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JAEA Reports

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$$^{circ}$$. 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.

Journal Articles

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

 Times Cited Count:5 Percentile:5.27

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.

Journal Articles

Commissioning results on the cryogenic hydrogen system for moderators in JSNS

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

Proceedings of 19th Meeting of the International Collaboration on Advanced Neutron Sources (ICANS-19) (CD-ROM), 8 Pages, 2010/07

In the J-PARC, the cryogenic hydrogen system for the 1MW pulsed spallation neutron source (JSNS) plays a role in supplying supercritical hydrogen at a temperature of 18 K and pressure of 1.5 MPa to three moderators in which spallation neutrons generated in a mercury target are slowed down to cold neutrons. Through the off-beam commissioning until April 2008, we confirmed that the specifications of the cryogenic system were satisfied as expected, and we could succeed in circulating supercritical hydrogen with the maximum flow rate of about 190 g/s. We have succeeded in generating first neutrons in the mercury target and providing moderated neutrons through the hydrogen moderators without any problems in May 2008. We also confirmed characteristics of the cryogenic hydrogen system with accepting the proton beam on the mercury target as on-beam commissioning.

Journal Articles

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.

Journal Articles

Performance test of a centrifugal supercritical hydrogen pump

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

Proceedings of International Cryogenic Engineering Conference 23 (ICEC-23) and International Cryogenic Materials Conference 2010 (ICMC 2010), p.377 - 382, 2010/07

A dynamic gas bearing centrifugal pump that circulated supercritical hydrogen with a large flow rate of more than 0.16 kg/s was developed to minimize the hydrogen density change at the moderator. The two pumps were simultaneously operated in parallel for redundancy. The performance test results indicated that the dimensionless characteristics for the single and the parallel operations existed on an identical curve. An outstanding peak adiabatic efficiency exited at the flow coefficient of 0.046, independently of the revolution. It was verified that the developed hydrogen pump satisfied the design requirement.

Journal Articles

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.

Journal Articles

Development of the cryogenic hydrogen system for a spallation neutron source in J-PARC

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

AIP Conference Proceedings 1218, p.297 - 304, 2010/04

 Times Cited Count:2 Percentile:21.02

In JSNS, supercritical hydrogen at around 20 K and 1.5 MPa was selected as a moderator material. Three kinds of hydrogen moderators are installed to provide pulsed neutron beam with higher neutronic performance. A cryogenic hydrogen system, in which a hydrogen circulation system is cooled by a helium refrigerator system with the refrigerator capacity of 6.45 kW at 15.6 K, provides the supercritical hydrogen to the moderators and absorbs nuclear heating in the moderators. Through the off-beam commissioning, we have confirmed that the cryogenic hydrogen system can be cooled down to 18 K within 19 hours. The supercritical hydrogen with the mass flow rate of 190 g/s can be circulated at the rated condition. It is verified that the cryogenic hydrogen system is satisfied with the performance requirements. In May 2008, we have succeeded in providing the first cold neutron beam cooled by the cryogenic hydrogen system.

Journal Articles

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

 Times Cited Count:1 Percentile:37.53

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.

Journal Articles

Pressure drop evaluation of the hydrogen circulation system for JSNS

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

AIP Conference Proceedings 1218, p.1162 - 1169, 2010/04

 Times Cited Count:0 Percentile:100

In J-PARC, an intense spallation neutron source (JSNS) driven by a proton beam of 1 MW has selected supercritical hydrogen with a temperature of around 20 K and the pressure of 1.5 MPa as a moderator material. A hydrogen circulation system has been designed to provide supercritical hydrogen to the moderators and remove the nuclear heating there. It is important for the cooling design of the hydrogen circulation system to understand the pressure drops through the equipments. In this work, the pressure drop through each component was analyzed by using a CFD code, STAR-CD. The correlation of the pressure drops through the components that can describe the analytical results within 14 % differences has been derived. It is confirmed that the pressure drop in the hydrogen circulation system would be estimated to be 37 kPa for the circulation flow rate of 160 g/s by using the correlations derived here, and is sufficiently lower than the allowable pump head of 100 kPa.

Journal Articles

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

 Times Cited Count:2 Percentile:21.02

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.

Journal Articles

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

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

Teion Kogaku, 45(4), p.181 - 190, 2010/04

To mitigate pressure fluctuation caused by the load, a pressure control system is a necessary requirement. Accordingly, a control system was designed and installed, using a heater and an accumulator. Changes in pressure caused by operation of a 120-kW and a 302-kW proton beam were studied. It was confirmed that the pressure control system was effective in mitigating the pressure fluctuation caused by the load. A simulation code was also developed and the pressure rise behavior and the accumulator variation were studied. The simulation results indicated good agreement with the experimental data within 10%. The pressure fluctuation for a 1-MW proton beam was predicted to be 33.9 kPa, which is lower than the allowable pressure rise of 0.1 MPa, and produced an accumulator variation of 11.35 mm. We believe that the pressure control system is effective for use with the operation of a 1-MW proton beam.

Journal Articles

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

 Times Cited Count:1 Percentile:86.46(Instruments & Instrumentation)

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.

Journal Articles

Performance test of a helium refrigerator for the cryogenic hydrogen system in J-PARC

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.711 - 716, 2009/00

In J-PARC, a cryogenic hydrogen system, which plays a role in providing supercritical hydrogen with a pressure of 1.5 MPa and a temperature of 20 K to three moderators, has been designed. The performance test of the helium refrigeration system was conducted independently. The helium refrigeration system was cooled down to 18 K within 4.5 hours, and the refrigerator power of 6.45 kW at 15.6 K was confirmed. The performance test results proved that the helium refrigerator met the performance requirements.

Journal Articles

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.

Journal Articles

Commissioning of the cryogenic hydrogen system in J-PARC; Preliminary operation by helium gas

Aso, Tomokazu; Tatsumoto, Hideki; Hasegawa, Shoichi; Otsu, Kiichi; Uehara, Toshiaki; Kawakami, Yoshihiko; Sakurayama, Hisashi; Maekawa, Fujio; Futakawa, Masatoshi; Ushijima, Isamu*

Proceedings of International Cryogenic Engineering Conference 22 (ICEC-22) and International Cryogenic Materials Conference 20 (ICMC 2008), p.741 - 746, 2009/00

no abstracts in English

Journal Articles

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

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.

Journal Articles

Numerical analysis of forced convection heat transfer of subcooled liquid nitrogen

Tatsumoto, Hideki; Shirai, Yasuyuki*; Hata, Koichi*; Kato, Takashi; Aso, Tomokazu; Otsu, Kiichi; Shiotsu, Masahiro*

IEEE Transactions on Applied Superconductivity, 18(2), p.1483 - 1486, 2008/06

 Times Cited Count:4 Percentile:67.13(Engineering, Electrical & Electronic)

The knowledge of forced flow heat transfer of liquid hydrogen is important for cooling design of hydrogen moderator system and HTS superconducting magnets such as MgB$$_{2}$$ magnet. The use of a CFD code is necessary to understand the heat transport phenomena in the practical cooling channel of the magnets. As a first step of the study, forced flow heat transfer of liquid nitrogen in a horizontal tube, instead of liquid hydrogen, was analyzed in this work by using a CFD code. The solutions were compared with the authors' experimental data under the corresponding conditions. The solutions obtained by using the low Reynolds number ${it k-$epsilon$}$ model as a turbulent model agreed well with the experimental data for the Reynolds numbers (${it Re}$) higher than 1$$times$$$$10^{4}$$. For ${it Re}$ $$<$$ 1$$times$$$$10^{4}$$, the solutions become lower than the experimental data. The heat transport mechanism in the horizontal tube was also clarified by the analyses.

Journal Articles

Thermal stress analysis for a transfer line of hydrogen moderator in J-PARC

Tatsumoto, Hideki; Teshigawara, Makoto; Aso, Tomokazu; Otsu, Kiichi; Maekawa, Fujio; Kato, Takashi

AIP Conference Proceedings 985, p.1225 - 1232, 2008/03

In JSNS, cryogenic hydrogen at supercritical pressure is selected as a moderator material. Three kinds of hydrogen moderator are installed to provide higher neutronic performance. The transfer lines around the moderators should be changed every 6 years due to its radiation damage. The detachment of the transfer line will be only performed by a hands-on. Therefore, minimum pipe size and elbow-type bend sections are installed to reduce the radiation dose by the radiation streaming. Some spacers are installed so as to avoid touching the hydrogen pipe to the outer vacuum pipe due to thermal shrinkage. In the design, we should consider mechanical stress concentration, deformation, and, touching between the pipes due to the thermal shrinkage at the cryogenic hydrogen temperature. The appropriate locations of spacers to keep the thermal stress below an allowable stress and to avoid touching between the pipes were determined.

Journal Articles

Spallation neutron source at J-PARC and its cryogenic hydrogen system

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

Teion Kogaku, 42(8), p.244 - 254, 2007/08

The JAEA and the KEK are collaborating in the construction of the Japan Proton Accelerator Research Complex (J-PARC). The J-PARC has four science experimental facilities, a materials and life science experimental facility, a nuclear and particle experimental facility, a neutrino experimental facility, and a nuclear transmutation facility (planned for the future). At the materials and life science experimental facility, a spallation neutron source has been constructed to provide experiment users with neutron beams that have the world's highest pulse intensity. Neutrons produced using spallation reaction should possess a high energy of MeV order, but neutrons used for experiments should have energy of a low meV order. Therefore, an effective material that is capable of moderating neutron energy is required. That material is supercritical hydrogen; and the spallation neutron source should therefore be equipped with a cryogenic hydrogen system that provides supercritical hydrogen to the neutron energy moderating system. This paper discusses the spallation neutron source and the cryogenic hydrogen system.

Journal Articles

Safety design of the cryogenic hydrogen system at J-PARC

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

Teion Kogaku, 42(8), p.255 - 264, 2007/08

JAEA has been constructing the J-PRAC in collaboration with the KEK. The materials and life science experimental facility (MLF) has been constructed as one of the experimental science facilities at J-PARC. A spallation neutron source that produces neutrons through nuclear spallation reaction using high-energy proton beam injection and provides neutron beams for experimental users has been installed at the MLF. Hydrogen nuclei are used as a neutron moderating material (moderator) to reduce the neutron energy from MeV to meV order. Therefore, a cryogenic hydrogen system should be installed at the spallation neutron source to provide supercritical hydrogen to moderators. This paper describes the safety design of the cryogenic hydrogen system. Especially, the system is subject to high-pressure gas safety laws, and refrigeration safety regulations are applied to the system for the first time. We also discuss the technical contents that were argued through this application.

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