MAAP code analysis focusing on the fuel debris conditions in the lower head of the pressure vessel in Fukushima-Daiichi Nuclear Power Station Unit 3

Sato, Ikken; Yoshikawa, Shinji; Yamashita, Takuya; Shimomura, Kenta; Cibula, M.*; Mizokami, Shinya*

Nuclear Engineering and Design, 414, p.112574_1 - 112574_20, 2023/12

https://doi.org/10.1016/j.nucengdes.2023.112574

Sodium-cooled Fast Reactors

Ohshima, Hiroyuki; Morishita, Masaki*; Aizawa, Kosuke; Ando, Masanori; Ashida, Takashi; Chikazawa, Yoshitaka; Doda, Norihiro; Enuma, Yasuhiro; Ezure, Toshiki; Fukano, Yoshitaka; et al.

Sodium-cooled Fast Reactors; JSME Series in Thermal and Nuclear Power Generation, Vol.3, 631 Pages, 2022/07

https://shop.elsevier.com/books/sodium-cooled-fast-reactors/morishita/978-0-12-824076-2

This book is a collection of the past experience of design, construction, and operation of two reactors, the latest knowledge and technology for SFR designs, and the future prospects of SFR development in Japan. It is intended to provide the perspective and the relevant knowledge to enable readers to become more familiar with SFR technology.

Prediction of RPV lower structure failure and core material relocation behavior with MPS method (Contract research)

Yoshikawa, Shinji; Yamaji, Akifumi*

JAEA-Research 2021-006, 52 Pages, 2021/09

JAEA-Research-2021-006.pdf:3.89MB

In Fukushima Daiichi Nuclear Power Station (referred to as "FDNPS" hereafter) unit2 and unit3, failure of the reactor pressure vessel (RPV) and relocation of some core materials (CRD piping elements and upper tie plate, etc.) to the pedestal region have been confirmed. In boiling water reactors (BWRs), complicated core support structures and control rod drive mechanisms are installed in the RPV lower head and its upper and lower regions, so that the relocation behavior of core materials to pedestal region is expected to be also complicated. The Moving Particle Semi-implicit (MPS) method is expected to be effective in overviewing the relocation behavior of core materials in complicated RPV lower structure of BWRs, because of its Lagrangian nature in tracking complex interfaces. In this study, for the purpose of RPV ablation analysis of FDNPS unit2 and unit3, rigid body model, parallelization method and improved calculation time step control method were developed in FY 2019 and improvement of pressure boundary condition treatment, stabilization of rigid body model, and calculation cost reduction of debris bed melting simulation were achieved in FY2020. These improvements enabled sensitivity analyses of melting, relocation and re-distribution behavior of deposited solid debris in RPV lower head on various cases, within practical calculation cost. As a result of the analyses of FDNPS unit2 and unit3, it was revealed that aspect (particles/ingots) and distribution (degree of stratification) of solidified debris in lower plenum have a great impact on the elapsed time of the following debris reheat and partial melting and on molten pool formation process, further influencing RPV lower head failure behavior and fuel debris discharging behavior.

Post-processor coding for large-scale transient simulation computer codes

Yoshikawa, Shinji

JAEA-Technology 2019-024, 22 Pages, 2020/03

JAEA-Technology-2019-024.pdf:1.76MB
JAEA-Technology-2019-024-appendix(CD-ROM).zip:73.55MB

In various technical fields of nuclear energy, computer codes are often used for transient simulations of target phenomena. Some of the codes were developed many years ago and have been revised with newly acquired findings, rather than newly developed, because of many encompassed numerical models and complexity of algorithms. In many cases, available outputs for users are output text files and graphs showing temporal variations of parameters, despite diversified and huge number of output information items are posing difficulty to the users in grasping the whole picture of the reproduced phenomena. This report compiles a series of know-hows in building a post-processor software for large simulation codes which serves as an interactive tool for code users in understanding the reproduced consequence with visually understandable information items. These know-hows are acquired through post-processor developments for LWR severe accident simulation codes RELAP/SCDAPSIM and MELCOR.

Progress of divertor simulation research toward the realization of detached plasma using a large tandem mirror device

Nakashima, Yosuke*; Takeda, Hisahito*; Ichimura, Kazuya*; Hosoi, Katsuhiro*; Oki, Kensuke*; Sakamoto, Mizuki*; Hirata, Mafumi*; Ichimura, Makoto*; Ikezoe, Ryuya*; Imai, Tsuyoshi*; et al.

Journal of Nuclear Materials, 463, p.537 - 540, 2015/08

https://doi.org/10.1016/j.jnucmat.2014.12.063

Trial visualization of fast reactor design knowledge

Yoshikawa, Shinji; Minami, Masaki*; Takahashi, Tadao*

Journal of Nuclear Science and Technology, 48(4), p.709 - 714, 2011/04

https://doi.org/10.3327/jnst.48.709

In design problems of large-scale systems like fast breeder reactors, inter-relations among design specifications are very important where a selected specification option is transferred to other specification selections as a premise to be taken account in engineering judgments. These inter-relations are also important in design case studies with hypothetical adoption of rejected design options for evaluation of deviation propagations among design specifications. Some of these rejected options have potential worth for future reconsideration by some circumstance changes (e.g., advanced simulations to exclude needs for mock-up tests, etc), to contribute for flexibility in system designs. In this study, a computer software is built to visualize design problem structure by representing engineering knowledge nodes on individual specification selections along with inter-relations of design specifications, to validate the knowledge representation method and to derive open problems.

Nuclear Facilities Management Section Mutsu Office, Aomori Research and Development Center operations report; FY 2008

Nagane, Satoru; Matsuno, Satoru; Yamamoto, Makoto; Tobinai, Kazuhito; Ozaki, Shinji; Sato, Yasuo; Kitahara, Katsumi; Yoshikawa, Seiji

JAEA-Review 2009-018, 39 Pages, 2009/08

JAEA-Review-2009-018.pdf:7.71MB

Nuclear Facilities Management Section is, Liquid nuclear waste facility, a small nuclear fuel treatment facility, operation, maintenance and decommissioning of the nuclear ship "MUTSU", which carried out the operation and maintenance services of solid waste facilities. This paper, the nuclear facilities Management Section, Office of FY2008 year (April 2008-March 2009) summarized results of operations.

Data description for coordinated research project on benchmark analyses of sodium natural convection in the upper plenum of the Monju reactor vessel under supervisory of Technical Working Group on Fast Reactors, International Atomic Energy Agency

Yoshikawa, Shinji; Minami, Masaki*

JAEA-Data/Code 2008-024, 28 Pages, 2009/01

JAEA-Data-Code-2008-024.pdf:5.83MB

A series of information required for numerical simulation of sodium thermal stratification observed at the plant trip test of "Monju" conducted in 1995 is provided, which consists of the test outline, geometry data of the reactor vessel upper plenum between the reactor core top and reactor outlet nozzles, and flow inlet boundary conditions at the reactor core top surface.

Effects of composition and structure on hydrogen incorporation in tungsten oxide films deposited by sputtering

Inoue, Aichi; Yamamoto, Shunya; Nagata, Shinji*; Yoshikawa, Masahito; Shikama, Tatsuo*

Nuclear Instruments and Methods in Physics Research B, 266(15), p.3381 - 3386, 2008/08

https://doi.org/10.1016/j.nimb.2008.05.008

The effects of composition and structure on hydrogen incorporation property in tungsten oxide films were investigated. The tungsten oxide was deposited on carbon and SiO substrates to form films by varying the temperature from 30 to 600 C using a reactive sputtering in argon and oxygen mixture. We obtained amorphous structure in the films deposited below 400 C and (0 1 0) oriented monoclinic WO in the films deposited beyond 400 C. Hydrogen concentration in the films increased from 0.1 to 0.7 H/W with changing the composition from WO to WO. The hydrogen concentration in WO films decreased to 0.4 H/W with increasing the substrate temperature during deposition. The Raman spectra of the WO films revealed that decreasing of W=O terminals was related to that of the hydrogen concentration. It was considered in detail that the incorporated hydrogen in tungsten oxide films was bonded at the end of W=O terminals.

Hydrogen behavior in gasochromic tungsten oxide films investigated by elastic recoil detection analysis

Inoue, Aichi; Yamamoto, Shunya; Nagata, Shinji*; Yoshikawa, Masahito; Shikama, Tatsuo*

Nuclear Instruments and Methods in Physics Research B, 266(2), p.301 - 307, 2008/01

https://doi.org/10.1016/j.nimb.2007.11.016

Changes in the composition and crystalline structure of gasochromic tungsten oxide films resulting from the incorporation of hydrogen were investigated. An uniaxial oriented films in the (0 1 0) plane of monoclinic WO were obtained by reactive RF magnetron sputtering at 600 C. The elastic recoil detection analysis for the films on glassy carbon revealed that the hydrogen impurity was uniformly distributed up to a concentration of 0.24 H/W. The Pd-coated films on SiO turned to blue when they were exposed to a mixture of Ar and 5% H gases. When the sample became colored, the hydrogen concentration in the film increased to 0.47 H/W and the crystalline structure of the film changed from monoclinic to tetragonal. These results indicated that the gasochromic coloration of the tungsten oxide films was accompanied by formation of hydrogen compounds called tungsten bronze (H WO).