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

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

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

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

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

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

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

Greenblocks added Top plank

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  - -  Roof2 @ He vent 4000 1000  1500  30  <=13 Roof2 @ maze 100 3000  10000  2  <0.2 North Annex, 2nd floor 3 10  <2 

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

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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 225 keV @ 13.4 mA through QCM (off) to FC (without shield)*** 1350 Few/year 0.5 2 8 Drifting 450 keV @ 3 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.

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 (10 MeV @ 300 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.

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 (10 MeV @ 300 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.

Test Lab including UITF

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 [mrad/h] @ 1 m [ft] [m] [in] mrad/h 3.60E+02 4 6.7308984 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

Initial Estimates: Cave 2 at 100 nA

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”

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

Cave 1 at 100 mA

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

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

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

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