1. Vashek Vylet, RadCon UITF Conduct of Operations Review April 24, 2019
UITF Shielding
Vashek Vylet, RadCon
UITF Conduct of Operations Review
April 24, 2019

2. Outline Shielding Policy Planned Operation Initial shielding estimates
Monte Carlo simulations
Conclusions

3. Shielding Policy Normal operation (incl. beam mis-steering)
< 250 mrem/y in occupied RCAs
< 100 mrem/y in other occupied areas
< 10 mrem/y at site boundary (also “design goal” for general employees per RadCon Manual)
radionuclides in groundwater per VPDES permit
Max. credible accident: <15 rem per incident

4. Planned Operation A HDIce: operation at 10 MeV for 900 h/y
Iav = 5 nA for 80% of time
Iav = 100 nA for 20% of time (for tuning)
B – Operation at 10 MeV with Iav = 100 mA, with normal (unshielded) losses < 100 nA

5. Initial Shielding Estimates
Source terms and shielding evaluated by semi-empirical methods using data from NCRP reports and other sources
Cave 1: Existing shielding : 55”/28” west side, 30” roof thickness (with penetrations)
Cave 2: Available 4 ft blocks – adequate for side shielding, not quite enough forward

6. Initial Shielding Estimates
CAVE 1
Scenarios 
Dose rate
[mrem/h]
Note
Side 100% loss 41 RA
Side 0.1% loss
0.04
below RCA
Side up 0.1% loss
2.6
RCA
Roof 100% loss
2973
HRA
Roof 0.1% loss
3.0
Roof penetration(1) 100% loss
40621
Roof penetration(1) 0.1% loss
40.6
(1) with current 3.25” local steel slab shield
Cave 1
100 mA loss
(MeV area)
Location
Beam loss
E [mrem/h]
Note
Side wall 5%
2.21E-03
below RCA
100%
4.42E-02
Forward
0.28
RCA
5.6 RA
Roof
2.76
55.2
Cave 2
100 nA loss

7. Monte Carlo Calculations
Simple estimates: side shielding fine for Cave 1 & 2 if losses < 100 nA
Roofs & penetrations > RCA or >RA
Challenges: He/ODH vent, skyshine,North Annex 2nd floor, roof and floor penetrations – addressed by Monte Carlo
Simulations using FLUKA code helped with shielding improvements, e.g. north wall in Cave 2 and He vent changes

8. Greenblocks added
Top plank

12. Summary of MC Results Cave 1 10 MeV, 100 mA loss Dose rate [mrem/h]
West side floor
< 0.3
West side up
< 10
Roof (no penetration)
< 30
Cable trench exit - Control Room 40
Shielded 10 inch roof penetrations
Big vent at Cave 2 boundary 5
Source location
HDIce
facing maze
Electron energy [MeV] 10 5
0.450
0.225
Current lost
100 mA
 100 mA
 841 mA
3 mA 
13.3 mA
Cave 2 
Dose rate [mrem/h]
Cv2 side*
< 2.0
4.0
2.0  -
<=0.1 
Cv2 maze exit
0.4
6.0 
9.0 
0.5
<=0.4 
Cv2 forward 1st floor**
1.0
0.8 
0.4  - - 
He vent
4000
1000 
1500 
30 
<=13
maze
100
3000 
10000  2 
<0.2
North Annex, 2nd floor 3
10 
<2 

13. Conclusions
Current shielding is adequate for HDIce operation (100 nA) and for 100 mA if routine losses do not exceed 100 nA.
Monte Carlo predicts in general lower dose rates, drastically so in case of shielded roof Cave 1 penetrations
Analysis of normal operation and accident scenarios shows results comply with Jlab shielding policy

14. END

15. EXTRA

16. Normal Operations Beam Loss/ Termination Point Beam Loss Condition
(Watt)
Duration
Frequency
Duty Cycle*
Exposure Location
Dose rate
(mrem/h)
Dose/Event
(mrem)
Annual Dose**
Notes
Lower beam line opposite maze 1
8 hr
Continuous
0.09
Cave 2 entry gate
0.006
0.008
1.1
Represents 0.1% of the beam power (100 nA) for high current operation (100 μA); assumes robustly shielded dump(s) and 100% occupancy.
Cave 2 roof is HRA - not routinely occupied. Cave 1 roof is RCA, assumed 100% occupancy.
2nd floor office
0.010
0.016
1.8
Source lab
<0.001
<0.008
<0.2
Cave 2 roof 3 24
N/A
Cv 1 roof boundary
0.8
6.4
144
HDICE Line
0.05
0.36
All -
Conditions all bounded by 100 nA
60 min
2/day
West wall
<0.005
<0.9
Full loss (100 nA) in low current mode (beam loss, or delivery of tune beam to F-cup)
Roof is posted radiological area and not routinely occupied
0.003
0.54
0.001
0.18
He Vent/C2 roof 4
Gun Test Mode – Not Accelerator Operations
3000
4 hr
 Few/year
<0.4
<1.6
<6.4
Drifting mA through QCM (off) to FC (without shield)***
1350
Few/year
0.5 2 8
Drifting mA through QCM (off) to FC (without shield)***
* Assumes 900 hours operation/y; 20% high-current, 80% lo-current mode (25% of low current running at 100 nA)
** Non-RCA design goal is 10 mrem/y, RCA design goal is 250 mrem/y
*** Routine condition is beam delivery to a shielded Faraday cup. Dose rate shown is for off-normal event upstream of FC. CARM probe at entry gate protects.

17. Beam loss/ termination point
Accident Conditions
Beam loss/ termination point
Beam Loss Condition
(Watt)
Duration
Exposure Location
Dose rate
(mrem/h)
Dose/Event
(mrem)
Notes
Lower beam line
opposite maze
3000
15 min
West wall 12 3
Worst plausible overcurrent condition at full energy ( uA).
Includes assumption of simultaneous, complete beam spill in lower beam line (may not be credible).
2nd floor office 30
7.5
North wall
2.4
0.6
C2 Roof (over loss point)
9000
2250
C2 Roof (He vent)
750
C1 Roof boundary
2400
600
Carve 2 access gate 18
4.5
HDICE Line
1000
<2
<0.5
Overcurrent condition (100 uA) in low current mode; loss point in HDICE line, vicinity of target
0.75 1
0.4
He Vent/roof
4000
<1000
<250
Cave 2 access gate
0.1
4200 2
0.5
Worst plausible overcurrent condition – beam loading degrades gradient to 5 MeV, current is 840 μA. Beam is lost in lower beam line.
C2 roof (over loss point)
10,000
2500 9
2.25
All cases result in integrated dose < 15 rem.

18. Accident Conditions (cont’d)
Beam loss/ termination point
Beam Loss Condition
(Watt)
Duration
Exposure Location
Dose rate
(mrem/h)
Dose/Event
(mrem)
Notes
QCM Exit
3000
15 min
West wall (cont. room)
< 0.9
< 0.23
Worst plausible overcurrent condition at full energy ( uA).
Includes assumption of simultaneous, complete beam spill at CM exit (may not be credible).
Above cont. room
< 30
< 7.5
Roof
< 90
< 23
Roof penetration*
40,621
10,155
Cable trench (cont. room)**
120 30
Vent duct exit
< 15
< 3.75
4200
< 1
<0.25
Worst plausible overcurrent condition – beam loading degrades gradient to 5 MeV, current is 840 μA. Beam is lost at CM exit.
Values conservatively scaled from same accident in cave 2.
< 33
< 8.5
< 100
< 25
45,090
11,272
133 34
< 17
< 4.5
* Based on analytical methods, modeling expected to reduce value significantly.
** Results without shielding
All cases result in integrated dose < 15 rem.

19. Test Lab including UITF

20. Initial Estimates: Cave 2 at 100 nA
10 MeV,
100 uA ACCIDENT
Side wall
Roof
[rad/h]
0.044
55.2
Distance to wall [ft] 18
E [eV]
I[A]
P[W]
Distance to ceiling [ft]
4.5
1.00E+07
1.00E-07
1.00E+00
verified 5/6/16
90 deg src term - photons
1.20E+03
rad.m^2.mA^-1.min^-1
7.20E+07
rad at 1 m per A per h
Side wall
100 nA
Note
SRC term for 5% loss
Shield thickness
Dist + shield
TVL conc
Dose rate
1 m
[ft]
[m]
[in]
mrad/h
3.60E+02 4
13.5
2.21E-03
below RCA
Side wall - mis-steering
SRC term for 100% loss
7.20E+03
4.42E-02
Roof
1.75
1.905
2.76E+00
RCA
Roof - mis-steering
7200
5.52E+01
RA/RCA
Similar approach done for Cave 1

21. Initial Estimates: Cave 2 at 100 nA

22. Cave 1 at 100 mA CAVE 1 Dose rate [mrem/h] Note Side 100% loss 41 RA
[mrem/h]
Note
Side 100% loss 41 RA
Side 1% loss
0.4
RCA
Side up 1% loss 26
Thinner wall may be an issue for stairs (and ground due to skyshine).
Cable penetrations under
west wall must be filled
with grout or similar
28”
27”
30”

23. Cave 1 at 100 mA
CAVE 1
Dose rate
[mrem/h]
Roof 100% loss
2973
Roof 1% 30
Penet* 100%
40621
Penet* 1%
406
* with current 3.25" Fe shield
30” concrete
3” steel
7.8” steel
Penetrations are above the beamline – about 8” of steel is needed for same attenuation as the 30” concrete slab. Roof will have to be inaccessible; Depending on results of measurements, full 100 mA may not be feasible at 10 MeV

24. Cave 1 at 100 mA

25. Cave 2 at 100 nA
Existing side shielding (4 ft) adequate for both 5% and 100% loss
RCA on roof, potential for RA for large losses
Local shielding needed for FARCs and beam dump
Local shielding needed at ODH vent
HDIce config & forward shielding to be modeled in detail for forward shielding

26. Cave 2 at 100 nA
42” dump
Side 5%
loss
Side 100 %
Existing shielding is adequate in this regime; HDIce dump to be designed + few other details

27. Cave 2 at 100 nA Local shielding needs to be added on the roof to keep
streaming radiation from ODH
vent reaching occupied areas
Skyshine on ground and adjacent
Areas may be an issue – will be
addressed by monitoring

28. Summary Both caves sufficiently shielded for 100 nA
100 uA in Cave 2 has issues
Monitoring layout (CARMs) to be defined (include probes for skyshine)
MC calculations needed to address HDIce dump and possible special configurations