Development of a hybrid method for evaluating the long-term structural soundness of nuclear reactor buildings using response monitoring and damage imaging technologies (Contract research); FY2021 Nuclear Energy Science & Technology and Human Resource Development Project

Collaborative Laboratories for Advanced Decommissioning Science; Tohoku University*

JAEA-Review 2022-071, 123 Pages, 2023/03

JAEA-Review-2022-071.pdf:6.07MB

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 FY2021. 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 FY2021, this report summarizes the research results of the "Development of a hybrid method for evaluating the long-term structural soundness of nuclear reactor buildings using response monitoring and damage imaging technologies" conducted in FY2021. The present study aims to develop an evaluation method necessary to obtain a perspective on the long-term structural soundness of accident-damaged reactor buildings, where accessibility to work sites is extremely limited due to high radiation dose rate and high contamination. In FY2021, the first year of the three-year plan, the following research items were undertaken by clarifying specific research methods, setting research directions, making necessary preparations, and conducting some tests and other activities.

Investigation and consideration on evaluation of radiation doses to residents in the case of a nuclear emergency

Hashimoto, Makoto; Kinase, Sakae; Munakata, Masahiro; Murayama, Takashi; Takahashi, Masa; Takada, Chie; Okamoto, Akiko; Hayakawa, Tsuyoshi; Sukegawa, Masato; Kume, Nobuhide*; et al.

JAEA-Review 2020-071, 53 Pages, 2021/03

JAEA-Review-2020-071.pdf:2.72MB

In the case of a nuclear accident or a radiological emergency, the Japan Atomic Energy Agency (JAEA), as a designated public corporation assigned in the Disaster Countermeasures Basic Act and the Armed Attack Situation Response Law, undertakes technical supports to the national government and local governments. The JAEA is requested to support to evaluate radiation doses to residents in a nuclear emergency, which is specified in the Basic Disaster Management Plan and the Nuclear Emergency Response Manual. For the dose evaluation, however, its strategy, target, method, structure and so on have not been determined either specifically or in detail. This report describes the results of investigation and consideration discussed in the "Working Group for Radiation Dose Evaluation at a Nuclear Emergency" established within the Nuclear Emergency Assistance and Training Center to discuss technical supports for radiation dose evaluation to residents in the case of a nuclear emergency, and aims at contributing to specific and detailed discussion and activities in the future for the national government and local governments, also within the JAEA.

External dose evaluation based on detailed air dose rate measurements in living environments

Sato, Tetsuro*; Ando, Masaki; Sato, Masako*; Saito, Kimiaki

Journal of Environmental Radioactivity, 210, p.105973_1 - 105973_7, 2019/12

https://doi.org/10.1016/j.jenvrad.2019.05.005

A method was devised for estimation of external doses of Fukushima residents expected to return to their homes after evacuation orders are lifted. 211 residents expected to return to six towns and villages were surveyed in FY 2014, FY 2015, and FY2016. Interviewing returning residents about their expected life patterns after returning, air dose rate were measured along the reported personal trails representing their patterns of movement in daily life. Excluding 15 residents from whose homes we were unable to take air dose rate measurements, the maximum external effective dose and the average external effective dose were estimated respectively as 4.9 mSv/y and 0.86 mSv/y. Although the mean values and dispersion of external effective doses differ depending on the evacuation level, for 93.3% of all residents, the estimated external effective doses were less than 2 mSv/y. The average exposure dose at home accounts for 66.8% of the annual exposure dose.

Repeatability and reproducibility of measurements of low dissolved radiocesium concentrations in freshwater using different pre-concentration methods

Kurihara, Momo*; Yasutaka, Tetsuo*; Aono, Tatsuo*; Ashikawa, Nobuo*; Ebina, Hiroyuki*; Iijima, Takeshi*; Ishimaru, Kei*; Kanai, Ramon*; Karube, Jinichi*; Konnai, Yae*; et al.

Journal of Radioanalytical and Nuclear Chemistry, 322(2), p.477 - 485, 2019/11

https://doi.org/10.1007/s10967-019-06696-2

We assessed the repeatability and reproducibility of methods for determining low dissolved radiocesium concentrations in freshwater in Fukushima. Twenty-one laboratories pre-concentrated three of 10 L samples by five different pre-concentration methods (prussian-blue-impregnated filter cartridges, coprecipitation with ammonium phosphomolybdate, evaporation, solid-phase extraction disks, and ion-exchange resin columns), and activity of radiocesium was measured. The z-scores for all of the Cs results were within 2, indicating that the methods were accurate. The relative standard deviations (RSDs) indicating the variability in the results from different laboratories were larger than the RSDs indicating the variability in the results from each separate laboratory.

Application of nuclear data to the decommissioning of the Fukushima Daiichi Nuclear Power Station

Okumura, Keisuke; Riyana, E. S.

JAEA-Conf 2018-001, p.63 - 68, 2018/12

https://doi.org/10.11484/jaea-conf-2018-001

The decommissioning of the Fukushima Daiichi Nuclear Power Station (1F) is an unexplored field. Although the investigations for inside primary containment vessel (PCV) by robots have been underway by IRID, actual situation inside the PCV and the characteristics of fuel debris have not been sufficiently clarified yet. Under such circumstances, the computational simulation with reliable data is an effective means for solving many problems for the 1F decommissioning. Here, as application examples using nuclear data such as JENDL-4.0, we will introduce some researches and developments on (1) prediction of dose rate distribution in PCV, (2) remotely operated vehicle (ROV) system to explore submerged fuel debris in PCV, (3) non-destructive assay of nuclear fuel materials in a fuel debris canister.

CIELO collaboration summary results; International evaluations of neutron reactions on uranium, plutonium, iron, oxygen and hydrogen

Chadwick, M. B.*; Capote, R.*; Trkov, A.*; Herman, M. W.*; Brown, D. A.*; Hale, G. M.*; Kahler, A. C.*; Talou, P.*; Plompen, A. J.*; Schillebeeckx, P.*; et al.

Nuclear Data Sheets, 148, p.189 - 213, 2018/02

https://doi.org/10.1016/j.nds.2018.02.003

The CIELO collaboration has studied neutron cross sections on nuclides that significantly impact criticality in nuclear facilities - U, U, Pu, Fe, O and H - with the aim of improving the accuracy of the data and resolving previous discrepancies in our understanding. This multi-laboratory pilot project, coordinated via the OECD/NEA Working Party on Evaluation Cooperation (WPEC) Subgroup 40 with support also from the IAEA, has motivated experimental and theoretical work and led to suites of new evaluated libraries that accurately reflect measured data and also perform well in integral simulations of criticality. This report summarizes our results and outlines plans for the next phase of this collaboration.

Methods and approaches to provide feedback from nuclear and covariance data adjustment for improvement of nuclear data files

Palmiotti, G.*; Salvatores, M.*; Yokoyama, Kenji; Ishikawa, Makoto

NEA/NSC/R(2016)6 (Internet), 42 Pages, 2017/05

Proceedings of the 2014 Symposium on Nuclear Data; November 27-28, 2014, Conference hall, Hokkaido University, Sapporo Japan

Aikawa, Masayuki*; Iwamoto, Osamu; Ebata, Shuichiro*; Kunieda, Satoshi; Nakamura, Shoji; Koura, Hiroyuki

JAEA-Conf 2015-003, 332 Pages, 2016/03

JAEA-Conf-2015-003.pdf:30.22MB

The 2014 Symposium on Nuclear Data was held at Conference Hall, Hokkaido University, on November 27 and 28, 2014. The symposium was organized by the Nuclear Data Division of the Atomic Energy Society of Japan, Hokkaido Branch of the Atomic Energy Society of Japan, and Nuclear Reaction Data Centre, Faculty of Science, Hokkaido University in cooperation with Nuclear Science and Engineering Directorate of Japan Atomic Energy Agency. In the symposium, there were two tutorials, "Cross section measurement strategy for long lived fission product" and "Physics and Nuclear Data in Radiation Therapy" and four sessions, "A Neutron TOF Measurement Instrument desired by Nuclear Data Community", "Recent Topics", "Application of Nuclear Data", and "Nuclear Theory and Nuclear Data". In addition, recent research progress on experiments, evaluation, benchmark and application was presented in a poster session. Among 88 participants, all presentations and following discussions were very active and fruitful. This report consists of total 62 papers including 2 tutorials, 16 oral and 44 poster presentations.

Measurements and evaluations of air dose rates around the Fukushima NPP site, 6; Status and issues on evaluation of individual doses due to external exposures

Saito, Kimiaki; Kurihara, Osamu*; Matsuda, Norihiro; Takahara, Shogo; Sato, Tetsuro*

Radioisotopes, 65(2), p.93 - 112, 2016/02

https://doi.org/10.3769/radioisotopes.65.93

Late information is introduced on dose evaluation due to external exposures which employ an important role in the exposures due to the Fukushima accident. First, merits and demerits of the currently used two methods, that is the estimation based air dose rates and the measurements using personal dosimeters, are discussed indicating some basic data after a fundamental concept of external dose evaluation is provided. Next, main activities are summarized on external dose measurements and evaluations after the accident. Finally, a new trial on dose evaluation in introduced.

Thermodynamic evaluation on chemical reaction between degraded nuclear fuel and BC control rod in severe accident of LWR

Shirasu, Noriko; Kurata, Masaki; Ogawa, Toru*

Proceedings of 2014 Water Reactor Fuel Performance Meeting/ Top Fuel / LWR Fuel Performance Meeting (WRFPM 2014) (USB Flash Drive), 6 Pages, 2014/09

In the accident of Fukushima-Daiichi Nuclear Power Plant, degraded fuels containing Zircaloy probably reacted with BC control blades containing stainless steel cladding or blade sheath. Since light elements like B and C are able to react easily with various elements and form various chemical species, several concerns are pointed out, such as variation in volatility and heat generation by oxidation of B and C. The chemical states of degraded fuel were evaluated on the assumption of thermodynamic equilibrium under various conditions of oxygen potential and temperature. The chemical behavior of B affects significantly the variation in oxygen potential with progressing severe accident, and many kinds of volatile compounds are formed by oxidation. The behavior of B causes the changes of volatility of FPs, such as Sr, Cs and Mo.