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Journal Articles

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.

JAEA Reports

Continuous improvement activities on nuclear facility maintenance in Nuclear Science Research Institute of Japan Atomic Energy Agency in 2021

Task Force on Maintenance Optimization of Nuclear Facilities

JAEA-Technology 2022-006, 80 Pages, 2022/06

JAEA-Technology-2022-006.pdf:4.24MB

The Task force on maintenance optimization of nuclear facilities was organized in the Nuclear Science Research Institute (NSRI) of Japan Atomic Energy Agency (JAEA) since November 2020, in order to adequately respond to "the New nuclear regulatory inspection system since FY 2020" and to continuously improve the facility maintenance activities. In 2021, the task force has studied (1) optimization of the importance classification on maintenance and inspection of nuclear facilities, and (2) improvement in setting and evaluation of the performance indicators on safety, maintenance and quality management activities, considering "the Graded approach" that is one of the basic methodologies in the new nuclear regulatory inspection system. Each nuclear facility (research reactors, nuclear fuel material usage facilities, others) in the NSRI will steadily improve their respective safety, maintenance and quality management activities, referring the review results suggested by the task force.

Journal Articles

Prediction of thermodynamic data for radium suitable for thermodynamic database for radioactive waste management using an electrostatic model and correlation with ionic radii among alkaline earth metals

Kitamura, Akira; Yoshida, Yasushi*

Journal of Radioanalytical and Nuclear Chemistry, 327(2), p.839 - 845, 2021/02

https://doi.org/10.1007/s10967-020-07527-5

Times Cited Count：3 Percentile：45.99(Chemistry, Analytical)

Thermodynamic data for radium for radioactive waste management have been predicted using an electrostatic model and correlation with the ionic radii of the alkaline earth metals. Estimation of the standard Gibbs free energy of formation and standard molar entropy of aqueous radium species and compounds has been based on such approaches as extrapolation of the thermodynamic properties of strontium and barium, and use of a model of ion pair formation. The predicted thermodynamic data for radium have been compared with previously reported values.

Journal Articles

Development of thermodynamic database for performance assessment of geological disposal of high-level radioactive waste and TRU waste

Kitamura, Akira

Nihon Genshiryoku Gakkai-Shi ATOMO, 62(1), p.23 - 28, 2020/01

Thermodynamic databases (TDBs) for performance assessment of geological disposal of high-level waste and TRU waste have been developed to predict solubility and speciation of radionuclides in groundwater in some countries including Japan. The present manuscript briefly describes current status of development of the TDB organized by the Nuclear Energy Agency within the Organisation of Economic Co-operation and Development (OECD/NEA) and the TDBs in some countries including Japan.

JAEA Reports

Geopolymers and their potential applications in the nuclear waste management field; A Bibliographical study

Cantarel, V.; Motooka, Takafumi; Yamagishi, Isao

JAEA-Review 2017-014, 36 Pages, 2017/06

JAEA-Review-2017-014.pdf:3.37MB

After a necessary decay time, the zeolites used for the water decontamination will eventually be conditioned for their long-term storage. Geopolymer is considered as a potential matrix to manage radioactive cesium and strontium containing waste. For such applications, a correct comprehension of the binder structure, its macroscopic properties, its interactions with the waste and the physico-chemical phenomena occurring in the waste form is needed to be able to judge of the soundness and viability of the material. Although the geopolymer is a young binder, a lot of research has been carried out over the last fifty years and our understanding of this matrix and its potential applications is progressing fast. This review aims at gathering the actual knowledge on geopolymer studies about geopolymer composites, geopolymer as a confinement matrix for nuclear wastes and geopolymer under irradiation. This information will finally provide guidance for the future studies and experiments.

Journal Articles

Thermodynamic model for Zr solubility in the presence of gluconic acid and isosaccharinic acid

Kobayashi, Taishi*; Teshima, Takeshi*; Sasaki, Takayuki*; Kitamura, Akira

Journal of Nuclear Science and Technology, 54(2), p.233 - 241, 2017/02

https://doi.org/10.1080/00223131.2016.1255573

Times Cited Count：6 Percentile：51.46(Nuclear Science & Technology)

Zr solubility in the presence of gluconic acid (GLU) and isosaccharinic acid (ISA) was investigated as a function of hydrogen ion concentration (pH $_{rm c}$ ) and the total concentration of GLU or ISA. The dependence of the increase in Zr solubility on the pH $_{rm c}$ and GLU concentration suggested the existence of Zr(OH) $_{4}$ (GLU) $_{2}$ $^{2-}$ in the neutral pH region and Zr(OH) $_{4}$ (GLU)(GLU $_{rm -H}$ ) $^{3-}$ in the alkaline pH region above pH $_{rm c}$ 10 as the dominant species in the presence of 10 $^{-3}$ - 10 $^{-1}$ mol/dm $^{3}$ (M) GLU. In the presence of ISA, the dominant species Zr(OH) $_{4}$ (ISA) $_{2}$ $^{2-}$ and Zr(OH) $_{4}$ (ISA)(ISA $_{rm -H}$ ) $^{3-}$ were proposed to occur in the neutral and alkaline pH regions, similar to those found in the presence of GLU. From X-ray diffraction analysis, the solubility-limiting solid phase in the presence of GLU and ISA was considered to be Zr(OH) $_{4}$ (am). The formation constants of the Zr gluconate and isosaccharinate complexes were determined by least squares fitting analysis of the solubility data, and the obtained values were discussed in comparison with those of tetravalent actinides.

Journal Articles

Report on the planed session by the NUCE in 2016 AESJ Fall Meeting, "How is the ability of the waste form glass?; Current status of the performance assessment of the waste form glass in the geological disposal system"

Kamei, Gento

Genshiryoku Bakkuendo Kenkyu (CD-ROM), 23(2), p.201 - 202, 2016/12

https://nuce.aesj.or.jp/jnuce/vol23/Jnuce-Vol23-2-p201-202.pdf

This paper reports an overview of a planed session, "How is the ability of the waste form glass?; Current status of the performance assessment of the waste form glass in the geological disposal system", held by the NUCE in 2016 AESJ Fall Meeting. Five panelists respectively introduced case studies and/or aspects from the view point of performance assessment, current status in the world including Japan, basic sciences and computation sciences.

Journal Articles

Parametric survey on possible impact of partitioning and transmutation of high-level radioactive waste

Oigawa, Hiroyuki; Yokoo, Takeshi*; Nishihara, Kenji; Morita, Yasuji; Ikeda, Takao*; Takaki, Naoyuki*

Proceedings of International Conference on Nuclear Energy System for Future Generation and Global Sustainability (GLOBAL 2005) (CD-ROM), 6 Pages, 2005/10

The benefit of implementing Partitioning and Transmutation (P&T) of high-level wastes was parametrically surveyed. The possible reduction of the geological repository area was estimated. By recycling minor actinides (MA), the repository area required for unit spent fuel was reduced significantly in the case of MOX-LWR. This effect was caused by removal of $^{241}$ Am which is a long-term heat source. By partitioning the fission products, in addition to MA recycling, further 70-80% reduction from the MA-recovery case can be expected for both UO and MOX. This significant reduction was independent of the cooling time before the partitioning process.

Journal Articles

Leaching behavior of simulated bituminized radioactive waste form under deep geological conditions

Nakayama, Shinichi; Iida, Yoshihisa; Nagano, Tetsushi; Akimoto, Toshiyuki

Journal of Nuclear Science and Technology, 40(4), p.227 - 237, 2003/04

https://doi.org/10.3327/jnst.40.227

Times Cited Count：12 Percentile：62.23(Nuclear Science & Technology)

Leaching behavior of synthetic bituminized waste form was studied to inquire data for performance assessment of the geologic disposal. Laboratory-scale leaching tests were performed. The bituminized samples were contacted with an alkaline solution representing cement-contacting groundwater, with a saline solution simulating seawater for a possible repository construction at the coastal area, and with deionized water as reference. The release of soluble components, Na and Cs, was enhanced by the swelling, and considered to be diffusion controlled in the swelled layers of the specimens. The release of insoluble components such as Ba and Np was solubility-limited in addition to control by the progression of leaching. Neptunium, a redox-sensitive element, showed a distinct difference in release reflecting the difference between the anoxic and atmospheric conditions. The concentrations of Pu were below the detection limit ( $2 times 10^{-10}$ mol/L) under all of the leaching conditions in this study.