x ray diffraction safety information

7/30/2019 x ray diffraction safety information

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X-RAY DIFFRACTION

SAFETY INFORMATION


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Restricted Item List

Any proposed purchase or acquisition, and

installation of x-ray equipment must be

reviewed and approved in advance by the

Tufts Radiation Safety/EHS.

Radiation symbols inform persons of

radiation producing

equipment or RAM

use.


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Caution XRD can be hazardous

Detailed instructions on the operation, hazards, andradiation safety features of a specific analytical unit

must be provided by the owner of the equipment.Before starting to work on an analytical unit, makesure you receive specific instruction on the units

safe operation from the Tufts person responsible forthe unit. All x-ray users must have attended

Tufts radiation safety training, but that is NOT a

substitute for unit specific operation and safety

training.


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Introduction

Analytical x-ray devices are important tools in

various areas of modern research. X-ray

crystallography and x-ray fluorescence

spectrometry rely on x-radiation.

But, X-ray diffraction equipment [XRD] can be

very dangerous, and operators of this equipment

must not become complacent or overconfident

about the potential danger of the x-ray beam.


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X-ray Production

When high energy electrons strike ananode in a sealed vacuum, x-rays aregenerated. Anodes are often made of

copper, iron or molybdenum.

X-rays are electromagnetic radiation.

They have enough energy to causeionization.


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Radiation Units

Roentgen R unit of exposure, in air

for photons only. One R equals enough energy to

deposit 2.58 x 10 -4 coulombs per kg in dry air.

Rad unit of absorbed dose. Equal to

one hundred ergs per gram

Rem unit of dose equivalent. For x-rays,

1 rad = 1 rem

Milli 1/1000th, as in millirem or mRem


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Typical X-ray Beam Intensities*

Primary beam 400,000 Rem/min, or

2.4 x 10 7 Rem/hr

Diffracted beam 80 Rem/hr

* For comparison, the annual whole body

occupational exposure limit is 5 Rem. Radio-isotope users at Tufts generally receive

< 100 mRem/yr.


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MA DPH Occupation Exposure

Limits

Area: Annualdose limit, Rem:

Whole body,

lens of eye,

head, trunk 5

Hands, arms, 50

skin of whole

body


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ALARA

ALARA stands for as low as reasonably

achievable. Regulators recognize that it

is an individual workers responsibility to performtasks on a daily basis keeping best practices in

mind, and striving to keep radiation exposure as

low as possible. Workers are responsible for

knowing all hazards and safety practices that

relate to the equipment in use.


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Biological Effects of Radiation

Effect Dose, Exposure time inRem primary beam, seconds

Erythema 300-600 0.075-0.12

Epilation 350 temporary 0.05251200 permanent 0.180

Acute dermatitis 3000-4000 0.45-0.60

Chronic dermatitis thousands of Rem in

many small doses over NA

many years

Skin Cancer small doses over a long ???

period of time


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GENERAL RADIATION

INFORMATION

IONIZING RADIATION CAN CAUSE

CHEMICAL CHANGES IN BIOLOGICAL

TISSUE. THESE CAN LEAD TO CELL

DEATH, CELL TRANSFORMATION, AND

DAMAGE WHICH CAN NOT BE

REPAIRED.


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WARNING

Very serious injuries

have resulted from

the use of XRDequipment. Large

doses of radiation

have caused painful

burns and permanentinjuries to workers.


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You could be injured without

initially knowing it -

People are not able to sense radiation. Even

very large doses of radiation can not be felt. Justbecause there was no sensation at the time the

dose is received, does not mean you are safe.

Serious injury can result for radiation exposure.

It is up to the individual x-ray user to ensure thatthey are trained, follow all precautions, and use

all x-ray equipment safely.


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Sources of Exposure

The primary beam,

Leakage of primary beam through cracks

in shielding,

Penetration of primary beam through shutters,cameras, beam stops, etc.,

Secondary emission (fluorescence) from a sampleor shielding material,

Diffracted rays from crystal,

Radiation generated by rectifiers in the highvoltage power supply of older units.


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Sealed Tube/Microfocus Systems:

What are the danger areas?

1. Primary Beam 2. Scattered

Radiation

3. Leakage


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Three regions of high exposure include the

primary beam, scattered radiation, and leakage

radiation.


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1.Primary Beam The critical radiation exposure problem with analyticalX-ray equipment is the primary beam. Exposure to the primary beam can

cause localized acute exposure. Consequently, the analytical operator

must never intentionally place any part of their body in the primary beam.Typically, these beams are relatively soft X-rays resulting in maximal

energy deposition in epithelial tissues. Erythema or reddening of the skin

can occur when skin is acutely exposed to 300-600 R (much less than a

second). Radiation burns may occur from longer exposures.

2.Scattered Radiation When the primary beam intersects a materialsuch as a sample or elements of the X-ray unit including the beam stop,

some of the radiation is scattered out of the primary beam. While these

radiation fields are considerable less intense than the primary beam, they

still represent a potential hazard. Scattered radiation fields can be

measured by the analytical operators with a survey meter.

3.Leakage Some radiation may leak around the tube housing structure.The source housing construction must be such that when all the shutters

are closed, the leakage radiation must not exceed that of radiation limits

for the general public.


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Monitoring Equipment is Essential


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Radiation monitoring instruments

Instruments which arecalibrated for radiation thatuniformly exposes the activearea of the detector will give

incorrect low readings whenexposed to a beam having asmaller area. To determinethe true reading, the measuredreading must be multiplied by f,where

f = area of detector/area ofbeam

Check instrument batteries

Have audio on

Begin on fast or F setting

Precise measurements may betaken using slow or S

setting, as the needle will not

bounce as much

Scales will vary with each

instrument modelBegin on X1 scale


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Safety Basics

Time minimizing time around a radiation

source will reduce total exposure

Distance maximize distance from aradiation source to reduce total exposure

See Inverse Square Law

Shielding material used to attenuate radiationand reduce occupational exposure. For x-rays,

shielding is most often lead.


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Inverse Square Law

Radiation exposure varies inversely as

the square of the distance from the source

E 1 / d 2


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DETAILED INSTRUCTION ON THE SAFE USEOF XRD MUST BE PROVIDED BY THESUPERVISING PI AND/OR HIS/HER DESIGNEE.THIS INSTRUCTION MUST INCLUDE

DEMONSTRATION OF ALL SAFETYFEATURES OF ALL SPECIFIC EQUIPMENT TOBE USED. BEFORE BEGINNING USE OF ANYXRAY EQUIPMENT, BE SURE YOUUNDERSTAND ALL OF THE TRAINING. IF

PROBLEMS OR QUESTIONS ARISE, STOPWORK AND CONSULT YOUR SUPERVISORAND THE EQUIPMENT OWNER/SUPERVISOR.


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Characteristics of XRD Beams

Both primary and diffracted beams are

generally small and well collimated.


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Wavelengths used in crystallography are

often in the range of 0.6 to 2.5 A.

The 1.54 A wavelength corresponds to

CuKa radiation.


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Characteristic and Bremsstrahlung

radiation are present


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Safety Devices and Features

All units require a clear, visible warning light whatilluminates only when the unit is producing X-rays.

Shutter status shall be indicated clearly. Shutters must notbe able to open without a collimator or coupling device

in place.Safety interlocks shall not be bypassed or defeated.

Unused ports shall be secured to prevent accidentalopening.

Shielding or other devices must be used to preventphysical access to open beam areas. All open beamareas must be as small as feasible.


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Examples of warning lights and

labels

A label which has the following or similar

words must be in place on the x-ray

source housing:

Caution High Intensity X-ray Beam


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Interlocks

Safety interlocks should not be used to de-

activate the x-ray beam, except in

emergencies and when testing the

interlock system.


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Warning Labels continued

A label which has the following or similar

words must be on the control panel of

each XRD unit near the switch used to

energize the unit:

Caution Radiation

This unit produced radiation when

energized


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Warning Lights

Each port must have a readily discernible

indication of shutter status [opened or

closed]. There must be a warning light

that is illuminated when the x-ray tube is

energized. The light must be near the

x-ray tube housing or port and be inthe operators field of view.


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XRD units should not be open and allow

inadvertent radiation exposure.

Older model open type units do not

meet current radiation safety standards.


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Current standards require interlocked

Plexiglas enclosures to prevent access

to the primary beam when the unit is in

operation. Enclosures can also protectpersons from leakage and scatter

radiation.


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Administrative Controls

Detailed training by PI or his/her designee

Detailed SOPs policies and procedures

Close supervision by knowledgeable user Authorized users only unit security

Constant vigilance and alertness to the

dangers.


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Who May Use XRD?

Only trained, authorized persons may use,

install, maintain, or repair x-ray diffraction

equipment [XRD] at Tufts University.

All such persons should attend the Tufts

Radiation Safety Training, and should

receive radiation dosimetry devices.


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General Precautions

Only Trained personnel shall be permitted to operate an analytical unit.

Be familiar with the procedure to be carried out.

Never expose any part of your body to the primary beam.

Turn the X-ray beam OFF before attempting to make any changes to the

experimental set-up (except for beam alignment) While the beam is on DO NOT attempt to handle, manipulate or adjust

any object (sample, sample holder, collimator, etc.) which is in the direct

beam path (except for beam alignment procedures).

Examine the system carefully for any system modifications or

irregularities. Follow the operating procedures carefully. DO NOT take short cuts!

Never leave the energized system unattended in an area where access in

not controlled.


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General Precautions

Survey the area frequently to evaluate scatter and leakage radiationfields.

Never remove auxiliary shielding without authorization from the owner

of the analytical equipment or the Radiation Safety Officer.

Never bypass safety circuits, such as interlocks.

Report all unusual occurrences to the owner of the analytical unit for

possible corrective actions.

Only authorized, trained individuals as specified by the units owner and

the Safety Office may repair, align or make modifications to the X-ray

apparatus.


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Special Tasks

Only trained, authorized experts are allowed

to repair, maintain or reconfigure XRD

equipment.


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Unauthorized repair or modification

Do not remove shielding, or tube housing.

Do not modify shutters, collimators or

beam stops.

Individuals may not operate an XRD unit

in a manner inconsistent with SOPs and

safe operating standards.


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Problems with equipment

If there are any questions or concerns

about the functioning of an XRD unit, it

must be taken out of service immediately

and reported to the unit supervisor.

Be aware that shutter mechanisms can

fail. Warning lights can fail.

Emergencies and Accidents


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Emergencies and Accidents

Call Tufts Police for all emergencies 6-6911

Get medical treatment immediately for

all injuries and exposures - at TMC

[or the nearest hospital for Grafton or Medford.]

ASAP notify your supervisor and EHS,

Take XRD unit out of service to preventinjuries to others,

Provide information during the incident

investigation.


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Radiation Badges

Anyone at TuftsUniversity who uses x-raydiffraction equipment andmost other types of x-ray

equipment should wearradiation monitoringbadges. Contact HealthPhysics at 636-6168to make arrangements to

obtain monitoring badges.In Medford, contact EHS

at 636-3450.


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Important Notes About Dosimetry

Due to the small cross sectional area of the

primary x-ray beam, whole body and ring

badges may not accurately record the

maximum dose received by the XRD

user.Dosimeters should be exchanged every

quarter. Wear only your own badge/ring.

T f l ti d ti f


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Transfers, relocations, donations of

XRD equipment

ALL XRD must be registered with the MADPH -RCP prior to its arrival/use at Tufts.

Contact EHS PRIOR to any transfer,relocation, donation or disposal of XRDunits so that the MA DPH registration can

be handled.Donations of used XRD equipment willrequire a signed waiver from the recipient.

Additi l I f ti


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Additional Information or

AssistanceFor emergencies call Tufts Police at 6-6911.

In Boston, contact Environmental Health & Safety at 636-3450, 636-3615 {Main Office #}, or using the RSOs

cell phone at 617 308-3781.

In Grafton and Medford, call Tufts Environmental Healthand Safety as above during normal business hours.

After hours, contact Campus Police who can summonassistance for you.


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Acknowledgments

Special thanks to Rigaku, and Global

Dosimetry Solutions for allowing use of

photos, images and/or other information

from their respective websites.

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