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methodNauchi, Yasushi*; Sato, Shunsuke*; Hayakawa, Takehito*; Kimura, Yasuhiko; Suyama, Kenya; Kashima, Takao*; Futakami, Kazuhiro*
Nuclear Instruments and Methods in Physics Research A, 1050, p.168109_1 - 168109_9, 2023/05
Times Cited Count：0 Percentile：0.02(Instruments & Instrumentation)Measurement of neutrons from spent nuclear fuel is performed in this study using the H method, which detects 2.223 MeV 
rays from neutron capture reaction of hydrogen using a highly pure germanium (HPGe) detector. The detection of the 2.223 MeV ray is affected by intense ray emission from fission products (FPs) because the emission rate of rays from the FP is seven orders of magnitude higher than the emission rate of neutrons. To shield the intense ray from the FP, the HPGe detector is placed off the axis of a collimator, whereas a polyethylene block is placed on the axis. In this geometry, the detector is shielded from the intense rays from the FP, but the detector can measure 2.223 MeV rays from the H reactions in the polyethylene block. The measured count rate of the 2.223 MeV rays is consistent with the expected rate within the statistical error, which is calculated based on the nuclide composition, which is primary 
Cm, estimated via depletion and decay calculations. Accordingly, the H method is considered feasible to quantify the number of neutron leakage from spent nuclear fuel assembly, which is applicable to certify burn up of the assembly.
Cs activity in spent nuclear fuel with calculated detector response functionSato, Shunsuke*; Nauchi, Yasushi*; Hayakawa, Takehito*; Kimura, Yasuhiko; Kashima, Takao*; Futakami, Kazuhiro*; Suyama, Kenya
Journal of Nuclear Science and Technology, 60(6), p.615 - 623, 2022/06
Times Cited Count：0 Percentile：0.01(Nuclear Science & Technology)A new non-destructive method for evaluating Cs activity in spent nuclear fuels was proposed and experimentally demonstrated for physical measurements in burnup credit implementation. Cs activities were quantified using gamma ray measurements and numerical detector response simulations without reference fuels, in which Cs activities are well known. Fuel samples were obtained from a lead use assembly (LUA) irradiated in a commercial pressurized water reactor (PWR) up to 53 GWd/t. Gamma rays emitted from the samples were measured using a bismuth germinate (BGO) scintillation detector through a collimator attached to a hot cell. The detection efficiency of gamma rays with the detector was calculated using the PHITS particle transport calculation code considering the measurement geometry. The relative activities of 
Cs, Cs, and 
Eu in the sample were measured with a high-purity germanium (HPGe) detector for more accurate simulations of the detector response for the samples. The absolute efficiency of the detector was calibrated by measuring a standard gamma ray source in another geometry. Cs activity in the fuel samples was quantified using the measured count rate and detection efficiency. The quantified Cs activities agreed well with those estimated using the MVP-BURN depletion calculation code.
Shirasu, Noriko; Kuramoto, Kenichi; Nakano, Yoshihiro; Yamashita, Toshiyuki; Kimura, Yasuhiko; Nihei, Yasuo; Ogawa, Toru
Journal of Nuclear Materials, 376(1), p.88 - 97, 2008/05
Times Cited Count：13 Percentile：64.63(Materials Science, Multidisciplinary)The concept of the rock-like oxide (ROX) fuel has been developed for the annihilation of excess plutonium in light water reactors. Irradiation tests and post-irradiation examinations were carried out on candidate ROX fuels. The ternary fuel of YSZ-spinel-corundum system, the single-phase fuels of YSZ, the particle dispersed fuels of YSZ in spinel or corundum matrix, and the blended fuels of YSZ and spinel or corundum matrix were fabricated and submitted to irradiation tests. The fuels containing spinel showed chemical instabilities with the vaporization of MgO component, which caused fuel restructuring. The swelling behavior was improved with the particle-dispersed fuels. However, the particle-dispersed fuels showed higher fractional gas release (FGR) than blended type fuels. The FGR of YSZ single-phase fuels were comparable to what would be expected for UO
fuels. The YSZ single-phase fuel showed the best irradiation performance among the ROX fuels investigated.
Onuki, Toshihiko; Aoyagi, Hisao*; Kitatsuji, Yoshihiro; Samadfam, M.; Kimura, Yasuhiko; Purvis, O. W.*
Journal of Environmental Radioactivity, 77(3), p.339 - 353, 2004/08
Times Cited Count：16 Percentile：34.04(Environmental Sciences)no abstracts in English
Yamashita, Toshiyuki; Kuramoto, Kenichi; Shirasu, Noriko; Nakano, Yoshihiro; Akie, Hiroshi; Nagashima, Hisao; Kimura, Yasuhiko; Omichi, Toshihiko*
Journal of Nuclear Materials, 320(1-2), p.126 - 132, 2003/07
Times Cited Count：10 Percentile：56.43(Materials Science, Multidisciplinary)Two irradiation tests on the rock-like oxide (ROX) fuels, small disk-shape fuel targets and pellet-type fuels, were performed in order to clarify in-pile irradiation stabilities. Swelling, fractional fission gas release (FGR) and phase change were examined by puncture test, profilometry and ceramography. YSZ single-phase fuel showed an excellent irradiation behavior, ie. low fission gas release (less than 3%), negligible swelling and no appreciable restructuring. The particle dispersed fuels showed lower swelling and higher fission gas release than those of mechanically blended fuels. Spinel decomposition and subsequence restructuring in the spinel matrix fuels was observed for the first time in the present investigation. It would be possible to reduce the FGR of the spinel matrix fuels, if the maximum fuels temperature is limited below 1700 K where neither spinel decomposition nor restructuring was observed. Damaged area of spinel matrix due to fission fragment irradiation seemed to be confined to thin layers around the surface of YSZ particles.
Iwai, Takashi; Nakajima, Kunihisa; Kikuchi, Hironobu; Nagashima, Hisao; Kimura, Yasuhiko; Matsui, Hiroki; Arai, Yasuo
JAERI-Research 2002-038, 69 Pages, 2003/01
JAERI-Research-2002-038.pdf:12.46MB
Uranium-plutonium mixed carbide and nitiride fuel pins were fabricated in JAERI and irradiated at fast test rector JOYO based on the JAERI-JNC joint research program. The results of non-destructive and destructive post irradiation examinations cariied out at JNC were reported elsewhere. This report summarizes the results of destructive post irradiation examinations of (U,Pu)C and (U,Pu)N fuel pins carried out at JAERI.
Shirasu, Noriko; Yamashita, Toshiyuki; Kanazawa, Hiroyuki; Kimura, Yasuhiko; Sudo, Kenji; Magara, Masaaki; Inagawa, Jun; Kono, Nobuaki; Nakahara, Yoshinori
JAERI-Research 2001-018, 23 Pages, 2001/03
JAERI-Research-2001-018.pdf:1.48MB
no abstracts in English
Iwai, Takashi; Nakajima, Kunihisa; Kikuchi, Hironobu; Kimura, Yasuhiko; Nagashima, Hisao; Sekita, Noriaki; Arai, Yasuo
JAERI-Research 2000-010, p.110 - 0, 2000/03
JAERI-Research-2000-010.pdf:20.61MB
no abstracts in English
Iwai, Takashi; Nakajima, Kunihisa; Kikuchi, Hironobu; Kimura, Yasuhiko; Kanaitsuka, Fumio; Sekita, Noriaki; Arai, Yasuo
JAERI-Research 2000-009, p.36 - 0, 2000/03
JAERI-Research-2000-009.pdf:6.16MB
no abstracts in English
Onuki, Toshihiko; Samadfam, M.; Kimura, Yasuhiko; Kitatsuji, Yoshihiro; Aoyagi, Hisao; Purvis, O. W.*
Proceedings of the International Workshop on Distribution and Speciation of Radionuclides in the Environment, p.174 - 180, 2000/00
no abstracts in English
Yanagisawa, Kazuaki; Omichi, Toshihiko*; Shirasu, Noriko; Yamashita, Toshiyuki; ; Onozawa, Atsushi; ; Kanazawa, Hiroyuki; Kanaitsuka, Fumio; Amano, Hidetoshi
JAERI-Tech 99-044, 46 Pages, 1999/05
no abstracts in English
Iwai, Takashi; Arai, Yasuo; Nakajima, Kunihisa; Kimura, Yasuhiko; ;
JAERI-Research 96-066, 26 Pages, 1996/12
JAERI-Research-96-066.pdf:1.91MB
no abstracts in English
Iwai, Takashi; Arai, Yasuo; Nakajima, Kunihisa; Kimura, Yasuhiko; ;
JAERI-Research 96-065, 47 Pages, 1996/12
JAERI-Research-96-065.pdf:4.1MB
no abstracts in English
Yanagisawa, Kazuaki; Soyama, Kazuhiko; Ichikawa, Hiroki; ; Hoshino, Osamu; ; ; ; Kanazawa, Hiroyuki; Kimura, Yasuhiko; et al.
JAERI-M 91-114, 67 Pages, 1991/08
no abstracts in English
fuel under reactivity initiated accident conditionsYanagisawa, Kazuaki; Mimura, Hideaki; Kimura, Yasuhiko
JAERI-M 90-164, 64 Pages, 1990/09
no abstracts in English
Kamada, Yutaka; Yoshino, Ryuji; ; Ozeki, Takahisa; Kawasaki, Kozo; Hiratsuka, Hajime; Miyo, Yasuhiko; Kimura, Haruyuki; Nishitani, Takeo; Yoshida, Hidetoshi; et al.
JAERI-M 89-050, 33 Pages, 1989/05
no abstracts in English
Kaminaga, Norihisa; Nihei, Yasuo; Kimura, Yasuhiko; Kikuchi, Hiroyuki; Takahashi, Ishio; Matsuura, Takanobu; Suzuki, Kazuhiro; Kitamura, Toshikatsu; Sato, Yasuo; Hatanaka, Kazuo*
no journal, ,
no abstracts in English
Sato, Atsushi; Shiina, Hidenori; Kataoka, Kentaro*; Otomo, Susumu*; Kakiuchi, Kazuo*; Ohira, Koichi*; Itagaki, Noboru*; Kaminaga, Norihisa; Kimura, Yasuhiko; Suzuki, Kazuhiro; et al.
no journal, ,
Obata, Hiroki; Toyokawa, Takuya; Tomita, Takeshi; Kimura, Yasuhiko
no journal, ,
Hydrogen absorption to the fuel cladding is increase on the high burn-up fuel. The concentration of absorbed hydrogen causes the cladding embrittlement which might become the origination of fractures of the cladding. Therefore, it's important to measure the hydrogen volume in the cladding to estimate the safety margin of the irradiated cladding. In the previous method of hot vacuum extraction, the hydrogen is released and measured as the melting condition of the cladding. It cannot be evaluated the hydrogen volume only in the cladding metal phase. The hydrogen absorption in the cladding metal phase is strongly-correlated the cladding embrittlement. The two-step heating method has the benefit to measure the hydrogen in metal phase and oxide layer separately. The measuring method including the extraction temperature condition using unirradiated cladding will be reported.
Obata, Hiroki; Toyokawa, Takuya; Tomita, Takeshi; Kimura, Yasuhiko
no journal, ,
The amount of hydrogen absorbed to the fuel cladding increases by extended burnup fuel. The absorbed hydrogen that exceed solid solubility limit precipitates as the hydride phase. The high concentration of hydride causes the fuel cladding embrittlement which might become the origination of fractures of the cladding. Therefore, it is important to measure the hydrogen content in the cladding to estimate the safety margin of the irradiated cladding. Hydrogen is absorbed not only in the cladding metal phase, but in the oxide layer. To evaluate the embrittlement of the cladding, it is necessary to measure the hydrogen content in the cladding metal phase and oxide layer separately. Therefore, the two-step heating method can measure the amount of hydrogen in the metal phase and the oxide layer separately. This paper shows the technical review of measuring method including the technique for the determination of extraction temperature.
