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Status of a Cryogenic System for J-PARC Neutrino - Availability, Tritium creation, Volatilization of the ammonia etc. - KEK : Y. Makida, H. Ohata, O. Araoka,

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Presentation on theme: "Status of a Cryogenic System for J-PARC Neutrino - Availability, Tritium creation, Volatilization of the ammonia etc. - KEK : Y. Makida, H. Ohata, O. Araoka,"— Presentation transcript:

1 Status of a Cryogenic System for J-PARC Neutrino - Availability, Tritium creation, Volatilization of the ammonia etc. - KEK : Y. Makida, H. Ohata, O. Araoka, M. Iida T. Ogitsu, N. Kimura, T. Okamura, T. Nakamoto, K. Sasaki, M. Iio, M. Yoshida

2 Contents 1.J-PARC and T2K Overview. 2.Cryogenic Plant for T2K. 3.Status of Cryogenic Plant. – History and Rate of Operation – Initial Failure at Turbine and Pump – Watching Impurities and Unexpected Volatilization. – Creation of Tritium and Radiation Control 4.Conclusion

3 J-PARC (Japan Proton Accelerator Research Complex) Linac 330 m 3 Gev rapid cycle synchrotron (RCS) 350 m circ., 25 Hz Main synchrotron 1500 m circ., 25 Hz 30 GeV (in future 50GeV) Neutrino Facility To Super - Kamiokande Hadron Experimental Facility Material and Life Science Facility Transmutation Experimental Facility (in future) The J-PARC accelerator complex consists of 3 accelerators, a linear accelerator, a rapid cycle synchrotron (RCS, 3GeV) and a 50 GeV (now 30 ) synchrotron. Each accelerator provides a high intensity beam for the experimental facilities (materials and life science, hadron physics, neutrinos, transmutation). The secondary particles, such as neutrons and mesons as well as neutrinos, are produced by bombarding a target with the proton beam. Jan, 2007, 181 MeV Nov, GeV Dec, 2008 MR beam Apr., 2009 Neutrino Beam

4 Purpose of T2K experiment The T2K (Tokai to Kamioka) experiment is a neutrino-oscillation experiment to study nature of neutrinos. Artificial neutrino beam generated in the J-PARC is shoot toward the 50kton water Cherenkov detector, Super-Kamiomande, which is located about 1000m underground in Kamioka mine (Gifu) and is 295km away from Tokai.

5 5 Preparation Section SC combined func mags Target-Horn System Target Station Decay Volume Beam Dump Final Focusing Section Muon Monitoring Pit Near Neutrino Detector 295km to Super-Kamiokande 100m T2K neutrino facility in J-PARC P beams accelerated up to 30 GeV are directed westward through the Primary Part. A string of SC. Mag is a core part in the Primary Part. P collide with a graphite target and produce  -mesons, which decay into neutrinos. 30 GeV (50 GeV)

6 Present status of T2K 20kW, upto 240 kW 65x10 19 for physics analysis Although two long shut-down periods due to an earthquake and a radiation accident, T2K resumed data taking. Statistic of P beam became enough to announce its experimental result. The international T2K collaboration announced a definitive observation of muon neutrino to electron neutrino transformation on July T2K saw its first event in antineutrino beam mode on June Electron-neutrino candidate in Super Kamiokande HD hall radiation accident History of accumulated proton number and beam power improvement

7 Contents 1.J-PARC and T2K Overview. 2.Cryogenic Plant for T2K. 3.Status of Cryogenic Plant. – History and Rate of Operation – Initial Failure at Turbine and Pump – Watching Impurities and Unexpected Volatilization. – Creation of Tritium and Radiation Control 4.Conclusion

8 8 8 Primary line components - One string of Superconducting Magnets - The neutrino beam line has a bending section with a radius of 105 m, where single string of 28 superconducting magnets has been installed. The magnet design is very unique. It has a combined function of 2.6 T dipole field with 19.6 T/m quadrupole field gradient by a left-right asymmetric distribution of conductors.

9 Cryogenic Plant overview LN 2 CE S.C. Magnet MCP, CB, Sub-cooler, CLB Cryogenic devices, 4 He tanks, 1 LN 2 CE, a compressor, a cold box, a sub-cooler and a current lead box, are set on surface. The magnets are at -12 m under ground and coolant SHE is transported between them. He Tank Pacific Ocean (5m Tsunami arrived)

10 Superconducting Magnet Main Synchrotron 10 m Overall Layout (Ground Plan) Neutrino Beam Line Superconducting Magnet Arc in main tunnel at -12m level Radius 105m, Length 150m Cold Box 、 Subcooler SHE Max 300 g/s 4.5 K LHe pot : 800 ℓ C/L flow : 1 g/s Main Compressor (MCP) : 570 kW, 1.4 MPa, 150g/s Buffer Vessel (for MCP) Volume 100m 3 ×1 LN 2 : ℓ Only pre-cooling & cold purification pre-cool 300 – 100 K Magnet String & Transfer Line Inventor 3900 ℓ, Cold mass 225 ton(Fe) 90 m transfer line with SC bus Heat Leak 220 W + Beam Loss max 150 W Recovery Vessel (for Quench) As Storage Vessel for Inventory Volume 100m 3 ×3

11 Conceptual Flow excitation A cascade refrigerating system, composed a Claude cycle refrigerator with a centrifugal pump, supplys 4.5 K, 0.4 MPa, 300 g/s She. Turbine flow goes through radiation shield cooling line in the magnet. LN 2 is consumed for pre-cooling and gas purification. 1.4MPa, 150 g/s He gas is supplied by the compressor. 70 g/s flow expands and works at turbines, and the rest expand at JT valve in the sub-cooler.

12 Refrigerator capacity 1500 W need the 900 W offset by using LHe level control heater. Saving refrigerator capacity by reducing unloader and supply pressure results in lower power consumption at the compressor. Power saving mode. Saving 1.5 MYen/month

13 Contents 1.J-PARC and T2K Overview. 2.Cryogenic Plant for T2K. 3.Status of Cryogenic Plant. – History and Rate of Operation – Initial Failure at Turbine and Pump – Watching Impurities and Unexpected Volatilization. – Creation of Tritium and Radiation Control 4.Conclusion

14 History and Rate of Operation FY2011 FY2012 Earthquake 11/3 After MSS Miss Trigger trouble is solved, Nu cryogenic system has caused no interruptions of T2K experiment. Rate of operation (availability) is beyond Although cryogenic system did not stop, some devices did abnormal movement. It was only lucky. 11/12 7/3 15/3 6/5 17/5 4/12 8/12

15 History and Rate of Operation FY2014 FY2013 HD Radioactive Material Leak Accident on 23/May About HD radiation material leak accident please refer To restart J-PARC operation, Radiation control management became severe. Nu cryogenic facility and its maintenance method were examined in radiation evaluation committee. T2K experiment resumed on April J-PARC operation was not admitted until improved radiation management was established.

16 Contents 1.J-PARC and T2K Overview. 2.Cryogenic Plant for T2K. 3.Status of Cryogenic Plant. – History and Rate of Operation – Initial Failure at Turbine and Pump – Watching Impurities and Unexpected Volatilization. – Creation of Tritium and Radiation Control 4.Conclusion

17 Notches in Turbine We found some notches at 2 nd turbine blades by the visual inspection after 2009 autumn operation. We observed abnormal start movement of 2 nd turbine. LINDE TED turbine needs bearing gas supply during only start-up. And bearing gas stops, after the rotation reach to normal speed. But 2 nd turbine could not start with bearing gas, and it could start when bearing gas stopped. Once start-up, 2 nd turbine rotated normal condition during the beam operation, and cooling power did not degra de. Measured mechanical strength of the turbine material is rather low. Linde also reported that the bearing gas pressure at 14 bar in Nu cold box is higher than its design pressure of >10 bar in standard liquefiers. New turbine made with inspected material was set. Pressure reducing valve was installed into the bearing gas supply line. Remade 2 nd Turbine and 1 st Turbine PRV addition into bearing line HP LP MAG CP

18 Rubbing of SHE pump Cold bearing is Exchanged annually by Taiyo Nippon Sanso, Main contract of Nu cryogenics. And removed bearing is inspected by Barber Nichols to analyze its operation life. We found burrs on the pump impeller blades by the visual inspection after 2010 autumn -> 2011 winter operation. We heard abnormal large and shrill noise during the operation. But flow rate of 300 g/s at nominal rotation improved 310 g/s. So, the operation continued. Lower position of the pump impeller caused scratch of the impeller blades with the pump housing. New tool and gage to set the blade at the design position are prepared. Cold Bearing Tuning Bolt of Rod Length

19 Contents 1.J-PARC and T2K Overview. 2.Cryogenic Plant for T2K. 3.Status of Cryogenic Plant. – History and Rate of Operation – Initial Failure at Turbine and Pump – Watching Impurities and Unexpected Volatilization. – Creation of Tritium and Radiation Control 4.Conclusion

20 Watching and measuring impurities Inner Detectors (Measured gas go to the LP line) – Dew-point meter : MICHLL Ins. Water detection < - 60 ۫C ( before cool down ), -90 ۫C (usually) – Discharge light spectrometer : KEK original N 2, < 1 ppm – Gas chromatograph : SHIMAZU → LINDE multi component detector N 2, O 2, CO, CO 2 < 1 ppm Gas sampling ( at warm-up 25 K ) – Quadruples mass spectrometer : ULVAC & JAEA H 2 < 1 ppm H 2 from polymers in the magnets by beam irradiation. – Liquid scintillator : Radiation Control Equipment HT < 7 Bq/cc, HTO < 5 mBq/cc (Radiation control criteria) Tritium transmuted from 3He

21 Oil separation check Oil return Solenoid valve with Counter and Action signal Oil must be ≦ 0.001vol.ppm Level Switch Sight Glass Action Signal Controller Counting Interval check Screw Compressor 5 th Separator Molecular Sieve Adsorption 4 th Separator Active Charcoal Adsorption 1 st Separator Demister Separation Water Cooler 2 nd & 3 rd Separator Filter Element Coalescence Controller checks oil return valve action interval. If the interval become longer, that means filter elements are saturated. Filter element selection is important. Activity of DOMINICK HUNTER is short. This element caused RIKEN Oil diffusion accident. TAIHEIYOU filter is activate longer. So, filters in 2 nd separator were exchanged. Oil check sampling annually. Daily check through sight glass.

22 Unexpected Volatilization : Ammonia from Magnet Glass-reinforced Phenolic Thermosets Rin=102 mm, t=20 mm, L= 100 mm *PM9640 by Sumitomo Bakelite, Arisawa Ammonia Origin Ammonia Properties Molecular FormulaNH 3 Molecular Mass g/mol Density0.86 kg/m 3 (1.013 bar at boiling point) kg/m 3 at −33.3 ℃ (liquid) Melting point−77.73 °C ( K) Boiling point−33.34 °C ( K) We found that irritant odor in vent helium gas from the magnet at maintenance. Gas analyzing showed that the odor material is ammonia. Search found the plastic spacer is its origin. Why the Nu refrigerator was not blocked up? Molecular Sieve (Crystalline Zeolite) in 5 th oil separator can adsorb large quantity of ammonia. 5 th separator has large enough quantity of MS, which can adsorb 79 kg ammonia. And MS can be re-activate by heating at 150 ℃. Atmosphere Ammonia Detector Pump Dew point mater MS (13X) Adsorb He Recovery N 2 gas for reactivation He ppm NH 3 to watch adsorption He for carburation Thermo- meter Heater

23 Contents 1.J-PARC and T2K Overview. 2.Cryogenic Plant for T2K. 3.Status of Cryogenic Plant. – History and Rate of Operation – Initial Failure at Turbine and Pump – Watching Impurities and Unexpected Volatilization. – Creation of Tritium and Radiation Control 4.Conclusion

24 HT (Bq/L)HTO (Bq/L)Beam P (kW) May/ ~ 80 July/201000~ 80 Sep./ ~ 200 Dec./ ~ 220 Mar./ ~ 230 May/ ~ 230 Aug./ ~ 230 July/ ~ 250 Measurement Record of Tritium (HT & HTO) Sample gas is analyzed by Liquid scintillater with precision of 5Bq/L. Analysis is done at RT, AP. Radiation Management in J-PARC require Larger Beam Power may produce more tritium. HT (BP 25K) and HTO inside Beam Time -> Sampling at > 25 Return from MAG 24 HTHTO Boiling Point (K)25373 Melting Point (K) A. Limit * (Bq/L)70005 * Allowable limit in discharging gaseous radioactive waste Law Concerning Prevention from Radiation Hazards due to Radio‐Isotopes, etc. (≈ ICRP90) Regulation << A. Limit Gaseous waste must be vent through authorized vent stack with radiation monitor. Even small gas vent from maintained equipment must follow the guideline. The work place, where gaseous waste is vent, is set as a radiation management area temporally.

25 Same Operation and Modified Maintenance due to Tritium But Radiation Management in J-PARC accept Nu cryogenic system, which is designed and is inspected by High Pressure Gas Regulation, holds enough air-tightness to prevent tritium leakage. Consequently, Nu cryogenic area on surface need not become radiation management area permanently. It is only set, when the helium gas part is exposed. Temporal Radiation Management Area Cryo. Room Tank Yard Air Vent Stack Tank Evaporator Tank Evaporator MCP Oil Separator CB Subcooler C/L Box Otherwise Air

26 Guide Line of Temporal Radiation Management MCP Surface Vacuum Vessel Sub- Cooler Sub- Cooler CB Tank CL BOX CL BOX Vac. Pump Vac. Pump Existing Vent Stack Cryogenics Room = Temporal Backup Seal Radiation Monitor Beam Pipe Under Ground Radiation Management He Vent Line 0.1 mm Metal Mesh 1 mm Metal Mesh Magnet Temporal Vent Line Temporal 1 st Seal Backup Seal

27 Actual Method : Filter Exchange at 2nd,3 rd Oil Separator 1 st seal Oil Separator Unit is covered by an air-tight plastic sheet room. Backup seal Cryogenic Room becomes radiation management area. 400 m 3 /h blower exhausts air from the room to the vent line. Oil Filter Exchange Radiation Safety Check By gas sampling and smearing. Analysis takes 1day Setting Management Area Radiation Safety Check By smearing. Analysis takes 1day Cancel Management Area

28 Actual Method : Relief Valve Exchange at outdoor Tanks RVRV vent Stop Valve He must be vent before RV removal Rope set management area. Rope is back-up seal ??? Wrench is kept inside plastic bag as 1 st seal. Back up seal is rope. Radiation Safety Check By smearing. Analysis takes 0.5day Setting Management Area Radiation Safety Check By smearing. Analysis takes.5day Cancel Management Area Removed RV Smear Inspection Send RV to maker for calibration

29 CONCLUSION After initial troubles were solved, Nu cryogenic system has been stable since FY2012 autumn. It was not expected that volatilization of the ammonia from the magnet, but fortunately, molecular sieve in the 5 th oil separator can adsorb a gross quantity. Tritium of 40 Bq/L has been detected in refrigerant. In spite of lower value than its allowable limit of 7000 Bq/L, Nu cryogenic operation and maintenance method were examined in radiation evaluation committee. Helium vent must be through authorized line and stack after radiation measurement. Fortunately vent line from RV and the vacuum pumps had been constructed. Gas monitor and metal filters were installed into the vent line additionally. Some maintenance works, RV and oil filter etc. exchange, need setting of temporal radiation management area and complicated procedures.

30 Backup Slied

31 Conceptual Flow excitation A pair of cooling gas flow for the current leads is divided from the SHE supply line simply. SC cables directly enter the SHE line SHE pump outlet is connected with the inlet of JTV. The pressure in this connection line is kept at 0.4 MPa by the JTV. This control scheme spontaneously complements the current leads cooling gas which falls out from the pumped circulation.

32 Specifications of each component in the cryogenic plant(1). ComponentItemSpecification CompressorTypeOil injected two stage screws compression Manufacture / Model nameMAYEKAWA/HE3225MSC-KLBM Discharge pressure1.4 MPa Discharge stream160 g/s Oil separation5 stages, Demister, 2 stage Coalescer, Activated charcoal, Molecular sieve RefrigeratorTypeClaude cycle Manufacture/Model nameLINDE/ TCF200S Refrigeration power without LN Supplied gas pressure of 1.4 MPa Return gas pressure of 0.12 Mpa 1500 W at 4.5 K for pumped SHE stream W at 80 K for radiation shields g/s from 4.5 K for current leads Turbine typeDynamic bearing expansion turbine Turbine and JT stream at steady state70 g/s, 80 g/s Shield stream70 g/s (equal with turbine stream ) Sub-coolerManufactureJECC TORISHA Phase separator ( LHe reservoir) capacity1600 ℓ Stored LHe volume at steady state800 ℓ SHE pump manufactureBarber-Nichols SHE pump bearing typeBall bearing Nominal pumped flow rate300 g/s Available pressure head at nominal flow100 kPa

33 Specifications of each component in the cryogenic plant(2). ComponentItemSpecification LN 2 cold evaporator Volumetric capacity Operation pressure ℓ (stored volume ℓ) 0.5 MPa ManufactureCRYO-ONE DryerMoisture absorberSynthetic zeolite Amount of throughput200 Nm 3 /h ×24 h Absorption abilityOutlet impurity 1.2 ppm, dew point -75 ۫C Cryogenic purifierImpurity absorber Amount of throughput Activated carbon 200 Nm 3 /h ×24 h Absorption abilityOutlet impurity 1.2 ppm Pressure vesselVolume100 m 3 ×4, one for buffer, others for storage Operation pressure1.5 MPa COP, FOM , 16 % External set of a dryer and a cryogenic purifier is installed, because large amount of moisture and air from magnet electric insulator were predicted. The capacity of this purification unit is large enough for the 1000 ppm inventory. Impurities in helium gas was actually removed in two days before cooling down, so the rate of operation of the dryer and the purifier is very low.

34 Effort of Power Saving Mode beforeafter High (discharge) pressure controlMPaG Refrigerator cycle flow rateg/s LHe level control heaterW Refrigerator capacityW Lower unloader posision%10095 Compressor power consumptionkW Power cost per month (\15/kwh)K YEN6,1564,644 CO 2 emission per month (0.555kg/kWh)* ton(CO 2 ) SHE flow (just for information)g/s300 Saving 1.5 MYen/month, 55 ton CO 2 /month

35 CB&SC pre-cooling Magnet Pre-cooling Gas transport Shield Pre-cooling Conceptual Flow pre-cooling The cooling He gas circulation through the magnets is driven by the compressor. The shield circulation is driven by the compressor, too. The pump circulation is bypassed for its pre-cooling. Magnets is cooled down for 8 days.

36 Liquefaction Gas Recovery Shield Cooling Quench Emergent Exhaustion C/L Cooling Pump Protection CP 0.45MPa Conceptual Flow Quench At quench, the pump circulation quickly switch to the bypass line and is isolated from the magnets. The quenched magnet pressure is released to the storage tanks through the exhaustion lines directly.

37 Tritium Estimation at 1W/m beam Loss ( in case of All beam loss in the SC ) After 4000 h 1w/m loss – Beam Tube Periphery 180 Bq/cc * 5 litter – Cooling Hole 25 Bq/cc * 10 litter – Press Shoulder etc 10 Bq/cc * 15 litter – End Space 50 Bq/cc * 40litter – 3He to tritium 7 Bq/cc* ( ) litter – Total 54 Bq/cc


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