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Journal Articles

Development of evaluation method for variability of groundwater flow conditions associated with long-term topographic change and climate perturbations

Onoe, Hironori; Kosaka, Hiroshi*; Matsuoka, Toshiyuki; Komatsu, Tetsuya; Takeuchi, Ryuji; Iwatsuki, Teruki; Yasue, Kenichi

Genshiryoku Bakkuendo Kenkyu (CD-ROM), 26(1), p.3 - 14, 2019/06

https://doi.org/10.3327/jnuce.26.1_3

In this study, it is focused on topographic changes due to uplift and denudation, also climate perturbations, a method which is able to assess the long-term variability of groundwater flow conditions using the coefficient variation based on some steady-state groundwater flow simulation results was developed. Spatial distribution of long residence time area which is not much influenced due to long-term topographic change and recharge rate change during the past one million years was able to estimate through the case study of the Tono area, Central Japan. By applying this evaluation method, it is possible to identify the local area that has low variability of groundwater flow conditions due to topographic changes and climate perturbations from the regional area quantitatively and spatially.

JAEA Reports

Biosphere modeling with climate changes for safety assessment of high-level radioactive waste geological isolation

Kato, Tomoko; ; Suzuki, Yuji*; ; Ishiguro, Katsuhiko; Ikeda, Takao*; Richard, L.*

JNC TN8400 2001-003, 128 Pages, 2001/03

JNC-TN8400-2001-003.pdf:6.09MB

In the safety assessment of a high-level radioactive waste (HLW) disposal system, it is required to estimate radiological impacts on future human beings arising from potential radionuclide releases from a deep repository into the surface environment. In order to estimate the impacts, a biosphere model is developed by reasonably assuming radionuclide migration processes in the surface environment and relevant human lifestyles. Releases from the repository might not occur for many thousands of years after disposal. Over such timescales, it is anticipated that the considerable climatic change, for example, induced by the next glaciation period expected to occur in around ten thousand years from now, will have a significant influence on the near surface environment and associated human lifestyles. In case of taking these evolution effects into account in modeling, it is reasonable to develop several alternative models on biosphere evolution systems consistent with possible future conditions affected by expected climatic changes. In this study, alternative biosphere models were developed taking effects of possible climatie change into account. In the modeling, different climatic states existing in the world from the present climate condition in Japan are utilized as an analogy. Estimation of net effects of the climatic change on biosphere system was made by comparing these alternative biosphere models with a constant biosphere model consistent with the present climatic state through flux to dose conversion factors derived from each one.

JAEA Reports

The Primary evaluation of the impacts of naturaI phenomena on the safety functions of the geological disposal system; An Example study on site generic phase

Makino, Hitoshi; ; Miyahara, Kaname

JNC TN8400 2000-033, 74 Pages, 2000/11

JNC-TN8400-2000-033.pdf:9.19MB

Natural phenomena is one of the potential factors perturbing the long-term stability of the geological environment, and for natural phenomena, it is necessary to consider uncertainties relevant to time, frequency and effect. Therefore it will be important to have information about the potential impacts of natural phenomena on the safety functions of geological disposal system in the future by assuming that natural phenomena perturbs the safety functions of the geological disposal system. In this report, we have considered 4 natural phenomena, 'uplift, subsidence and denudation', 'climatic and sea-level changes', 'earthquakes and fault movement' and 'volcanism', which had been extracted by investigation in foreign countries and by considering the characteristics of Japan as natural phenomena which may perturb the long-term stability of the geological environment. And we have considered mainly typical effects of naturaI phenomena on geological environment and investigated the typical impacts of those natural phenomena on the safety functions of the geological disposal system. On perturbation scenarios, the maximum of total doses have been less than regulatory guidelines in foreign countries in all situations except the cases assuming that a new fault, which causes significant pathway of groundwater flow and nuclide migration, intersects the waste packages. In the case, the maximum of total doses may reach the same level as regulatory guidelines in foreign countries or natural radiation exposure in Japan depending on fault generation time or grandwater flow rate through the fault. And, on isolation failure scenarios, it has been implied that nuclide mass/flux originated from geological disposal is comparable level with nuclide mass/flux in natural environment. These results could give useful information about the potential impacts of natural phenomena on the safety functions of geological disposal system, and also could show the potential importance of ...

JAEA Reports