Consideration on roles and relationship between observations/measurements and model predictions for environmental consequence assessments for nuclear facilities

Togawa, Orihiko; Okura, Takehisa; Kimura, Masanori

JAEA-Review 2022-049, 76 Pages, 2023/01

JAEA-Review-2022-049.pdf:3.74MB

Before construction and after operation of nuclear facilities, environmental consequence assessments are conducted for normal operation and an emergency. These assessments mainly aim at confirming safety for the public around the facilities and producing relief for them. Environmental consequence assessments are carried out using observations/ measurements by environmental monitoring and/or model predictions by calculation models, sometimes using either of which and at other times using both them, according to the situations and necessities. First, this report investigates methods, roles, merits/demerits and relationship between observations/measurements and model predictions which are used for environmental consequence assessments of nuclear facilities, especially holding up a spent nuclear fuel reprocessing plant at Rokkasho, Aomori as an example. Next, it explains representative examples of utilization of data on observations/measurements and results on model predictions, and considers points of attention at using them. Finally, the report describes future direction, for example, improvements of observations/measurements and model predictions, and fusion of both them.

Safe, efficient cementation of challenging radioactive wastes using alkali activated materials with high-flowability and high-anion retention capacity (Contract research); FY2020 Nuclear Energy Science & Technology and Human Resource Development Project

Collaborative Laboratories for Advanced Decommissioning Science; Hokkaido University*

JAEA-Review 2021-036, 95 Pages, 2021/12

JAEA-Review-2021-036.pdf:5.13MB

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 FY2020. 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 FY2019, this report summarizes the research results of the "Safe, efficient cementation of challenging radioactive wastes using alkali activated materials with high-flowability and high-anion retention capacity" conducted in FY2020. For safe storage and disposal of iron sludge generated from contaminated water treatment, the present study aims to 1) explore alkali activated materials (AAM) with high-flowability and high-anion retention capacity and its recipe, 2) try mock-up manufacture and evaluation for one-tenth the size of real waste and propose the concept of the manufacturing equipment for a real plant, 3) show potential of AAM as the material for the solidification of waste with various physicochemical properties and radioactive nuclide compositions from the result ...

Hazard curve evaluation method development for a forest fire as an external hazard on nuclear power plants

Okano, Yasushi; Yamano, Hidemasa

Journal of Nuclear Science and Technology, 53(8), p.1224 - 1234, 2016/08

https://doi.org/10.1080/00223131.2015.1102662

A method to obtain a hazard curve of a forest fire was developed. The method has four steps: a logic tree formulation, a response surface evaluation, a Monte Carlo simulation, and an annual exceedance frequency calculation. The logic tree consists domains of forest fire breakout and spread conditions, weather conditions, vegetation conditions, and forest fire simulation conditions. The new method was applied to evaluate hazard curves of a reaction intensity and a fireline intensity for a typical location around a sodium-cooled fast reactor in Japan.

Effects of -radiation on a direct disposal system for spent nuclear fuel, 2; Review of research into safety assessments of direct disposal of spent nuclear fuel in Europe and North America

Kitamura, Akira; Takase, Hiroyasu*; Metcalfe, R.*; Penfold, J.*

Journal of Nuclear Science and Technology, 53(1), p.19 - 33, 2016/01

https://doi.org/10.1080/00223131.2015.1014874

Not only geological disposal of vitrified waste generated by spent fuel (SF) reprocessing, but also the possibility of disposing of SF itself in deep geological strata (hereinafter "direct disposal of SF") may be considered in the Japanese geological disposal program. In the case of direct disposal of SF, the radioactivity of the waste is higher and the potential effects of the radiation are greater. Specific examples of the possible effects of radiation include: increased amounts of canister corrosion; generation of oxidizing chemical species in conjunction with radiation degradation of groundwater and accompanying oxidation of reducing groundwater; and increase in the dissolution rate and the solubility of SF. Therefore, the influences of radiation, which are not expected to be significant in the case of geological disposal of vitrified waste, must be considered in safety assessments for direct disposal of SF. Focusing especially on the effects of -radiation in safety assessment, this study has reviewed safety assessments in countries other than Japan that are planning direct disposal of SF. The review has identified issues relevant to safety assessment for the direct disposal of SF in Japan.

Nuclear hot spot factor of JMTR-LEU core

Nagaoka, Yoshiharu; Komukai, Bunsaku; ; Saito, Minoru;

JAERI-M 92-042, 92 Pages, 1992/03

JAERI-M-92-042.pdf:2.18MB

no abstracts in English

Health and safety excecutive.Safety assessment principles for nuclear chemical plant.

Kosako, Toshiso*; *; *; *; *; *; Yamaki, J.;

Genshiryoku Kagaku Puranto Ni Taisuru Anzen Shinsa Shishin (Eikoku), 75 Pages, 1986/00

no abstracts in English

Effects of -radiation on a disposal of spent nuclear fuel

Kitamura, Akira

no journal, , 

The Japanese geological disposal program has started researching disposal of spent nuclear fuel (SF) in deep geological strata (hereafter "direct disposal of SF") as an alternative management option other reprocessing followed by vitrification and geological disposal of high-level radioactive waste. In the case of direct disposal of SF, specific examples of the possible effects of radiation include: generation of oxidizing chemical species in conjunction with decomposition of groundwater and accompanying oxidation of reducing groundwater; and increase in the dissolution rate of SF and the solubility of radionuclides. Focusing especially on the effects of -radiation in safety assessment, this study has reviewed research into the effects of -radiation on the spent nuclear fuel, canisters and environment outside the canisters, and safety assessments in countries other than Japan that are planning direct disposal of SF. It was found that the effects of -radiation on SF disposal are not significant due to suppression of water radiolysis by hydrogen gas generated from canister corrosion according to the latest research.