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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：0.00(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.
Nauchi, Yasushi*; Nomi, Takayoshi; Suzuki, Risa; Kosuge, Yoshihiro*; Shiba, Tomooki; Takada, Akira*; Kaburagi, Masaaki; Okumura, Keisuke
Proceedings of International Topical Workshop on Fukushima Decommissioning Research (FDR2022) (Internet), 4 Pages, 2022/10
Shiba, Tomooki; Kaburagi, Masaaki; Nomi, Takayoshi; Suzuki, Risa; Kosuge, Yoshihiro*; Nauchi, Yasushi*; Takada, Akira*; Nagatani, Taketeru; Okumura, Keisuke
Proceedings of International Topical Workshop on Fukushima Decommissioning Research (FDR2022) (Internet), 3 Pages, 2022/10
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：0.00(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.
Nagatani, Taketeru; Komeda, Masao; Shiba, Tomooki; Nauchi, Yasushi*; Maeda, Makoto; Sagara, Hiroshi*; Kosuge, Yoshihiro*; Kureta, Masatoshi; Tomikawa, Hirofumi; Okumura, Keisuke; et al.
Energy Procedia, 131, p.258 - 263, 2017/12
Times Cited Count：10 Percentile：97.40(Energy & Fuels)Nagatani, Taketeru; Komeda, Masao; Shiba, Tomooki; Maeda, Makoto; Nauchi, Yasushi*; Sagara, Hiroshi*; Kosuge, Yoshihiro*; Kureta, Masatoshi; Tomikawa, Hirofumi; Okumura, Keisuke; et al.
Proceedings of INMM 57th Annual Meeting (Internet), 10 Pages, 2016/07
Nauchi, Yasushi*; Takezawa, Hiroki*; Tonoike, Kotaro
Nihon Genshiryoku Gakkai-Shi ATOMO
, 58(4), p.247 - 252, 2016/04
no abstracts in English
Ueda, Nobuyuki*; Fukushima, Masahiro; Okajima, Shigeaki; Takeda, Toshikazu*; Kitada, Takanori*; Nauchi, Yasushi*; Kinoshita, Izumi*; Matsumura, Tetsuo*
Proceedings of 2009 International Congress on Advances in Nuclear Power Plants (ICAPP '09) (CD-ROM), p.9493_1 - 9493_9, 2009/05
A series of critical experiments were carried out in the JAEA fast critical facility (FCA) named FCA XXIII cores with placing emphases on the reflector reactivity worth and the sodium void reactivity which are especially important from the view point of safety features of the 4S. The analyses of those physics mockup experiments have been carried out by the neutron transport calculation methods with continuous energy Monte Carlo code MVP and 70 energy-group discrete ordinate P0-S8 transport code DANTSYS using libraries processed from JENDL-3.3 data file. The results showed that combination of the stochastic and deterministic transport calculation methods (Monte Carlo and Sn) provided good prediction bases for criticality, reflector worth, sodium void reactivity, reaction rate ratios and absorber reactivity worth for the 4S nuclear design.
Okumura, Keisuke; Nauchi, Yasushi*; Suzuki, Risa; Nomi, Takayoshi; Shiba, Tomooki; Kaburagi, Masaaki; Takada, Akira*; Kosuge, Yoshihiro*; Nagatani, Taketeru
no journal, ,
no abstracts in English
Sato, Shunsuke*; Nauchi, Yasushi*; Hayakawa, Takehito; Kimura, Yasuhiko; Suyama, Kenya
no journal, ,
The ray spectrum measurement was conducted for a sample taken from a PWR lead used assembly and photon spectrum data for higher energy region than usual case was obtained. Burnup calculation adopting MVP-BURN code was carried out for the sample and the agreement between experimental data and the calculation results was confirmed.
detectorKaburagi, Masaaki; Shiba, Tomooki; Okumura, Keisuke; Nauchi, Yasushi*; Suzuki, Risa; Nomi, Takayoshi; Nagatani, Taketeru; Takada, Akira*; Kosuge, Yoshihiro*
no journal, ,
The passive gamma-ray spectroscopy for plutonium nuclear fuels was performed using a small volume CeBr
detector specific to high dose-rate measurements. This presentation reports that the wide energy range of gamma-ray spectra was obtained by the spectroscopy, and the energy range covered the principal gamma-decay lines of 59.5 keV emitted from 
Am and 2615 keV emitted from 
Tl, which is a descendant nuclide of 
Pu, comparing the measurements using HPGe.
Nauchi, Yasushi*; Nomi, Takayoshi; Suzuki, Risa; Kosuge, Yoshihiro*; Shiba, Tomooki; Takada, Akira*; Kaburagi, Masaaki; Okumura, Keisuke
no journal, ,
no abstracts in English
Kaburagi, Masaaki; Shiba, Tomooki; Nomi, Takayoshi; Suzuki, Risa; Kosuge, Yoshihiro*; Nauchi, Yasushi*; Okumura, Keisuke
no journal, ,
no abstracts in English
Nagatani, Taketeru; Komeda, Masao; Shiba, Tomooki; Nauchi, Yasushi*; Sagara, Hiroshi*; Kosuge, Yoshihiro*; Okumura, Keisuke; Maeda, Makoto; Toh, Yosuke; Hori, Keiichiro
no journal, ,
Okumura, Keisuke; Sato, Wakaei*; Nagatani, Taketeru; Komeda, Masao; Shiba, Tomooki; Nauchi, Yasushi*; Takada, Akira*
no journal, ,
In order to contribute to the development of quantitative technology for the nuclear fuel materials in the fuel debris at the Fukushima Daiichi Nuclear Power Station, we examined the evaluation method and prediction accuracy of the nuclear fuel material quantity in the fuel debris based on the detector responces of the non-destructive assay simulation and on the fuel burnup calculation results.
Nagatani, Taketeru; Komeda, Masao; Shiba, Tomooki; Nauchi, Yasushi*; Sagara, Hiroshi*; Kosuge, Yoshihiro*; Miyaji, Noriko; Okumura, Keisuke
no journal, ,
no abstracts in English
Miyaji, Noriko; Takada, Akira*; Iwafuchi, Junichi; Tomikawa, Hirofumi; Shiba, Tomooki; Okumura, Keisuke; Nagatani, Taketeru; Nauchi, Yasushi*
no journal, ,
Nuclear materials in fuel debris need to be properly managed in order to assure to the international and national communities that no nuclear materials have been diverted. In order to provide this assurance, specific measures appropriate to the characteristics of the fuel debris are required. There is experience at managing fuel debris in similar situations, as it was the case of the partial meltdown at the TMI-2 in the US. The nuclear material in the fuel debris retrieved from the reactor was quantified in order to fulfill domestic law requirements in the US. NDA, DA, and visual observation were applied to the residual fuel in the reactor. On that specific accident, IAEA safeguards were not applied because the USA is a nuclear weapon state and therefore this power plant was not inspected by the IAEA. Nuclear material accounting (NMA)is an important measure to manage nuclear materials for states under IAEA safeguards. In this presentation a report on NMA as a measure to manage fuel debris will be discussed.
Okumura, Keisuke; Terashima, Kenichi; Nagatani, Taketeru; Komeda, Masao; Shiba, Tomooki; Nauchi, Yasushi*; Takada, Akira*; Kosuge, Yoshihiro*
no journal, ,
no abstracts in English
Nauchi, Yasushi*; Kosuge, Yoshihiro*; Nomi, Takayoshi; Suzuki, Risa; Nagatani, Taketeru; Shiba, Tomooki; Takada, Akira*; Kaburagi, Masaaki; Okumura, Keisuke
no journal, ,
no abstracts in English
Suzuki, Risa; Nomi, Takayoshi; Nagatani, Taketeru; Shiromo, Hideo; Shiba, Tomooki; Kaburagi, Masaaki; Okumura, Keisuke; Kosuge, Yoshihiro*; Takada, Akira*; Nauchi, Yasushi*
no journal, ,
no abstracts in English
