Convergence behavior of statistical uncertainty in probability table for cross section in unresolved resonance region

Tada, Kenichi; Endo, Tomohiro*

Journal of Nuclear Science and Technology, 60(11), p.1397 - 1405, 2023/11

https://doi.org/10.1080/00223131.2023.2204102

The probability table method is a well-known method for addressing self-shielding effects in the unresolved resonance region. A long computational time is required to generate the probability table. The effective way to reduce the generation time of the probability table is the reduction of the number of ladders. The purpose of this study is the estimation of the optimal number of ladders using the statistical uncertainty in the probability table. To this end, the statistical uncertainty quantification method of the probability table was developed and the convergence behavior of the statistical uncertainty was investigated. The product of the probability table and the average cross section was considered the target of the statistical uncertainty. The convergence rate was affected by the average level spacing and reduced neutron width. The generation time of the probability table was less than half when the input parameter was changed from the number of ladders to the tolerance value.

Aerosol characterization during heating and mechanical cutting of simulated uranium containing debris; The URASOL project in the framework of Fukushima Daiichi fuel debris removal

Porcheron, E.*; Leblois, Y.*; Journeau, C.*; Delacroix, J.*; Molina, D.*; Suteau, C.*; Berlemont, R.*; Bouland, A.*; Lallot, Y.*; Roulet, D.*; et al.

Proceedings of International Topical Workshop on Fukushima Decommissioning Research (FDR2022) (Internet), 5 Pages, 2022/10

One of the important challenges for the decommissioning of the damaged reactors of the Fukushima Daiichi Nuclear Power Station (1F) is the fuel debris retrieval. The URASOL project, which is undertaken by a French consortium consisting of ONET Technologies, CEA, and IRSN for JAEA/CLADS, is dedicated to acquiring basic scientific data on the generation and characteristics of radioactive aerosols from the thermal or mechanical processing of fuel debris simulant. Heating process undertaken in the VITAE facility simulates some representative conditions of thermal cutting by LASER. For mechanical cutting, the core boring technique is implemented in the FUJISAN facility. Fuel debris simulants have been developed for inactive and active trials. The aerosols are characterized in terms of mass concentration, real time number concentration, mass size distribution, morphology, and chemical properties. The chemical characterization aims at identifying potential radioactive particles released and the associated size distribution, both of which are important information for assessing possible safety and radioprotection measures during the fuel debris retrieval operations at 1F.

Overview of event progression of evaporation to dryness caused by boiling of high-level liquid waste in Reprocessing Facilities

Yamaguchi, Akinori*; Yokotsuka, Muneyuki*; Furuta, Masayo*; Kubota, Kazuo*; Fujine, Sachio*; Mori, Kenji*; Yoshida, Naoki; Amano, Yuki; Abe, Hitoshi

Nihon Genshiryoku Gakkai Wabun Rombunshi (Internet), 21(4), p.173 - 182, 2022/09

https://doi.org/10.3327/taesj.J21.021

Risk information obtained from probabilistic risk assessment (PRA) can be used to evaluate the effectiveness of measures against severe accidents in nuclear facilities. The PRA methods used for reprocessing facilities are considered immature compared to those for nuclear power plants, and to make the methods mature, reducing the uncertainty of accident scenarios becomes crucial. In this paper, we summarized the results of literature survey on the event progression of evaporation to dryness caused by boiling of high-level liquid waste (HLLW) which is a severe accident in reprocessing facilities and migration behavior of associated radioactive materials. Since one of the important characteristics of Ru is its tendency to form volatile compounds over the course of the event progression, the migration behavior of Ru is categorized into four stages based on temperature. Although no Ru has been released in the waste in the high temperature region, other volatile elements such as Cs could be released. Sufficient experimental data, however, have not been obtained yet. It is, therefore, necessary to further clarify the migration behavior of radioactive materials that predominantly depends on temperature in this region.

Thermal-hydraulics to risk assessment; Roles of thermal-hydraulics simulation to risk assessment

Maruyama, Yu; Yoshida, Kazuo

Nihon Genshiryoku Gakkai-Shi ATOMO, 63(7), p.517 - 522, 2021/07

https://doi.org/10.3327/jaesjb.63.7_517

no abstracts in English

Iodine-129 in the Tokai Reprocessing Plant and the environment

Nakano, Masanao

Hoken Butsuri (Internet), 56(1), p.17 - 25, 2021/03

https://doi.org/10.5453/jhps.56.17

The Tokai Reprocessing Plant is the first reprocessing plant in Japan which started hot test in 1977, and had reprocessed 1140 tons of spent nuclear fuel by May 2007. The gaseous and liquid radioactive wastes has been discharged to the environment. Since iodine-129 (I) is one of the most important nuclides for environmental impact assessment. Therefore, I in the exhaust and effluent has been controlled, and a precise analysis method of I in the environmental samples was developed, and the concentration of 129I in the environment was investigated. This report presents an overview of these activities. Not limited to I on reprocessing facilities, it is essential for nuclear operators to reduce the amount released to the environment in the spirit of ALARA, and to continuously develop the further upgrading environmental monitoring methods and evaluation methods in order to foster a sense of safety and security among residents living in the vicinity of the facilities.

Radiation-induced effects on the extraction properties of hexa--octylnitrilo-triacetamide (HONTA) complexes of americium and europium

Toigawa, Tomohiro; Peterman, D. R.*; Meeker, D. S.*; Grimes, T. S.*; Zalupski, P. R.*; Mezyk, S. P.*; Cook, A. R.*; Yamashita, Shinichi*; Kumagai, Yuta; Matsumura, Tatsuro; et al.

Physical Chemistry Chemical Physics, 23(2), p.1343 - 1351, 2021/01

https://doi.org/10.1039/D0CP05720G

The candidate An(III)/Ln(III) separation ligand hexa--octylnitrilo-triacetamide (HONTA) was irradiated under envisioned SELECT (Solvent Extraction from Liquid waste using Extractants of CHON-type for Transmutation) process conditions using a solvent test loop in conjunction with cobalt-60 gamma irradiation. We demonstrate that HONTA undergoes exponential decay with increasing gamma dose to produce a range of degradation products which have been identified and quantified by HPLC-ESI-MS/MS techniques. The combination of HONTA destruction and degradation product ingrowth, particularly dioctylamine, negatively impacts the extraction and back-extraction of both americium and europium ions. The loss of HONTA was attributed to its reaction with the solvent (-dodecane) radical cation of (HONTA + R) = (7.61 0.82) 10 M s obtained by pulse radiolysis techniques. However, when this ligand is bound to either americium or europium ions, the observed -dodecane radical cation kinetics increase by over an order of magnitude. This large reactivity increase to additional reaction pathways occurring upon metal-ion binding. Lastly nanosecond time-resolved measurements showed that both direct and indirect HONTA radiolysis yielded the short-lived (100 ns) HONTA radical cation as well as a longer-lived (s) HONTA triplet excited state. These HONTA species are important precursors to the suite of HONTA degradation products observed.

Study on the mechanism of radiolytic degradation of an extractant for minor actinides separation

Toigawa, Tomohiro; Murayama, Rin*; Kumagai, Yuta; Yamashita, Shinichi*; Suzuki, Hideya; Ban, Yasutoshi; Matsumura, Tatsuro

UTNL-R-0501, p.24 - 25, 2020/12

This report summarizes the results obtained in FY2019 at Electron Linac Facility of University of Tokyo. The radiolysis process of a diglycolamide extractant, which is expected to be used in the separation process of minor actinides (MA), in dodecane and octanol solutions was investigated by pulse radiolysis. As a result, it was suggested that by adding alcohol, the decomposition process of the diglycolamide extractant was different from the decomposition processes in the single solvent of dodecane considered that the decomposition occurred via a radical cation species of the extractant.

Phase-field model for crystallization in alkali disilicate glasses; LiO-2SiO, NaO-2SiO and KO-2SiO

Kawaguchi, Munemichi; Uno, Masayoshi*

Journal of the Ceramic Society of Japan, 128(10), p.832 - 838, 2020/10

https://doi.org/10.2109/jcersj2.20145

This study developed phase-field method (PFM) technique in oxide melt system by using a new mobility coefficient (). The crystal growth rates () obtained by the PFM calculation with the constant were comparable to the thermodynamic driving force in normal growth model. The temperature dependence of the was determined from the experimental crystal growth rates and the . Using the determined , the crystal growth rates () in alkali disilicate glasses, LiO-2SiO, NaO-2SiO and KO-2SiO were simulated. The temperature dependence of the was qualitatively and quantitatively so similar that the PFM calculation results demonstrated the validity of the . Especially, the obtained by the PFM calculation appeared the rapid increase just below the thermodynamic melting point () and the steep peak at around -100 K. Additionally, as the temperature decreased, the apparently approached zero ms, which is limited by the representing the interface jump process. Furthermore, we implemented the PFM calculation for the variation of the parameter in the . As the increased from zero to two, the peak of the became steeper and the peak temperature of the shifted to the high temperature side. The parameters and in the increased exponentially and decreased linearly as the atomic number of the alkali metal increased due to the ionic potential, respectively. This calculation revealed that the and in the were close and reasonable for each other.

Assessment report on research and development activities in FY2019; Activity "Research and development on high temperature gas-cooled reactor and related heat application technology" (Interim report)

Sector of Fast Reactor and Advanced Reactor Research and Development

JAEA-Evaluation 2020-001, 128 Pages, 2020/08

JAEA-Evaluation-2020-001.pdf:7.44MB

Japan Atomic Energy Agency consulted with the "Evaluation Committee of Research Activities for High Temperature Gas-cooled Reactor (hereinafter referred to as "HTGR") and Related Hydrogen Production Technology" (hereinafter referred to as "Evaluation Committee"), which consists of specialists in the fields of the evaluation subjects of high temperature gas-cooled reactor and related heat application technology, for interim assessment in the 3rd Mid-and Long-Term Plan about the relevance of the management and research activities of the HTGR and related application technology during the period from April 2017 to March 2020. As a result, three members of the Evaluation Committee concluded a score of "S", and seven members of the Evaluation Committee concluded a score of "A". The interim assessment to research and development activities from April 2017 to March 2020 was concluded a score of "A". In addition, the Evaluation Committee recommended that the judgement to move to the construction phase of the HTTR-heat utilization test plant be made after 2 years, after the HTTR will be restarted and the thermal load fluctuation tests using HTTR will be carried out. This report lists the members of the Evaluation Committee and outlines the assessment item and the review process for procedure of the assessment. The assessment report which was issued by the Evaluation Committee is attached.

Analysis of debris samples of Tokyo Electric Power Company Holdings Fukushima Daiichi Nuclear Power Station

Task Force on Research Strategy for Debris of Fukushima Daiichi Nuclear Power Station

JAEA-Review 2020-004, 140 Pages, 2020/05

JAEA-Review-2020-004.pdf:4.22MB

Design, planning and control of debris-related processes, namely retrieval, storage management, processing and disposal of the debris, are required for the safe and steady decommissioning of Fukushima Daiichi Nuclear Power Station (1F). Status inside primary containment vessel of 1F must be known by the PCV investigation and fuel debris sample analysis. Continuous updating and improvement of the process design are important through ascertainment of the cause of the accident. The roadmap for the 1F decommissioning have shown the milestone of commencement of trial retrieval of fuels debris within 2021, which indicates the analysis of fuel debris sample begin in earnest. This report recommends required debris analysis in relation with issues for the retrieval, storage management, processing and disposal, and ascertainment of the cause of the 1F accident. Practical analysis plan is expected to be prepared based on this report.