Evolution of radionuclide transport and retardation processes in uplifting granitic rocks, Part 1; Key processes, conceptual models and scenario

Metcalfe, R.*; Tachi, Yukio; Sasao, Eiji; Kawama, Daisuke*

Science of the Total Environment, 957, p.177375_1 - 177375_17, 2024/12

https://doi.org/10.1016/j.scitotenv.2024.177375

A safety case for an underground radioactive waste repository must show that groundwater will not in future transport radionuclides from the repository to the near-surface environment (the biosphere) in harmful quantities. Safety cases are developed step-wise throughout a programme to site and develop a repository. At early stages, before a site is selected, safety cases are generic and based on simplified safety assessment models of the disposal system that have conservative parameter values. Later, when site-specific conditions are known, more realistic models are needed for the long-term geo-environmental evolution and their impacts on radionuclide migration/retention. Uplift is one such environmental change, which may be particularly important in countries near active tectonic plate boundaries, such as Japan. Here we review the state of knowledge about how the properties of fractured granitic rocks evolve during uplift, based on studies in Japan. Hence, we present conceptual models and a generic scenario for mass transport and retardation processes in uplifting granitic rocks as a basis for realistic numerical models to underpin safety assessment.

Stochastic estimation of radionuclide composition in wastes generated at Fukushima Daiichi Nuclear Power Station using Bayesian inference

Sugiyama, Daisuke*; Nakabayashi, Ryo*; Tanaka, Shingo*; Koma, Yoshikazu; Takahatake, Yoko

Journal of Nuclear Science and Technology, 58(4), p.493 - 506, 2021/04

https://doi.org/10.1080/00223131.2021.1884137

Long-lived radionuclide transport; An In-situ field column study

D.R.Champ*; J.O.Jirovec*; J.L.Young*; Kumata, Masahiro

Transport and Mass Exchange Processes in Sand and Gravel Aquifers; Field and Modelling Studies,Vol. 2, p.725 - 736, 1991/00

no abstracts in English

Evaluation of off-site distribution of radionuclides near the Fukushima Dai-ichi Nuclear Power Station in order to estimate on-site distribution

Iijima, Kazuki; Dohi, Terumi; Koma, Yoshikazu; Takahatake, Yoko; Fujiwara, Kenso; Niizato, Tadafumi

no journal, , 

To develop a model to estimate on-site distribution, detailed evaluation of the off-site distribution of radionuclides deposited on the soil and trees in the environment was carried out. Six traces of the radioactive plume, which we defined as NNW, W (divided into W-N and W-S), SW and S (divided into S-W and S-E) from a north to south direction, were clearly identified based on the off-site distribution of air dose rate measured by a car-borne survey within 5 km from the FDNPS. The tendency that the Transport Ratios for Sr and Pu to topsoils obtained in the west direction were higher than those of south direction was consistent with that observed in the previous on-site sampling. Therefore, the data suggest that the estimation of on-site distribution of radionuclides inventory based on the off-site distribution was applicable.