Riyana, E. S.; Okumura, Keisuke; Sakamoto, Masahiro; Matsumura, Taichi; Terashima, Kenichi
Journal of Nuclear Science and Technology, 59(4), p.424 - 430, 2022/04
Hain, K.*; Martschini, M.*; Glce, F.*; Honda, Maki; Lachner, J.*; Kern, M.*; Pitters, J.*; Quinto, F.*; Sakaguchi, Aya*; Steier, P.*; et al.
Frontiers in Marine Science (Internet), 9, p.837515_1 - 837515_17, 2022/03
Recent major advances in accelerator mass spectrometry (AMS) at the Vienna Environmental Research Accelerator (VERA) regarding detection efficiency and isobar suppression have opened possibilities for the analysis of additional long-lived radionuclides at ultra-low environmental concentrations. These radionuclides, including U, Cs, Tc and Sr, will become important for oceanographic tracer application due to their generally conservative behavior in ocean water. In particular, the isotope ratios U/U and Cs/Cs have proven to be powerful fingerprints for emission source identification as they are not affected by elemental fractionation. Improved detection efficiencies allowed us to analyze all major long-lived actinides, i.e. U, Np, Pu, Am as well as the very rare U, in the same 10 L water samples of an exemplary depth profile from the northwest Pacific Ocean. Especially for Sr analysis, our new approach has already been validated for selected reference materials (e.g. IAEA-A-12) and is ready for application in oceanographic studies. We estimate that a sample volume of only (1-3) L ocean water is sufficient for Sr as well as Cs analysis, respectively.
Lind, T.*; Herranz, L. E.*; Sonnenkalb, M.*; Maruyama, Yu
Proceedings of 19th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-19) (Internet), 15 Pages, 2022/03
Rizaal, M.; Miwa, Shuhei; Suzuki, Eriko; Imoto, Jumpei; Osaka, Masahiko; Goullo, M.*
ACS Omega (Internet), 6(48), p.32695 - 32708, 2021/12
Shiotsu, Hiroyuki; Ito, Hiroto*; Sugiyama, Tomoyuki; Maruyama, Yu
Annals of Nuclear Energy, 163, p.108587_1 - 108587_9, 2021/12
Rodriguez, D.; Abbas, K.*; Koizumi, Mitsuo; Nonneman, S.*; Rossi, F.; Takahashi, Tone
Nuclear Instruments and Methods in Physics Research A, 1014, p.165685_1 - 165685_10, 2021/10
Udagawa, Yutaka; Tasaki, Yudai
JAEA-Data/Code 2021-007, 56 Pages, 2021/07
Japan Atomic Energy Agency (JAEA) has released FEMAXI-8 in 2019 as the latest version of the fuel performance code FEMAXI, which has been developed to analyze thermal and mechanical behaviors of a single fuel rod in mainly normal operation conditions and anticipated transient conditions. This report summarizes a newly developed model to analyze intragranular fission gas behaviors considering size distribution of gas bubbles and their dynamics. While the intragranular fission gas behavior models implemented in the previous FEMAXI versions have supported only treating single bubble size for a given fuel element, the new model supports multiple gas groups according to their size and treats their dynamic behaviors, making the code more versatile. The model was first implemented as a general module that takes arbitrary number of bubble groups and spatial mesh division for a given fuel grain system. An interface module to connect the model to FEMAXI-8 was then developed so that it works as a 2 bubble groups model, which is the minimum configuration of the multi-grouped model to be operated with FEMAXI-8 at the minimum calculation cost. FEMAXI-8 with the new intragranular model was subjected to a systematic validation calculation against 144 irradiation test cases and recommended values for model parameters were determined so that the code makes reasonable predictions in terms of fuel center temperature, fission gas release, etc. under steady-state and power ramp conditions.
Kakiuchi, Kazuo; Udagawa, Yutaka; Amaya, Masaki
Annals of Nuclear Energy, 155, p.108171_1 - 108171_11, 2021/06
Lind, T.*; Pellegrini, M.*; Herranz, L. E.*; Sonnenkalb, M.*; Nishi, Yoshihisa*; Tamaki, Hitoshi; Cousin, F.*; Fernandez Moguel, L.*; Andrews, N.*; Sevon, T.*
Nuclear Engineering and Design, 376, p.111138_1 - 111138_12, 2021/05
This is the third part of the three part paper describing the accidents at the FDNPS as analyzed in the Phase 2 of the OECD/NEA project "Benchmark Study of the Accident at the Fukushima Daiichi Nuclear Power Plant" (BSAF). In this paper, we describe the accident progression in unit 3. In the BSAF project, eight organizations from five countries analyzed severe accident scenarios for Unit 3 at the Fukushima Daiichi site using different severe accident codes. The present paper for Unit 3 describes the findings of the comparison of the participants' results against each other and against plant data, the evaluation of the accident progression and the final status inside the reactors. Special focus is on the status of the reactor pressure vessel, melt release and fission product release and transport. Unit 3 specific aspects, e.g., the complicated accident progression following repeated containment venting actuations and attempts at coolant injection at the time of the major core degradation, are highlighted and points of consensus as well as remaining uncertainties and data needs will be summarized. FP transport is analyzed, and the calculation results are compared with dose rate measurements in the containment. The release of I-131 and Cs-137 to the environment is compared with analysis conducted by using WSPEEDI code.
Rodriguez, D.; Bogucarska, T.*; Koizumi, Mitsuo; Lee, H.-J.; Pedersen, B.*; Rossi, F.; Takahashi, Tone; Varasano, G.*
Nuclear Instruments and Methods in Physics Research A, 997, p.165146_1 - 165146_13, 2021/05
Khatib-Rahbar, M.*; Barrachin, M.*; Denning, R.*; Gabor, J.*; Gauntt, R.*; Herranz, L. E.*; Hobbins, R.*; Jacquemain, D.*; Maruyama, Yu; Metcalf, J.*; et al.
NUREG/CR-7282, ERI/NRC 21-204 (Internet), 160 Pages, 2021/04
Collaborative Laboratories for Advanced Decommissioning Science; Tohoku University*
JAEA-Review 2020-032, 97 Pages, 2021/01
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 FY2018, this report summarizes the research results of the "Basic Research on the Stability of Fuel Debris Including Alloy Phase" conducted in FY2019. In the present study, we focus on fuel debris consisting of oxide phase and alloy phase generated by the high-temperature chemical reaction between structure materials (SUS pipes, pressure vessels, etc.) and fuels (melted fuels, claddings components, etc.). We synthesize the simulated debris of UO-SUS system and UO-Zr(ZrO)-SUS system by high-temperature heat treatment, and measure their chemical property and dissolution behavior in water. Also, we will conduct research and development to spectroscopically analyze secular changes of oxide phase and alloy phase in the simulated debris.
Kitamura, Akira; Akahori, Kuniaki; Nagata, Masanobu*
Genshiryoku Bakkuendo Kenkyu (CD-ROM), 27(2), p.83 - 93, 2020/12
Direct disposal of spent nuclear fuel (SNF) in deep underground repositories (hereafter "direct disposal") is a concept that disposal canisters stored fuel assemblies dispose without reprocessing. Behavior of radionuclide release from SNF must be different from that from vitrified glass. The present study established a methodology on determination of instant release fraction (IRF) of radionuclides from SNF, which is the one of the parameters on radionuclide release based on the latest safety assessment reports in other countries, especially for IRF values proportional to a fission gas release ratio (FGR). Recommended and maximum values of FGR have been estimated using the fuel performance code FEMAXI-7 after collecting FGR values on Japanese SNFs. Furthermore, recommended and maximum values of IRF for Japanese SNFs used in a pressurized water reactor (PWR) have been estimated using the presently obtained FGR values and experimentally obtained IRF values on foreign SNFs. The recommended and maximum IRF values obtained in the present study have been compared with those of the latest safety assessment reports in other countries.
Miyahara, Naoya; Miwa, Shuhei; Goullo, M.*; Imoto, Jumpei; Horiguchi, Naoki; Sato, Isamu*; Osaka, Masahiko
Journal of Nuclear Science and Technology, 57(12), p.1287 - 1296, 2020/12
In order to clarify the cesium iodide (CsI) transport behavior with a focus on the mechanisms of gaseous iodine formation in the reactor coolant system of LWR under a severe accident condition, a reproductive experiment of CsI transport behavior was conducted using a facility equipped with a thermal gradient tube. Various analyses on deposits and airborne materials during transportation could elucidate two mechanisms for the gaseous iodine formation. One was the gaseous phase chemical reaction in Cs-I-O-H system at relatively high-temperature region, which led to gaseous iodine transport to the lower temperature region without any further changes in gas species due to the kinetics limitation effects. The other one was the chemical reactions related to condensed phase of CsI, namely those of CsI deposits on walls with surface of stainless steel to form CsCrO compound and CsI aerosol particles with steam, which were newly found in this study.
Udagawa, Yutaka; Fuketa, Toyoshi*
Comprehensive Nuclear Materials, 2nd Edition, Vol.2, p.322 - 338, 2020/08
Miwa, Shuhei; Nakajima, Kunihisa; Miyahara, Naoya; Nishioka, Shunichiro; Suzuki, Eriko; Horiguchi, Naoki; Liu, J.; Miradji, F.; Imoto, Jumpei; Afiqa, B. M.; et al.
Mechanical Engineering Journal (Internet), 7(3), p.19-00537_1 - 19-00537_11, 2020/06
We constructed the fission product (FP) chemistry database named ECUME for LWR severe accident. This version of ECUME is equipped with dataset of the chemical reactions and their kinetics constants for the reactions of cesium(Cs)-iodine(I)-boron(B)-molybdenum(Mo)-oxygen(O)-hydrogen(H) system in gas phase, the elemental model for the high temperature chemical reaction of Cs with stainless steel applied as the structural material in a reactor, and thermodynamic data for CsBO vapor species and solids of CsSiO and CsFeSiO for these chemical reactions. The ECUME will provide estimation of Cs distribution due to the evaluation of effects of interaction with BWR control material B and stainless steel on Cs behavior in the Fukushima Daiichi Nuclear Power Station.
Collaborative Laboratories for Advanced Decommissioning Science; Tohoku University*
JAEA-Review 2019-035, 61 Pages, 2020/03
JAEA/CLADS, had been conducting the Center of World Intelligence Project for Nuclear Science/Technology and Human Resource Development (hereafter referred to "the Project") in FY2018. The Project aims to contribute to solving problems in nuclear energy field represented by the decommissioning of the Fukushima Daiichi Nuclear Power Station, Tokyo Electric Power Company Holdings, Inc. 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 FY2018, this report summarizes the research results of the "Basic Research on the Stability of Fuel Debris Including Alloy Phase". In the present study, we focus on fuel debris consisting of oxide phase and alloy phase generated by the high-temperature chemical reaction between structure materials (SUS pipes, pressure vessels, etc.) and fuels (melted fuels, claddings components, etc.). We synthesize the simulated debris of UO-SUS system and UO-Zr(ZrO)-SUS system by high-temperature heat treatment, and measure their chemical property and dissolution behavior in water. Also, we will conduct research and development to spectroscopically analyze secular changes of oxide phase and alloy phase in the simulated debris.
Development Group for LWR Advanced Technology
JAEA-Data/Code 2019-017, 59 Pages, 2020/03
ECUME (ffective hemistry database of fission products nder ultiphase raction) is the database for the analyses of FP chemistry which strongly affects all the FP behaviors in a severe accident (SA) of nuclear facility like LWR. ECUME consists of three kinds of datasets: CRK (dataset for hemical eaction inetics), EM (lemental odel set) and TD (hermoynamic dataset). The present version of ECUME is prepared especially for the more accurate evaluation of cesium and iodine distribution in a reactor and release amount into an environment which should be of crucial importance towards the decommissioning of Fukushima Daiichi Nuclear Power Station of Tokyo Electric Power Company Holdings (1F) and the enhancement of LWR safety after the 1F SA.
Kurata, Masaki; Osaka, Masahiko; Jacquemain, D.*; Barrachin, M.*; Haste, T.*
Advances in Nuclear Fuel Chemistry, p.555 - 625, 2020/00
The importance of fuel chemistry has been revivaled since Fukushima-Daiichi Nuclear Power Station (FDNPS) accident. The inspection and analysis of damaged three units, which had been operated in March 11, 2011, showed large differences in the accident progression sequence for these units, because operators attempted to prevent or mitigate the accident progression of each unit by all means possible. Characteristics of fuel debris are considered to be largely influenced by the difference in the sequence and, hence, deviated from those predicted from prototypic accident scenarios, which had been mainly identified from the analysis of Three Mile Island-2 (TMI-2) accident and the following sim-tests. For the proper improvement of our knowledge on severe accident (SA), including non-prototypic conditions, one has to start improving the phenomenology of fuel/core degradation and fission product (FP) behavior. Advances in the chemistry is the most essential approach. The present review attempts to focus on the recent updates and remaining concerns after the FDNPS accident.
Nakatsuka, Toru; Maeda, Toshikatsu; Sugiyama, Tomoyuki; Maruyama, Yu
Proceedings of 18th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-18) (USB Flash Drive), p.1650 - 1656, 2019/08
The OECD/NEA is launching a new project named "Analysis of Information from Reactor Buildings and Containment Vessels of Fukushima Daiichi Nuclear Power Station (ARC-F)" Project. This project will serve as the successor to the precedent NEA project, "Benchmark Study of the Accident at the Fukushima Daiichi Nuclear Power Station (BSAF) Phase II" which investigated the accident scenarios, associated fission products behavior in the damaged units and source term to the environment. The ARC-F project comprises three tasks: Task 1: Refinement of analysis for accident scenarios and associated fission product transportation and dispersion; Task 2: Compilation and management of data and information; and Task 3: Discussion for future long-term project. Japan Atomic Energy Agency is the operating agent, responsible to lead all the tasks. Duration of the project is from January 2019 to December 2021 and the final report is planned to be published in 2022.