^ - s e c 80 n / c m ^ - s e c 97 n / c m 2 - s e c 4 6 n / c m ^ - s e c 69 n / c m 2 - s e c 52 n / c m 2 - s e c 38 n / c m ^ - s e c 31 n / c m ^ - s e c

~ 1 0 n / c m 2 - s e c ~ 1 0 n / c m ^ - s e c <10 n / c m ^ - s e c <10 n / c m ^ - s e c <10 n / c m 2 _ s e c <10 n / c m ^ - s e c <10 n / c m ^ - s e c <10 n / c m ^ - s e c

14 n / c m ^ - s e c <10 n / c m 2 - s e c <10 n / c m ^ - s e c ~10 n / c m ^ - s e c MO n / c m ^ - s e c

17 n / c m ^ - s e c 12 n / c m ^ - s e c 60 n / c m ^ - s e c 17 n / c m ^ - s e c 14 n / c m ^ - s e c 19 n / c m 2 - s e c 2 6 n / c m 2 - s e c 21 n / c m ^ - s e c 73 n / c m ^ - s e c 145 n / c m 2 - s e c 1 9 - 3 3 n / c m 2 - s e c No t d e t e c t a b l e Not d e t e c t a b l e

i n s t r u m e n t s 16 n / c m 2 _ s e c 12 n / c m ^ - s e c 0.22 m r e p / h r 29 n / c m ^ - s e c 88 n / c m 2 - s e c 0 .85 m r e p / h r 17 n / c m ^ - s e c 31 n / c m ^ - s e c 0 .36 m r e p / h r

MO n / c m 2 - s e c 18 n / c m ^ - s e c 21 n / c m ' - s e c 0.22 m r e p / h r 0 .24 m r e p / h r

F r a c t i o n M P E

•vO.7 1.3 1.4 2 .8 3.7 2 .9 5.3 6.5 3.1 4 . 6 3.5 2 .5 2 .1

~ 0 . 7 •^0.7 < 0 . 7 < 0 . 7 < 0 . 7 <0 .7 <0 .7 <0 .7

0 .9 <0 .7 <0 .7 ~ 0 . 7 ~ 0 . 7

1.1 0 .8 4 ,0 1.1 0,9 1.3 1.7 1.4 4 . 9 9.7

1 .3-2 ,2 •vO.O ~0,0

1.1 0 .8 0 ,6 1.9 5.9 2 .3 1.1 2 .1 0.96

~0.70 1.2 1.4

0 .6

19

3 ^ 37

Table 12

Radiation levels at the Nuclear Research Center synchrocyclotron, January Operating condition: Meson target (ir+); reverse field; BMIC: 65 (xa. (100

5, 1953. meg).

Raychronix fast neutron dosimeter (#128) used for survey; all measurements made approximately 4 ft above floor of Cyclotron Room.

Neutron level Location mrep/hr Fraction MPE

110 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126

.24 0.64

.59 1.57

.46 1.23

.54 1.44 2.3 6.13

.80 2.13 3.0 8.00 1.58 4.21 .84 2.24

3.0 8.00 5.0 13.33

30.0 80.0 20.0 53.33

6.0 16.00 8.0 21.33

15.0 40.00

Neutron level Location mrep/hr

127 2.85 128 2.9 129 5.0 130 3.0 140 18.0 2 01 .70 202 .12 204 .12 206 .21 207 .67 501 .73 502 .22 503 .35 504 .17 505 .70 304 .78

Fraction MPE

7.60 7.73

13.33 8.00

48.00 1.87 0.32 0.32 0.56 1.79 1.95 0.59 0.93 0.45 1.87 2.08

Radiation levels Operating

Location

101-103

103

103 Repeat

103 Repeat

(1 hr delay)

at the Nuclear condition: May have

Instrument

FND #128 FND #43 FND #36 FND #44 FND #139

ZnS FND #128 FND #36 FND #139 FND #44 FND #43

ZnS FND #128 FND #36 FND #139 FND #44 FND #43

ZnS FND #128 FND #36 FND #139 FND #44 FND #43

ZnS

Table 13

Research Cente r synchrocyclotron January been operating with both meson aind neutron

Neutron flux or

1560

670

670

dose rate

13.7 19.2 18.7

n /cm^-sec

8.5

4.8 n /cm^-sec

-10.7

4.0 n /cm^-sec

-19.2

18.7 13.7

1560 n /cm^-sec

F r

5, 1954. targets.

action MPE

36.5 51.2 49.9

104

22.7

12.8 44.7

-28.5

10.7 44.7

-51.2

49.9 36.5

104

11 — , . , , 1 1 1 1 1 • ' * " "•

Location

106 (4 ft high)

105

110

113 115

123

123

301

302

Garage 108 112 130 129 128 128a

Table

Instrument

CH4 ZnS CH4 ZnS

FND #36 CH4 ZnS CH4 CH4 ZnS CH4 ZnS

FND #128 FND #36

ZnS FND #36 FND #128

ZnS FND #36

FND #128 ZnS ZnS ZnS ZnS ZnS ZnS ZnS

13 (Continued)

Neutron flux or dose rate

24 n/cm^-sec <10 n/cm^-sec

37 n /cm^-sec 20 n/cm^-sec 0.50 mrep/hr

<10 n/cm^-sec <10 n /cm2-sec M 0 n/cm^-sec

13 n /cm^-sec <10 n/cm^-sec

67 n /cm^-sec 37 n /cm^-sec 0.505 mrep/hr 0.57 mrep/hr 21-33 n/cm^-sec 0.69 mrep/hr 0.67 mrep/hr 320 n/cm^-sec 3 mrep/hr 2.35 mrep/hr 5 mrep/hr Nothing detected

<10 n/cm^-sec MO n/cm2-sec

31 n/cm^-sec 26 n/cm^-sec 19 n/cm^-sec 19 n /cm^-sec

Fraction MPE

1.6 <0.7

2 .5 1.3 1.9

<0,7 <0,7 ~0.7

0.9 <0.7

4.5 2,5 -2.2

1.4-2.2 2 . 6 -

21.3 11.4

8.9 -

<0.7 ~0.7

2.1 1.7 1.3 1.3

Location

A B C D E

Center (max)

N.B. - Highes

Radiation levels at the One

t leve

-fifth to one-2:00

SIC-17C (Juno)

41 mr/hr 95 mr/hr

220 mr/hr 170 mr/hr 70 mr/hr

700 mr/hr

sixth a.m.

Table 14

Nuclear Researc radiation levels

h Center synchrocyclotron. inside

to 9:30 a.m., January

Fraction MPE

5.46 12.6 29,4 22.7

9.35 93.5

I in any location was about I r/hr.

vault after 6, 1954.

S1C-7C (CP meter)

42 mr/hr 100 mr/hr 380 mr/hr 200 mr/hr

75 mr/hr 110-0 mr/hr

shutdown

Fraction MPE

5.60 13.4 50.7 26.7 10.0

actually worked in any given week. Because of the uncertainties in the measurement of fast neutron levels , as well as in the knowledge of biological damage due to fast neutrons, it was suggested that the Carnegie group adjust personnel occupancy time so that accumulated doses remain well below the maximum permissible dose.

- .41

^6 39

SCALE I IN = lOFT

EYE

EXPERIMENTAL AREA

220 225

Figure 20. Plan of the Nuclear Research Center synchrocyclotron, Carnegie Institute of Technology, January 1954,

Recommendations (1954): On the basis of the measurements recorded in Table 14, as well as sustained significant gamma radiation exposures (of the order of two-thirds maximum permiss ib le dose) reported by Brookhaven over a period of several months, it was recommended that operations inside the vault, during the shutdown, be con­ducted so that personnel exposures are kept well below 75 m r (25 percent of maximum permiss ible dose) in any given week, since these same persons may also be exposed to unknown quantities of fast neutrons. Fu r the rmore , it was pointed out that the ex­perimental a rea (100 area) shown in the floor plan. Figure 20, should not be used on a fulltime occupancy bas i s .

It was suggested that the following c r i t e r ia be used in the design of new cyclotron shields at sites under contract to NYOO. For regular ly occupied areas (Figures 21 and 22), i .e. , a reas generally occupied 40 hours per week, the shielding should be sufficient to reduce radiation levels to not more than 25 percent of the maximum p e r ­missible weekly dose as measured by current ly available fast neutron ins t ruments . If this amount of shielding is not consistent with the economics of the site under con­sideration, the occupancy time should be adjusted to insure that 25 percent of the weekly maximum permiss ib le exposure is not exceeded. Finally it was recommended that the Brookhaven National Laboratory fast neutron film badge service be extended to personnel in the equipment room (200 area) . In this same area , the west wall shield should be built up to the ceiling and extended to the centrifuge area (Location 208, Figure 20).

^2

40 4M^ /

F igure 21 This is the northwest ent rance to the Nuclear Resea rch Cen te r ' s synchrocyclotron vault The warning light above the en­

t rance IS shown, and the local shield blocks near the stairway

Figure 22 The work a r e a nor theast of the Nuclear F igure 23 Outside the Nuclear Resea rch Cen te r ' s Resea rch Cen te r ' s synchrocyclo t ronis bounded (in synchrocyclotron building, to the east , is a chain the background) by movable local shielding blocks link fence and earth mound which enclose an ex-and an e lec t r ic eye. The surveyor is standing by eluded a rea A flashing light above the door m -

the control panel dicates ' b eam on

LJ- 2—— 41

Nevis Cyclotron Laboratory, Columbia University

The Nevis accelera tor is a 164-in. frequency modulated cyclotron capable of a c ­celerating protons to an energy of 385 Mev. The Nevis cyclotron and its control room are in separate buildings to permit remote operation. The cyclotron a rea is entered by means of a door located near the roof level at the southeast corner of the cyclotron building. By descending a stairway, one a r r ives at the main floor of the cyclotron building at the southeast corner of the shield. The experimental a rea is located in the northern side of the building (Figure 24). Outside the eas t wall of the cyclotron build­ing is a large ear th mound between the cyclotron and control buildings.

Originally, the Nevis cyclotron was shielded by 6 ft of concrete. At the time of the survey, the shield between the machine and the experimental a rea had been r e ­placed by essentially 8 ft of iron. Some local shielding had been located south of the accelerator inside the vault. This local shielding reduces the neutron intensities caused by the four se ts of graphite c l ippers , which protect the rotating condenser and dee walls from the proton beam. Radiation measurements were made during both

Table 15

Radiation levels at the Nevis Cyclotron Laboratory, Columbia Unive

Location

1 2 3 4 5

6

7

8

9 10

11

12 13 14 15 16 17 18

19

May 18, 1953. Cyclotron operation: I

tr" production, beryllium atemeter monitor = 16-20.

Description

Experimental Experimental Expe r imental Experimental Expe r imental

Exper imental

Expe r imental

Experimental

Experimental Experimental

Experimental

Experimental Experimental Experimental Experimental Experimental Experimental

area area area area area

area

area

area

area area

area

area area area area area area

West side cyclotron

Lavatory

Stairs - first landing

Stairs - top landing

Radiation

55 nf /cm^-sec 75 nf /cm^-sec 150 nf/cm^-sec 55 nf/cm^-sec 60 nf /cm2-sec 1.3 mrep/hr 85 n^/cmr-sec 1.3 mrep/hr 40 nf /cm^-sec 0.95 mrep/hr 60 nf /cm^-sec 0.95 mrep/hr 70 n£/cm2-sec 30 nj /cm^-sec 0.87 mrep/hr 40 n£/cm2-sec 0.91 mrep/hr 55 nf /cm^-sec

"V'20 nf /cm^-sec 40 nf /cm^-sec

~20 nf /cm^-sec ~20 n£/cm2-sec

25 nx/cm^-sec 180 nf /cm2-sec 3.7 mrep/hr 300 nf /cm^-sec 5 mirep/hr 800 nf /cm^-sec 10 mrep/hr 500 nf/cm^-sec 13 mrep/hr

rsity (CO-SC), target,

Fraction MPE

3.7 5.0

10 3.7 4.0 3.4 5.7 3.4 2.7 2.5 4 .0 2 .5 4 . 7 2.0 2.3 2.7 2.4 3.7 1.3 2 .7 1.3 1.3 1.7

12.0 9.6

20 13 53 26 33 34

44

42 4J

.'MS*

S ft.t^

» . j»

Figure 24. Double door is the entrance to the exper imenta l a r ea on north side of the Nevis

synchrocyclotron.

F igure 25. A lavatory located in the south portion of the Nevis synchrocyclotiron building

was subject to significant neutron levels .

F igure 26. The Nevis cyclotron, Columbia University.

F igure 27. The Nevis cyclotron, Columbia Universi ty.

^f 43

Location

1

2

3

4

5

6

7

8 9

Radiation levels at the Nevis Cy May 20, 1953. Cyclotron oper

ratennete

Description

Experimental area

Experimental area

Experimental area

Experimental area

Experimental area

West side area

West side area

West side area Lavatory

Stairs - first landing

Stairs - top landing

Table

clotroE ation:

16

Laboratory, Columbia University, •n-+ production, bei

r monitor = 13-16.

Radiation

145 nc/cmr-sec ~50 n^/cm^-sec

1.8 mrep/hr ~50 i i f /cm2-sec

0.66 mrep/hr 68 nf/cm^-sec 0.66 mrep/hr 30 nf/cmr-sec

MOO n^cm^-sec 0.52 mrep/hr 100 nf /cm^-sec 130 n^/cm^-sec 1,0 mrep/hr 350 nf /cm2-sec 100 nt /cm2-sec 3.6 mrep/hr 260 nf /cm^-sec 6.0 mrep/hr 250 nf/cm^-sec 150 nf/cm2_sec 1.75 mrep/hr 380 n£/cm2-sec 3,8 mrep/hr

MOO nj /cm^-sec 2.1 mrep/hr

yllium target.

Fraction MPE

9.7

4 . 7 3.3 1.7 4.5 1.7 2.0

L 3 6.7

2.6 23.3

9.4 17.3 15.6 16.7 16.7 4.6

25.3 9.9 6.7 5.5

negative meson (clockwise beam) and positive meson production (counter-clockwise beam).

Recommendations: Under the conditions of the survey, persons in a reas to the north, west , 2ind south of the cyclotron a re subject to radiation levels in excess of the maximum permiss ib le . It was suggested that occupancy t imes be regulated to avoid continuing exposure to high levels of radiation. The use of the Brookhaven National Labora tory film badge was suggested. The presence of nar row radiat ion beams was noted, and the value of appropriately positioned radiation signs to locate narrow beams was pointed out. It was noted that the south a r ea of the cyclotron building was e s sen­tially a passageway, and adequate warning signs were in appropriate places (Figure 25).

If the cyclotron is operated at significantly higher intensit ies than were encount­ered at this t ime, then additional shielding would almost cer tainly be requi red or ex­clusively remote operation would have to be vindertaken.

Massachuset ts Institute of Technology

Radiation surveys were performed at the following MIT part icle acce le ra to r s : 1) The 42-in. pole piece diameter , fixed frequency cyclotron for accelerat ing deuterons to 15 Mev (Figure 28). 2) The 12-Mev positive ion e lec t ros ta t ic generator (Building 58, Figure 29). 3) The 5-Mev positive ion Van de Graaff (Rockefeller Generator) .

4ft

44

Table 17

Radiation levels at MIT's 42-in. cyclotron, October 27, 1953. Operating conditions: 15-Mev deuterons on Be ta rge t to produce approximately 19-Mev neutrons;

beam cur ren t = 60 (la.

Posi t ion

1

2

2a

3

3a

3b

3c

4

4 a

5

6

8

9

*Correct ion

Remarks

Recess for vault door at wall

Recess-for vault door at wall

Same as 2; 3 ft from wall

Inside scat ter ing chamber

Scattering chamber about 15 in. behind plumbing

Adjacent to plumbing

Aper ture to scat ter ing chamber

At console

Same as 4 with door to scat ter ing chamber open

Corr idor between safe and scat ter ing chamber

Between radiochemical bench and cabinet

Outside building near t racks

Outside building as shown

Fac tors of 1.5 and 2.0 were

Inst rument

CH4 ZnS # 3 6 #123

CH4 ZnS # 3 6 #123 #130

CH4 ZnS

ZnS

CH4 ZnS # 3 6

ZnS

ZnS # 3 6 #123 #130

CH4 ZnS

CH4

ZnS

CH4

ZnS Juno

ZnS Juno

applied to #36,

Average cor rec ted dose or flux r a t e *

480 n / c m 2 - s e c 140 n / c m 2 - s e c 3.6 m r e p / h r 5.0 m r e p / h r

110 n / c m ^ - s e c 46 n / c m 2 - s e c 2.2 m r e p / h r 2.7 m r e p / h r 2.7 m r e p / h r

35 n / c m ^ - s e c 21 n / c m ^ - s e c

165 n / c m 2 - s e c

90 n / c m ^ - s e c 600 n / c m ^ - s e c 8.10 m r e p / h r

140 n / c m ^ - s e c

>4000 n / c m 2 - s e c 105 m r e p / h r 160 m r e p / h r 140 m r e p / h r

<2 n / c m 2 - s e c ~ 0

5 n / c m ^ - s e c

15 n / c m ^ - s e c

<2 n / c m 2 - s e c

46 n / c m -sec 20 m r / h r

21 n / c m ^ - s e c 12 m r / h r

#123, and #130, respec

F i

t ively.

action MPE

32.0 9.3 9 .6

13.3

7.3 3.1 5,9 7.2 7,2

2 .3 1.4

11.0

6.0 40.0 21.6

9.3

>267 280 5 6 8 373

<0.1 <0.1

0.3

1.0

<0.1

3.1 2.67

1.4 1.60

Table 18

45

Radiation levels at MIT's 42-in. cyclotron, October 28, 1^53. Operating conditions: 15-Mev deuterons on Mg target; 0.2-0.3 (la split beam into scattering chamber;

beam current 25 jia, 21-Mev neutrons.

Position

1

Ir

Is

It

2

4

5

6

7

10

11

Remarks

See Table 17

3 ft from Position 1, along wall

6 ft from Position 1. along wall

9 ft from Position 1. along wall

See Table 17

See Table 17

See Table 17

See Table 17

Between radiochemical bench and cabinet as shown

See Position 7 as shown

At entrance to scattering chamber as shown

Instrument

CH4 ZnS

ZnS

ZnS

ZnS

ZnS

CH4 ZnS

ZnS

ZnS

ZnS

ZnS

ZnS

Average corrected dose or flux rate

100 n/cm^-sec 66 n/cm^-sec

<5 n/cm^-sec

<5 n/cm^-sec

7 n/cm^-sec

46 n / c m 2 . s e c

10 n /cm2-sec 10 n /cm2-sec

53 n /cm -sec

15 n/cm^-sec

15 n/cm^-sec

21 n /cm2-sec

21 n/cm^-sec

Fraction MPE

6.7 4 . 4

<0.3

<0.3

0.5

3.1

0 .7 0 .7

3.5

1.0

1,0

1.4

1.4

1.

2.

3.

4.

Radiation levels October 28,

Position

Between tank and stairwell

Downstairs 3 to 4 ft away from beam

Six in. away from beam

In beam

at MIT's 5 -Mev pos

Table

five ion 1953. Operating conditions:

on

p energy Mev

1.9 2.26 3.07

1.9 2.26 3.07

1.9 2.26 3.07

1.9 2.26 3.07

Li7. 0.2-

n energy Mev

0,125 0.531 1.38

0.125 0.531 1.38

0.125 0.531 1.38

0.125 0.531 1.38

to 0 .3-

19

Van de Graaff (Rockefeller Generator), 2 - t o 3-(la proton beam; 1

Mev

B F 3 c / m

6 x 4.7 X 3,8 X

6 x 4.7 X 3.8 X

6 x 4.7 X 3.8 X

6 x 4.7 X 3.8 X

103 104 i o 4

103 104 104

103 104 104

103 104 104

neutrons.

ZnS n/cm^-sec

-v-O •v-O

-V/Q

~o 0 . 0

-vO

_

-M 5

-vO ~ 3 6 ~ 8 0

# 3 6

0 , 0

~o ~o

_

--

.

--

_ --

9-MevHl

#123

_ --

.

_ -

_ 2.5 mrep/hr 3.3 mrep/hr

_ .

7.3 mrep/hr

Juno

1-0

~ 0 ~0

_

--

.

--

. --

48

46

Table 20

Posi t ion

1

2

3

4

5

Radiation levels at MIT's October 29, 1953. Oper b e a m c u r r e n t .01 to 0.1 (j

Remarks

South surface of Van de Graaff te rminal

North surface of Van de Graaff te rminal

West surface of Van de Graaff te rminal

Approximately 15 ft from terminal as shown

At water window to 12-Mev lab

Target changed at 1345

6

7

*With thi profiles

At door to 12-Mev lab

Neighborhood of beam in 12-Mev lab

12-Mev positive ion accelera tor (Building 58), ating conditions*: 6.5-Mev protons; target a; Al target ; approximately 1-Mev neutrons .

Ins t rument

Juno ZnS

Juno ZnS

Juno ZnS

Juno ZnS

C H 4

CH4

ZnS

Average cor rec ted dose of flux ra te

400 m r / h r ~0

1800 m r / h r 33 n / c m ^ - s e c

1000 m r / h r 21 n / c m ^ - s e c

10 m r / h r 1.0

<2 n / c m ^ - s e c

<2 n / c m ^ - s e c

33 n / c m ^ - s e c

F faction MPE

53,3 <0.10

240 1 2.2

133 1.4

1.33 <0.10

<0.10

<0.10

2.2

s type of acce le ra tor , the same nominal operating condition can give ent i rely different of sca t te red radiation. This fact was called to our attention by Professor Buechner,

Posit ion

1

l a

2

3

8

9

10

11

Radiation levels at MIT's 12-Me Operating conditions: Same

Remarks

South surface of Van de Graaff

Eas t surface of Van de Graaff t e rmina l

North surface of Van de Graaff te rminal

West surface of Van de Graaff te rminal

Inside door to 12-Mev lab

Outside door to 12-Mev lab

Inside 12-Mev lab at position shown

At duct opening in shielding of 12-Mev lab

Table 21

V positive ion acce lera tor , October 29, 1953 as for Table 20 with 6.5-Mev deuterons.

Instrument

Juno

Juno

Juno

Juno

ZnS

ZnS BF3

ZnS

CH4 #36* #130 BF3

Average cor rec ted dose or flux ra te

400 m r / h r

350 m r / h r

2500 m r / h r

1400 m r / h r

21 n/cm.2-sec

10 n / c m ^ - s e c 70 n / c m ^ - s e c

>4000 n / c m ^ - s e c

15 n / c m ^ - s e c 0.32 m r e p / h r 0.40 m r e p / h r 35 n / c m -sec

Frac t ion MPE

53.3

46.7

333

187

1.4

0.7 4.7

>267

1.0 0.9 1.1 2.3

^t 47

LEAD SAFE [|L^ STEPS-

EH 'mmEEM

w/////////////^<

7ZZ2L

TRANSFORMER VAULT

TRANSFORI«R-

1 ^ y / / / / / / / / / / / / / / / / / / / / .

3b

3a

10

•znism

\ -IN

4 4a

0 CONSOLE

'• 2 CONTACT-2o WNEL

h////////y///^/^////^//^J^777i Y//////M

z

4 ;

u X o

rt"^^^"^sks^M

KEY PLAN

Figure 28. The Massachusetts Institute of Technology cyclotron.

Figure 29. The Massachusetts Institute of Technology 12-Mev positive ion accelerator.

A survey of the 340-Mev electron synchrotron was not performed because of the e r r a t i c action of the neutron counters . In par t icu lar , the methane proportional and zinc-sulfide-lucite scintillation counters gave spurious "neutron" responses . These were attributed to x - r a y "pile-up" - - that i s , the radiat ion appeared in sufficiently in­tense burs ts to overr ide the bias setting of the d iscr iminator .

Recommendations: The radiation survey, as well as the Brookhaven National Laboratory film badge r eco rds , points to good control of radiation hazards at the MIT par t ic le acce l e ra to r s . Well i l lustrated at this institution is the mer i t of having an in ­dependent group responsible for radiological saifety.

Nuclear Research Laboratory, Brown University

The Brown University Cockcroft-Walton linear acce le ra tor produces neutrons with energies of about 14 Mev by the H^(d,n)He^ react ion. The deuterons can be accel­era ted to energies of 250 kev, although the radiation surveys were conducted during the use of 120-kev and 150- to 160-kev deuterons. It should be noted that the f i rs t sur­vey (Table 22) was performed during the f i rs t production of neutrons by this acce le r ­ator . The Brown acce lera tor is located in a fenced-in field inside a brick building (Figure 30). The control building is located in one corner of the field, for remote op­erat ion of the acce le ra tor .

Recommendations (4/8/54): It was recommended that 1) a beta-gamma survey meter be available for use in the accelerator building during shutdown; 2) the Brook­haven neutron film badge be used for personnel monitoring; 3) the operator be sure that all persons in the a r e a are in the control building pr ior to s tar t - \ ip .

50

48

These recommendations were implemented by June 1954. Recommendations (6/23/54): It was suggested that 1) a fast neutron survey mete r

should be available for use at this site; 2) the installation of signs indicating "beam-on" should be considered.

Table 22

Radiation levels at the Nuclear Research Labora tory , Brown University (BR-CW), April 8, 1954. Cockcroft-Walton operation: 0.120-kev jH^ on , H 3 to produce

i-M-Mev neutrons; beam cur ren t M ma.

Location Description Radiation Frac t ion MPE

cm^-sec Near #1 outside control 5 nj building door

50 ft west on acce lera tor building door

Eas t fence near accelera tor building

Near acce lera tor column 5 m r / h r * 5 minutes after shutdown

10 minutes after shutdown 2 m r / h r *

200-400 nf /cm^-sec

30 n f /cm^-sec

0.3

2.0

•Since this date was that of the first neutron production at the Brown acce le ra tor , the radiat ion near the column was attributed to newly activated and shor t - l ived isotopes.

Table 23

Radiation levels at Brown University Nuclear Resea rch Laboi June 23, 1954. Cockcroft-Walton operation: 0.15 to 0.16

to produce M4-Mev neut rons .

Location

1

2

3

4

5

6

7

Description

Control room

Along walk

Along walk

Along walk

Opposite door

Northwest corner of building

Opposite door

•T issue equivalent ionization chamber measur

Radiation

6 n f / cm^-sec

10 n j / c m ^ - s e c

20 n f / cm^-sec

22 n j / c m -sec

33 n f / cm^-sec 2 m r e p / h r *

130 n^/cm -sec

93 n£/cm -sec 5.3 m r e p / h r *

ements .

a tory (BR iH^ on jH

-CW)

Frac t ion MPE

0.4

0.7

1.3

1.5

2.2 5.3

8.7

6.2 14.1

- . . . ^51

49

CONTROL BLDG

Figure 30. The Cockcroft-Walton acce le ra tor building (Brown University) is entered through F igure 31 . The Nuclear Resea rch

this excluded a r e a near Posit ion 7. Labora to ry , Brown University.

Sloane P h y s i c s L a b o r a t o r y , Yale U n i v e r s i t y

The Yale c y c l o t r o n i s a 4 - M e v d e u t e r o n a c c e l e r a t o r (28 - in . pole p i e c e d i a m e t e r ) l o c a t e d in r o o r a 27 of the b a s e m e n t of Sloane L a b o r a t o r y (cf. f loor p lan . F i g u r e s 32 and 33) on the c a m p u s . The c o n t r o l a r e a is n e a r b y in r o o m 26. D i r e c t l y above the c y c l o ­t r o n a r e two l e c t u r e r o o m s (51 and 52), one of which w a s in r e s t r i c t e d use du r ing t i m e s of c y c l o t r o n o p e r a t i o n . D e t a i l s of the s u r v e y s a r e l i s t e d in T a b l e s 24 and 2 5 .

R e c o m m e n d a t i o n s : I m p r o v e m e n t s in the Yale c y c l o t r o n have r e s u l t e d in an a u g ­m e n t e d b e a m c u r r e n t and, consequen t ly , i n c r e a s e d s t r a y r a d i a t i o n l eve l s ins ide and ou t s ide S loane . 1) It w a s s u g g e s t e d that r a d i a t i o n l e v e l s in a pub l i c , uncon t ro l l ed a r e a

Figure 32. The f i rs t floor of the Sloane F igure 33. The basement of the Sloane Phys ics Laboratory , Yale Universi ty. Phys ics Labora tory , Yale Universi ty.

r *?

Table 24

Radiation levels at Sloane Physics Laboratory, Yale University (YA-CY), December 2, 1953. Cyclotron operation: 4-Mev ,H^ on lead to produce

•~5.5-Mev neutrons; split beam into analyzer; beam current = 0.5 |j.a.

Location

1

2

6

8

9

10

12

13

15

16

17

18

19

20

22

23

24

25

26

Description

Vault entrance

Vault entrance

Vault entrance center, 6 ft high

Pump room

Pump room

Pump room

Hallway

Foot of stairway

Outside walk atop wall

Outside walk atop wall

Near console

Doorway,room 51

Southwest corner. room 51

Doorway, room 52

Library, room 53

Room 45

Room 51

Room 52

Corridor

Radiation

72 nf /cm^-sec 22.5 mrep/hr

1200 nj /cm^-sec 105 mrep/hr

100 nf /cm^-sec 15 mrep/hr

22 nf /cm^-sec

250 nr/cm^-sec 10,5 mrep/hr

29 n^/cm^-sec

10 nf /cm^-sec

22 nf /cm^-sec

120 nf /cm^-sec 19 mrep/hr

30 nf /cm^-sec 2.8 mrep/hr

<10 nf /cm - sec

22 nf /cm^-sec 6 mrep/hr

35 n£/cm^-sec 5.2 mrep/hr

10 nf/cna^-sec 3.3 mrep/hr

Nothing detected

Nothing detected

29 nf /cm^-sec 9 mrep/hr

22 nf /cm^-sec

10 nf /cm^-sec

Fraction MPE

4 .8 60

80 2 8 0

6.7 40

1.5

16.7 2 8

1.9

0 .7

1.5

8.0 50.7

2.0 7.5

0 .7

1.5 16.0

2.3 13.9

0.7 8.8

-

-

--

-

0.7

'x. iJ u

Table 25

Location

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

18

19

Radiation levels at Sloane Physics Laboratory, Yale University (YA-CY), December 9. 1953. Cyclotron operation: 4-Mev jH^ on Be-Cu target

to produce neutrons; beam cu r ren t = 25 to 30 jia.

Descript ion

Vault entrsuice

Vault entrance

Right of vault entrance

Console

Control room doorway

Pump room doorway

Pump room

Behind HV t ransformer

Near HV t rans former

Pump room, r e a r

Door, room 28

Blocked-up door, room 27

Foot of s t a i r s

Main door, Sloane Laboratory

Outside walk (maximum radiation)

Outside walk

Doorway, room 51

Room 50, r e a r

Radiation

I 130 n f / c m ^ - s e c 7.5 m r e p / h r

175 Uf/cm^-sec 56 m r e p / h r

38 n f / cm^-sec 0.8 m r e p / h r

Nothing detected

Nothing detected

70 n f / cm^-sec 2.4 m r e p / h r

22 n f / cm^-sec 4.5 m r e p / h r

10 n f / c m ^ - s e c 0.33 m r e p / h r

76 nf /cm - sec 2.03 m r e p / h r

46 n f / c m ^ - s e c

170 n^ /cm^-sec 4.65 m r e p / h r

12 n f / cm^-sec 0.46 m r e p / h r

14 n f / cm - sec

Nothing detected

250 n f / c m ^ - s e c 13.9 m r e p / h r

330 n f / c m ^ - s e c 3.4 m r e p / h r

61 nr/cmr-sec 2.1 m r e p / h r

165 n f / c m ^ - s e c 4.7 m r e p / h r

Frac t ion MPE

8.7 20.0

11.7 149

2.5 2.1

--

4.7 6.4

1.5 12.0

0.7 0.9

5.1 5.4

3.1

11.3 12.4

0.8 1.2

0.9

-

16.7 37.1

22.0 9.1

4.1 5.6

11.0 12.5

The rma l neutron levels for above situation (indium foil activation).

Location

1

Room 51

15

Corresponding fraction fast Thermal level Frac t ion MPE meiximum permiss ib le flux

3150

2500

1500

2.1

1.7

1.0

8.7

11.0

16.7

34

52 '"i...

\

IP

C:

^

i ^

J-\

-I

Figure 34. The entrance to the cyclotron vault of Sloane Physics Laboratory is located at Posit ions 1 and 2. Water cans to the left shield the control

a rea from sca t te red radiat ion.

'v.. R Sff^S^ " ^

^y •

• \

4

,-

% 1

\M ^ -

\:-

^\

M

it..,,»-..' • — « ^ ^

I i

f;l / ' ^ ^

m

• - ' V >••>•

AiSifSf

El*

Figure 35. The concre te blocks (Position 12) in the basement c o r r i d o r along the wall adjacent lu the cyclotron vault provide radiation shielding.

(Sloane Phys ics Laboratory.)

Figure 36. Significant neutron levels (due to sca t te r through windows) were encountered atop the r e ­taining wall adjacent to this sidewalk on the campus

outside Sloane Phys ics Labora tory .

^ i^ 53

should not exceed 10 percent of the maximum permiss ible exposure rate for working a reas . The windows between the cyclotron and adjacent Locations 15 and 16 (Figure 33) should, then, be blocked up (Figure 34). 2) Though limited occupancy of lecture rooms 51 and 52 might seem permiss ible , the surveyors suggested that the use of these rooms be wholly res t r i c t ed during cyclotron operation. Radiation levels should, in general , be kept as low as practicable, especially with respect to persons not oc-cupationally exposed to radiation. 3) It was suggested that the cyclotron personnel, as well .as persons who work more or less frequently in the pump room (Location 29), avail themselves of the Brookhaven fast neutron film badge. This suggestion was actu­ally implemented at the time of the survey.

University of Rochester 130-in. Synchrocyclotron

The Rochester synchrocyclotron is a 250-Mev proton accelerator located adjacent to the main campus of the University. The cyclotron and control a reas are in separate buildings for remote operation ^cf. plot plaoi. Figure 37). A large ear th dike is located between the cyclotron and control buildings (Figure 38), and local concrete shielding attenuates much of the cyclotron radiation at the source. A 6-ft-high chain link fence encloses the cyclotron a reas . At the time of the survey, additional shielding was con­templated to permit higher beam currents which were then impract ical because of the

X^^^OLO ELM WOOD AVENUE

CHAIN LINK FENCE

Figure 37. Plot plan of the University of Roches ter synchrocyclotron.

-- - 5 S^

54

Ml

H' v.

1

• 1

Figure 38. ,The closeup view of the synchrocyclo­tron building (University of Roches ter ) shows the excluded a rea near the west end of the ear th dike.

v-\ '

X'r-^.ri

Figure 39. F r o m the nor th corner of the chain-link fence, one sees the control building (left), the ear th dike for radiat ion shielding, and the synchrocyclo­

tron building (in front of stack).

F igure 40. This public bus stop, near the southwest co rne r of the chain-link fence (Posit ion 8), was occasional ly subject to significant neutron levels

during 1954 (RO-SC).

r e s u l t i n g high r a d i a t i o n l eve l s on the c a m p u s and i n t e r f e r e n c e wi th n e a r b y r a d i a t i o n e x p e r i m e n t s .

S u r v e y s w e r e p e r f o r m e d dur ing the n o r m a l and r e v e r s e p ro ton b e a m m o d e s of o p e r a t i o n . In both c a s e s , the beain c u r r e n t w a s be l i eved to be about 0.2 (j.a. Along the n o r t h fence , h i g h e r r a d i a t i o n l eve l s w e r e found for the n o r m a l or c l ockwi se m o d e (•n-+ p roduc t ion) t han for the r e v e r s e mode (ir" p r o d u c t i o n ) . T a b l e s 26 and 27 show p r i m a r i l y t h e . f a s t n e u t r o n l eve l s encoun te r ed .

/

^ff^^iys ' i .^i^ fr^^itr .p<"i.-^!^'^^i« mw r fs-r

rs 55

Table 26

Radiation levels at the 130-in. synchrocyclotron January 21, 1954, Cyclotron operation: ir" pi

Location

1

2

3

4

5

6

7

8

-

9

-

Description

Machine shop southwest corner

Machine shop west

Machine shop door

Control room

North gate

75 ft west of north corner

75 ft north of southwest corner

Southwest corner

Bus stop near Location 8

Old Elmwood Avenue

West end of dike

University of Rochester eduction; beam current =

Radiation

80 nf/cm^-sec 280 nj /cm^-sec 0.61 mrep/hr

10 nf/cm^-sec 280 n^/cm^-sec 0.40 mrep/hr

~2 nf /cm2-sec 75 nt /cm^-sec 0.1 mrep/hr

Nothing detected

Nothing detected

52 nf/cvnr-sec

165 nf /cm2-sec 3.65 mrep/hr

80 nf/cm^-sec

33 nf /cm2-sec

98 nf/cm^-sec 2.1 mrep/hr

80 nf/cm^-sec

(RO-SC), ~2 (la.

Fraction MPE

5.3 0.2 1.6

0.7 0.2 1.1

0.1

0.3

-

-

3.5

11.0 9.7

5.3

2 .2

6.5 5.6

5.3

Location

1

2

6

7

10

Table 27

Radiation levels at the 130-in. synchrocyclot ron. University of Roche Jamuary 21, 1954. Cyclotron operation: ir+ production;

beam current = ~2

Description

Machine shop southwest corner

Machine shop west

75 ft west of north corner

75 ft north of southwest corner

Northwest corner

^a.

R adiation

80 Uf/cm^-sec 260 nf/cm^-sec 0.45 mrep/hr

7 nf/cm^-sec 95 nj /cm^-sec 0.35 mrep/hr

10 Hf/cm^.sec

61 nf/cm^-sec

165 nf /cm2-scc 3.4 mrep/hr

ster.

Fraction MPE

5.3 0.2 1.2

0.5 0.06 0.93

0 .7

4 .1

11.0 9.1

J . ^

56 5-7 Recomnnendations: It was suggested that, in areas having a work factor (fraction

of a 40-hr week) of one, the shielding should be sufficient to attenuate radiation levels to not more than 25 percent of the maximum perntiissible dose ra te . This was e s s e n ­tially in agreement with a University of Rochester shielding proposal.

It was suggested that the work factor be adjusted to insure radiation levels at or below 25 percent of the maximum permiss ib le , if the amount of shielding required to fulfill the above cr i ter ion is impract ical .

Radiation levels in the control building were generally unimportajit from a r ad ia ­tion SEifety viewpoint, except near the south and west windows. It was suggested that these windows be shielded.

The use of the Brookhaven fast neutron film badge for the ent i re cyclotron staff was urged. Previous to the survey, it was the practice of the Rochester groujj to wear film badges only when entering the cyclotron a rea (during shutdown). The value of wearing film badges all the time was emphasized.

Finally, the advisability of keeping radiation to very low levels outside the chain link fence on the campus and along the public sidewalk was pointed out (Figures 39 and 40).

Bartol Research Foundation

Radiation measurements of the Bartol positive ion VandeGraaff genera tors and the Cockcroft-Walton linear accelerator are summarized. The surveyors ass is ted the Bartol staff in evaluating the probable efficacy of proposed shielding in the new control room in the Vaji de Graaif building.

1) VandeGraaff for 1. 8-MevDeuterons. Measurements were made during the p r o ­duction of neutrons by the interaction of the deuteron beam with only the carbon target (approximately 1-Mev neutrons) which was located near the analyzing magnet; this condition will be re fer red to as "No D, D." Measurements were also made during the simultaneous production of neutrons in the deuterium located in the target room (ap-proximiately 3.4-Mev neutrons), as well as the neutrons resulting from the carbon r e ­action; this is the "D, D" case . The D, D react ion was prevented by placing a quartz block in front of the deuterium target.

Measurements of the attenuation of the "D, D" neutrons in concrete blocks were made in the new control room. The half value layer of the blocks was found to be about 4.3 in. of concrete block for the neutrons detected by the fast neutron dosim­e ters and about 5.5 in. for the ZnS-luci te-detector-measured neutrons. The d i s ­crepancy is probably explained by the fact that the fast neutron dos imeters a re sub­stantially more sensitive to neutrons with energies below about 0.4 Mev.

2) Van de Graaff for 5-Mev Protons. During the interaction of 2.1-Mev protons with lithium (0.4-Mev neutrons), fast neutron dosimeter measurements at Position A, with both Van de Graaffs operative, showed no detectable neutron levels.

The t issue equivalent chamber indicated that the neutron exposure ra te , in the large Van de Graaff neutron beam about 4 in. from the lithium target , was 13 m r e p / h r while the exposure rate , determined with the fast neutron dosimeter , was about 60 mrep /h r . A possible explanation of this difference is that the neutron beam in te r ­cepted only a portion of the tissue equivalent chamber while the fast neutron dosimeter was entirely in the beam. At about 3 ft from the target , at Position D near one of the control panels, the neutron exposure ra te was found to be 1.56 m r e p / h r .

During operation, x-radiation measurements were made in the second floor gen­erating room near the tanks. Levels due to the 5-Mev Van de Graaff tank were neg­ligible up to about 8 ft above floor level. Levels from the small Van de Graaff tank ranged from 40 to 50 m r / h r at waist level to about 1500 m r / h r 8 ft above the floor and

5f

r^ R a d i a t

P o s i t i o n

1

1

1

2

2

3

4

5

6

7

7

8

8

8

9

* F N D -**ZnS -

Lon l e v e l s n e a r the B a r t o l Foundat ion 1 . 3 - M e v deuterons on deuter ium; be

D e s c r i p t i o n

Contro l r o o m bench ( D , D c a s e )

Contro l r o o m bench (no D , D)

Control r o o m bench (no b e a m )

Control r o o m b a r r i e r

Atop contro l r o o m b a r r i e r

E n t r a n c e to magne t r o o m

N e a r a n a l y z e r magne t (about 3 ft f r o m carbon targe t )

Halfway b e t w e e n d e u t e r i u m t a r g e t and outs ide door

D o o r w a y f r o m targe t r o o m

Outs ide of d o o r w a y at P o s i t i o n 6

S a m e a s above (no D , D reac t ion)

New c o n t r o l r o o m n e a r opening ( b e a m = 20 |jLa)

New contro l r o o m , 8 - in . c o n c r e t e block ( b e a m = 20 )j.a)

New contro l r o o m , l 6 - i n . c o n c r e t e block ( b e a m = 20 (la)

New c o n t r o l r o o m 4 ft behind opening ( b e a m = 20 (jia)

Table 2 8

•s 1 . 8 - M e v I H 2 a m c u r r e n t = 11

I n s t r u m e n t

T E F N D * #130 ZnS

TE

TE

ZnS SGM

ZnS SGM

F N D # 4 4 F N D #130 F N D

F N D # 4 4 F N D #130 ZnS** Juno

F N D #130 ZnS

F N D # 4 4 F N D #130 Juno

F N D # 4 4 F N D #130 ZnS

F N D #130 ZnS

F N D # 4 4 F N D # 1 3 0 ZnS

F N D # 4 4 F N D #130 ZnS

F N D # 4 4 F N D #130 ZnS

ZnS

Van de Graaff. August 2 5 - 2 6 . 1954. I )ia, or a s ind icated .

Radiat ion l e v e l

0 ,61 m r e p / h r Nothing d e t e c t e d Nothing d e t e c t e d

0 .46 m r e p / h r

Nothing d e t e c t e d

Nothing d e t e c t e d 0 . 6 - 1 . 2 m r / h r

~10 n / c m ^ - s e c 1.2 m r / h r

4 .1 m r e p / h r 5.1 m r e p / h r 60 n / c m 2 - s e c

79 m r e p / h r 71 m r e p / h r 235 n / c m ^ - s e c 8 m r / h r

40 m r e p / h r 340 n / c m 2 - s e c

5.1 m r e p / h r 5.5 m r e p / h r 4 - 5 m r / h r

1.4 m r e p / h r 1.5 mrej^/hr 20 n / c n / . s e c

Nothing d e t e c t e d O c c a s i o n a l count

5.2 m r e p / h r 5 ,7 m r e p / h r 185 n / c m ^ - s e c

1.42 m r e p / h r 1,50 m r e p / h r 65 n / c m ^ - s e c

0 ,48 m r e p / h r 0 .53 m r e p / h r 29 n / c m ^ - s e c

140 n / c m ^ - s e c

F a s t neutron d o s i m e t e r , S P C - 6 A , R e s p o n s e d e c r e a s e d n o t i c e a b l y a s nnagnet w a s approached .

F r a c t i o n MPE

-

-

-

-

0.5

10.9 13.5

4 .0

209 189

15 .7

109 2 2 . 7

13,5 14 .6

3 ,8 4 .0 1.3

-

14,0 15.1 12 .3

3 . 8 4 ,0 4 . 3

1.3 1.4 1,9

9,3

^ ^

58

ENTRANCE

NEW CONTROL ROOM

8 9

Figure 41 . The Bartol R e s e a r c h Foundation Van de Graaff a c c e l e r a t o r s .

at contact with the tank. At the entrance to the room, levels had decreased to about 1 m r / h r . Moving the aluminum shield on the SIC-17C over the chamber window had no perceptible effect on the x-radiat ion measurements , which indicates that the radiation had the energy to be expected from back electron current bremsst rahlung of up to 5 Mev,

3) Cockcroft-Walton Accelerator , 90-Kev Deuterons, At the time of the survey, the accelerating potential was 90 kv, and the beam current about 15 jia. Neutrons with energies up to about 14 Mev were obtained from the jH (d,n)2He^ reaction. A neutron flux density measurement made 75 cm from the tritiuna-zirconiunn target suggested a neutron yield of about 3 x 10" n / s e c .

In the control room, fast neutron levels were sornewhat less than 0.1 m r e p / h r . X-radiat ion near the ion source, ups ta i r s , with beam off produced exposure ra tes of about 30 m r / h r at a distance of 1 ft.

Recommendations: The following general recommendations were made. 1) That when the new control room in the Vaua de Graaff building is in operation,

concrete blocks (3 deep) be stacked over the opening leading to the small Van de Grastff vault (Position 8). This thickness (approximately 22 in.) should reduce fast neutron levels to a value well below the MPE.

- ^ C l

^0 59

Position

A

B

C

D

E

Table 29

Radiation levels near The Bartol Foundation's 2.1-Mev protons on lithium.

Description

New control room (opening to accelerator)

In neutron beam 4 in. from target

Off beam center 4 in. from target and 4 in, from center line

Off beam center 3 ft from target

On table near entrance to 1.8-Mev Van de Graaff

*Beam intercepted only a small part of the t issue

Instrument

FND #130

FND #130 TE*

FND #130

FND #130

TE

large Van de Graaff.

Radiation level

Nothing detected

61 mrep/hr 13 mrep/hr

6.8 mrep/hr

1.56 mrep/hr

0.28 mrep/hr

equivalent ionization chamber.

Fraction MPE

-

163

18.1

4 .2

-

Table 30

X-radiation levels near tops of Van de Graaff tsmks (second floor) during simultaneous

operation.

Position description

Entrance to second floor room Waist level - 3 ft from small tank 8 ft up, at contact Contact, large tank, waist level

Radiation level

'^1 mr/hr 40-50 mr/hr 1000-1500mr/hr

~1 mr/hr

Position

1

2

3

4

Radiation measurements near 90-kev deuterons

Description

75 cm from tritium-zirconium target

145 cnti from target

Control area 2 ft behind blocks

Near ion source 1 ft away

Table 31

Bartol Institute's on tritium; beam

Instrument

FND #44 FND #130 ZnS TE

TE

FND #130 TE

Juno

•

Cockcroft-Walton acce current = ~15 (la.

Radiation level

0.80 mrep/hr 0.93 mrep/hr 43 n/cm^-sec 0.69 mrep/hr

0.15 mrep/hr

<0.1 mrep/hr 0.08 mrep/hr

30 mr/hr

lerator.

Fraction MPE

2.13 2.48 2.15

-

-

. -

4 .0

60 u 2) In the future, the thermal neutron flux density measurement in the new control

room may be indicated, 3) It was suggested that visible warning signals should be located at both en­

t rances to the accelerator rooms to indicate when the machines a r e in opera­tion. These warning devices should be interlocked with the accelerat ing volt­age circui ts of each Vaui de Graaif.

4) The voltage should be turned down when the deuterium target a rea is entered in order to place the quartz block in position near the target , or, alternatively, provision should be made to move the quartz block into and out of position, r e ­motely, from the new control room,

5) The upstairs Van de Graaff tank room appears to present no special problem in radiation safety. A sign indicating that high x- ray levels do exist near the small tank can be posted outside the tank ^generator) room door.

6) Under the conditions of the survey of the Cockcroft-Walton acce le ra tors (90-kev deuterons and a 15-jia beam), any place beyond a distance of about 4 ft from the tr i t ium target is below the permissible neutron level.

7) In the upsta i rs room of the Cockcroft-Walton building, radiation levels are of little importance. However, the electrocution hazard from the unshielded high voltage points in this room appears to be a rea l one.

8) The installation of a warning sign (e.g., a blinking red light), outside the en­trance to the Cockcroft-Walton building, indicating the "radiation beam on or off," was recommended.

Conclusions and Recommendations

The investigations reported here have led the wr i te rs to the following conclusions: (a) We are not inclined to the opinion that sizable groups of accelera tor personnel are

being exposed to radiation intensities which will resul t in long t e r m deleterious ef­fects. This belief is tempered, however, by the large gaps remaining in pract ica l dosimetry and the utter insufficiency of information on the biological effects of heavy charged par t ic les in the range exceeding 14 Mev.

b) Accelerators are now being designed which will produce charged par t ic les (and s t ray radiations) up to 25 Bev, Proton synchrotrons in the 1- to 6-Bev region are already in operation. Synchrocyclotrons have been operating since 1949 which produce protons and stray neutrons in the range of 200 to 500 Mev. In this connection it is most important to observe that almost all the biological information to date on fast neutron irradiat ion of biological mater ia l has been with neutrons of 14 Mev and less .

The extrapolation of permiss ible levels from these data to energies more than one hundred and even one thousand tinries grea te r i s , in our judgement, inadnnissible.

One may argue on the basis of l inear energy transfer considerations that par t ic les resulting from very high energy machines a re less deleterious in biological effect than lower energy par t ic les of higher specific ionization. However, this is a conjecture which should be established empirically.

It is recommended that an intensive p rogram of animal experimentation be under­taken in the neutron energy region from 14 Mev to 6 Bev with current ly available a c ­ce le ra tors to delimit as expeditiously as possible areas of potential hazard.

c) There is a tendency at many acce lera tors for the total site personnel exposure to be accumulated by a very few individuals. Project d i rectors should be made cognizant of this tendency so that it nnay be guarded against by appropriate rotation of personnel in those accelerator operations associated with significant radiation exposure.

d) The possible effect of microwave production by radiofrequency sources at high energy particle acce lera tors appears to require more attention than it has received.

_i :6^

^ 61

Acknowledgments

We should like to thank our contractors for the help, cooperation, and hospiteility which we have received from all of them without exception.

A part icular ly large contribution to our work we owe to the Health Physics Divi­sion of Brookhaven National Laboratory, the staff of the Nuclear Research Center of the Carnegie Institute of Technology, the Radiological Safety Office of the Massachuset ts Institute of Technology, and the Radiological Physics Department of Columbia University.

The contributions of our colleagues in all capacities at the Health and Safety Laboratory is gratefully acknowledged. We should like to make part icular mention of the aid of H.J. DiGiovanni who cheerfully augmented his already heavy work load with the problems of the ins t ruments used in the surveys . ' We should a lso like to thank Dr. William T. Ham, J r . for his helpful reading of the section on biological effects. Appreciation is expressed to Dr . Titus Evans, Dr. George Mer r i am, Captain D.V.L. Brown, Colonel J .E . Pickering and Dr, H,H. Vogel for permiss ion to use the resu l t s of their work reported at meetings of the National Committee on Radiation Cata rac t s .

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4 5

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8

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11

''' 12. f 13,

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a^