Trial measurement for para-to-orthohydrogen back conversion under the Fe(OH) catalyst condition at J-PARC cryogenic moderator system

Ariyoshi, Gen; Tatsumoto, Hideki*; Teshigawara, Makoto; Hasegawa, Takumi*; Shiro, Yuki*; Horikawa, Yuka*

IOP Conference Series; Materials Science and Engineering, 1327(1), p.012155_1 - 012155_6, 2025/05

https://doi.org/10.1088/1757-899X/1327/1/012155

The Spallation Neutron Source (SNS) at the Oak Ridge National Laboratory in the United States of America, which operates at 1.4 MW of high-power proton beam, has recently measured "back conversion production" in which parahydrogen, a nuclear spin isomer, is converted to orthohydrogen in an intense neutron field in a liquid hydrogen circulation system not installing any catalyst, for the first time in the world. The amount of para-to-orthohydrogen back conversion was 0.374 [m/MW/day]. Comparing parahydrogen and orthohydrogen, the total neutron cross section differs more than two orders of magnitude, so the increase in orthohydrogen has a significant impact on the generated neutron performance. Therefore, in the J-PARC hydrogen circulation system, a catalyst is introduced to maintain the parahydrogen state. However, at present, methods have not been developed yet to directly diagnose catalyst performance and/or degradation in-situ. In this study, we devised a new method to easily and intentionally change the amount of orthohydrogen in the J-PARC hydrogen circulation system, and attempted to evaluate catalyst kinetics by intentionally introducing an increase in orthohydrogen equivalent to back conversion into the circulation system. This method has the potential to contribute to the in-situ diagnostic catalyst characterization and to the calculation of neutron performance that depends on the ortho-to-parahydrogen ratio.

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.

Performance evaluation of a developed orifice type heater for thermal compensation control at J-PARC cryogenic hydrogen system

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

IOP Conference Series; Materials Science and Engineering, 101, p.012108_1 - 012108_8, 2015/12

https://doi.org/10.1088/1757-899X/101/1/012108

Supercritical hydrogen with a temperature of less than 20 K and a pressure of 1.5 MPa is used as moderator material at J-PARC. Total nuclear heating of 3.75 kW is generated by three moderators for a 1-MW proton beam operation. We have developed an orifice-type high-power heater for thermal compensation to mitigate hydrogen pressure fluctuation caused by the abrupt huge heat load and to reduce the fluctuation in the temperature of the supply hydrogen to less than 0.25 K. Through a performance test, we confirmed that the developed orifice-type heater could be heated uniformly and showed fast response, as expected. Furthermore, a simulation model that can describe heater behaviors has been established on the basis of the experimental data. The heater control approach was studied using the aforementioned heater simulation model and a dynamic simulation code developed by the authors.

Transient heat transfer from a wire to a forced flow of subcooled liquid hydrogen passing through a vertically-mounted pipe

Tatsumoto, Hideki; Shirai, Yasuyuki*; Shiotsu, Masahiro*; Naruo, Yoshihiro*; Kobayashi, Hiroaki*; Nonaka, Satoshi*; Inatani, Yoshifumi*

IOP Conference Series; Materials Science and Engineering, 101, p.012177_1 - 012177_8, 2015/12

https://doi.org/10.1088/1757-899X/101/1/012177

Transient heat transfers from PtCo wire heaters inserted into vertically-mounted pipes, through which forced flow subcooled liquid hydrogen was passed, were measured by increasing the exponential heat input with various time periods at a pressure of 0.7 MPa and inlet temperature of 21 K. The flow velocities ranged from 0.3 to 7 m/s. The PtCo wire heaters had a diameter of 1.2 mm and lengths of 60 mm, 120 mm and 200 mm and were inserted into the pipes with diameters of 5.7mm, 8.0 mm, and 5.0 mm, respectively. With increase in the heat flux to the onset of nucleate boiling, surface temperature increased along the curve predicted by the Dittus-Boelter correlation for longer period, where it can be almost regarded as steady-state. For shorter period, the heat transfer became higher than the Dittus-Boelter correlation. In nucleate boiling regime, the heat flux steeply increased to the transient critical heat flux (CHF), which became higher for shorter period. Effect of flow velocity, period, and heated geometry on the transient CHF was clarified.

Development of a partitionable accumulator with pressure tolerance for the cryogenic hydrogen system at J-PARC

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

Physics Procedia, 67, p.123 - 128, 2015/00

https://doi.org/10.1016/j.phpro.2015.06.022

A partitionable accumulator with pressure tolerance has been developed to achieve a stable long-term operation for the J-PARC cryogenic hydrogen system. The accumulator has a bellows structure to spontaneously change the volume according to the pressure fluctuation, which is mainly caused by the proton beam operation. The developed accumulator had been installed in 2014 and uniformly expands and contracts with no hysteresis. It is confirmed through a 300-kW proton beam operation that the pressure rise agrees with the predicted value and becomes lower than that for the previous one. It is confirmed that the performance satisfies the requirements.

Development of an experimental system for characterization of high-temperature superconductors cooled by liquid hydrogen under the external magnetic field

Tatsumoto, Hideki; Shirai, Yasuyuki*; Shiotsu, Masahiro*; Naruo, Yoshihiro*; Kobayashi, Hiroaki*; Inatani, Yoshifumi*

Journal of Physics; Conference Series, 507(2), p.022042_1 - 022042_4, 2014/05

https://doi.org/10.1088/1742-6596/507/2/022042

An experimental system has been developed to investigate electro-magnetic properties of high-Tc superconductors cooled by liquid hydrogen under the external magnetic field of up to 7 T. A LH cryostat with a LH inventory of 61 L is concentrically mounted on the inside of a LHe cryostat to cool a NbTi superconducting magnet. The experimental system is installed in an explosion-proof room and explosion proof electrical devices are used. The current leads are covered with an enclosure filled with nitrogen gas. A remote control system has been developed to maintain safety distance. Furthermore, the effects of stray magnetic field on the existing and the new devices are investigated and electro-magnetic shielding panels and enclosure made of iron were designed using ANSYS analysis. It is confirmed through the cryogenic test that the experimental system meets the design requirements.

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.

Forced convection heat transfer from a wire inserted into a vertically-mounted pipe to liquid hydrogen flowing upward

Tatsumoto, Hideki; Shirai, Yasuyuki*; Shiotsu, Masahiro*; Naruo, Yoshihiro*; Kobayashi, Hiroaki*; Inatani, Yoshifumi*

Journal of Physics; Conference Series, 568, p.032017_1 - 032017_5, 2014/00

https://doi.org/10.1088/1742-6596/568/3/032017

Forced convection heat transfer from a PtCo wire with a length of 120 mm and a diameter of 1.2 mm that was inserted into a vertically-mounted pipe with a diameter of 8.0 mm to liquid hydrogen flowing upward was measured with a quasi-steady increase of a heat generation rate for wide ranges of flow rate under saturated conditions. The pressures were varied from 0.4 MPa to 1.1 MPa. The non-boiling heat transfer characteristic agrees with that predicted by Dittus-Boelter correlation. The critical heat fluxes are higher for higher flow rates and lower pressures. Effect of Weber number on the CHF was clarified and a CHF correlation that can describe the experimental data is derived based on our correlation for a pipe.

Dynamic behavior of the cryogenic hydrogen system using only a heater control

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

AIP Conference Proceedings 1434, p.391 - 398, 2012/06

https://doi.org/10.1063/1.4706944

A pressure control system, which consists of a heater for the thermal compensation and a cryogenic accumulator with a bellows acting as a volume controller, is prepared to mitigate a pressure fluctuation caused by the sudden heat load of kW-order. A stable operation of the cryogenic hydrogen system has been conducted since May 2008. However, a major cryogenic accumulator failure was encountered during a short maintenance period, in February 2010. In order to resume the 120-kW proton beam operation as soon as possible, we studied the temporary operational approach without using the cryogenic accumulator because the heat load was relatively low and improved a part of the hydrogen loop temporarily. It was confirmed through an on-beam commissioning that the pressure rise could be mitigated below the allowable value of 100 kPa using only the heater control. The 120-kW proton beam operation was successfully resumed two months later.

Effect of a heated pipe length on DNB heat flux in forced flow of liquid hydrogen

Tatsumoto, Hideki; Shirai, Yasuyuki*; Shiotsu, Masahiro*; Hata, Koichi*; Naruo, Yoshihiro*; Kobayashi, Hiroaki*; Inatani, Yoshifumi*; Narita, Norihiko*

Proceedings of 24th International Cryogenic Engineering Conference (ICEC 24) and International Cryogenic Materials Conference 2012 (ICMC 2012) (CD-ROM), p.157 - 160, 2012/05

The heat transfer in a forced flow of saturated liquid hydrogen was measured using vertically-mounted heated pipes with an inner diameter d of 6.0 mm and lengths L of 50, 100, 200 and 250 mm for wide ranges of flow velocity and pressure. The heat fluxes at departure from nucleate boiling were higher for higher flow velocities, lower pressures and shorter L. The effect of L on the DNB heat flux was clarified and could be described by the modified authors' DNB correlation.