W. T. ShmaydaUniversity of RochesterLaboratory for Laser Energetics

Tritium Focus Group MeetingLos Alamos, New Mexico

3–5 November 2015

1

Radiological Challenges at theLaboratory for Laser Energetics

OMEGA Laser BayMainamplifiers

OMEGA EPLaser Bay

Compressionchamber

OMEGA EPtargetchamber

Boosteramplifiers

Beam 1 2 3 4

OMEGA targetchamber

• Faculty equivalent staff: 110• Professional staff: 162• Associated faculty: 24• Contract professionals: 5• Graduate and undergraduate students: 124

Successful radioactivity management requires a blend of training, situational awareness, and engineered systems

•  Introduce the Laboratory for Laser Energetics (LLE)

•  Describe Radiation Safety initiatives to address LLE needs

•  Discuss engineered systems used at LLE

•  Closing remarks

OMEGA Laser BayMainamplifiers

OMEGA EP Laser Bay

Compressionchamber

OMEGA EPtargetchamber

Boosteramplifiers

Beam 1 2 3 4

OMEGA targetchamber

OMEGA EP Laser System• Operating since mid-2008• Adds four National Ignition Facility

(NIF)-like beamlines; 6.5-kJ UV (10 ns)• Two beams can be high-energy petawatt – 2.6-kJ IR in 10 ps – can propagate to the OMEGA

or OMEGA EP target chamber

OMEGA Laser System• Operating at LLE since 1995• Up to 1500 shots/year• 60 beams• >30-kJ UV on target• Flexible pulse shaping• Short shot cycle (1 h)

More than half of OMEGA’s shots are for external users.

The Laboratory for Laser Energetics (LLE) operates two of the world’s largest lasers for high-energy-density-physics research

G10425e

3

LLE is exploring the possibility of installing a multi-MA pulsed-power machine coupled to OMEGA EP

I2186b

• This machine would fill the gap between the 1-MA university machines and the 25-MA Z machine

• The coupling of OMEGA EP will allow new physics platforms to be developed

– magnetized liner inertial fusion (MagLIF)– Thomson scattering in warm dense matter– novel bright x-ray sources

4

• Neutrons• Tritium• X-ray

Source terms:

LLE has an infrastructure designed to fill and handle DT targets and contaminated equipment safely

E24654

• Site inventory limit: 15,000 Ci

• Hold gaseous emissions below NYS-DEC environmental limits (0.1 nCi/m3)

Tritium Facility: 4.0 Ci OMEGA: 2.2 Ci Tritium Laboratory: 3.2 Ci

• Maintain airborne tritium concentrations:

Radiological work areas: <20 nCi/m3 Uncontrolled areas: <0.1 nCi/m3

• Maintain exposed-surface contamination

– levels below 1000 dpm/100 cm2 in radiological work areas

5

Cryogenic targets enable a greater mass of DT to be imploded

TC5701b

6

Warm gas target Cryogenic target

Plastic(CH)

Plastic(CH)

Solid DT(0.2 g/cm3)

20 nm 3 nm 60 nm

1 mm

Mass of DT = 2 ng = 10 mCi

1 mm

Mass of DT = 50 ng = 200 mCi

DT gas (4 mg/cm3)

DT gas (0.3 mg/cm3)

E17573d

7

Principal radiation sources at LLE

• DT fusion—prompt neutron radiation

– maximum credible yield shot of 3 × 1015 neutrons yield 516 rem at the surface of the OMEGA target chamber (radius = 1.6 m)

– maximum neutron yield on OMEGA EP is ~1012 neutrons

• Activated structures—short-term gamma radiation

– neutrons interact with OMEGA

– protons interact with film pack on OMEGA EP

• Tritium—contaminate equipment

– surface contamination

– airborne releases

• Fast-electron deceleration in high-Z materials in OMEGA EP—prompt, high-energy x rays

long-term diffuse radiation

E17006e

8

The aim of radiation protection is to reduce exposure to As Low As Reasonably Achievable: the ALARA principle

H = Dose rate × timeAt LLE, time = number of target shots

Closed access during shots

Provide shielding– energetic betas " aluminum, plastic– x rays, c rays " lead, concrete– neutrons " concrete, paraffin Surface activity (dpm/100 cm2)

400-mCi cryoDT shot

1/100 monolayer/h(each particle labeled with a T atom)

Ou

tgas

sin

g r

ate

(nC

i/h/1

00

cm2 )

105104103

102

101

100

10–1

10–2

10–3

106 107 108 109 1010

VENTILATE

DECONTAMIN

ATE

Contact for 2000 h leadsto 5-rem whole-body dose

Fixed/Activated Sources Diffuse Sources

The application of ALARA differs for activated and diffuse sources.

Implementing radiation safety effectively at LLE requires several approaches

E24655a

• Training

– annual recertification

– proficiency evaluation

• Procedures

– living documents

– referenced during the evolution

– no changes on the fly

• Monitoring

– thermoluminescent devices

– bioassays

– airborne activity/radiation fields

• Engineered safety systems

9

After radiation safety, the overarching goal is to minimize the impact of tritium on nonradiological facilities

E24656

• Compartmentalization

– isolate processes

– tailor gloveboxes to suit the application

– secondary containment

• Staged commissioning

– D2 " trace DT " high-activity DT

• Minimize the chronic release of tritium

• Monitor all effluent streams and work spaces to get a better handle on tritium operations

– permits fine-tuning of the procedures

– reduces the number of surprises

10

E13735e

Gloveboxcleanup getters

Helium

P

TM

AirlockBubblers

2 kPa

DP

Drier ZrFe

Ni

Ni

ZrFe

TFS process loop

TM

DP

Legend:DP = dew pointTM = tritium monitorP = pressure sensorRT = room temperature

Processgetters

Glovebox

To stack

DP

TM

U bed Assay

U bedCold

finger

RTpermeation

cell

Tritium Fill Station (TFS) functions – store tritium – remove helium-3 from DT fuel – remove residual tritium from process loop – assay tritium – permeation fill gas targets (<50 bar) – provide fail-safe recovery of tritium – transfer DT to a DTHPS* to fill cryo targets

Tritium is captured from each processand inert containment stream with getters

11

*DTHPS = DT high-pressure system

The getter-based Glovebox Cleanup System provides a robust platform against accidental releases

E13094b

12

0

50

100

150

200

250

0 2 4 6 8

Time (h)

19 February 2004

Act

ivit

y (m

Ci/m

3 )

Valve in GloveboxCleanup System

Ni and ZrFe bedsvalved out

Ni and ZrFe bedsvalved in

GloveboxCleanup effluentModel results

Cryogenic targets are formed by cooling DT gas at 1000 bar to 17 K in the Fill Transfer System (FTS)

G6548g

13

Target

Target slotTarget rack

Permeation cell

FTS

TFS

DTHPS

Glovebox

Cryostat

Diaphragm

Glovebox

U beds

MCTC is moved to theCharacterization Station

Moving CryostatTransfer Cart (MCTC)

Shroud pullerwith uppershroud

Movingcryostat

Targetmanipulator

CondensationcellAssay

volume

2ndcontainment

Syringepump

Targetstalk

Rackinserter

High- and low-activity streams of air and inert gas are treated separately

E13091b

14

Processeffluentdetritiation

Gloveboxcontainmentdetritiation

Stack

StackClean gas

Clean gas

Driers

High specific activity

Low specific activity

Clean gas

Driers

Nonoxidativecleanup systems

To glove boxes

Hydride bed/cryotrap

DTO/HTO

DT/CQ4

DT/CQ4

DTO/HTO

Hydride beds

Oxidation-basedcleanup system

Getter-basedcleanup system

Tritiated air

Tritiatedhelium

Tritiatedhelium

DT gas-filled (warm) targets are transported to the TC in sealed plastic containers

E11597l

15

Scrubber

Targetchamber (TC)

Tritium Facility

ToStack

TritiumFill Station

Argon

Box cleanuploop

Processcleanuploop

E11598j

Cryogenic targets are transferred to and held at target chamber center under vacuum and at 17 K until shot time

TritiumFill Station

Transfer cart

Targetchamber

Shroudretractor

Scrubber

TC-TRS**stack

TC-TRS

DTHPS

AirTRS

TRS* stack

Lowerpylon

16

*TRS = Tritium Removal System**TC-TRS = Target Chamber Tritium Removal System

The TC cryopumps collect ~75% of the DT fielded; the balance adsorbs on the TC wall as DTO

E13738d

17

A 200-mCi (7.4-GBq) DT cryo target will deposit ~48 mCi (1.7 GBq) on the TC walls.

Radiological limit for2000 exposure

Time (h)

Str

eam

act

ivit

y (n

Ci/m

3 )

10

120

160

80

40

0 2 3

AirTarget Bay

Argon

Scrubber

Tostack

To TC-TRS

Time (h)2 1

0.5

0.00 3 4 5

Str

eam

act

ivit

y (C

i/m3 )

From cryopump

After mole sieve

Only 3% of the tritium collected by the cryopump is oxide

Room-temperature, moist air purges decontaminate the TC interior to negligible dose levels within 2 h for gas targets and within 4 h for DT cryo targets.

The TC-TRS is based on classical “burn-and-dry” technology

T2515c

• All tritiated air streams are sent to the TC-TRS

18

• MCTC’s are decontaminated before maintenance to reduce outgassing and dose uptake

Pre

hea

ter

Cooler

TC-TRS

TM1

TM2

Recycle valve

Roomair

Recirculationloop

Rea

cto

r

Dri

er

Blower

To stack

Lo

w-p

ress

rece

iver

TC-TRS bypass

MCTC Air

00

1

2

3

4

5

1 2

Time (h)T

C-T

RS

(m

Ci/m

3 )

3

Heatexchanger

Each TIM* is purged with air before it is opened to prevent a “tritium puff”

T2513b

• Each TIM is decontaminated overnight following any DT campaign

19

Targetchamber

Flappervalve

TC-TRS bypass

Pre

hea

ter

Cooler

TC-TRSP

TM1

TM2

Recycle valve

CMR

Recirculationloop

Rea

cto

r

Dri

er

H/X

Blower

To stack

Lo

w-p

ress

rece

iver

Payload door Vent

Purge bypass

Aux roughing

Air purge

OtherTIMS

TIM

Air N2

0

15

30

Str

eam

act

ivit

y (n

Ci/m

3 )

15

20

10

5

01 h

Time

Flo

w (

sCF

M)

*TIM = ten-inch manipulator

Chronic, low-level releases can be identified with a Stephenson diffusion cell

E24710

20

Release in onecorner or room

Act

ivit

y (n

Ci/m

3 )

2015

Cart Maintenance Room #1Cart Maintenance Room #2Pump House #1Pump House #2

Activitytransferto PumpHouse

0

1

2

3

4

5

6

7

Jan Feb Mar April May June July Aug Sept Oct

†Airborne activitymnCi

TD

2h

dpm3 )=c m

†7.5 mm-diam-orifice

Tritium throughput has increased 15-fold since 2005, while emissions from the OMEGA stack have dropped twofold

E24652

• The OMEGA stack is permitted to discharge up to 2.2 Ci/year

21

Tritium throughput has increased fivefold since 2005, while emissions from the Tritium Facility stack have dropped continuously

E24653

• The Tritium Facility stack is permitted to discharge up to 4 Ci/year

22

The OMEGA neutron shield is performing satisfactorily

G6712b

Point no.

Location

Integrated dose1 (mrem)

Dose for max. cred. yield2 (mrem)

Shield design (mrem)

1 Experimental System Operator station <10 <10 7

2 TB anteroom 318 42 21

3 Stairway opposite TB entrance 378 57 40

4 TB north emergency exit 119 2 <1

9 Room 134 damage test lab. north <10 <10 1

10 LaCave darkroom 10 2 <1

11 LaCave/Capacitor Bay wall <10 <10 <1

12 Control Room conference room 12 3 30

13 Rod amplifier room east wall <10 <10 40

14 Amplifier test and assembly area 20 5 27

15 Amplifier test and assembly area 20 5 20

16 Laser Bay north wall, center 70 16 36

17 LaCave below TC for type-6 shots <10 <10 <13

18 Laser Bay west wall 10 2 1

19 Laser Bay south wall, center 30 7 17

20 Laser Bay south wall, east 40 9 30

1 Dose for 1995 to 2015 for integrated neutron yield of 2.22 × 1016.2 Extrapolated dose for maximum credible neutron yield of 3 × 1015 per shot.3 Badge 17 was put in place to determine if there was any exposure risk from hard electrons when the area below the target chamber was accessible. The result indicates that there is no risk.

23

Average low-energy neutron dose at various locations per 1014 neutrons produced in OMEGA

E24529

24

14.9 m

18.4 m

22.8 m

1.9mrem

Targetchamber

center

OMEGA Control Room

22.5 m4.4

mrem

1.2 mremESO desk

1.2 mremShot Director

desk

Summary

•  Engineered systems have been robust against emissions to

the environment despite increased throughputs

•  No reportable doses to radiation workers from tritium or

activated materials

•  Tritium contamination outside the radiological areas less than

1000 DP/100 cm2

•  Emissions from all stacks below 10% of the authorized New

York State (NYS) Department of Environmental Conservation

(DEC) – Part 380 discharge limit