7th High Power Targetry Workshop 4-8 June 2018 at MSU Target system maintenance experience in hot cell at J-PARC Hidetaka Kinoshita, Katsuhiro Haga, Tetsuya Kai, Takashi Wakui, Hiroyuki Kogawa, Makoto Teshigawara, Takashi Naoe , Hiroshi Takada Neutron Source Sec:on, Materials and Life Science Division, J-PARC Center, Japan Atomic Energy Agency
Contents • Mercury target for J-PARC spalla:on neutron source • Hot cell design policy for liquid metal target • Maintenance experience • Improvements based on experience • Summary �2 /15
J-PARC 1MW spallaOon neutron source Materials and Life science Facility (MLF) Mercury target vessel Total length : 2 m Total weight : 1.6 ton Cryogenic hydrogen system Material : SS 316L Width: 0.49 m Mercury target vessel Helium vessel Moderators Target trolley Mercury circulation system 3 GeV 25 Hz proton beams Proton beam �3 /15 Neutron beam lines (23) window
Mercury target and circulaOon system Target trolley Red: experience replacement Total length : 12 m Height : 4 m Mercury inventory : 1.5 m 3 Width : 2.6 m Rated flow rate : 41 m 3 /h Target exchange truck Total weight : 315 ton Mercury pipe Pressure sensors (150A) Heat exchanger Helium (550 kW) Mercury Target vessel Surge tank Mercury pump (0.7 m 3 ) Gas supplying • Target vessel fixing on target trolley with Mercury CirculaOon System system • Target vessel, MCS components (pressure sensor, gas supplying system, etc) can be replaced by remote handling • Possibility to drop radioacOve mercury from opening porOon in replacement work ⇒ Special care for treat liquid metal target �4 /15
Hot cell design policy for J-PARC mercury target Mercury collectable structure, in case of mercury leak in hot cell • ➞ Stainless lining floor and drain piping in hot cell and trolley A few hands-on maintenance are necessary in hot cell • ➞ Keep low-level contamina:on in hot cell Control high-radioacOve noble gas and triOum exhaust • ➞ Off-gas processing system to filtering and decaying noble gas �5 /15
Hot cell design policy Remote handling area in hot cell (1F) M/S manipulators Hot cell (MLF 1F) L : 40 m × W : 13 m × H : 12 m Separate two area Target vessel Mercury area, moderator area Ceiling hatch : 12×5 (2), 4×4 (1), 2.4×2.4 (5) m Carry equipments into Target trolley hot cell from high-bay Floor hatch : 2.4×2.4 (3) Carry used components into Stainless lining storage room/dry up room to dump tank Mercury target handling area (Stainless lining for mercury) Moderator, etc. handling area Target trolley 23 m Dike Opera:on posi:on Maintenance posi:on �6 /15 40 m 5 m
Hot cell design policy Storage room for used components Storage room (MLF B1F) From hot cell L : 20 m × W : 8 m × H : 10 m Ceiling hatch : 2.4×2.4 (1) m In-cell crane 12 ton M/S manipulator 2 pairs High bay Capacity:6~8 used targets Hot cell (1F) Target storage container B1F to dump tank Storage area for used target etc. SecOonal plan Drying area for PBW, moderators �7 /15 B1F Plan
Maintenance experience Equipments for target vessel replacement 20ton crane: 1 M/S manipulator: 9 pairs Power manipulator: 1 In-cell camera: 10 (target area) Master/Slave manipulator 6-axis power manipulator 20 ton in-cell (Max. fastening torque 250 Nm) crane Tools for power manipulator M20 angle Hand Video camera tube tool In-cell camera M12 & M20 nut runners •Target replace by remote handling using these equipments �8 /15 because used target has high-dose rate (ca.350 Sv/h)
Maintenance experience Outline of target vessel replacement Off-gassing and flushing Tools for target replacement Target vessel removal sequence Storage container 1 Installation sequence is reverse to the removal procedure 3 4 2 Target exchange truck • Separate target from target trolley • Target exchange truck and storage • Remove bolts and H 2 O, He, Hg pipings • Raise storage container and change to new target container sets in front of target • Insert target into storage container • Off-gassing and flushing inside mercury vessel and circula:on system • Dose rate of target vessel is ca. 350 Sv/h aier 77 days opera:on • 21 staff members involved for replacement work • Actual result in 2017 was 20 working days (12 days for exclude off-gas processing) �9 /15 (Optimized replacement procedure, adopt new tools, increase worker skill)
Maintenance experience ContaminaOon control in hotcell Target trolley Target vessel Water coupling Helium gas Mercury Plug Catch pan for bubbling line Catch pan for water line • Regularly inspec:on and maintenance work should be done in hot cell • Catch pans are placed before removing mercury and water piping to contamina:on control of hot cell floor �10 /15
Maintenance experience Off-gas processing system at J-PARC Exhaust HgCT Target vessel Surge tank Storage container 7x2.4 m 3 Drain tank Gas holders Role of off-gas processing system HgCT • Remove mercury from cover gas in MCS • Remove tri:um Tritium removal system • Separate and decay noble gas (mainly Xe-127 for 0.5~1 Y) MS HTO←HT CCT Catalyst • Move cover gas from MCS, and flushing in MCS before MS opening mercury piping Cold Charcoal Trap Unit • Off-gas caused by leak test and fill-up mercury should be (Noble gas removal) processed Off-gas processing room • Evacuate gas from MCS to off-gas processing system to make flow when MCS piping is opening (Airflow control) �11 /15
Improvements based on experience Measures to reduce triOum release Wires for crane Removable shaft 540 mm Evacuation by off-gas processing system Storage container Silicone rubber plug Put plugs into water pipings Water and helium lines Put plugs into two Mercury piping mercury pipes *North and South of photos are inverted • Plugs made of silicon rubber was inserted into mercury pipe by MSM with crane • Evacuation of mercury piping was continued until new target vessel was installed �12 /15 • Tritium release is reduced to <15% by adopting air flow control and plugs
壁貫通口 Improvements based on experience AddiOonal shield for in-cell maintenance ������� ��� Isolation room ����57�:2��1:���.��5�78���:�7� Manipulator room W/O additional shield Unit : μSv/h With additional shield Manipulator & Window Additional shield 10 25 50 3 5 6 （内径 70mm パイプ） Work area 5000 600 110 45 --- 200 350 500 5 Reduced to 1/20 14 18 20 Hot cell 100 L : 40 m × W : 13 m 70 Exhaust filter • Need regularly in-cell work for preparation of target cutting and crane inspection, etc • Dose rate in hot cell is increased after draining mercury Spallation products (Osmium, etc.) attached inside mercury pipe may increase dose rate Additional shield �13 /15
Improvements based on experience Sniffer helium leak test by remote handling Hiltap couplings Exhaust connect to stuck Detectable small leak in short period Helium (10A) Sniffer prove tube insert into cell through wall plug Water (50A) Helium leak detector placed outside of hot cell Leak test by remote handling • Takes long time for detecting small leakage by pressure change method (1 month for 10 -6 Pa·m 3 /s) • Impossible to detect leak location in the system with multiple test section • Adoption of sniffer leak test with remote handling for reducing test time �14 /15
Summary • Introduced hot cell design policy for the J-PARC liquid mercury target: mercury collectable structure, frequently enter in hot cell, noble gas and tri:um control • Measures to reduce tri:um release by air flow control with off-gas processing system made a fine performance for the safety target replacement • Improvements learned from 10 years opera:on experience were introduced �15 /15
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