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Furuya, Osamu*; Fujita, Satoshi*; Muta, Hitoshi*; Otori, Yasuki*; Itoi, Tatsuya*; Okamura, Shigeki*; Minagawa, Keisuke*; Nakamura, Izumi*; Fujimoto, Shigeru*; Otani, Akihito*; et al.
Proceedings of ASME 2021 Pressure Vessels and Piping Conference (PVP 2021) (Internet), 6 Pages, 2021/07
Since the Fukushima accident, with the higher safety requirements of nuclear facilities in Japan, suppliers, manufacturers and academic societies have been actively considering the reconstruction of the safety of nuclear facilities from various perspectives. The Nuclear Regulation Authority has formulated new regulatory standards and is in operation. The new regulatory standards are based on defense in depth, and have significantly raised the levels of natural hazards and have requested to strengthen the countermeasures from the perspective of preventing the simultaneous loss of safety functions due to common factors. Facilities for dealing with specific serious accidents are required to have robustness to ensure functions against earthquakes that exceed the design standards to a certain extent. In addition, since the probabilistic risk assessment (PRA) and the safety margin evaluation are performed to include the range beyond the design assumption in the safety improvement evaluation, it is very important to extent the special knowledge in the strength of important equipment for seismic safety. This paper summarizes the research and examination results of specialized knowledge on the concept of maintaining the functions of important seismic facilities and the damage index to be considered by severe earthquakes. In the other paper, the study on reliability of seismic capacity analysis for important equipment in nuclear facilities will be reported.
Sato, Hiroyuki; Nishida, Akemi; Ohashi, Hirofumi; Muramatsu, Ken*; Muta, Hitoshi*; Itoi, Tatsuya*; Takada, Tsuyoshi*; Hida, Takenori*; Tanabe, Masayuki*; Yamamoto, Tsuyoshi*; et al.
Proceedings of 2017 International Congress on Advances in Nuclear Power Plants (ICAPP 2017) (CD-ROM), 7 Pages, 2017/04
JAEA, in conjunction with Tokyo City University, The University of Tokyo and JGC Corporation, have started development of a PRA method considering the safety and design features of HTGR. The primary objective of the project is to develop a seismic PRA method which enables to provide a reasonably complete identification of accident scenario including a loss of safety function in passive system, structure and components. In addition, we aim to develop a basis for guidance to implement the PRA. This paper provides the overview of the activities including development of a system analysis method for multiple failures, a component failure data using the operation and maintenance experience in the HTTR, seismic fragility evaluation method, and mechanistic source term evaluation method considering failures in core graphite components and reactor building.
Matsuda, Kosuke*; Muramatsu, Ken*; Muta, Hitoshi*; Sato, Hiroyuki; Nishida, Akemi; Ohashi, Hirofumi; Itoi, Tatsuya*; Takada, Tsuyoshi*; Hida, Takenori*; Tanabe, Masayuki*; et al.
Proceedings of 2017 International Congress on Advances in Nuclear Power Plants (ICAPP 2017) (CD-ROM), 7 Pages, 2017/04
This paper proposes a set of procedures for accident sequence analysis in seismic PRAs of HTGRs that can consider the unique accident progression characteristics of HTGRs. Main features of our proposed procedure are as follows: (1) Systematic analysis techniques including Master Logic Diagrams are used to ensure reasonable completeness in identification of initiating events and classification of accident sequences, (2) Information on factors that govern the accident progression and source terms are effectively reflected to the construction of event trees for delineation of accident sequences, and (3) Frequency quantification of seismically-initiated accident sequence frequencies that involve multiplepipe ruptures are made with the use of the Direct Quantification of Fault Trees by Monte Carlo (DQFM) method by a computer code SECOM-DQFM.
Choi, B.; Nishida, Akemi; Itoi, Tatsuya*; Takada, Tsuyoshi*; Furuya, Osamu*; Muta, Hitoshi*; Muramatsu, Ken
Proceedings of 13th Probabilistic Safety Assessment and Management Conference (PSAM-13) (USB Flash Drive), 8 Pages, 2016/10
In this study, we address epistemic uncertainty in structure fragility estimation of nuclear power plants (NPPs). In order to identify and quantify dominant factors in fragility assessment, sensitivity analyses of seismic analysis results are conducted for a target NPP building using a three-dimensional finite element model and a conventional lumped mass model (embedded sway rocking model), and the uncertainty caused by the major factors is then evaluated. The results are used to classify epistemic uncertainty levels in a fragility estimation workflow for NPPs in several stages, and a graded knowledge tree technique, which can be used for future fragility estimations, is proposed.
Muta, Hitoshi*; Muramatsu, Ken*; Furuya, Osamu*; Uchiyama, Tomoaki*; Nishida, Akemi; Takada, Tsuyoshi*
Transactions of 23rd International Conference on Structural Mechanics in Reactor Technology (SMiRT-23) (USB Flash Drive), 10 Pages, 2015/08
Seismic PRA is an effective measure to consider the countermeasures and improvement plans to secure the further safety of nuclear power plants regarding to seismic risk for the earthquake exceeding the reference ground motion. However, the application of the seismic PRA has not been utilized sufficiently so far. One of the reasons is that there is not enough consensus among stakeholders regarding to the evaluation methods and consideration of uncertainty for decision-making. This study proposes the mathematic framework to treat the uncertainty properly related to the evaluation of Core Damage Frequency induced by earthquake, the method to evaluate the fragility utilizing expert knowledge, the probabilistic model to cope with the aleatory uncertainty as well as the development of analyzing code including these considerations for the improvement of the reliability of the method and enhancement of utilization of the products of Seismic PRA.
Katayama, Masahito*; Adachi, Jun*; Kurosaki, Ken*; Osaka, Masahiko; Miwa, Shuhei; Tanaka, Kenya; Muta, Hiroaki*; Uno, Masayoshi*; Yamanaka, Shinsuke*
no journal, ,
no abstracts in English
Muramatsu, Ken*; Takada, Tsuyoshi*; Itoi, Tatsuya*; Nishida, Akemi; Uchiyama, Tomoaki*; Furuya, Osamu*; Fujimoto, Shigeru*; Hirano, Mitsumasa*; Muta, Hitoshi*
no journal, ,
In this research project, study on probabilistic models and treatment of epistemic uncertainty, study on quantification of epistemic uncertainty on fragility assessment and verification of usefulness of proposed method are performed for reliability enhancement of seismic risk assessment. In this report, program plan and objectives are shown as part 1.
Muramatsu, Ken*; Furuya, Osamu*; Fujimoto, Shigeru*; Hirano, Mitsumasa*; Muta, Hitoshi*; Takada, Tsuyoshi*; Itoi, Tatsuya*; Nishida, Akemi; Uchiyama, Tomoaki*
no journal, ,
This project, focusing on uncertainty assessment framework and utilization of expertise, and finally developing relevant computer codes to improve reliability of seismic probabilistic risk assessment (SPRA) and to promote its further use of the SPRA, develops methodology for quantification of uncertainty associated with final results from SPRA in the framework of risk management of NPP facilities. The following scopes are set. (1) Development of framework of probabilistic models for uncertainty quantification and Computer codes (2) Aggregation of expert opinion on structure/equipment fragility estimation and development of implementation guidance on epistemic uncertainty (modeling uncertainty) (3) Study on applicability of SPRA to model plant. In this report, program plan of our research and new probabilistic models and treatment of epistemic uncertainty will be explained as part 1.
Muramatsu, Ken*; Takada, Tsuyoshi*; Nishida, Akemi; Uchiyama, Tomoaki*; Muta, Hitoshi*; Furuya, Osamu*; Fujimoto, Shigeru*; Itoi, Tatsuya*
no journal, ,
This is the first of a series of papers on a study on next generation seismic probabilistic safety assessment methodology being conducted by the authors as a three-year project "Reliability Enhancement of Seismic Risk Assessment of Nuclear Power Plants as Risk Management Fundamentals", which was started in 2012 and is funded by the Ministry of Education, Culture, Sports, Science & Technology (MEXT) of Japan. This paper gives an overview of the program plan and a proposal of new mathematical framework of S-PRA. We developed a computer code based on SECOM2-DQFM developed by JAEA. The proposed mathematical framework will be built-in it in order to make it possible to estimate the accident sequence occurrence probability and its uncertainty.
Muramatsu, Ken*; Uchiyama, Tomoaki*; Muta, Hitoshi*; Nishida, Akemi
no journal, ,
In this research project, study on probabilistic models and treatment of epistemic uncertainty, study on quantification of epistemic uncertainty on fragility assessment and verification of usefulness of proposed method are performed for reliability enhancement of seismic risk assessment. We are performing examination to treat the epistemic uncertainty in the analysis by using SECOM2-DQFM code developed by JAEA. Development of the program is now performed considered about uncertainty analysis method based on Direct Quantification of Fault Tree using Monte Carlo Simulation (DQFM) method. In this report, parallelization of the SECOM2-DQFM code, improvement to enhance the uncertainty analysis function, and the result of a trial analysis to target the BWR will be explained.
Muramatsu, Ken*; Muta, Hitoshi*; Furuya, Osamu*; Fujimoto, Shigeru*; Takada, Tsuyoshi*; Itoi, Tatsuya*; Nishida, Akemi; Uchiyama, Tomoaki*
no journal, ,
This project, focusing on uncertainty assessment framework and utilization of expertise, and finally developing relevant computer codes to improve reliability of seismic probabilistic risk assessment (SPRA) and to promote its further use of the SPRA, develops methodology for quantification of uncertainty associated with final results from SPRA in the framework of risk management of NPP facilities. The following scopes are set. (1) Development of framework of probabilistic models for uncertainty quantification and Computer codes, (2) Aggregation of expert opinion on structure/equipment fragility estimation and development of implementation guidance on epistemic uncertainty (modeling uncertainty), (3) Study on applicability of SPRA to model plant. In this report, new probabilistic models and treatment of epistemic uncertainty will be explained.
Furuya, Osamu*; Fujimoto, Shigeru*; Muramatsu, Ken*; Muta, Hitoshi*; Nishida, Akemi
no journal, ,
This project, focusing on uncertainty assessment framework and utilization of expertise, and finally developing relevant computer codes to improve reliability of seismic probabilistic risk assessment (SPRA) and to promote its further use of the SPRA, develops methodology for quantification of uncertainty associated with final results from SPRA in the framework of risk management of NPP facilities. The following scopes are set. (1) Development of framework of probabilistic models for uncertainty quantification and Computer codes, (2) Aggregation of expert opinion on structure/equipment fragility estimation and development of implementation guidance on epistemic uncertainty (modeling uncertainty), (3) Study on applicability of SPRA to model plant. In this report, epistemic uncertainty of the equipment and piping responses on the same floor is estimated by analytical point of view.
Honda, Yuki; Sato, Hiroyuki; Ohashi, Hirofumi; Nishida, Akemi; Muta, Hitoshi*; Muramatsu, Ken*; Itoi, Tatsuya*; Tanabe, Masayuki*
no journal, ,
We have been conducting a source term evaluation method development for high temperature gas-cooled reactors considering structural failures in the major components. We will present the outline of evaluation method and results of transient analysis for unprotected depressurized loss-of-forced cooling accident which may be initiated by Beyond-Design-Basis Earthquake.
Muramatsu, Ken*; Muta, Hitoshi*; Matsuda, Kosuke*; Sato, Hiroyuki; Nishida, Akemi; Ohashi, Hirofumi; Itoi, Tatsuya*; Tanabe, Masayuki*
no journal, ,
As part of PRA method development for High temperature Gas-cooled Reactor, domestic and international PRA standards are investigated to identify requirements related to accident scenario assessment and reliability database development. It was concluded that there are three key thing to note for the PRA method development, that is, detail analysis for passive components, integration of mechanistic source term evaluation and supplementation of reliability data.
Sato, Hiroyuki; Nishida, Akemi; Muramatsu, Ken*; Muta, Hitoshi*; Itoi, Tatsuya*; Takada, Tsuyoshi*; Tanabe, Masayuki*; Yamamoto, Tsuyoshi*
no journal, ,
Japan Atomic Energy Agency, in conjunction with Tokyo City University, The University of Tokyo and JGC Corporation, have started development of a probabilistic risk assessment method considering the safety and design features of High Temperature Gas-cooled Reactor (HTGR). The presentation will focus on project overview and progress in FY2017 and FY2018.
Matsuda, Kosuke*; Muramatsu, Ken*; Muta, Hitoshi*; Sato, Hiroyuki; Nishida, Akemi; Itoi, Tatsuya*
no journal, ,
The selection of initiating model for seismic PRA is studied. System analysis are conducted and compared for the case with initiating event hierarchy tree and the case with a multiple branching event tree. The analysis is performed with SECOM2-DQFM code developed by Japan Atomic Energy Agency. As a result of study, we have found the effective classification method for the seismic initiating events with satisfactory accuracy.
Noguchi, Kazuhiko*; Miyano, Hiroshi*; Muramatsu, Ken*; Narumiya, Yoshiyuki*; Takata, Takashi; Muta, Hitoshi*; Itoi, Tatsuya*; Matsumoto, Masaaki*; Matsunaga, Yoko*; Sugiyama, Kenichiro*
no journal, ,
The risk is used for an index to judge. The risk to be considered varies according to the purpose of the judgment. The analysis of the risk needs the knowledge of the nuclear energy system and society.
Miyano, Hiroshi*; Muramatsu, Ken*; Noguchi, Kazuhiko*; Narumiya, Yoshiyuki*; Takata, Takashi; Muta, Hitoshi*; Itoi, Tatsuya*; Matsumoto, Masaaki*; Matsunaga, Yoko*; Sugiyama, Kenichiro*
no journal, ,
In considering nuclear safety, it is an important task to clarify the relationship with "peace of mind" that is the heart of people. What is the state that scientific safety is something that people feel safe? We considered the relationship between quantified risk and safety, and ways to acquire peace of mind. We analyzed the thresholds of safety risks as a social common, showed a safe condition, and showed the importance of forming a consensus to obtain peace of mind.
Matsumoto, Masaaki*; Miyano, Hiroshi*; Noguchi, Kazuhiko*; Muramatsu, Ken*; Narumiya, Yoshiyuki*; Takata, Takashi; Muta, Hitoshi*; Itoi, Tatsuya*; Matsunaga, Yoko*; Sugiyama, Kenichiro*
no journal, ,
In society, understanding of risk is various. We will show how to understand risk and describe how to face risks in the society. Individual risks are accepted by individuals, but it is necessary for society to construct a structure in society that allows risks to be tolerated by society. For that purpose, we also describe what social risk is and how society and individuals face social risks and how to choose risks to accept. We consider not only the concept of nuclear risk but also how nuclear risk should be accepted from the viewpoint of disaster prevention for the public.
Matsunaga, Yoko*; Miyano, Hiroshi*; Noguchi, Kazuhiko*; Muramatsu, Ken*; Narumiya, Yoshiyuki*; Takata, Takashi; Muta, Hitoshi*; Itoi, Tatsuya*; Matsumoto, Masaaki*; Sugiyama, Kenichiro*
no journal, ,
After Fukushima Daiichi nuclear accident, it becomes more important risk communication with the public. In discussions with the public in nuclear safety, communication and discussions on risks that not only nuclear risks also social risks are important. Differences in viewpoints, understanding, and thought about risks become communication difficult. We need to discuss risks fairly, appropriately with the public and reduce total social risks.