Technical note for the cavitation damage inspection for interior surface of the mercury target vessel, 1; Development of specimen cutting machine for remote handling

Naoe, Takashi; Kinoshita, Hidetaka; Wakui, Takashi; Kogawa, Hiroyuki; Haga, Katsuhiro

JAEA-Technology 2022-018, 43 Pages, 2022/08

JAEA-Technology-2022-018.pdf:7.84MB

In the liquid mercury target system for the pulsed spallation neutron source of Materials and Life science experimental Facility (MLF) at the Japan in the Japan Proton Accelerator Research Complex (J-PARC), cavitation that is generated by the high-energy proton beam-induced pressure waves, resulting severe erosion damage on the interior surface of the mercury target vessel. The erosion damage is increased with increasing the proton beam power, and has the possibility to cause the leakage of mercury by the penetrated damage and/or the fatigue failure originated from erosion pits during operation. To achieve the long term stable operation under high-power proton beam, the mitigation technologies for cavitation erosion consisting of surface modification on the vessel interior surface, helium gas microbubble injection, double-walled beam window structure has been applied. The damage on interior surface of the vessel is never observed during the beam operation. Therefore, after the target operation term ends, we have cut out specimen from the target nose of the target vessel to inspect damaged surface in detail for verification of the cavitation damage mitigation technologies and lifetime estimation. We have developed the techniques of specimen cutting out by remote handling under high-radiation environment. Cutting method was gradually updated based on experience in actual cutting for the used target vessel. In this report, techniques of specimen cutting out for the beam entrance portion of the target vessel in high-radiation environment and overview of the results of specimen cutting from actual target vessels are described.

Primary knock-on atoms for accelerator facilities; Simulations and experimental design

Tsai, P.-E.; Iwamoto, Yosuke; Hagiwara, Masayuki*

Transactions of the American Nuclear Society, 121(1), p.13 - 16, 2019/11

The importance of PKA characteristics to radiation damage assessment for proton accelerators has been demonstrated in the paper by the PHITS simulations. In order to obtain accurate results of displacement cross section calculated by PHITS, it is therefore critical to have the physics models implemented in PHITS be properly validated by experimental data. With the new measurement system, which has been being developed here at JAEA, it is expected to provide experimental PKA data with low measurement thresholds and good mass resolutions. The test result we obtained at CYRIC, Tohoku University, for the - gas ionization chamber as a part of the new measurement system was very promising. We were able to successfully distinguish C, B, Be, Li, and He elements with threshold energies lower than 1 MeV/nucleon in the configuration of 70-MeV proton beam and 920-nm thick C target. More experiments and tests shall continue in the future with heavier targets and higher proton beam energies.

Study on magnetic property change on neutron irradiated austenitic stainless steel

Nemoto, Yoshiyuki; Oishi, Makoto; Ito, Masayasu; Kaji, Yoshiyuki

Nihon Hozen Gakkai Dai-12-Kai Gakujutsu Koenkai Yoshishu, p.105 - 112, 2015/07

Authors previously reported that Eddy current method and AC magnetization method have potential to be applied for development of diagnostic technics to detect the sign of material degradation before cracking on the austenitic stainless steels used as structural material in nuclear power plants. In typical austenitic stainless steels such as type304, magnetic ferrite phase would exist in the alloy before irradiation, and it is concerned to disturb the magnetic measurement on irradiated material. Magnetic measurements were conducted in this work on type304 austenitic stainless steel specimens irradiated up to different doses. In addition, microstructure observation was conducted on the area including grain boundary to discuss the correlation of magnetization on irradiated austenitic stainless alloy and grain boundary cracking. Obtained magnetic data on irradiated type304 stainless steel were seen clearly different from that on un-irradiated specimen, and showed positive correlation with radiation dose, therefore it was thought that magnetic measurement technics can be applied for the material which contains certain quantity of ferrite phase before irradiation. In the microstructural observation, magnetic phase (FeNi) formation along the grain boundary was revealed.

Investigation of single-event damages on silicon carbide (SiC) power MOSFETs

Mizuta, Eiichi*; Kuboyama, Satoshi*; Abe, Hiroshi; Iwata, Yoshiyuki*; Tamura, Takashi*

IEEE Transactions on Nuclear Science, 61(4), p.1924 - 1928, 2014/08

https://doi.org/10.1109/TNS.2014.2336911

An Irradiation test of heat-resistant ceramic composite materials, 2; Interim report on post-irradiation examinations of the second and third preliminary test, 98M-41A, 99M-30A

Baba, Shinichi; Nemoto, Makoto*; Sozawa, Shizuo; Yamaji, Masatoshi*; Ishihara, Masahiro; Sawa, Kazuhiro

JAERI-Tech 2005-055, 157 Pages, 2005/09

JAERI-Tech-2005-055.pdf:19.06MB

The Japan Atomic Energy Research Institute (JAERI) has been carrying out the research on radiation damage mechanism of heat-resistant ceramics composite materials, as one of the subjects of the innovative basic research on high temperature engineering using the High Temperature Engineering Test Reactor (HTTR). A series of preliminary irradiation tests is being made using the Japan Materials Testing Reactor (JMTR). The present report describes results of post-irradiation examinations so far on specimens irradiated in the second and third capsule, designated 98M-41A and 99M-30A, to fast neutron fluences of 1.010m(E1MeV) at temperatures of 973K-1173K and 1273K-1473K. The PIE were conducted as the fundamental statistics index of the diametral dimensions for irradiated specimen, irradiation induced dimensional change rate and thermal expansion rate.

Failure probability analysis on mercury target vessel

Ishikura, Shuichi*; Shiga, Akio*; Futakawa, Masatoshi; Kogawa, Hiroyuki; Sato, Hiroshi; Haga, Katsuhiro; Ikeda, Yujiro

JAERI-Tech 2005-026, 65 Pages, 2005/03

JAERI-Tech-2005-026.pdf:2.86MB

Failure probability analysis was carried out to estimate the lifetime of the mercury target which will be installed into the JSNS (Japan spallation neutron source) in J-PARC (Japan Proton Accelerator Research Complex). The lifetime was estimated as taking loading condition and materials degradation into account. Considered loads imposed on the target vessel were the static stresses due to thermal expansion and static pre-pressure on He-gas and mercury and the dynamic stresses due to the thermally shocked pressure waves generated repeatedly at 25 Hz. Materials used in target vessel will be degraded by the fatigue, neutron and proton irradiation, mercury immersion and pitting damages, etc. The imposed stresses were evaluated through static and dynamic structural analyses. The material-degradations were deduced based on published experimental data. As results, it was quantitatively confirmed that the failure probability for the lifetime expected in the design is very much lower, 10 in the safety hull, meaning that it will be hardly failed during the design lifetime. On the other hand, the beam window of mercury vessel suffered with high-pressure waves exhibits the failure probability of 12%. It was concluded, therefore, that the leaked mercury from the failed area at the beam window is adequately kept in the space between the safety hull and the mercury vessel to detect mercury-leakage sensors.

EPR studies of 5-bromouracil crystal after irradiation with X-rays in the bromine K-edge region

Yokoya, Akinari; Takakura, Kaoru*; Watanabe, Ritsuko; Akamatsu, Ken*; Ito, Takashi*

Radiation Research, 162(4), p.469 - 473, 2004/10

https://doi.org/10.1667/RR3230

Radicals induced in a single crystal of 5-bromouracil (BrUra) by synchrotron soft X-rays in the Br K-edge region (13.461-13482 keV) were investigated using the X-band EPR method. The crystal was irradiated at three peak energies in the absorption spectrum at room temperature or at 80K. A hydrogen abstraction radical derived from N1 atom of the pyrimidine ring was commonly observed for all of the energies used, though with some variation in quantity. Similar characteristics were also observed in the EPR signal for the off-K-edge low energy (13.42 keV) and when Co -ray irradiation was employed as the reference. When irradiated at 80K, a much larger exposure (roughly 10 times) of soft X-rays was needed to obtain the same signal intensity as that observed at room temperature. EPR signals were not detectable with g-irradiation at liquid nitrogen temperature.

Present status of the liquid lithium target facility in the international fusion materials irradiation facility (IFMIF)

Nakamura, Hiroo; Riccardi, B.*; Loginov, N.*; Ara, Kuniaki*; Burgazzi, L.*; Cevolani, S.*; Dell'Ocro, G.*; Fazio, C.*; Giusti, D.*; Horiike, Hiroshi*; et al.

Journal of Nuclear Materials, 329-333(1), p.202 - 207, 2004/08

https://doi.org/10.1016/j.jnucmat.2004.04.013

International Fusion Materials Irradiation Facility (IFMIF), being developed by EU, JA, RF and US, is a deuteron-lithium (Li) reaction neutron source for fusion materials testing. In the end of 2002, 3 year Key Element technology Phase (KEP) to reduce the key technology risk factors has been completed. This paper describes these KEP tasks results. To evaluate Li flow characteristics, a water and Li flow experiments have been done. To develop Li purification system, evaluation of nitrogen and tritium gettering materials have been done. Conceptual design of remote handling and basic experiment have been donde. In addition, safety analysis and diganostics design have been done. In the presentation, the latest design and future prospects will be also summarized.

Damage evaluation techniques for FBR and LWR structural materials based on magnetic and corrosion properties along grain boundaries

Hoshiya, Taiji*; Takaya, Shigeru*; Ueno, Fumiyoshi; Nemoto, Yoshiyuki; Nagae, Yuji*; Miwa, Yukio; Abe, Yasuhiro*; Omi, Masao; Tsukada, Takashi; Aoto, Kazumi*

Transactions of the Materials Research Society of Japan, 29(4), p.1687 - 1690, 2004/06

JAERI and JNC have begun the cooperative research of evaluation techniques of structural material degradation in FBR and LWR, which based on magnetic and corrosion properties along grain boundaries. Magnetic method has been proposed as the one of the non-destructive detection techniques on the early stage of creep-damage before crack initiation for aged structural materials of FBRs. The effects of applied stress on natural magnetization were investigated on paramagnetic stainless steels having creep-damages. On the other hand, corrosion properties and magneto-optical characteristics of ion-irradiated stainless steels in the vicinity of grain boundaries were estimated by AFM and Kerr effect microscope, respectively. These degradations were induced by changes in characteristics in the vicinity of grain boundaries. It is found that the initial level of progressing process of damage can detect changes in magnetic and corrosion properties along grain boundaries of aged and degraded nuclear plants structural materials.

Estimation of tritium permeation through reduced-activation ferritic steel at IFMIF target backwall damaged by neutron irradiation

Matsuhiro, Kenjiro; Ando, Masami; Nakamura, Hiroo; Takeuchi, Hiroshi

JAERI-Research 2004-003, 12 Pages, 2004/03

JAERI-Research-2004-003.pdf:0.85MB

The effect of neutron irradiation damage on tritium permeation through reduced-activation ferritic steel (F82H) at IFMIF target backwall has been estimated. From the results, it has been found that the effective diffusion coefficient of hydrogen in F82H will decrease by 10 % to 20 % under neutron irradiation. Therefore, the amount of tritium permeation for several hundred seconds at the beginning of permeation will be smaller than 80 % to 90 % of that before neutron irradiation. The amount of tritium permeation of F82H at IFMIF target backwall is 1.3x10 g/d (4.7x10 Bq/d). It is 30 times larger than that of 316SS, and is about 8 % of tritium permeation at main loop of IFMIF.