Ver. 1.1 [Nov.09]NBI2012, CERN, Geneva, Switzerland, 6 th – 10 th November 2012 Ishida et al. J-PARC/KEK T2K Radioactivity in the Exhaust Air T2K Radioactivity in the Exhaust Air T.Ishida, Y.Yamada, M.Tada & Y.Oyama Neutrino Experimental Facility Group J-PARC / KEK [CONTENTS] 1. Exhaust monitor signal & improvements for air-tightness 2. Ventilation system trouble by neutrons 3. Bypass line installation and operation 4. Summary 1

Ver. 1.1 [Nov.09]NBI2012, CERN, Geneva, Switzerland, 6 th – 10 th November 2012 Ishida et al. J-PARC/KEK Radiation Monitors 2 TS NU2 NU3 BLUE311G Exhaust air monitor (gamma): 3 pairs(S/BG) NaI (TI) scintillation counter Level of exhaust at upstream of the exhaust chimney stack. Should be no signal during beam < 0.5 mBq/cc for 3 month average Environment air monitor (gamma): 3 NaI (TI) Scintillation counter level of environment at pits/machine rooms at TS / NU3 Entry prohibited with signal > 10mBq/cc NU2 exhaust is also monitored. Area monitor (gamma/n): 4 pairs Ionization chamber / 3 He counter Near the boarders of rad. controlled area Gamma: < 0.3uSv/h [alert 0.8uSv/h] Neutron: < 0.01uSv/h [alert 0.5uSv/h] Integration over every 1 hour is used for PPS: limit: 0.5uSv/h x 1hr.

Ver. 1.1 [Nov.09]NBI2012, CERN, Geneva, Switzerland, 6 th – 10 th November 2012 Ishida et al. J-PARC/KEK Radiation monitors at TS 3 Exhaust monitor Environment monitor Area monitor NU3 also has the monitors 10L （ 3atm ）, 50mm thick Pb 3inφx3in NaI 41L（1atm） 30mm thick Pb 2inchφx2inch NaI 10atm 1inchφ×10inch He-3 Prop. Counter YEL301 YEL302 BLU302 BLU312 2 cells (A/B) for signal / B.G. for signal / B.G. Exhaust chimney stack

Ver. 1.1 [Nov.09]NBI2012, CERN, Geneva, Switzerland, 6 th – 10 th November 2012 Ishida et al. J-PARC/KEK 0.05Bq/cc TS exhaust 01:50 07:50 NU3 exhaust 0.07 Exhaust monitor signal (Dec.24, 2009) MR R#28: The first continuous (20kW) beam NU3 exhaust signal: Alert level= 0.05Bq/cc(Raw data) ⇔ Observed 0.06 Bq/cc Beam operation was limited within only ~30min due to the radiation in the exhaust air Bq/cc 20min 25min 30min 20min 25min 30min

Ver. 1.1 [Nov.09]NBI2012, CERN, Geneva, Switzerland, 6 th – 10 th November 2012 Ishida et al. J-PARC/KEK Flow chart of NU3 Air Conditioning (Beam Operation Mode) If air tightness of the pits / rooms are bad, irradiated air in BD can go to the hot machine room We started to investigate air flow / air tightness of pits / rooms 5 mupit BeamDump Hot machine room(1F) polution test room (1F) Stair room Super-hot machine room (B1F) -20Pa Exhaust monitor Env. monitor Leak-tightened damper OUR GUESS Exhaust chimney stack

Ver. 1.1 [Nov.09]NBI2012, CERN, Geneva, Switzerland, 6 th – 10 th November 2012 Ishida et al. J-PARC/KEK NU3: Neutrino Utility Building #3 Beam Dump Pit / μ Pit Water circulation system for downstream half of DV and BD [B1] Air circulation system for BD / MuPit [B1+4.5] Decay Volume Beam Dump Pit Muon Pit Pipe/Duct Shaft Passage Neutrino Utility Building #3 (NU3) Beam 1 st FL B stand B1 FL B2 FL [Super Hot] [Hot Machine Room] Cross section of NU m 10.2m1m4m 6m 6

Ver. 1.1 [Nov.09]NBI2012, CERN, Geneva, Switzerland, 6 th – 10 th November 2012 Ishida et al. J-PARC/KEK Drain water pit at muon pit The drain port connecting to dump pit was closed by a flange with thinner pipe. 2010/1/6 1/18 Dump pit pit End of pipe under water level 7

Ver. 1.1 [Nov.09]NBI2012, CERN, Geneva, Switzerland, 6 th – 10 th November 2012 Ishida et al. J-PARC/KEK Smoke Test 8 B2 PS/DS ⇒ smoke around heat-retention of square-ducts / penetration of cable bundles B1 ⇒ around service hatch / penetration of cable pipe/duct shaft (B2) 1/14 Dump pit PS/DS B1 Test with a smoke machine, normally used for theater plays !

Ver. 1.1 [Nov.09]NBI2012, CERN, Geneva, Switzerland, 6 th – 10 th November 2012 Ishida et al. J-PARC/KEK 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 9

Ver. 1.1 [Nov.09]NBI2012, CERN, Geneva, Switzerland, 6 th – 10 th November 2012 Ishida et al. J-PARC/KEK Jan （ MR Run#29 ） NU3 exhaust monitor signal becomes much smaller TS exhaust becomes 0.05Bq/cc with 2 hours of beam operation 10 TS Exhaust 0.05Bq/cc NU3 exhaust 0.05Bq/cc

Ver. 1.1 [Nov.09]NBI2012, CERN, Geneva, Switzerland, 6 th – 10 th November 2012 Ishida et al. J-PARC/KEK Flow of the Irradiated Air at NU3 (beam commissioning mode) mBq/cc 400mBq/cc 30mBq/cc Exhaust monitor 50mBq/cc (Raw data) Service hatch Super-hot Machine Room (B1F) Machine room (1F) Dump pit Cooling loop Mupit cooling loop Environment air monitor suggests that irradiated air was leaked into super-hot machine room from (air-tightened) dump pit cooling loop. The air is going into 1F through service hatch and cable penetrations Negative Pressure control [-20Pa] Cable penetrations Clean air

Ver. 1.1 [Nov.09]NBI2012, CERN, Geneva, Switzerland, 6 th – 10 th November 2012 Ishida et al. J-PARC/KEK Flow of the Irradiated Air at TS 12 Service pit / storage area covered with concrete blocks. Service Pit Super hot Machine room chimney stack Cooling loop negative pressure Clean air 300mBqcc 900mBq/cc Exhaust line (closed) Duct /pipe/ cable penetrations, including horn power cables. The job was much much harder

Ver. 1.1 [Nov.09]NBI2012, CERN, Geneva, Switzerland, 6 th – 10 th November 2012 Ishida et al. J-PARC/KEK Ex.Monitor Measurements mBq/cc 3 mBq/cc 0 BLU302A （ Signal) BLU302B （ BG) Exhaust to enter into TS 0.06Bq/cc 0.045Bq/cc Both A(cell with 3 atm. exhaust air) and B(closed, BG cell) have signal Gamma ray from 1F environment (outside of the cell) air is observed as common signal. Radiation level in Exhaust = [ {A – Pedestal} - {B – Pedestal} ] / 3 (atm.) 1mBq/cc~1.5mBq/cc  law limit ＜ 0.5mBq/cc [3-month average] January: 3 days operation / 30days  0.5m x 10 = 5mBq/cc acceptable. Exhaust to enter into TS （ R#29, Jan.2010)

Ver. 1.1 [Nov.09]NBI2012, CERN, Geneva, Switzerland, 6 th – 10 th November 2012 Ishida et al. J-PARC/KEK TS air tightening （ Feb ） Stop air flow coming out between concrete blocks by backup material and caulking 14 We now learn how to sense tiny air leak by hand ! Smoke tester Need to do after every summer maintenance !

Ver. 1.1 [Nov.09]NBI2012, CERN, Geneva, Switzerland, 6 th – 10 th November 2012 Ishida et al. J-PARC/KEK Cable penetration 15 Horn Power Cables Two Signal Cable trays Two square opernings Not only by smoke, but also by smell of smoke, we can find leak… apply neg.pressure to 1F: -100Pa

Ver. 1.1 [Nov.09]NBI2012, CERN, Geneva, Switzerland, 6 th – 10 th November 2012 Ishida et al. J-PARC/KEK R#29 Jan.30~Feb.6  R#30 Feb.22~Mar  0.5mBq/cc (20kW, factor 2 reduction)  0.5~0.8mBq/cc (27kW) mBq/cc

Ver. 1.1 [Nov.09]NBI2012, CERN, Geneva, Switzerland, 6 th – 10 th November 2012 Ishida et al. J-PARC/KEK Add MVDs in the Underg. Vent Line (Mar.30~Apr.2,2010) We doubted leak in the ducts to vent undergr. rooms 17 Chimney stack New Motorized Volume Dumpers To exhaust monitor Inlet Filter Unit Outlet HEPA Filter Unit Inlet Filter Unit Ventilation FANS (outlet) VentilationFAN(inlet) MVD room press. control

Ver. 1.1 [Nov.09]NBI2012, CERN, Geneva, Switzerland, 6 th – 10 th November 2012 Ishida et al. J-PARC/KEK Install MVD Mar.30~Apr.2 Add air-tightened MVDs (bought for NU3..) Later replaced to bigger ones / install the small ones to NU3 18 Normal damper Air-tightened dumper Air-tightened Welding thick plates Normal thin duct

Ver. 1.1 [Nov.09]NBI2012, CERN, Geneva, Switzerland, 6 th – 10 th November 2012 Ishida et al. J-PARC/KEK Cover Shield Block Surface During ventilation, sheets swollen by the air, leaking through the sealed block floor.. 19

Ver. 1.1 [Nov.09]NBI2012, CERN, Geneva, Switzerland, 6 th – 10 th November 2012 Ishida et al. J-PARC/KEK Mar.19-25(R#31)  Apr (R#32) Signal (A-B) highly reduced (but not perfect) mBq/cc (40kW) 0.5mBq/cc 20

Ver. 1.1 [Nov.09]NBI2012, CERN, Geneva, Switzerland, 6 th – 10 th November 2012 Ishida et al. J-PARC/KEK Air under the cover ~ 90mBq/cc Radiation level under the cover: ~ 90mBq/cc 21 Ar40(n,γ)Ar41 (1.83hrs) K40 (1460keV) N-14 (n, 2n) N-13 (9.97 m) O-16 (n, p) N-16 (7.3 s)

Ver. 1.1 [Nov.09]NBI2012, CERN, Geneva, Switzerland, 6 th – 10 th November 2012 Ishida et al. J-PARC/KEK Sudden Stop of TS Ventilation System [Apr.20-21, 2010] 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 2009, summer. 22

Ver. 1.1 [Nov.09]NBI2012, CERN, Geneva, Switzerland, 6 th – 10 th November 2012 Ishida et al. J-PARC/KEK Install MVDs (Jun.2~4, 2010) TS/NU3 underg rooms separated by the dumpers 2010Jun: ~50kW 23 TS NU3

Ver. 1.1 [Nov.09]NBI2012, CERN, Geneva, Switzerland, 6 th – 10 th November 2012 Ishida et al. J-PARC/KEK 2011 Feb.~Mar. 24 We have introduced the second layer of sheets to shield floor. ~0.3mBq/cc for 145kW : ⇒ hit 0.5mBq/cc limit with 240kW beam 1 month average for Jan.:0.14mBq/cc ⇒ 1/28~2/28: 0.32mBq/cc

Ver. 1.1 [Nov.09]NBI2012, CERN, Geneva, Switzerland, 6 th – 10 th November 2012 Ishida et al. J-PARC/KEK Bypass line: Idea & Expectation 25 13,000m 3 /h Total 13,000m 3 /h 1,300m 3 /h Use TS 1F volume as a reservoir of irradiated air to decay. Airflow in the room / Total 41 Ar x C x N x O x0.10 Now T 1/2 41 Ar ： 110 min 11 C ： 20 min 13 N ： 10 min 15 O ： 2 min 10% Ratio (1F radiation level) 41 Ar x C x N x O x1.0 Airflow in the room / Total Now10% Ratio (exh. radiation level) Idea by Oyama-san

Ver. 1.1 [Nov.09]NBI2012, CERN, Geneva, Switzerland, 6 th – 10 th November 2012 Ishida et al. J-PARC/KEK Design 26 10~100% 90~ 0% TS 1F VAV ： Variable Air Volume CAV ： Constant Air Volume Inverter control for inlet fans Bypass line

Ver. 1.1 [Nov.09]NBI2012, CERN, Geneva, Switzerland, 6 th – 10 th November 2012 Ishida et al. J-PARC/KEK Construction Dec.2011-Jan.2012 Duct: 600x1,000  4D=4m straight section needed fro VAV/CAV. Works completed on Jan.13, Bypass flow set to zero for Jan. beam. Flow control was carefully tuned on February. 27 To chimney To 1F 1F return HEPA Inlet Filter VAV(1F) VAV(Bypass) CAV Inv.fan

Ver. 1.1 [Nov.09]NBI2012, CERN, Geneva, Switzerland, 6 th – 10 th November 2012 Ishida et al. J-PARC/KEK Tuning for Air Flow Control (Feb., 2012) 28 VAV opening ratio (%) 1F In 1F Out Bypass Negative pressure Control Bypass 0% 100% 0m 3 /h 13,000m 3 /h Bypass 1F Total

Ver. 1.1 [Nov.09]NBI2012, CERN, Geneva, Switzerland, 6 th – 10 th November 2012 Ishida et al. J-PARC/KEK Mar.~Apr m(127kW)  0.13mBq/cc( kW) with 90% bypass March beam: 145/ 0.13 x0.5=558kW acceptable April beam: 176/ 0.16 x0.5=550kW acceptable 29

Ver. 1.1 [Nov.09]NBI2012, CERN, Geneva, Switzerland, 6 th – 10 th November 2012 Ishida et al. J-PARC/KEK Balloon Sheet Installation (Apr.2012) Improve shield cover: Continuous 2-layer sheets for balloon was installed in Apr.2012 during beam. Radiation level after installation reduced by factor ~2 ~0.1mBq/cc for 190kW 30 * Photo taken on Nov.2, 2012 The radiation level in the 1F w bypass 50mBq/cc ⇒ (70+-5)mBq/cc [w/o beam: 35mBq/cc] Still low compared to regulation [<500mBq/cc]

Ver. 1.1 [Nov.09]NBI2012, CERN, Geneva, Switzerland, 6 th – 10 th November 2012 Ishida et al. J-PARC/KEK Summary ObservedAcceptable <0.5m 2010 Jan.-Feb.1.5mBq/cc (20kW)~7kW * Air tightening for floor blocks, seal cable penetration holes, & smoke tests 2010 Feb.-Mar.0.5(20)  0.8(27kW)~17kW * Add MVDs for ducts to underground rooms / cover block floor by water-proof sheets 2010 Jun.0.1~0.15(50kW)170kW * Add blocks to gaps at shield floor, upgrade of air-tightened doors 2010 Nov.~2011 Feb.0.28(105)  0.4(125kW)160kW * Add second layer of sheets 2011 Mar.0.3(145kW)240kW * Install bypass line to 1F vent line 2012 Mar.~Apr.0.13(145)  0.16(176kW)550kW * Balloon sheet installation 2012 May.~Jun.  0.1mBq/cc(190kW)950kW 31 Acceptable beam is being improved by 2 order, now ~ 1MW Radiation in exhaust air of TS was being the bottleneck of our beam power

Ver. 1.1 [Nov.09]NBI2012, CERN, Geneva, Switzerland, 6 th – 10 th November 2012 Ishida et al. J-PARC/KEK Backups 32

Ver. 1.1 [Nov.09]NBI2012, CERN, Geneva, Switzerland, 6 th – 10 th November 2012 Ishida et al. J-PARC/KEK Regulations on Radiation Radiation level, ( ) = J-PARC design rule Boundary of radiation control area: <0.5  Sv/h (<0.25  Sv/h) Accessible area for radiation worker: <25  Sv/h (<12.5  Sv/h) (Boundary between building and underground soil: <5mSv/h) Radioactivity in disposed water 3 H: <60 Bq/cm 3 7 Be: <30 Bq/cm 3 22 Na: <0.3 Bq/cm 3 Radioactivity in exhausted air through a stack 3 H: <5 mBq/cm 3 in three months average 41 Ar: <0.5 mBq/cm 3 in three months average 33

Ver. 1.1 [Nov.09]NBI2012, CERN, Geneva, Switzerland, 6 th – 10 th November 2012 Ishida et al. J-PARC/KEK Additional Concrete Shields (2010 Summer) Blocks should be sealed and covered after every summer maintenance ! 34 Air-tightened door upgraded

Ver. 1.1 [Nov.09]NBI2012, CERN, Geneva, Switzerland, 6 th – 10 th November 2012 Ishida et al. J-PARC/KEK 2010 Jun.  2010 Nov.~Dec. 2010Jun: ~50kW  2010Nov.~Dec:  Signal levels of A/B were reduced, but not for B-A… 35 Nov.~Dec.Jun. 2010

Ver. 1.1 [Nov.09]NBI2012, CERN, Geneva, Switzerland, 6 th – 10 th November 2012 Ishida et al. J-PARC/KEK 2011 Jan.~Feb. Smoke test on Jan.13, fix some leaks at cable penetration holes. 0.5mBq/cc when the additional shields were removed (105kW)  0.4mBq/cc with shields(105kW), 0.4mBq/cc for 125kW 36 W/o additional concrete shields