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Tanaka, Masaaki; Kudo, Yoshiro*; Nakada, Kotaro*; Koshizuka, Seiichi*
Proceedings of 18th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-18) (USB Flash Drive), p.1473 - 1484, 2019/08
Verification and validation (V&V) including uncertainty quantification on modeling and simulation activities has been very much focused on. Due to increase of requirement for standardization of the procedures on the V&V and prediction process to enhance the simulation credibility, "Guideline for Credibility Assessment of Nuclear Simulations (AESJ-SC-A008: 2015)" was published on July 2016 from the AESJ through ten-year discussion. The paper describes brief history of discussion in the AESJ to the publication and introductory explanation of the procedures in the five major elements and one scheme described in the Guideline. And also, a practical experience of the V&V activity according to the fundamental concept indicated in the Guideline is introduced.
Chai, P.; Yamashita, Susumu; Nagae, Yuji; Kurata, Masaki
Proceedings of 9th Conference on Severe Accident Research (ERMSAR 2019) (Internet), 14 Pages, 2019/03
In order to obtain a precise understanding of molten material behavior inside RPV and to improve the accuracy of the SA code, a new computational fluid dynamics (CFD) code with multi-phase, multi-physics models, which is called JUPITER, was developed. It optimized the algorithms of the multi-phase calculation. Besides, the chemical reactions are also modeled carefully in the code so that the melting process could be treated precisely. A series of verification and validation studies are conducted, which show good agreement with analytical solutions and previous experiments. The capabilities of the multi-physics models in JUPITER code provide us another useful tool to investigate the molten material behaviors in the relevant severe accident scenario.
Nakada, Kotaro*; Kudo, Yoshiro*; Koshizuka, Seiichi*; Tanaka, Masaaki
Nihon Genshiryoku Gakkai-Shi ATOMO
, 60(3), p.173 - 177, 2018/03
The Atomic Energy Society of Japan (AESJ) published "Guideline for Credibility Assessment of Nuclear Simulations 2015" in June, 2016 which specifies the concepts on methodology for the prediction with uncertainty quantification and the quality management based on the concept of verification and validation (V&V) of modeling and simulation. In this report, the outlines of activities in AESJ for publication of the guideline and the expectation for effective implementation of the guideline are described including that of the lectures with major respondents of the questionnaires.
Kamide, Hideki; Ohshima, Hiroyuki; Sakai, Takaaki; Tanaka, Masaaki
Proceedings of 16th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-16) (USB Flash Drive), p.8141 - 8155, 2015/08
In this paper, the authors focus on four kinds of thermal-hydraulic issues associated with the SDC, i.e. fuel assembly thermal-hydraulics, natural circulation decay heat removal, thermal striping phenomena, and core disruptive accidents, and provide a description of their evaluation method developments including verification and validation and necessary experimental studies for the Japan Sodium-cooled Fast Reactor (JSFR). These evaluation methods are planned to be eventually integrated into a comprehensive numerical simulation system that can be applied to all phenomena envisioned in SFR systems and that can be expected to become an effective tool for the development of human resource and the handing down of knowledge/technologies.
Shimazaki, Yosuke; Isaka, Kazuyoshi; Nomoto, Yasunobu; Seki, Tomokazu; Ohashi, Hirofumi
JAEA-Technology 2014-038, 51 Pages, 2014/12
JAEA-Technology-2014-038.pdf:3.84MB
The analytical models for the evaluation of graphite oxidation were implemented into the THYTAN code, which employs the mass balance and a node-link computational scheme to evaluate tritium behavior in the High Temperature Gas-cooled Reactor (HTGR) systems for hydrogen production, to analyze the graphite oxidation during the air or water ingress accidents in the HTGR systems. This report describes the analytical models of the THYTAN code in terms of the graphite oxidation analysis and its verification and validation (V&V) results. Mass transfer from the gas mixture in the coolant channel to the graphite surface, diffusion in the graphite, graphite oxidation by air or water, chemical reaction and release from the primary circuit to the containment vessel by a safety valve were modeled to calculate the mass balance in the graphite and the gas mixture in the coolant channel. The computed solutions using the THYTAN code for simple questions were compared to the analytical results by a hand calculation to verify the algorithms for each implemented analytical model. A representation of the graphite oxidation experimental was analyzed using the THYTAN code, and the results were compared to the experimental data and the computed solutions using the GRACE code, which was used for the safety analysis of the High Temperature Engineering Test Reactor (HTTR), in regard to corrosion depth of graphite and oxygen concentration at the outlet of the test section to validate the analytical models of the THYTAN code. The comparison of THYTAN code results with the analytical solutions, experimental data and the GRACE code results showed the good agreement.
Ito, Kei; Kunugi, Tomoaki*; Ohshima, Hiroyuki
no journal, ,
no abstracts in English
Tanaka, Masaaki
no journal, ,
Author has proposed a procedure combined with V&V and numerical prediction processes called as V2UP (V&V plus Uncertainty quantification and Prediction) in a numerical estimation by multi-dimensional simulation codes. In the V2UP, uncertainty quantification by Grid Convergence Index (GCI) is required in the verification and the fundamental validation steps. The numerical simulations and the uncertainty quantifications were conducted using several GCI estimation methods in order to specify the reference method in the V2UP. Through the examinations, the SLS-GCI (Simplified Least Square version GCI) method modified from the Eca's least-square version GCI method could be defined.
Tanaka, Masaaki
no journal, ,
In development of numerical simulation codes and estimation methods for plant design and safety assessment, implementation of verification and validation (V&V) and uncertainty quantification is required. To establish the practical procedures of the uncertainty quantification, the SLS-GCI (Simplified Least Square version GCI) method modified from the Eca's least-square version GCI method was established. Through the several examinations, the applicability of the SLS-GCI method was confirmed.
Tanaka, Masaaki
no journal, ,
In the lecture course of "Guideline for Credibility Assessment of Nuclear Simulations: 2015", the latest situation in overseas regarding V&V activities is to be introduced during the panel discussion (Part 1).
Tanaka, Masaaki
no journal, ,
In the lecture course of "Guideline for Credibility Assessment of Nuclear Simulations: 2015", the outline of the V2UP (V&V Plus Uncertainty Quantification and Prediction) procedure for high cycle thermal fatigue in sodium-cooled fast reactor is to be introduced.
Tanaka, Masaaki
no journal, ,
In the lecture course of "Guideline for Credibility Assessment of Nuclear Simulations: 2015", the latest situation in overseas regarding V&V activities is to be introduced during the panel discussion (Part 1).
Tanaka, Masaaki
no journal, ,
In the lecture course of "Guideline for Credibility Assessment of Nuclear Simulations: 2015", the outline of the V2UP (V&V Plus Uncertainty Quantification and Prediction) procedure for high cycle thermal fatigue in sodium-cooled fast reactor is to be introduced.
Tanaka, Masaaki
no journal, ,
In the development of the simulation code and the numerical estimation for high cycle thermal fatigue on a structure caused by thermal striping phenomena in sodium cooled fast reactors, implementation of verification and validation (V&V) process is indispensable. A procedure named V2UP (Verification and Validation plus Uncertainty quantification and Prediction) has been made by referring to the existing guidelines regarding the V&V published by AESJ. In this presentation, installation of quality management procedures into the V2UP procedure is attempted based on the existing standard regarding guidelines of quality management system.
Tanaka, Masaaki
no journal, ,
Activities of the subcommittee in Atomic Energy Society of Japan (AESJ) for the publication of "Guideline for Credibility Assessment of Nuclear Simulations 2015" are introduced and a case study of VVUQ (verification and validation plus uncertainty quantification) application to the numerical simulation of the T-junction piping system is briefly presented.
Takamatsu, Kuniyoshi; Okita, Shoichiro; Tachibana, Yukio; Nishimura, Yosuke*; Okamoto, Koji*
no journal, ,
In this study, accident analyses of high-power density HTGRs adopting SiC-matrixed fuel compacts and feasibility study were conducted. Specifically, for the feasibility study, rapid depressurization accidents were analyzed using the two-dimensional unsteady heat transfer analysis code for safety evaluation of HTGRs. As a result of the rapid depressurization accident analyses, the fuel temperature and RPV temperature distributions in the HTGRs with high-power density were clarified, and it was confirmed that the maximum fuel temperature does not exceed 1400
C. In other words, even if a rapid depressurization accident occurs, the high-power density HTGRs adopting SiC-matrixed fuel compacts will be able to have excellent passive safety features.
Nishimura, Yosuke*; Anna, G.*; Yoshida, Katsumi*; Takamatsu, Kuniyoshi; Okamoto, Koji*
no journal, ,
In this study, fuel compacts adopting SiC matrix are developed for HTGRs with high power density. In manufacturing SiC matrix, it was found that reactive sintering method can be applied from the thermal and chemical properties of SiC. Additionally, high-temperature oxidation tests simulating an accident showed the passive oxidation mode that forms a stable SiO
oxide film on the SiC surface; therefore, it was confirmed that SiC matrix has its excellent oxidation resistance. Furthermore, the chemical composition with more Si-rich showed the further improved oxidation resistance performance and the higher fuel integrity in accident conditions. As a result, even in an accident at 1400C, the SiC matrix will not corrode and the fuel integrity will be ensured.