Neutrino Section, J-PARC Taku Ishida Center, KEK Radiation Protection at J-PARC Neutrino Experimental Facility and Lessons Learnt T.Ishida | High Power Targetry R&D Roadmap WS, FNAL, 31 May 2017 1
thought capacity of beam intercepting devices - target, On the way of designing J-PARC neutrino facility, we beam window, electromagnetic horns and beam dump - will limit the acceptable beam power and operation. However in reality, radiation protection / safety issues become comparable or even severer limiting factors. As examples I will describe tough lessons learnt at J- PARC neutrino facility: Radioactive air ventilation/exhaust Disposal of tritiated cooling water Radiation Protection: Critical Limiting Factor on HPT Facility Operation T.Ishida | High Power Targetry R&D Roadmap WS, FNAL, 31 May 2017 2
TS: Targt Station, NU: Neutrino Utility building J-PARC Neutrino Experimental Facility N RCS Beam Near Decay Dump Muon Neutrino Volume Monitors Target Detectors Horns NA TS NM NU3 295km To Kamioka 110m NC NU2 280m J-PARC, Tokai NU1 MLF Extraction Point T.Ishida | High Power Targetry R&D Roadmap WS, FNAL, 31 May 2017 3
Water circulation system for downstream half of DV and BD [B1] Air circulation system for BD / NU3: Neutrino Utility Building #3 10.2m 1m 4m [Hot Machine Room] 1 st FL Beam Dump Muon Beam B1+ 4.5 stand [Super Hot] Decay Volume 6m Pit Pit 18.5 m B1 FL Beam Pipe/Duct Shaft Passage B2 FL Neutrino Utility Building #3 (NU3) MuPit [B1+4.5] T.Ishida | High Power Targetry R&D Roadmap WS, FNAL, 31 May 2017 4
Exhaust monitor signal (Dec.24, 2009) TS exhaust NU3 exhaust 0.05Bq/cc 0.07 0.05Bq/cc 07:50 01:50 20min 30min 20min 25min 30min 25min The first continuous (only 20kW) beam NU3 exhaust signal: Alert level= 0.05Bq/ cc(Raw data) ⇔ Observed 0.06 Bq/ cc Beam operation w as lim ited w ithin only ~ 3 0 m in due to the radiation in the exhaust air. T.Ishida | High Power Targetry R&D Roadmap WS, FNAL, 31 May 2017 5
Smoke Test Test with a smoke machine, normally used for theater plays ! @ pipe/duct shaft (B2) 1/14 B1 Dump pit PS/DS • B2 PS/DS ⇒ smoke around heat-retention of square-ducts / penetration of cable bundles • B1 ⇒ around service hatch / penetration of cable bundles T.Ishida | High Power Targetry R&D Roadmap WS, FNAL, 31 May 2017 6
Flow of the Irradiated Air at NU3 Negative Pressure control [-20Pa] Clean air Cable Service Machine penetrations hatch room (1F) Exhaust monitor Super-hot 50mBq/cc Dump pit Machine (Raw data) Cooling Room (B1F) loop 400mBq/cc Mupit cooling loop Contained, As-Is Pressure 30mBq/cc 900mBq/cc Environment air monitor suggests that irradiated air was leaked into super-hot machine room from (air-tightened) dump pit cooling loop. [ Most probably from degasifier of radioactive cooling water ] The air is going into 1F through service hatch and cable penetrations T.Ishida | High Power Targetry R&D Roadmap WS, FNAL, 31 May 2017 7
Air tightening (NU3) Remove insulation around ducts seal with thin iron plates and caulking Liquid silicone glue for the cable penetrations Seal edges of concrete blocks at the delivery entrance to downstairs Doors sealed with tape, repeat smoke tests to find remaining leaks T.Ishida | High Power Targetry R&D Roadmap WS, FNAL, 31 May 2017 8
Guess: Exhaust from pumps (evacuating hollow fiber membrane filters) may contain radioactive gas from cooling water Degasifier in BD/DV cooling water circuit Hollow fiber membrane DV BD T.Ishida | High Power Targetry R&D Roadmap WS, FNAL, 31 May 2017 9
Apparatus on the beam-line are highly irradiated after beam. Remote maintenance is the key issue. the wall of vessel by support modules. 3 electromagnetic horns / a baffle are supported from Target Station (TS) Horn dock Service pit Storage area Beam window Ti-alloy Horn-3 10.6m Horn-2 Horn-1 Beam OTR Target Baffle Graphite DV Collimator collimator J-PARC 2 0 1 4 : The 2 nd I nternational Sym posium on Science at J-PARC, Jul.1 5 , 2 0 1 4 1 0 T.I shida
Flow of the Irradiated Air at Target Station Caulking to block gap Sheemles balloon sheet ⇔ law ： 0.5mBq/cc Jan. 2010 20kW beam [ 3month average ] Chimney stack ~1.5mBq/cc 外気 13,000m 3 /h 【 Negative pressure control 】 Add cyricone Ventilation 【 closed 】 Service pit Storage area 【 circulating ] Air-tightened duct Superhot And dumper Machine room 900mBq/cc 300mBq/cc T.Ishida | High Power Targetry R&D Roadmap WS, FNAL, 31 May 2017 1 1
⇒ 950kW acceptable ! 0.1mBq/cc(190kW) signal×0.3 ：0.4mBq/cc@130 kW ⇒ 0.13mBq/cc Exhaust signal TS 1F Bypass Ventilation Reduce ventilation flow to 10% w/ o changing total flow ⇒ 41 Ａｒ (110 min) to decay Total 13,000m 3 /h 13,000m 3 /h 1,300m 3 /h 入口除塩 OA フィルタ OA EA 給気ファン EA 給気ファン 軸流ファン （インバータ） （インバータ） スタックへ スタックへ HEPA HEPA 排気ファン HEPA HEP 排気ファン 2012年1月 T.Ishida | High Power Targetry R&D Roadmap WS, FNAL, 31 May 2017 1 2
Stop of ventilation system by single event upset (2010 April) The control panel was located in B1F machine room, since limitation of 1F floor space. (Later we noticed it was around the level of target..) “Single event upset” on a CPU unit of the PLC by beam-induced fast neutrons. As temporary fix during Run-1, extract / relocate the CPU unit by 10m to area with less neutrons, then covered with LG blocks. Whole control panels of air-conditioning/ cooling water at TS moved to the ground floor in 2010, summer. T.Ishida | High Power Targetry R&D Roadmap WS, FNAL, 31 May 2017 1 3
Nested negative pressure control Negative pressure Negative pressure Control (-20Pa) Control (- 20Pa ) Very long duct (decay) Deeper Negative pressure (-40Pa) Pressure: As-Is It can be very standard idea at reactor facilities (JAEA ?) Worth to introduce to J-PARC Past CENF facility design T.Ishida | High Power Targetry R&D Roadmap WS, FNAL, 31 May 2017 1 4
= 3.5GBq/disposal 210 / 25 = 8.4 11.5GBq In Horn/TS He Vessel/Decay Volume Cooling Water 25GBq HTO produced per 1x10 20 POT (400kW x 10 7 sec) = 210GBq Radioactive cooling water drainage @ NU2 x ~2 larger than current capability 3.5GBq x 60disposal/year 84m 3 x 42 Bq/cc (70% of 60Bq/cc limit) hard to deal tritiated water from 750kW operation within the same year. Based on the working procedures by current drainage system, it is very Disposal after dilution under control of Radiation Hazard Prevention Act exchange resins, there is no way to extract tritiated water (HTO) . Although radioactive nuclear ions (7Be..) can be removed using ion- 13.5GBq 8.4x10 20 pot / year 750kW x 10 7 sec (116 days) = 15.6x10 20 pot 390GBq T.Ishida | High Power Targetry R&D Roadmap WS, FNAL, 31 May 2017 1 5
apply partial dilution 1. Shortcut in the circulation system and 3. Takeover by tank truck (+150kWx 10 7 s) 2. Frequency of drainage (every 3d/ 60 times 3 urgent improvements: New facility building with larger tanks ? Piles of the building are not strong enough. Upgrade water dilution tanks to x ~3 Radioactive cooling water drainage@ NU2 5.0 1.5 m m 4.0 2.0m m (5m x 5m x 5m) x 2tanks (5m x 5m x 2m) x 2tanks larger volume (84m 3 234m 3 ) Rehearsal of tank-truck 2d/90 : 600kWx10 7 s) takeover at NU3. (Dec. 2015) 1 st real takeover took place on Jan. 2016 T.Ishida | High Power Targetry R&D Roadmap WS, FNAL, 31 May 2017
Or, to carry forward (part of) tritiated water to following years by larger tank. It should be worth to emphasize that facility design wrt. Nested negative pressure control may solve the problem. successful to accept ~1MW beam) Radioactive exhaust air is another limiting factor (upgrade keeping them in the system (risk when water leak happens) target facility. In the future MW operation we need new facility building with vital importance to maximize the benefit of high power > 700kW operation. Improvement scenario is under consideration, which will count for limitation on total amount of tritiated water drainage. factor on beam power (400kW x 107sec/year) is from For J-PARC neutrino facility, currently most severe limiting radiation protection, safety, and waste treatment are of Summary T.Ishida | High Power Targetry R&D Roadmap WS, FNAL, 31 May 2017 1 7
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