Effectiveness evaluation methodology of the measures for improving resilience of nuclear structures against excessive earthquake

Kurisaka, Kenichi; Nishino, Hiroyuki; Yamano, Hidemasa

Proceedings of 30th International Conference on Nuclear Engineering (ICONE30) (Internet), 8 Pages, 2023/05

The objective of this study is to develop an effectiveness evaluation methodology of the measures for improving resilience of nuclear structures against excessive earthquake by applying the failure mitigation technology. This study regarded those measures for improving resilience of important structures, systems, and components for safety to enlarge their seismic safety margin. To evaluate effectiveness of those measures, seismic core damage frequency (CDF) is selected as an index. Reduction of CDF as an effectiveness index is quantified by applying seismic PRA technology. Accident sequences leading to loss of decay heat removal are significant contributor to seismic CDF of sodium-cooled fast reactors (SFRs), and those sequences result in core damage via ultra-high temperature condition. This study improved the methodology to evaluate not only the measures against shaking due to excessive earthquake but also the measures at the ultra-high temperature condition. To examine applicability of the improved methodology, a trial calculation was implemented with some assumptions for a loop-type SFR. Within the assumption, the measures for improving resilience were significantly effective for decreasing CDF in excessive earthquake up to several times of a design basis ground motion. Through the applicability examination, the methodology for the effectiveness evaluation was developed successfully.

Study of corrosion and degradation of the objects in the nuclear reactor by microorganisms (Contract research); FY2020 Nuclear Energy Science & Technology and Human Resource Development Project

Collaborative Laboratories for Advanced Decommissioning Science; Keio University*

JAEA-Review 2021-048, 181 Pages, 2022/01

JAEA-Review-2021-048.pdf:14.5MB

The Collaborative Laboratories for Advanced Decommissioning Science (CLADS), Japan Atomic Energy Agency (JAEA), had been conducting the Nuclear Energy Science & Technology and Human Resource Development Project (hereafter referred to "the Project") in FY2020. The Project aims to contribute to solving problems in the nuclear energy field represented by the decommissioning of the Fukushima Daiichi Nuclear Power Station (1F), Tokyo Electric Power Company Holdings, Inc. (TEPCO). For this purpose, intelligence was collected from all over the world, and basic research and human resource development were promoted by closely integrating/collaborating knowledge and experiences in various fields beyond the barrier of conventional organizations and research fields. The sponsor of the Project was moved from the Ministry of Education, Culture, Sports, Science and Technology to JAEA since the newly adopted proposals in FY2018. On this occasion, JAEA constructed a new research system where JAEA-academia collaboration is reinforced and medium-to-long term research/development and human resource development contributing to the decommissioning are stably and consecutively implemented. Among the adopted proposals in FY2019, this report summarizes the research results of the "Study of corrosion and degradation of the objects in the nuclear reactor by microorganisms" conducted in FY2019 and FY2020. Since the final year of this proposal was FY2020, the results for two fiscal years were summarized. The purpose of the study is to obtain knowledge related to microorganisms that will be useful in the decommissioning process of 1F. Therefore, we clarified the current conditions of the microbial community inhabiting the power plant and its premises. Environmental samples were taken from several sites such as, topsoil from the south of the plant site boundary (south of the treated water tanks), seabed soil and its above water near the plant, surface water 3km offshore …

Study of corrosion and degradation of the objects in the nuclear reactor by microorganisms (Contract research); FY2019 Nuclear Energy Science & Technology and Human Resource Development Project

Collaborative Laboratories for Advanced Decommissioning Science; Keio University*

JAEA-Review 2020-047, 63 Pages, 2021/01

JAEA-Review-2020-047.pdf:3.85MB

The Collaborative Laboratories for Advanced Decommissioning Science (CLADS), Japan Atomic Energy Agency (JAEA), had been conducting the Nuclear Energy Science & Technology and Human Resource Development Project (hereafter referred to "the Project") in FY2019. The Project aims to contribute to solving problems in the nuclear energy field represented by the decommissioning of the Fukushima Daiichi Nuclear Power Station, Tokyo Electric Power Company Holdings, Inc. (TEPCO). For this purpose, intelligence was collected from all over the world, and basic research and human resource development were promoted by closely integrating/collaborating knowledge and experiences in various fields beyond the barrier of conventional organizations and research fields. The sponsor of the Project was moved from the Ministry of Education, Culture, Sports, Science and Technology to JAEA since the newly adopted proposals in FY2018. On this occasion, JAEA constructed a new research system where JAEA-academia collaboration is reinforced and medium-to-long term research/development and human resource development contributing to the decommissioning are stably and consecutively implemented. Among the adopted proposals in FY2019, this report summarizes the research results of the "Study of corrosion and degradation of the objects in the nuclear reactor by microorganisms" conducted in FY2019. The purpose of the study is to obtain knowledge related to microorganisms that will be useful in the decommissioning process of the Fukushima Daiichi Nuclear Power Station. For this reason, the current conditions of the microbial community inhabiting the power plant and its premises will be clarified. In the first research year, we obtained environmental samples such as soils from the south of the boundary of the plant, seabed soils near the plant, and surface water 3 km offshore from the plant, and successfully prepared their microbial genomic DNAs.

Draft genome sequence of the radioresistant bacterium , isolated from freshwater fish in Japan

Sato, Katsuya; Onodera, Takefumi*; Omoso, Kota*; Takeda-Yano, Kiyoko*; Katayama, Takeshi*; Ono, Yutaka; Narumi, Issey*

Genome Announcements (Internet), 4(1), p.e01631-15_1 - e01631-15_2, 2016/01

https://doi.org/10.1128/genomeA.01631-15

Identification of the accident sequences for the evaluation of the effectiveness of severe accident measures on prototype Sodium-cooled Fast Reactor

Onoda, Yuichi; Kurisaka, Kenichi; Sakai, Takaaki

Proceedings of 10th International Topical Meeting on Nuclear Thermal Hydraulics, Operation and Safety (NUTHOS-10) (USB Flash Drive), 12 Pages, 2014/12

Draft genome sequence of calcium-dependent sp. strain TCA20, isolated from a hot spring containing a high concentration of calcium ions

Fujinami, Shun*; Takeda, Kiyoko*; Onodera, Takefumi*; Sato, Katsuya; Sano, Motohiko*; Takahashi, Yuka*; Narumi, Issey*; Ito, Masahiro*

Genome Announcements (Internet), 2(5), p.e00866-14_1 - e00866-14_2, 2014/09

https://doi.org/10.1128/genomeA.00866-14

Uncertainty and sensitivity studies with the probabilistic accident consequence assessment code OSCAAR

Homma, Toshimitsu; Tomita, Kenichi*; Hato, Shinji*

Nuclear Engineering and Technology, 37(3), p.245 - 258, 2005/06

This paper addresses two types of uncertainty: stochastic uncertainty and subjective uncertainty in probabilistic accident consequence assessments. The off-site consequence assessment code OSCAAR has been applied to uncertainty and sensitivity analyses on the individual risks of early fatality and latent cancer fatality in the population due to a severe accident. A new stratified meteorological sampling scheme was successfully implemented into the trajectory model for atmospheric dispersion and the statistical variability of the probability distributions of the consequence was examined. A total of 65 uncertain input parameters was considered and 128 runs of OSCAAR were performed in the parameter uncertainty analysis. The study provided the range of uncertainty for the expected values of individual risks of early and latent cancer fatality close to the site. In the sensitivity analyses, the correlation/regression measures were useful for identifying those input parameters whose uncertainty makes an important contribution to the overall uncertainty for the consequence.

Radionuclide release from mixed-oxide fuel under high temperature at elevated pressure and influence on source terms

Hidaka, Akihide; Kudo, Tamotsu; Ishikawa, Jun; Fuketa, Toyoshi

Journal of Nuclear Science and Technology, 42(5), p.451 - 461, 2005/05

https://doi.org/10.3327/jnst.42.451

The radionuclide release from MOX under severe accident conditions was investigated in VEGA program to contribute to the technical bases for safety evaluation including PSA for LWR using MOX. The MOX specimens irradiated at ATR Fugen were heated up to 3123K in helium at 0.1 and 1.0MPa. The release of volatile FP was slightly enhanced below 2200K compared with that of UO. The volatile FP release at elevated pressure was decreased as in the case with UO. The total fractional release of Cs reached almost 100% while almost no release of low-volatile FP even after the fuel melting. The release rate of plutonium above 2800K increased rapidly although the amount was small. Since the existing models cannot predict this increase, an empirical model was prepared based on the data. There is no large difference in FP inventories between UO and MOX, and the fractional releases from MOX can be mostly predicted by the model for UO. This suggests that the consequences of LWR using MOX are mostly equal to those using UO from a view point of risks.

Study on a new meteorological sampling scheme developed for the OSCAAR code system

Liu, X.*; Tomita, Kenichi*; Homma, Toshimitsu

JAERI-Research 2002-004, 37 Pages, 2002/03

JAERI-Research-2002-004.pdf:2.14MB

One important step in Level 3 Probabilistic Safety Assessment is meteorological sequence sampling, on which the previous studies were mainly related to code systems using straight line plume model and more efforts are needed for trajectory puff model such as the OSCAAR code system. This report describes the development of a new meteorological sampling scheme for the OSCAAR code system that explicitly considers population distribution. A group of principles was set forth for the development of this new sampling scheme, including completeness, stratification, sample allocation, practicability and so on. The calculation results illustrate that although it is quite difficult to idealize stratification of meteorological sequences based on a few environmental parameters the new scheme do gather the most inverse conditions in a single subset of meteorological sequences. The size of this subset may be as small as a few dozens, so that the tail of a CCDF curve is possible to remain relatively static in different trials of the PCA code system.

Variation of radiological consequences under various weather conditions

Liu, X.; Homma, Toshimitsu

JAERI-Tech 2001-054, 49 Pages, 2001/08

JAERI-Tech-2001-054.pdf:1.54MB

no abstracts in English