Improvement of accumulator in cryogenic hydrogen system used for 1-MW pulsed spallation neutron source

Aso, Tomokazu; Tatsumoto, Hideki*; Otsu, Kiichi*; Kawakami, Yoshihiko*; Komori, Shinji*; Muto, Hideki*; Takada, Hiroshi

JAEA-Technology 2019-013, 77 Pages, 2019/09

JAEA-Technology-2019-013.pdf:5.59MB

At Materials and Life Science experimental Facility (MLF) of the Japan Proton Accelerator Research Complex (J-PARC), a 1-MW pulsed spallation neutron source is equipped with a cryogenic hydrogen system which circulates liquid hydrogen (20 K and 1.5 MPa) to convert high energy neutrons generated at a mercury target to cold neutrons at three moderators with removing nuclear heat of 3.8 kW deposited there. The cryogenic system includes an accumulator with a bellows structure in order to absorb pressure fluctuations generated by the nuclear heat deposition in the system. Welded inner bellows of the first accumulator was failured during operation, forcing us to improve the accumulator to have sufficient pressure resistance and longer life-time. We have developed elemental technologies for manufacturing welded bellows of the accumulator by a thick plate with high pressure resistance, succeeding to find optimum welding conditions. We fabricated a prototype bellows block and carried out an endurance test by adding a pressure change of 2 MPa repeatedly. As a result, the prototype bellows was successfully in use exceeding the design life of 10,000 times. Since distortions given during welding and assembling affect functionality and lifetime of the bellows, we set the levelness of each element of the bellows as within 0.1. The improved accumulator has already been in operation for about 25,000 hours as of January 2019, resulting that the number of strokes reached to 16,000. In July 2018, we demonstrated that the accumulator could suppress the pressure fluctuation generated by the 932 kW beam injection as designed. As current operational beam power is 500 kW, the current cryogenic hydrogen system could be applicable for stable operation at higher power in the future.

Pressure and temperature fluctuation simulation of J-PARC cryogenic hydrogen system

Tatsumoto, Hideki; Otsu, Kiichi; Aso, Tomokazu; Kawakami, Yoshihiko

IOP Conference Series; Materials Science and Engineering, 101, p.012109_1 - 012109_8, 2015/12

https://doi.org/10.1088/1757-899X/101/1/012109

The J-PARC cryogenic hydrogen system provides supercritical cryogenic hydrogen to the moderators at a pressure of 1.5 MPa and temperature of 18 K and removes 3.8 kW of nuclear heat from the 1 MW proton beam operation. We prepared a heater for thermal compensation and an accumulator, with a bellows structure for volume control, to mitigate the pressure fluctuation caused by switching the proton beam on and off. In this study, a 1-D simulation code named DiSC-SH2 was developed to understand the propagation of pressure and temperature propagations through the hydrogen loop due to on and off switching of the proton beam. We confirmed that the simulated dynamic behaviors in the hydrogen loop for 300-kW and 500-kW proton beam operations agree well with the experimental data under the same conditions.

Operational characteristics of the J-PARC cryogenic hydrogen system for a spallation neutron source

Tatsumoto, Hideki; Otsu, Kiichi; Aso, Tomokazu; Kawakami, Yoshihiko; Teshigawara, Makoto

AIP Conference Proceedings 1573, p.66 - 73, 2014/01

https://doi.org/10.1063/1.4860684

The J-PARC cryogenic hydrogen system provides supercritical hydrogen provides to three moderators. A heater for the thermal compensation and a cryogenic accumulator are prepared to mitigate a pressure fluctuation. A feed temperature should be lower than 20 K and its fluctuation should be within 0.25 K to provide cold pulsed neutron beams of a higher neutronic performance. An ortho-para hydrogen convertor is installed to maintain the para-hydrogen concentration of more than 99.0%. In this study, it is confirmed that para-hydrogen always exists in the equilibrium concentration during the cool-down process. Propagation characteristics of temperature fluctuation caused by sudden heater power variations were studied. An allowable temperature fluctuation caused by the heater control approach is determined to be 1.05 K. It is found that the heater control would be applicable for the 1-MW proton beam operation by extrapolating from the experimental data for on-beam commissioning.

Pressure control characteristics of the cryogenic hydrogen system for a 300-kW proton beam operation

Tatsumoto, Hideki; Aso, Tomokazu; Otsu, Kiichi; Uehara, Toshiaki; Sakurayama, Hisashi; Kawakami, Yoshihiko; Kato, Takashi; Futakawa, Masatoshi

Proceedings of International Cryogenic Engineering Conference 23 (ICEC-23) and International Cryogenic Materials Conference 2010 (ICMC 2010), p.1009 - 1014, 2010/07

The cryogenic hydrogen system provides supercritical hydrogen to three hydrogen moderators and removes the nuclear heating of 3.75 kW for a 1-MW proton beam operation at the J-PARC. A pressure control system that used a heater and an accumulator was designed to mitigate a pressure fluctuation caused by the sudden heat load of kW-order. The temperature and pressure behaviors were studied for a 300-kW beam operation. It was confirmed that the pressure control system made it possible to reduce the pressure fluctuation below 13.5 kPa. A simulation model was derived and could describe the experimental results within 15% errors.

Safety interlock of the cryogenic hydrogen system at J-PARC

Tatsumoto, Hideki; Aso, Tomokazu; Otsu, Kiichi; Uehara, Toshiaki; Sakurayama, Hisashi; Kawakami, Yoshihiko; Kato, Takashi; Futakawa, Masatoshi

Proceedings of International Cryogenic Engineering Conference 23 (ICEC-23) and International Cryogenic Materials Conference 2010 (ICMC 2010), p.601 - 606, 2010/07

At the J-PARC, the cryogenic hydrogen system provides supercritical hydrogen to three hydrogen moderators and removes the nuclear heating evolved by converting high energy neutrons into cold neutrons. As safety countermeasure, fail-safe devices such as relief valves and rupture disks are installed and a hydrogen explosion-proof structure is adopted. Additionally, the safety interlock system that is divided into 7 categories based on the trouble events is established to protect the equipments and to ensure the safety at the occurrence of a trouble. It is confirmed that the interlock system can be operated without any problems. The recovery procedures are also established.

Development of a simulation code for a cool-down process of the cryogenic hydrogen system

Tatsumoto, Hideki; Aso, Tomokazu; Otsu, Kiichi; Kato, Takashi; Futakawa, Masatoshi

AIP Conference Proceedings 1218, p.1154 - 1161, 2010/04

https://doi.org/10.1063/1.3422279

Supercritical hydrogen with a pressure of 1.5 MPa and a temperature of 20 K has been selected as a moderator material in an intense spallation neutron source (JSNS), which is one of main experimental facilities in J-PARC. The cryogenic hydrogen system, in which a hydrogen circulation system is cooled by a helium refrigerator with the refrigeration power of 6.45 kW at 15.5 K, has been designed to provide the supercritical hydrogen to the moderator and to remove the nuclear heating generated there. In this study, we have developed a simulation code that predicts temperature behaviors in the hydrogen circulation system during its cool-down process. A cool-down process analyses have been performed, and an operational method for the cool-down process has been studied. The analytical results indicate that the hydrogen circulation system would be able to be cooled down to 18 K within 19 hours.

Pressure fluctuation behavior in the cryogenic hydrogen system caused by a 100 kW proton beam injection

Tatsumoto, Hideki; Aso, Tomokazu; Otsu, Kiichi; Uehara, Toshiaki; Sakurayama, Hisashi; Kawakami, Yoshihiko; Kato, Takashi; Hasegawa, Shoichi; Futakawa, Masatoshi

AIP Conference Proceedings 1218, p.289 - 296, 2010/04

https://doi.org/10.1063/1.3422366

A cryogenic hydrogen system provides the supercritical hydrogen to the moderators and removes the nuclear heating at the moderators, which is estimated to 3.8 kW for a proton beam power of 1 MW. In order to mitigate pressure fluctuation caused by suddenly turning a proton beam on and off, we should design a pressure control system, which is composed of a heater as an active controller for thermal compensation and an accumulator as a passive volume controller. In December 2007, a 109 kW proton beam was injected to the JSNS. The pressure fluctuation behaviors have been studied for the 109 kW proton beam operation. As soon as the proton beam is injected, the accumulator starts to spontaneously constrict. The heater control can succeed in maintaining a constant heat load applied to the cryogenic hydrogen system. The pressure control system can reduce the pressure fluctuation below 5 kPa. We have confirmed that the pressure control system should be effective.

Design of hydrogen vent line for the cryogenic hydrogen system in J-PARC

Tatsumoto, Hideki; Aso, Tomokazu; Kato, Takashi; Otsu, Kiichi; Hasegawa, Shoichi; Maekawa, Fujio; Futakawa, Masatoshi

Nuclear Instruments and Methods in Physics Research A, 600(1), p.269 - 271, 2009/02

https://doi.org/10.1016/j.nima.2008.11.042

As one of the main experimental facilities in J-PARC, an intense spallation neutron source (JSNS) driven by a 1-MW proton beam selected supercritical hydrogen at the temperature of 20 K and the pressure of 1.5 MPa as a moderator material. A cryogenic hydrogen system plays a role in cooling the moderators. For safety reasons, we have designed a hydrogen relief system that can release hydrogen to the outside safely, even if some off-normal events occur. The design of the hydrogen vent line should be considered to prevent the cryogenic hydrogen from freezing purge nitrogen gas in the vent line and freezing moisture in the stack placed in an outdoor location, and to inhibit the piping temperature drop at the building wall penetration. In this work, the temperature change behaviors in the hydrogen vent line were analyzed by using a CFD code, STAR-CD. We determined the required sizes of the vent line based on the analytical results and its layout in the building.

Commissioning of the cryogenic hydrogen system in J-PARC; First cool-down operation with helium

Tatsumoto, Hideki; Aso, Tomokazu; Kato, Takashi; Otsu, Kiichi; Hasegawa, Shoichi; Maekawa, Fujio; Futakawa, Masatoshi

Proceedings of International Cryogenic Engineering Conference 22 (ICEC-22) and International Cryogenic Materials Conference 20 (ICMC 2008), p.717 - 722, 2009/00

In J-PARC, an intense spallation neutron source (JSNS) driven by a 1-MW proton beam has been constructed. A cryogenic hydrogen system, which provides supercritical hydrogen at the temperature of around 20 K and the pressure of 1.5 MPa to the moderators and absorbs nuclear heating in the moderators, has been completed in November 2007 and the commissioning has been started. As a first step, the primary cryogenic operations were conducted by using helium, instead of hydrogen. We confirmed the system soundness at operation temperature, and established operation method of the cool-down process. The cryogenic tests have been successfully completed without problems.

Cryogenic hydrogen system for a spallation neutron source in J-PARC

Kato, Takashi; Tatsumoto, Hideki; Aso, Tomokazu; Hasegawa, Shoichi; Otsu, Kiichi

Teion Kogaku, 43(10), p.409 - 416, 2008/10

https://doi.org/10.2221/jcsj.43.409

The prime purpose of the J-PARC is to use the various secondary particle beams such as neutrons, mesons and neutrinos produced in proton-nucleus reactions. One of the facilities that has already been completed is a materials and life-science experimental facility (MLF) where materials and biological structures are analyzed by neutron beam-scattering experiments. In the MLF, a spallation neutron source that provides a high-intensity pulse neutron with low-order meV energy for scattering experiments has been completed, and has successfully produced the desired neutrons. Neutrons produced by spallation reaction have high-order MeV energy, and the high-energy neutron is then transformed to meV-order energy by passing it through a supercritical hydrogen moderator. Therefore, a cryogenic hydrogen system is equipped in the spallation neutron source system. This paper describes the first operation results of the cryogenic hydrogen system.