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Metcalfe, R.*; Benbow, S. J.*; Kawama, Daisuke*; Tachi, Yukio
Science of the Total Environment, 958, p.177690_1 - 177690_17, 2025/01
Uplifting fractured granitic rocks occur in substantial areas of countries such as Japan. A repository site would be selected in such an area only if it is possible to make a safety case, accounting for the changing conditions during uplift. The safety case must include robust arguments that chemical processes in the rocks around the repository will contribute sufficiently to minimise radiological doses to biosphere receptors. To provide confidence in the safety arguments, numerical models need to be sufficiently realistic, but also parameterised conservatively (pessimistically). However, model development is challenging because uplift involves many complex couplings between groundwater flow, chemical reactions between water and rock, and changing rock properties. The couplings would affect radionuclide mobilisation and retardation, by influencing diffusive radionuclide fluxes between groundwater flowing in fractures and effectively immobile porewater in the rock matrix and radionuclide partitioning between water and solid phases, via: (i) mineral precipitation/dissolution; (ii) mineral alteration; and (iii) sorption/desorption. It is difficult to represent all this complexity in numerical models while showing that they are parameterised conservatively. Here we present a modelling approach, illustrated by simulation cases for some exemplar radioelements, to identify realistically conservative process conceptualisations and model parameterisations.
Metcalfe, R.*; Tachi, Yukio; Sasao, Eiji; Kawama, Daisuke*
Science of the Total Environment, 957, p.177375_1 - 177375_17, 2024/12
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.
Kato, Tomoko
KURNS-EKR-11, p.19 - 28, 2021/03
In order to extract the knowledge that will be helpful in setting the biospheric dose assessment parameters and their database for safety assessment of radioactive waste disposal in Japan, a methodology of setting the biospheric dose assessment parameters was surveyed in the safety assessment of the radioactive waste disposal in Sweden. In this study, the handling in the biospheric dose assessment in SR-PSU was specifically focused. SR-PSU was the project about the safety assessment for final repository of short-lived radioactive waste in Sweden, SFR.
Sakaki, Toshihiro*; Komatsu, Mitsuru*; Takeuchi, Ryuji
Vadose Zone Journal (Internet), 15(8), 7 Pages, 2016/08
Times Cited Count：2 Percentile：8.62(Environmental Sciences)In the Groundwater Recovery Experiment in Tunnel which is underway at the MIU, water saturation is one of the key parameters to monitor in order to understand the recovery processes. In this study, the process of saturation increase in the quasi-saturated zone where trapped discrete air phase affects saturation due to further increase in water pressure was studied. The relationship between the positive water pressure and saturation was measured by laboratory test using sands with trapped air bubbles and the effect of compression of bubbles on the changes in saturation was analyzed. The experimental results showed that the water pressure-saturation curves closely followed the relationship estimated solely based on the air bubble compression using Boyle's law. Based on this observation, a mathematical model was established to define the water pressure - saturation curve for the region where the water pressure is positive.
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 
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.
Nakayama, Shinichi; Morita, Yasuji; Nishihara, Kenji; Oigawa, Hiroyuki
Proceedings of International Conference on Nuclear Energy System for Future Generation and Global Sustainability (GLOBAL 2005) (CD-ROM), 6 Pages, 2005/10
The effects of partitioning-transmutation (PT) technology to waste management was assessed based on the chemical and physical properties and estimated amounts of radioactively contaminated wastes that may be generated in the JAERI's PT cycle. The volume of high-level waste after partitioning was about a third that of non-partitioned vitrified waste form. The required repository area was about sixth, which implies increase in capacity of geologic repositories.
Okoshi, Minoru; Abe, Masayoshi; Yoshimori, Michiro; Sakai, Akihiro
Proc. of Waste Management'98 (CD-ROM), 5 Pages, 1998/00
no abstracts in English
; ; T.H.Pigford*
JAERI-M 9184, 39 Pages, 1980/11
no abstracts in English
Otomo, Shoji*; Hirose, Yukio*; Osawa, Hideaki; Onuma, Susumu*
no journal, ,
The study measured public acceptance depending on the area of personal relevance, and the general and personal consensus toward a geological repository. The results that the weaker area of personal relevance, the stronger public acceptance became. The NIMBY reaction to siting a repository was strong. However, the effect of area of personal relevance was mitigated in the scenario where a scientific approach was applied.
