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