Yokoyama, Kenji; Maruyama, Shuhei; Taninaka, Hiroshi; Oki, Shigeo
JAEA-Data/Code 2021-019, 115 Pages, 2022/03
In JAEA, several versions of unified cross-section set for fast reactors have been developed so far; we have developed a new unified cross-section set ADJ2017R, which is an improved version of the unified cross-section setADJ2017 for fast reactors. The unified cross-section set is used for reflecting information of C/E values (analysis / experiment values) obtained by integral experiment analyses in reactor core design via the cross-section adjustment methodology; the values are stored in the standard database for FBR core design. In the methodology, the cross-section set is adjusted by integrating the information such as uncertainty (covariance) of nuclear data, uncertainty of integral experiment / analysis, sensitivity of integral experiment with respect to nuclear data. ADJ2017R basically has the same performance as ADJ2017, but we conducted an additional investigation on ADJ2017 and revised the following two points. The first is to unify the evaluation method of the correlation coefficient of uncertainty caused by experiments (hereinafter referred to as the experimental correlation coefficient). Because it was found that the common uncertainty used in the evaluation of the experimental correlation coefficient was evaluated by two different methods, the experimental correlation coefficients were revised for all experimental data, and the evaluation method was unified. The second is the review of the integral experiment data used for the cross-section adjustment calculation. It was found that one of the experimental values of composition ratio after irradiation of the Am-243 sample has a problem in uncertainty evaluation because its experimental uncertainty is extremely small compared to the others. The cross-section adjustment calculation was, therefore, redone by excluding the experimental value. In the creation of ADJ2017, a total of 719 data sets were analyzed and evaluated, and eventually adopted 620 integral experimental data sets. In contrast, a total of 61
Callen-Kovtunova, J.*; Homma, Toshimitsu
International Journal of Disaster Risk Reduction (Internet), 70, p.102746_1 - 102746_10, 2022/02
This paper presents key lessons on protecting the public during an emergency at a nuclear power plant (NPP) that have been identified from the accident at the Fukushima Daiichi NPP. The paper describes what emergency arrangements were in place prior to the accident, what occurred during the emergency and then the ascertained lesson. The paper highlights the failings of dose project models, emphasizes several lessons identified from past emergencies, such as the importance of predetermined criteria and emergency zones for determining protective actions. It also presents an essential lesson previously overlooked: the need for arrangements to ensure the safe evacuation of patients from hospitals and care homes.
Nakayama, Yuta*; Ogawa, Fumio*; Hiyoshi, Noritake*; Hashidate, Ryuta; Wakai, Takashi; Ito, Takamoto*
ISIJ International, 61(8), p.2299 - 2304, 2021/08
This study discusses the creep-fatigue strength for Mod.9Cr-1Mo steel at a high temperature under multiaxial loading. A low-cycle fatigue tests in various strain waveforms were performed with a hollow cylindrical specimen. The low cycle fatigue test was conducted under a proportional loading with a fixed axial strain and a non-proportional loading with a 90-degree phase difference between axial and shear strains. The low cycle fatigue tests at different strain rates and the creep-fatigue tests at different holding times were also conducted to discuss the effects of stress relaxation and strain holding on the failure life. In this study, two types of multiaxial creep-fatigue life evaluation methods were proposed: the first method is to calculate the strain range using Manson's universal slope method with considering a non-proportional loading factor and creep damage; the second method is to calculate the fatigue damage by considering the non-proportional loading factor using the linear damage law and to calculate the creep damage from the improved ductility exhaustion law. The accuracy of the evaluation methods is much better than that of the methods used in the evaluation of actual machines such as time fraction rule.
Kobayashi, Takuya; Kawamura, Hideyuki; Kamidaira, Yuki
Nihon Genshiryoku Gakkai-Shi ATOMO, 62(11), p.635 - 639, 2020/11
It is important to predict the dispersion of radioactive materials released into the ocean due to nuclear accidents in the surrounding ocean of the east Asian countries. The Japan Atomic Energy Agency developed a Short-Term Emergency Assessment system of Marine Environmental Radioactivity (STEAMER) based on an oceanic dispersion model. STEAMER quickly predicts the oceanic dispersion of radioactive materials in the surrounding ocean of the east Asian countries using the online prediction data of oceanic condition. We validated the predictability of the oceanic dispersion and demonstrated the improvement of the predictability using an ensemble prediction method. Moreover, we developed a high resolution model in the coastal region using a Regional Ocean Modeling System (ROMS).
Iwasaki, Toshiki*; Sekiyama, Tsuyoshi*; Nakajima, Teruyuki*; Watanabe, Akira*; Suzuki, Yasushi*; Kondo, Hiroaki*; Morino, Yu*; Terada, Hiroaki; Nagai, Haruyasu; Takigawa, Masayuki*; et al.
Atmospheric Environment, 214, p.116830_1 - 116830_11, 2019/10
The utilization of numerical atmospheric dispersion prediction (NDP) models for accidental discharge of radioactive substances was recommended by a working group of the Meteorological Society of Japan. This paper is to validate the recommendation through NDP model intercomparison in the accidental release from the Fukushima Dai-ichi Nuclear Power Plant in 2011. Emission intensity is assumed to be constant during the whole forecast period for the worst-case scenario unless time sequence of emission is available. We expect to utilize forecasts of surface air contaminations for preventions of inhalations of radioactive substances, and column-integrated amounts for mitigation of radiation exposure associated with wet deposition. Although NDP forecasts have ensemble spread, they commonly figure out relative risk in space and time. They are of great benefit to disseminating effective warnings to public without failure. The multi-model ensemble technique may be effective to improve the reliability.
Uchida, Shunsuke; Chimi, Yasuhiro; Kasahara, Shigeki; Hanawa, Satoshi; Okada, Hidetoshi*; Naito, Masanori*; Kojima, Masayoshi*; Kikura, Hiroshige*; Lister, D. H.*
Nuclear Engineering and Design, 341, p.112 - 123, 2019/01
Improvement of plant reliability based on reliability-centered-maintenance (RCM) is going to be undertaken in NPPs. RCM is supported by risk-based maintenance (RBM). The combination of prediction and inspection is one of the key issues to promote RBM. Early prediction of IGSCC occurrence and its propagation should be confirmed throughout the entire plant systems which should be accomplished by inspections at the target locations followed by timely application of suitable countermeasures. From the inspections, accumulated data will be applied to confirm the accuracy of the code, to tune some uncertainties of the key data for prediction, and then, to increase their accuracy. The synergetic effects of prediction and inspection on application of effective and suitable countermeasures are expected. In the paper, the procedures for the combination of prediction and inspection are introduced.
Yokoyama, Kenji; Kitada, Takanori*
Proceedings of 2018 International Congress on Advances in Nuclear Power Plants (ICAPP 2018) (CD-ROM), p.1221 - 1230, 2018/04
no abstracts in English
Saito, Kimiaki; Nagai, Haruyasu; Kinase, Sakae; Takemiya, Hiroshi
Nihon Genshiryoku Gakkai-Shi ATOMO, 59(6), p.40 - 44, 2017/06
no abstracts in English
Yokoyama, Kenji; Maruyama, Shuhei; Numata, Kazuyuki; Ishikawa, Makoto; Takeda, Toshikazu*
Proceedings of International Conference on the Physics of Reactors; Unifying Theory and Experiments in the 21st Century (PHYSOR 2016) (USB Flash Drive), p.1906 - 1915, 2016/05
Shimomura, Yusuke; Hanari, Akira*; Sato, Isamu*; Kitamura, Ryoichi
JAEA-Technology 2015-062, 47 Pages, 2016/03
In response to new standards for regulating waste management facilities, it was carried out impact assessment of forest fires on the waste management facilities existed in Oarai Research and Development Center of Japan Atomic Energy Agency. At first, a fire spread scenario of forest fires was assumed. The intensity of forest fires was evaluated from field surveys, forest fire evaluation models and so on. As models of forest fire intensity evaluation, Rothermel Model and Canadian Forest Fire Behavior Prediction (FBP) System were used. Impact assessment of radiant heat to the facilities was carried out, and temperature change of outer walls for the assumed forest fires was estimated. The outer wall temperature of facilities was estimated around 160C at the maximum, it was revealed that it doesn't reach allowable temperature limit. Consequently, it doesn't influence the strength of concrete. In addition, a probability of fire breach was estimated to be about 20%. This report illustrates an example of evaluation of forest fires for the new regulatory standards through impact assessment of the forest fires on the waste management facilities.
Hayashi, Nobuhiko; Honda, Mitsuru; Shiraishi, Junya; Miyata, Yoshiaki; Wakatsuki, Takuma; Hoshino, Kazuo; Toma, Mitsunori; Suzuki, Takahiro; Urano, Hajime; Shimizu, Katsuhiro; et al.
Europhysics Conference Abstracts (Internet), 39E, p.P5.145_1 - P5.145_4, 2015/06
Nuclear Fusion, 45(11), p.1232 - 1246, 2005/11
Prediction of major disruptions observed at the -limit for tokamak plasmas has been investigated in JT-60U with developing neural networks. A sub-neural network is trained to output a value of the limit every 2 ms. The target limit is artificially set by the operator in the first step training and is modified in the second step training using the output limit from the trained network. To improve the prediction performance further, the difference between the estimated limit and the measured and the other 11 parameters are inputted to a main neural network to calculate the stability level. Major disruptions have been predicted with a prediction success rate of 80% at 10 ms prior to the disruption while the false alarm rate is lower than 4%. This 80% is much higher than about 10% previously obtained. A prediction success rate of 90% has been also obtained with a false alarm rate of 12% at 10 ms prior to the disruption. This 12% is about a half of previously obtained one.
Ono, Tomio*; Subekti, M.*; Kudo, Kazuhiko*; Takamatsu, Kuniyoshi; Nakagawa, Shigeaki; Nabeshima, Kunihiko
Nihon Genshiryoku Gakkai Wabun Rombunshi, 4(2), p.115 - 126, 2005/06
Control-rod withdrawal tests simulating reactivity insertion are carried out in the HTTR to verify the inherent safety features of HTGRs. This paper describes pre-test analysis method using artificial neural networks to predict the changes of reactor power and reactivity. The network model applied in this study is based on recurrent neural networks. The inputs of the network are the changes of the central control rods position and other significant core parameters, and the outputs are the changes of reactor power and reactivity. Furthermore, Time Synchronizing Signal(TSS) is added to input to improve the modeling of time series data. The actual tests data, which were previously carried out in the HTTR, were used for learning the model of the plant dynamics. After the learning, the network can predict the changes of reactor power and reactivity in the following tests.
Kugo, Teruhiko; Kojima, Kensuke; Ando, Masaki; Okajima, Shigeaki; Mori, Takamasa; Takeda, Toshikazu*; Kitada, Takanori*; Matsuoka, Shogo*
Proceedings of 2005 International Congress on Advances in Nuclear Power Plants (ICAPP '05) (CD-ROM), 10 Pages, 2005/05
We have preliminarily evaluated the reduction of prediction errors of the core characteristics of the breeding light water reactor core based on the bias factor method by utilizing the FCA critical experiments carried out for MOX fueled tight lattice light water reactor cores. The prediction uncertainty of k is reduced from 0.62% to 0.39% by utilizing the FCA-XV-2 (65V) result. As for the reaction rate ratio of U capture and Pu fission, it is found that the FCA XXII-1 (95V) and XV (95V) results are suitable for the upper core and the upper blanket of the real core and the FCA XXII-1 (65V) and XV-2 (65V) results are suitable for the lower core and the internal blanket.
Shibata, Yasushi*; Yamamoto, Kazuyoshi; Matsumura, Akira*; Yamamoto, Tetsuya*; Hori, Naohiko; Kishi, Toshiaki; Kumada, Hiroaki; Akutsu, Hiroyoshi*; Yasuda, Susumu*; Nakai, Kei*; et al.
JAERI-Research 2005-009, 41 Pages, 2005/03
The measurement of neutron flux and boron concentration in the blood during medical irradiation is indispensable in order to evaluate the radiation in boron neutron capture therapy. It is, however, difficult to measure the blood boron concentration during neutron irradiation because access to the patient is limited. Therefore we prospectively investigated the predictability of blood boron concentrations using the data obtained at the first craniotomy after infusion of a low dosage of BSH. When the test could not be carried out, the blood boron concentration during irradiation was also predicted by using the 2-compartment model. If the final boron concentration after the end of the infusion is within 95% confidence interval of the prediction, direct prediction from biexponential fit will reduce the error of blood boron concentrations during irradiation to around 6%. If the final boron concentration at 6 or 9 hours after the end of infusion is out of 95% confidence interval of the prediction, proportional adjustment will reduce error and expected error after adjustment to around 12%.
Kimura, Hideo; Sakai, Tomo*
JAERI-Data/Code 2004-008, 41 Pages, 2004/02
no abstracts in English
Amano, Hikaru; Uchida, Shigeo*
JAERI-Conf 2003-010, 394 Pages, 2003/09
The International Symposium : Transfer of Radionuclides in Biosphere, Prediction and Assessment was held at Mito on the 18th and 19th of Dec. 2002. This Symposium was organized by the Interchange Committee on Radionuclide Transfer in Soil Ecosphere. This project is the 3rd Phase Crossover Research, which is engaged in cooperation with five organizations:JAERI, MRI, NIRS, RIKEN and IES. The main objective of this symposium is to discuss and exchange recent findings and ideas in the area of the behavior and transfer of radionuclides in biosphere. One of the important topics in this symposium is to discuss a suitable transfer model and transfer parameters which may be adapted for Southeast Asian countries including Japan, as environmental conditions and foodstuffs in this region are significantly different from those in Europe and North America. The symposium consisted of 12 invited lectures and 44 poster presentations. The 120 participants attended the symposium, including 19 foreigners coming from 12 countries.
Amano, Hikaru; Takahashi, Tomoyuki*; Uchida, Shigeo*; Matsuoka, Shungo*; Ikeda, Hiroshi*; Hayashi, Hiroko*; Kurosawa, Naohiro*
JAERI-Conf 2003-010, p.32 - 36, 2003/09
MOGRA (Migration Of GRound Additions) is a migration prediction code for toxic ground additions including radioactive materials in a terrestrial environment. MOGRA consists of computational codes that are applicable to various evaluation target systems, and can be used on personal computers. The computational code has the dynamic compartment analysis block at its core, the graphical user interface (GUI) for computation parameter settings and results displays, data files and so on. The compartments are obtained by classifying various natural environments into groups that exhibit similar properties. MOGRA has varieties of databases, which consist of radionuclides decay chart, distribution coefficients between solid and liquid, transfer factors from soil to plant, transfer coefficients from feed to beef and milk, concentration factors, and age dependent dose conversion factors for many radionuclides. Here the status of development of MOGRA is presented.
Shibata, Yasushi*; Matsumura, Akira*; Yamamoto, Tetsuya*; Akutsu, Hiroyoshi*; Yasuda, Susumu*; Nakai, Kei*; Nose, Tadao*; Yamamoto, Kazuyoshi; Kumada, Hiroaki; Hori, Naohiko; et al.
Research and Development in Neutron Capture Therapy, p.1055 - 1060, 2002/09
We prospectively investigated the predictability of blood boron concentrations using the data obtained at the first craniotomy after infusion of a low dose of sodium undecahydroclosododecaborate (BSH). Nine patients with malignant glial tumors underwent Boron neutron capture therapy (BNCT) at the Japan Atomic Energy Research Institute (JAERI) between 1995 and 2001. In 7 patients, 1g of BSH was infused before the first tumor removal and boron concentrations were determined using prompt gamma ray analysis (PGA). Then, 12 hours before BNCT, patients were infused at a dose of 100mg/kg BSH, and the boron concentrations were determined again. The boron biodistribution data showed a biexponential pharmacokinetic profile. If the final boron concentration at 6 or 9 hours after the end of the infusion is within the 95% confidence interval of the prediction, direct prediction from biexponential fit will reduce the error of blood boron concentrations during irradiation to around 6%.