Main outputs from the OECD/NEA ARC-F Project

丸山 結; 杉山 智之*; 島田 亜佐子; Lind, T.*; Bentaib, A.*; Sogalla, M.*; Pellegrini, M.*; Albright, L.*; Clayton, D.*

Proceedings of 20th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-20) (Internet), p.4782 - 4795, 2023/08

http://dx.doi.org/10.13182/NURETH20-40302

The Analysis of Information from Reactor Buildings and Containment Vessels of Fukushima Daiichi Nuclear Power Station (FDNPS) (ARC-F) project was initiated in January 2019 for three years with 22 signatories from 12 countries. Three main tasks were implemented in the ARC-F project, which were relevant to 1) refinement of analysis for accident scenarios and associated fission product (FP) transport and dispersion, 2) compilation and management of data and information, and 3) discussion for the next-phase project. Various activities were performed in Task 1, covering improvement of analysis for accident scenarios, and in-depth analyses for specific phenomena such as in-vessel melt progression, molten core/concrete interaction, FP transport and source term, hydrogen combustion and atmospheric dispersion of FPs. Through these studies, analyses for accident scenarios with severe accident codes were refined and important phenomena with large uncertainties were clarified. In order to share well selected and organized information from the FDNPS with the project partners, two databases, information source database and sample database, were built under Task 2. The analysis techniques including the separation of iodine species were developed also in Task 2 and applied to the analysis of FPs in several samples taken from the FDNPS. The next-phase project was discussed in Task 3, resulting in launching the Fukushima Daiichi Nuclear Power Station Information Collection and Evaluation (FACE) project. The FACE project officially started in July 2022 with the participation of 23 organizations from 12 countries and the European Commission.

Overview and outcomes of the OECD/NEA benchmark study of the accident at the Fukushima Daiichi NPS (BSAF), Phase 2; Results of severe accident analyses for unit 3

Lind, T.*; Pellegrini, M.*; Herranz, L. E.*; Sonnenkalb, M.*; 西 義久*; 玉置 等史; Cousin, F.*; Fernandez Moguel, L.*; Andrews, N.*; Sevon, T.*

Nuclear Engineering and Design, 376, p.111138_1 - 111138_12, 2021/05

https://doi.org/10.1016/j.nucengdes.2021.111138

OECD/NEAプロジェクト"福島第一原子力発電所事故に関するベンチマーク研究"のフェーズ2において、5か国8組織が異なるシビアアクシデント解析コードを用いて3号機の事故解析を行った。本報告では、参加機関の3号機の解析結果やプラントデータとの比較から得られた知見、事故進展の評価及び最終的な原子炉内の状態について述べる。特に原子炉圧力容器の状態、溶融炉心の放出及びFP挙動及び放出について焦点を当てる。また、大きく炉心損傷の進展があったであろう時期に繰り返し行われた格納容器ベント操作や冷却水注水の試みという3号機の特徴に焦点を当て、不確かさや必要となるデータも含めコンセンサスを得た点についてまとめる。さらにFP移行挙動解析と格納容器内で測定された線量の比較、またI-131及びCs137の環境への放出量とWPSPEEDIコードによる解析結果との比較を行った。

Overview and outcomes of the OECD/NEA benchmark study of the accident at the Fukushima Daiichi NPS (BSAF) Phase 2; Results of severe accident analyses for Unit 1

Herranz, L. E.*; Pellegrini, M.*; Lind, T.*; Sonnenkalb, M.*; Godin-Jacqmin, L.*; Lpez, C.*; Dolganov, K.*; Cousin, F.*; 玉置 等史; Kim, T. W.*; et al.

Nuclear Engineering and Design, 369, p.110849_1 - 110849_7, 2020/12

https://doi.org/10.1016/j.nucengdes.2020.110849

OECD/NEAプロジェクト"福島第一原子力発電所事故に関するベンチマーク研究"のフェーズ2は2015年中期に開始された。このプロジェクトの目的は、解析期間を地震発生から3週間に拡張、核分裂生成物(FP)の挙動や環境への放出、そして放射線に関するデータや逆解析によるソースターム推定等の様々なデータとの比較を行うことである。6か国9組織が異なるシビアアクシデント解析コードを用いて1号機の事故解析を行った。本報告では、参加機関の1号機の解析結果やプラントデータとの比較から得られた知見、事故進展の評価及び最終的な原子炉内の状態について述べる。特に原子炉圧力容器の状態、溶融炉心の放出及びFP挙動及び放出について焦点を当てる。また、1号機特有の事柄に焦点を当て、不確かさや必要となるデータも含めコンセンサスを得た点についてまとめる。

Main findings, remaining uncertainties and lessons learned from the OECD/NEA BSAF Project

Pellegrini, M.*; Herranz, L.*; Sonnenkalb, M.*; Lind, T.*; 丸山 結; Gauntt, R.*; Bixler, N.*; Morreale, A.*; Dolganov, K.*; Sevon, T.*; et al.

Nuclear Technology, 206(9), p.1449 - 1463, 2020/09

https://doi.org/10.1080/00295450.2020.1724731

The OECD/NEA Benchmark Study at the Accident of Fukushima Daiichi Nuclear Power Station (BSAF) project, which started in 2012 and continued until 2018, was one of the earliest responses to the accident at Fukushima Daiichi. The project, divided into two phases addressed the investigation of the accident at Unit 1, 2 and 3 by Severe Accident (SA) codes until 500 h focusing on thermal-hydraulics, core relocation, Molten Corium Concrete Interaction (MCCI) and fission products release and transport. The objectives of BSAF were to make up plausible scenarios based primarily on SA forensic analysis, support the decommissioning and inform SA codes modeling. The analysis and comparison among the institutes have brought up vital insights regarding the accident progression identifying periods of core meltdown and relocation, Reactor Pressure Vessel (RPV) and Primary Containment Vessel (PCV) leakage/failure through the comparison of pressure, water level and CAMS signatures. The combination of code results and inspections (muon radiography, PCV inspection) has provided a picture of the current status of the debris distribution and plant status. All units present a large relocation of core materials and all of them present ex-vessel debris with Unit 1 and Unit 3 showing evidences of undergoing MCCI. Uncertainties have been identified in particular on the time and magnitude of events such as corium relocation in RPV and into cavity floor, RPV and PCV rupture events. Main uncertainties resulting from the project are the large and continuous MCCI progression predicted by basically all the SA codes and the leak pathways from RPV to PCV and PCV to reactor building and environment. The BSAF project represents a pioneering exercise which has set the basis and provided lessons learned not only for code improvement but also for the development of new related projects to investigate in detail further aspects of the Fukushima Daiichi accident.

The States of the art of the nondestructive assay of spent nuclear fuel assemblies; A Critical review of the Spent Fuel NDA Project of the U.S. Department of Energy's Next Generation Safeguards Initiative

Bolind, A. M.*; 瀬谷 道夫

JAEA-Review 2015-027, 233 Pages, 2015/12

JAEA-Review-2015-027.pdf:30.21MB

米国エネルギー省/国家安全保障庁の次世代保障措置イニシアティブ(NGSI)での「使用済み燃料非破壊測定プロジェクト」で検討されている14の最新の使用済み燃料集合体非破壊測定(NDA)技術手法に関する調査研究成果を報告するとともに、このNDAの精度の観点からの議論と批評を行う。この報告書では、現在提案されているNDA方法に関する主たる問題である測定結果の大きな曖昧さ(誤差)が、第一義的には独立な測定手法で行っていないことから発生していることを示す。この報告書では筆者らは、NDA結果を改善するためには、NDAの物理量が3次元構成となっているため、少なくとも3つの独立したNDA手法が必要であることを示す。

Investigation of early oxide-layer formation using neutron reflectometer

Rivai, A. K.; Bolind, A. M.*; 斎藤 滋; 山崎 大; 菊地 賢司*

no journal, , 

Investigation of early oxide-layer formation has been done using the neutron reflectometer, i.e., SUIREN (apparatus for Surface and Interface investigations with Reflection of Neutrons), at the nuclear reactor research JRR-3 of JAEA. The tested materials were pre-oxidized, solution-annealed, JPCA steel specimens. Two types of early oxide layers were investigated, i.e., oxidation in air at 900C for 1 minute and oxidation in air at 450C for 75 hours. The results showed that the neutron reflectometer was able to detect the early formation of oxide layers.