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Journal Articles

Consideration of decontamination model for severe accident consequence assessment

Silva, K.*; Okamoto, Koji*; Ishiwatari, Yuki*; Takahara, Shogo; Promping, J.*

Journal of Nuclear Science and Technology, 52(11), p.1402 - 1416, 2015/11

 Times Cited Count:2 Percentile:73.66(Nuclear Science & Technology)

Journal Articles

Development of accident consequence assessment scheme using accident cost and consideration of decontamination model

Silva, K.*; Okamoto, Koji*; Ishiwatari, Yuki*; Takahara, Shogo; Promping, J.*

Proceedings of 12th Probabilistic Safety Assessment and Management Conference (PSAM-12) (USB Flash Drive), 12 Pages, 2014/06

no abstracts in English

Journal Articles

Cost per severe accident as an index for severe accident consequence assessment and its applications

Silva, K.*; Ishiwatari, Yuki*; Takahara, Shogo

Reliability Engineering & System Safety, 123, p.110 - 122, 2014/03

AA2012-0781.pdf:0.77MB

 Times Cited Count:11 Percentile:46.26(Engineering, Industrial)

The experiences of the Fukushima Accident and also the Chernobyl Accident point out the needs to integrate the assessments of health effects, economic, social and environmental impacts of severe accidents in nuclear power plants, in order to perform a comprehensive consequence assessment. The authors introduced the cost per severe accident as an index for that purpose. The index is calculated based on the systematic accident consequence assessment method which consists of level 2 and 3 probabilistic risk assessments. In the present study, the index was used to evaluate the consequences of severe accidents of a virtual boiling water reactor. The breakdown of the cost per severe accident was provided, and the decontamination cost accounted for the greatest proportion. As applications of the index, it was used to optimize the management levels of protective actions for the public, and to evaluate the consequence-reduction effects of accident management.

Journal Articles

Nuclear reactor calculations

Okumura, Keisuke; Oka, Yoshiaki*; Ishiwatari, Yuki*

Nuclear Reactor Design, p.49 - 126, 2014/00

As necessary knowledge for nuclear reactor design, fundamental methods of nuclear reactor calculations are described. First, we explain, in an easy-to-understand manner, what kinds of numerical methods and procedures are employed in the codes which treat nuclear data processing, lattice calculation, lattice burnup calculation, core calculation, nuclear and thermal-hydraulic coupled calculation, core burnup calculation and space-dependent core calculation. Next we show the calculated examples of the optimizations for a fuel loading pattern and control rod insertion pattern in the thermal-hydraulic coupled core burnup calculation. Furthermore, we describe the methods of the plant dynamics analyses using a simple node junction model for the heat transfer calculation. The plant dynamics cover the analyses of control and startup properties, reactor stability, and safety analysis.

JAEA Reports

The International Atomic Energy Agency Nuclear Energy Management School 2012

Ohgama, Kazuya; Ando, Yoko; Yamaguchi, Mika; Ikuta, Yuko; Shinohara, Nobuo; Murakami, Hiroyuki; Yamashita, Kiyonobu; Uesaka, Mitsuru*; Demachi, Kazuyuki*; Komiyama, Ryoichi*; et al.

JAEA-Review 2013-004, 76 Pages, 2013/05

JAEA-Review-2013-004.pdf:13.53MB

JAEA together with the Japan Nuclear Human Resource Development Network (JN-HRD Net), the University of Tokyo (UT) and the Japan Atomic Industrial Forum (JAIF) cohosted the IAEA-Nuclear Energy Management School in Tokai Village, aiming that Japan will be the center of nuclear HRD in the Asian region. In the school, not only lectures by IAEA experts, but also lectures by Japanese experts and technical visits were included for foreign participants. The school contributed to the internationalization of Japanese young professionals, development of nuclear human resource of other countries, and enhancement of cooperation between IAEA and Japan. Additionally, collaborative relationship within JN-HRD Net was strengthened by the school. In this report, findings obtained during the preparatory work and the school period are reported for future international nuclear HRD activities in Japan.

Journal Articles

Estimation of cost per severe accident for improvement of accident protection and consequence mitigation strategies

Silva, K.*; Ishiwatari, Yuki*; Takahara, Shogo

Proceedings of Probabilistic Safety Assessment and Management Topical Conference; In light of the Fukushima Dai-ichi Accident (PSAM 2013) (USB Flash Drive), 10 Pages, 2013/04

The "cost per severe accident" was introduced as an index to analyze improvement of accident protection and consequence mitigation strategies. This index consists of various costs and consequences converted into monetary values. The evaluations of these costs and consequences were made based on the systematic consequence analysis using level 2 and 3 PSA. The accident sequences were taken from the results of level 2 seismic PSA. The doses to the public and the number of people affected were calculated using the level 3 PSA code OSCAAR. The data obtained from the open documents on the Fukushima Accident are used as much as possible. Sensitivity analyses are carried out to identify the sensitive assumptions or parameters to the cost per severe accident. Base on the results of the sensitivity analyses, optimized accident protection and consequence mitigation strategies are recommended taking into account the various aspects comprehensively using the cost per severe accident.

Journal Articles

Modification of severe accident consequence analysis calculation method of nuclear power plant and consideration of effect of discount rate

Silva, K.*; Ishiwatari, Yuki*; Takahara, Shogo

Proceedings of 2nd International Symposium on Technology for Sustainability (ISTS 2012) (USB Flash Drive), p.31 - 34, 2012/11

The authors introduced the external cost regarding severe accident as an index for severe accident consequence analysis of nuclear power plants in the previous work. In this research, we modify the calculation methods of two components of the external cost regarding severe accident; decontamination cost and health effect cost, in order to obtain more reality-based results. The decontamination cost calculation method is renewed based on data obtained from decontamination demonstration project of JAEA and land use data of Ibaraki Prefecture. Willingness to pay is used to estimate the health effect cost instead of human capital method. To investigate the effect of discount rate on severe accident consequence, sensitivity analysis was performed using discount rates from 0%, 1%, 3%, 5%. Changes of the fractions of the costs comprising the external cost regarding severe accident are very small even in the case of discount rate of 5%.

Journal Articles

Integration of direct/indirect influences of severe accidents for improvements of nuclear safety

Silva, K.*; Ishiwatari, Yuki*; Takahara, Shogo

Proceedings of 20th International Conference on Nuclear Engineering and the ASME 2012 Power Conference (ICONE-20 & POWER 2012) (DVD-ROM), 9 Pages, 2012/07

Journal Articles

Measurements of neutron capture cross section of $$^{237}$$Np for fast neutrons

Harada, Hideo; Nakamura, Shoji; Hatsukawa, Yuichi; Toh, Yosuke; Kimura, Atsushi; Ishiwatari, Yuki*; Yasumi, Atsushi*; Mabuchi, Yukio*; Nakagawa, Tsutomu*; Okamura, Kazuo*; et al.

Journal of Nuclear Science and Technology, 46(5), p.460 - 468, 2009/05

 Times Cited Count:2 Percentile:80.02(Nuclear Science & Technology)

The neutron capture cross section of $$^{237}$$Np has been measured for fast neutrons supplied at the center of the core in the Yayoi reactor. The activation method was used for the measurement, in which the amount of the product $$^{238}$$Np was determined by $$gamma$$-ray spectroscopy using a Ge detector. The representative neutron energy and the corresponding capture cross section of $$^{237}$$Np in the experiment were analytically deduced as 0.80 $$pm$$ 0.04 b at 0.214 $$pm$$ 0.009 MeV from the measured reaction rate by combining the energy dependence of the cross section in the nuclear data library ENDF/VII.0. The deduced cross section of $$^{237}$$Np at the representative neutron energy agrees with the evaluated data of ENDF/B-VII.0, but shows 15% larger value than that of JENDL-3.3 and 13% larger value than that of JENDL/AC-2008.

Journal Articles

Rationalization of the fuel integrity and transient criteria for the super LWR

Yamaji, Akifumi*; Oka, Yoshiaki*; Ishiwatari, Yuki*; Liu, J.*; Koshizuka, Seiichi*; Suzuki, Motoe

Proceedings of 2005 International Congress on Advances in Nuclear Power Plants (ICAPP '05) (CD-ROM), 7 Pages, 2005/05

Ensuring the fuel integrities is one of the most fundamental parts in the High Temperature Supercritical-Pressure Light Water Reactor. Most abnormal transient events of SCLWR-H last for a short period of time and the fuel rods are replaced after being irradiated in the core. In this study, the fuel integrity criteria are rationalized based on the fact that the fuel rod mechanical failures can be represented by the strain of the fuel rod cladding. A new fuel rod is designed with a Stainless Steel cladding. It is internally pressurized to reduce the stress on the cladding and also to increase the gap conductance between the pellet and the cladding. The fuel integrities both at normal operation and abnormal transient conditions are evaluated using the fuel analysis code FEMAXI-6 of JAERI.

Oral presentation

Study on fast-neutron capture cross section by an activation method

Nakamura, Shoji; Toh, Yosuke; Kimura, Atsushi; Hatsukawa, Yuichi; Harada, Hideo; Ishiwatari, Yuki*; Saito, Isao*; Yasumi, Atsushi*; Mabuchi, Yukio*; Nakagawa, Tsutomu*; et al.

no journal, , 

no abstracts in English

Oral presentation

Measurement of neutron capture cross section of $$^{237}$$Np for fast neutrons

Harada, Hideo; Nakamura, Shoji; Hatsukawa, Yuichi; Toh, Yosuke; Kimura, Atsushi; Ishiwatari, Yuki*; Yasumi, Atsushi*; Mabuchi, Yukio*; Nakagawa, Tsutomu*; Oka, Yoshiaki*

no journal, , 

Neutron capture cross section of $$^{237}$$Np for fast neutrons has been measured using an activation method. A small amount of $$^{237}$$Np sample was irradiated in the Grazing hole of the Yayoi reactor. The neutron flux at the irradiation point was monitored by Au activation foil. The duduced neutron capture cross section was compared with those in nuclear data libraries JENDL-3.3 and ENDF/B-VII.0.

Oral presentation

Measurement of fast-neutron capture cross-section of $$^{99}$$Tc

Nakamura, Shoji; Hatsukawa, Yuichi; Toh, Yosuke; Kimura, Atsushi; Harada, Hideo; Ishiwatari, Yuki*; Yasumi, Atsushi*; Nakagawa, Tsutomu*; Mabuchi, Yukio*; Saito, Isao*; et al.

no journal, , 

Technetium-99 samples were irradiated by fast neutrons at YAYOI reactor. The fast-neutron capture cross-section was measured by the activation method.

Oral presentation

Measurement of fast-neutron capture cross-section of $$^{237}$$Np, 2; Irradiation in the Gz hole of YAYOI reactor

Nakamura, Shoji; Hatsukawa, Yuichi; Toh, Yosuke; Kimura, Atsushi; Harada, Hideo; Ishiwatari, Yuki*; Yasumi, Atsushi*; Nakagawa, Tsutomu*; Mabuchi, Yukio*; Saito, Isao*; et al.

no journal, , 

The $$^{237}$$Np sample was irradiated at the Gz hole of YAYOI reactor, and the fast-neutron capture cross-section was obtained by an activation method. The production amount of $$^{238}$$Np was measured by $$gamma$$-ray spectroscopy. The neutron flux at the irradiation position was monitored by a gold foil. It was found that the present result of the fast-neutron capture cross-section was 15% larger than that in JENDL-3.3.

Oral presentation

Current status of research and development of supercritical water cooled fast reactor (super fast reactor) in Japan

Nakatsuka, Toru; Oka, Yoshiaki*; Ishiwatari, Yuki*; Okumura, Keisuke; Nagasaki, Shinya*; Tezuka, Kenichi*; Mori, Hideo*; Ezato, Koichiro; Akasaka, Naoaki; Nakazono, Yoshihisa*; et al.

no journal, , 

Pressure-vessel-type supercritical water cooled reactors (SCWRs) have been developed at the University of Tokyo (UT) since 1989 and are studied in Japan, Europe and other countries. UT's concepts of the reactor are termed "Super LWR" for thermal neutron spectrum and "Super Fast Reactor (FR)" for fast spectrum respectively. With the scope of developing an economical fast reactor system, a Japanese research project of the "Super FR" had been conducted since December 2005 to March 2010. UT, Kyushu University, Japan Atomic Energy Agency and Tokyo Electric Power Company have participated in the project. It consisted of three subjects: (1) development of the Super FR concept, (2) thermal-hydraulic experiments and (3) materials developments. All items have successfully finished. The present paper will summarize the results of the project.

Oral presentation

Measurement of fast-neutron capture cross-section of $$^{129}$$I

Nakamura, Shoji; Toh, Yosuke; Hatsukawa, Yuichi; Kimura, Atsushi; Harada, Hideo; Yasumi, Atsushi*; Nakagawa, Tsutomu*; Mabuchi, Yukio*; Saito, Isao*; Ishiwatari, Yuki*

no journal, , 

The fast-neutron capture cross section of $$^{129}$$I was measured at the YAYOI reactor by the activation method. The amount of $$^{130}$$I was obtained by measuring $$gamma$$-rays emitted from $$^{130}$$I. The neutron flux was monitored by a piece of gold foil. The fast-neutron capture cross section was derived from the information of the production amount of $$^{130}$$I and the neutron flux. This work found that the evaluated data might be overestimated by about 10% and more.

Oral presentation

Structure analysis of resin-filler compounds by small-angle neutron scattering

Yamaguchi, Daisuke; Koizumi, Satoshi; Ojima, Hitoshi*; Isoyama, Ryo*; Ishiwatari, Yoshiyuki*; Kodama, Hiroto*; Takeda, Hisanori*; Fukita, Hitoshi*; Takashima, Yoshiyuki*

no journal, , 

Resin-filler composites were investigated by small-angle neutron scattering (SANS). Two types of fillers, talc and TiO$$_{2}$$, were employed and compounded with polypropylene in this study. The dispersion state of the fillers was examined by SANS measurements. In addition, the size distribution of the fillers was separately measured through the laser right scattering and SEM. The calculated scattering function including the polydispersity of fillers whose size distribution reflects the results of laser right scattering and SEM consistently reproduced the experimental SANS scattering profiles.

Oral presentation

Research on methodology of external cost evaluation of nuclear power severe accident and its uses for risk reduction

Silva, K.*; Ishiwatari, Yuki*; Takahara, Shogo

no journal, , 

no abstracts in English

Oral presentation

Introduction of external cost regarding severe accident as an index of nuclear power plant risk and its relationship with sourceterm

Silva, K.*; Ishiwatari, Yuki*; Takahara, Shogo

no journal, , 

In this research, the authors introduce the "external cost regarding severe accident" as an index to evaluate the effect of severe accident in a nuclear power plant. This can contribute to an improvement in nuclear power plant risk evaluation which needs not only probability evaluations but also effect evaluations. To calculate the external cost regarding severe accident, typical sequences of severe accidents are picked up first. Containment failure frequency (CFF) and sourceterms of each sequence are taken from the results of level 2 PSA. The sourceterm of each sequence is input into the level 3 PSA code OSCAAR which was developed by Japan Atomic Energy Agency (JAEA). Using these outputs, the external cost regarding severe accident is calculated. The results were compared with the amount of sourceterms of each severe accident which can be one of the indexes to evaluate the effects of severe accident.

Oral presentation

Consideration of decontamination cost calculation model for severe accident consequence assessment indexed by cost per severe accident

Silva, K.*; Okamoto, Koji*; Ishiwatari, Yuki*; Takahara, Shogo; Promping, J.*

no journal, , 

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