1 Radiological design and controls of the cooling systems for LCLS-II high power electron dumpsJan Blaha and James Liu Radiation Protection Department SLAC National Accelerator Laboratory Menlo Park, CA, USA 94025 SATIF13 - Oct , 2016, Dresden, Germany

2 Outline Introduction to LCLS-II High Power DumpsEnergy deposition in dumps Hydrogen production and mitigation Induced activation of water coolant Radiological Design of Cooling System Shielding of system housing and pipes Radiological requirements and controls Summary and conclusions Jan Blaha - SATIF13, Oct 9-12, 2016

3 Linac Coherent Light SourceFirst Light April 2009 Injector at 2-km point Existing Linac (1 km) (with modifications) UCLA e– Transfer Line (340 m) Undulator (130 m) Near Experiment Hall Since October 2009 LCLS has provided x-rays to users Electron source is the original SLAC linac One fixed gap undulator X-ray energy, pulse length, is set by electron beam Six experimental stations One or two experiments scheduled at a time X-ray Transport Line (200 m) Jan Blaha - SATIF13, Oct 9-12, 2016 Far Experiment Hall

4 Linac Coherent Light SourceNew Injector and New Superconducting Linac New Cryoplant Linac Coherent Light Source Existing Bypass Line LCLS 2009 LCLS-II 2020 New Transport Line Two New Undulators Replacing the Existing One Repurpose Existing Experimental Stations Jan Blaha - SATIF13, Oct 9-12, 2016

5 LCLS-II high power dumps layout250-kW BSY Dump inside Muon Shield BYD Two 120-kW Main Dumps Jan Blaha - SATIF13, Oct 9-12, 2016

6 LCLS-II dumps powers LCLS-II beam power is at least 2 orders of magnitude higher than LCLS DumpBSY: high power dump in BSY ENDDMPS & ENDDMPH: high power dumps at end of SXR and HXR Rated Power [kW] Est. Average Power [kW] DUMPBSY 250 90*0.57 ENDDMPH 120 27*0.57 ENDDMPS 49*0.57 43 kW Shielding of prompt dose Environmental estimations Jan Blaha - SATIF13, Oct 9-12, 2016

7 LCLS-II high power dumps design 1/2Water dump (volume cooled) Al balls (60%) + water (30%) and Cu back plug Extensive experience with water dumps at SLAC (robust, operated at high powers ~ 1MW) High activation of water coolant (need more shielding and controls) Window AL body with balls AL plug Copper block Water IN Water OUT 150 cm 30 cm Jan Blaha - SATIF13, Oct 9-12, 2016

8 LCLS-II high power dumps design 2/2Solid dump Lower activation of water coolant Two options: Surface cooled dump Al slug + Cu back plug Powers up to 120 kW Internal cooling at ~1RM Base on CEBAF design Powers up to 250 kW Copper block Al body Steel sleeve Return/Supply pipes Vacuum pipe 175 cm 30 cm Internal cooling (at ~1 RM) Surface cooling Internally cooled (CEBAF type dump) has been chosen for BSY and End dumps Jan Blaha - SATIF13, Oct 9-12, 2016

9 Cooling system for high power dumpsHazards: 15O (2-min half-life) and 11C (20-min half-life) in water coolant; decay after beam off 3H (12.3-yr half-life, beta emitter) remained in cooling system Erosion/corrosion products (22Na, 54Mn, 60Co, 65Zn, etc.) and 7Be in resin/filters Potential leakage of radioactive water Explosion from H2 build-up in surge tank and release of radionuclides The LCW flowing through the dump cooling system will be activated via interactions of the secondary particles produced in the dump with the water compound and with erosion and corrosions products. Therefore, the operation and maintenance of the LCW system may lead to potential radiological impacts to workers and to the environment. There are over 150 site –wide separate LCW systems cooling various components: magnets, halo and protection collimators, dumps (80-100) BAS-II, BSY Collimators (HX1), SL10, SL30 (HX2), BDE, NFF, SFF systems Historically, during high power operations (A-line, SLC), ~35 systems have been radioactive Require RP coverage – All resin bottles, filters need to be monitored Plans are to use HX2 for LCW for a new high power BSY dump and the two EBD LCLS-I operations, Historically Requirements: Minimize worker exposure and environmental impacts Minimize impacts to accelerator operation Reliable system for long-term performance Jan Blaha - SATIF13, Oct 9-12, 2016

10 Activity calculationsBSY water dump FLUKA calculations: Detail geometry of the dumps inside a local shielding implemented in model Calculated energy deposition maps and energy balance in different components Use for optimization of dump design Estimation of hydrogen production in cooling system Activity evolution calculated from radionuclide production yields Scaled with nominal peak power for short lived radionuclides (O-15, N-13, C-11) Scaled with average power for long lived radionuclides (H-3, Be-7) Analysis of historical data: Induced activity of erosion/corrosion products (Na-22, Mn-54, Co-57, C0-60) was estimated for similar high power cooling systems operated at SLAC The measured activity in past was scaled with respect to volume of resin tank and average beam power Extraction of spent resin Jan Blaha - SATIF13, Oct 9-12, 2016

11 Energy deposition and energy balanceInternally cooled dump GeV 2 cm rastering Energy deposition in dumps components and associated shielding was calculated by FLUKA. Results used for: Optimization of dump and shielding design Thermo-mechanical studies (input to FHeat3D) Evaluation of damage to components around the dump (electronics, cables, etc.) Energy balance [%] Water dump Surface cooled dump Internally cooled dump Solid parts 76.97 96.78 96.07 Water 18.42 0.03 0.48 Rest 4.61 3.19 3.45 For instance, almost factor 40 higher energy deposition in internally cooled dump than in water dump Rastering (2 cm radius) increases energy deposition by about 40 % Jan Blaha - SATIF13, Oct 9-12, 2016

12 Absorbed power in water at 250 kWHydrogen production H2 production determined experimentally at SLAC G value = 0.14 H2 per 100 eV in water = 1.2 liter H2 / kW-hr Lower Explosive Limit (LEL) = 4%vol H2 in air, 1% H2 used at SLAC Example: water 250 kW 46 kW absorbed in water  55 liter H2 / h 2000-liter surge tank, 50% air assumed 1% H2 (10 liter of H2) is reached in 0.2 hours (11 min) Hydrogen-oxygen recombiner is required Absorbed power in water at 250 kW Hydrogen production [1/hour] 1% H limit [hour] Water dump 46 kW 54.7 0.2 Internally cooled dump 1.6 kW* 1.9 5.3 Surface cooled dump 75 W 0.1 100 * Assuming rastering To mitigate H2 explosion risk a recombiner is required for water and internally cooled dumps. Jan Blaha - SATIF13, Oct 9-12, 2016

13 3 CEBAF Dumps (internally-cooled)Induced activity in cooling system Induced activity and impact on cooling system design for three types of dumps BSY Dump (volume-cooled) 2 EBD Dumps (surface-cooled) 3 CEBAF Dumps (internally-cooled) 3H saturation activity (185 GBq/y discharge limit to sewer) kW average power 3,3 76 kW average power EBDs: 11 BSY: 18.5 7Be saturation activity @ average power 74 90 kW kW EBDs: 1,5 BSY: 2.4 15O, 11C, 13N saturation 240 or 250 kW maximum power; 1 TVL = 17 cm concrete 2850 GBq 15O, 703 GBq 11C & 0.56 Sv/h at 1 m 18.5 GBq 15O, 3.7 GBq 11C & 3.5 mSv/h at 1 m 222 GBq 15O, 48 GBq 11C & 42 mSv/h at 1 m 22Na, 54Mn, 60Co, 65Zn Maximum activities estimated from historical data 1 TVL = 23 cm concrete 5 mSv/h at 1 m from two 400-L resin tanks (= 15 GBq 60Co) 0.05 mSv/h at 1 m (= 0.15 GBq 60Co) 0.4 mSv/h at 1 m (= 1.2 GBq 60Co) Jan Blaha - SATIF13, Oct 9-12, 2016

14 Concrete shielding [cm]Shielding and radiological controls of heat exchanger 2 Systems (3 dumps) Concrete shielding [cm] Internally cooled Water dump 15O/11C in water Wall 48 63 Ceiling 60 74 Resin Activity 50 72 0.4 mSv/h @ 1 m resin tanks 42 1 m 15O/11C in surge tanks Shielding Limit: 5 µSv/h Radiation monitors Radiological Controls: Concrete housing and shielding for underground piping Access controls to housing with interlocked detectors High capacity resin tanks with efficient exchange and disposal features Hydrogen recombiner to eliminate H2 explosion hazard Containment of coolant leakage and management of its discharge with 3H Jan Blaha - SATIF13, Oct 9-12, 2016

15 Cooling system routing schemaJan Blaha - SATIF13, Oct 9-12, 2016

16 Residual activity [MBq/l]Shielding for supply and return pipes SXR and HXR lines 1 m Example: Undulator hall Pipes will be routed inside the accelerator enclosure providing sufficient shielding (otherwise 1m depth in soil) Routing distance about 600 m (from dumps to switch yard) Different distance from the pipes, area classifications, additional requirements (temperature stability) were considered Accelerator tunnel should be accessible 1 hour after beam off Design limit < 5 µSv/h at 1m for residual radiation Shielding calculation performed for a line source (less shielding amount over long distance) and different pipe diameters Significant impact to cost Residual activity [MBq/l] Dose rate at 1 m [μSv/h] Shielding [cm] Lead Iron Concrete Water dump 145.8 113 2.1 7.5 24.5 Internally cooled 3.56 5 - Surface cooled 0.96 1 After 1 hour shielding dominated by C-11 (C-11 accounts for 20% of total Asat) Shielding can be reduced by factor of 2 by extending access time to 1.5 hours (no shielding is required if access is permitted 2.5 hours after beam off) Jan Blaha - SATIF13, Oct 9-12, 2016

17 Other controls and requirementsRequirement on separate cooling systems, one for BSY and one for End beam dumps. This allows access downstream areas when beam is parked on BSY dump Requirements on radiation monitoring and access to the cooling system housing No access permitted during operation (High Radiation Area) Radiation detector interlocked to the access door (triggers a local alarm and will alert operators in control room) Requirements on system containment System housing with secondary containment (allowing easy decontamination) with a leak detection monitor Pressure difference between primary and secondary circuits Secondary containment for piping (accelerator enclosure is considered as a second containment) Requirements for resin tanks High capacity resin tanks (~ 400 l) to ensure no more than 1 exchange per year Tanks should have remote or auto-exchange feature to reduce exposure from their post processing At leas 2 resin tanks should be used. One for operation and one for decay (Be-7) Jan Blaha - SATIF13, Oct 9-12, 2016

18 Summary and conclusionsActivity analysis of water coolant has been performed for three types of high power dumps Shielding for the cooling system housing and piping has been defined Radiation controls for access and system containment has been discussed Radiological design of the cooling system has been completed at SLAC for three types of high power dumps. Same concept can be adapted by similar facilities worldwide. Jan Blaha - SATIF13, Oct 9-12, 2016

19 Thank You

20 Radioactive Air EffluentRadiological Requirements for Public/Environment Protection General Program Direct Radiation Radioactive Air Effluent Ground Water Waste Water Federal 40 CFR 61H (NESHAPs) 40 CFR 141 (NPDWR) 10 CFR 20K State & Local BAAQMD RWQCB Order CCR17, SBSA Permit DOE O458.1 Limit 1 mSv/y to MEI ALARA 0.1 mSv/y  MCL for 3H: 740 Bq/L 3H: 185 GBq/y All other radionuclides: 37 GBq/y to sewer SLAC Design Criteria 50 µSv/y 1 µSv/y for each release point so no continuous monitoring is needed EPA Detection Limit: 37 Bq/L 1) ES&H Manual, Chapter 9 “Radiological Safety” 2) Radiological Environmental Protection program manual and procedures 3) Radiation Safety Systems: Technical Basis Documents Jan Blaha - SATIF13, Oct 9-12, 2016

21 Linac Halo CollimatorsDesign Criteria, Mitigation, Controls and Monitoring Linac Halo Collimators BSY Dump BTH BYD and 2 EBDs Groundwater (no impact: < EPA detection limit of 1000 pCi/L 3H) Shielding for Some collimators 2 Wells Dump shielding 1 Well Dump shielding geomembrane Direct Radiation (5 mrem/y, 8 PMS site-boundary) >20’ earth 4’-6’ concrete roof Radioactive Air (10 mrem/y & 0.1 mrem/y to MEI, 1-DAC to worker) Cryo FE monitoring 3 AMS Vent for access 1 AMS Residual Dose Rate (5 mrem/h non-RA, 1-h delay access) Shielding for some collimators 2 RDM 1 RDM LCW System (housing, resin tanks, filter tanks, leak controls, Locked door interlocked to detector, H2 recombiner) 4 new LCW systems for S0-S10 & HX1 HX2 upgrades Jan Blaha - SATIF13, Oct 9-12, 2016

22 Radioactive Air ConcentrationRadiological Requirements for Worker Protection Prompt Radiation Residual Dose Rates Radioactive Air Concentration Ozone Federal Limit DOE 10 CFR 835 DOE Order 420.2c RWT 50 mSv/y GERT 1 mSv/y ALARA OSHA 29 CFR PEL = 0.1 ppm SLAC Design Criteria RWT 5 µSv/h GERT 0.5 µSy/h  Radiation Area 50 µSv/h Air Immersion 1 DAC  0.1 ppm 1) ES&H Manual, Chapter 9 “Radiological Safety” 2) Radiation Protection Program program manual and procedures 3) Radiation Safety Systems: Technical Basis Documents 1DAC-h= 2.5 mrem 2 DAC-h- RA limit External exposure of 1 DAC-h = 25 µSv For 11C, 13N and 15O, DOE Immersion 1 DAC = 0.22 MBq/m3 For 41Ar, DOE Immersion 1 DAC = 0.11 MBq/m3 Jan Blaha - SATIF13, Oct 9-12, 2016

23 Key values of tritium concentration in water1DAC-h= 2.5 mrem 2 DAC-h- RA limit Jan Blaha - SATIF13, Oct 9-12, 2016

24 LCLS-II Layout: Accelerator, BSY and UndulatorskeV (<1 MHz) keV* (120 Hz) proposed FACET-II LCLS-I Linac 3-15 GeV LCLS-II SCRF Linac SXU Sec Sec L2 L3 HXU 0.25 GeV 1.6 GeV 4.0 GeV 1-25 keV (120 Hz) 1-5 keV (<1 MHz) BSY Kickers Septums BEAM DIRECTION Beam Split by Kickers and Septums 4 Beamlines LCLS Cu Linac LCLS-II Hard LCLS-II Soft LCLS-II Dump Jan Blaha - SATIF13, Oct 9-12, 2016

25 HX2 (Slit 10/30) Required Upgrades for LCLS-II ($1.7M)Item Description Qty Unit Budgetary Subcontract Cost Comments 1 Circulating Pump gpm at 110 psi, stainless steel, double mechanical seal, bearing frame, TEFC, 460 VAC 2 Each $80K 316 Stainless Steel wetted components, double mechanical seal w/ seal cavity pump/reservoir Heat Exchanger - Plate Type, 316 wetted components $35K CTW pressure shall exceed the cooling system pressure (boost pump?), monitor pressure and interlock system 3 Surge Tank with H2 recombiner System Re-Use Existing See GP R0 and SD , 30, 31 for Existing SLAC Hydrogen Recombiner technology 4 Mixed Bed Resin Tanks gallon capacity, incorporating "disposable" tank concept. (Tank cost, including resin charge is $28K) $166K Shielding requirements: - maze inside the housing (limit 5 mrem/h): 6 cm of lead or 37 cm of concrete. 5 Pre- and After- filters for Resin System $5K 10 micron filtration to protect resin and system 6 Radiation Detector $26K HPI, new for HX and Bunker Enclosures 7 Concrete Bunker - Increase thickness of east wall and roof of the HX bunker to 24" (now 12"). Increase thickness of resin bunker east and west wall, and roof to 24". Construct new 24" thick concrete south wall and entry (with ramp). Provide waterproofing. Job $280K Shielding requirements: Outside walls (and top cover) at 24" thick. Floor/wall to provide secondary containment, containment shall be sealed with epoxy coating and equipped with a leak detection monitor. 8 RAD System Piping inside bunker $235K 316L Stainless Steel Piping, Schedule 10, welded. Allowance for valves and fittings. 9 Electrical Power $65K Pumps, lighting, valve actuators, controls 10 Controls/Monitoring $220K Distributed Control System (DCS) w/EPICS interface for monitoring, Radiation Monitoring and interlock, etc. Jan Blaha - SATIF13, Oct 9-12, 2016

26 Existing HX2 LCW System in MSY26 Installed in 1960’s Thin concrete walls Low capacity resin and filter bottles Old mechanical and LCW monitoring systems LCLS-II DOE Review, Oct , 2016

27 LCW HX2 System Upgrades (Radiological Perspectives)27 Item Description Qty Budgetary Subcontract Cost Comments Mixed Bed Resin Tanks gallon capacity, incorporating "disposable" tank concept. (Tank cost, including resin charge is $28K) 4 $165K Shielding requirements: - maze inside the housing (limit 5 mrem/h): 6 cm of lead or 37 cm of concrete. Pre- and After- filters for Resin System $5K 10 micron filtration to protect resin and system Radiation Detector 2 $26K HPI, new for HX and Bunker Enclosures Concrete Bunker - Increase thickness of east wall and roof of HX bunker to 24" (now 12"). Increase thickness of resin bunker east and west wall, and roof to 24". Construct new 24" thick concrete south wall and entry (with ramp). Provide waterproofing. 1 $270K Shielding requirements: outside walls (and roof) at 24" thick. Floor/wall to provide secondary containment, containment shall be sealed with epoxy coating and equipped with a leak detection monitor. LCLS-II DOE Review, Oct , 2016

28 Benchmark of cooling system with JLAB3 resin tanks, 2 filter tanks, drip pan (left), sealed concrete floor for contamination control three 100-gallon resin tanks Hall C dump LCW housing with gate alarm interlocked to beam Vented surge tank with hydrogen recombiner with H sensor (T shape on top) Jan Blaha - SATIF13, Oct 9-12, 2016