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 ; not registered; Miyahara, Kaname  

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 ...