旭硝子財団助成研究成果報告2020

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92Zaki Su'ud93Endra GunawanDevelopment of Modular 50-200 MWe Gas Cooled Fast Reactors with High Energy Conversion (Project 2019)Environmental Geoscience Investigation on Searching a Newly Unidentified Fault in Eastern Indonesia (Project 2019)64旭硝子財団　助成研究成果報告（2020）Gas cooled fast reactors are among Generation IV NPP with some advantages including possibility for high temperature operation to get high energy conversion efficiency and some specific applications. Current conventional Nuclear Power Plants (NPPs) generally have energy conversion efficiency about 33%. This value is quite low which means so many thermal pollution releases to the environment during its operation. To get energy conversion efficiency more than 50%or even 50% it is necessary to push the output temperature of the coolant up to 1000oC or even higher. Some important aspects need to be specifically prepared to anticipate this condition. First very high temperature materials are necessary and in this case most of them will come from high temperature ceramics materials. Secondly we need to improve safety margin to make sure the inherent safety capability still applicable with enough margin. In this study neutronic design optimization have been performed for nitride fuel and carbide fuel which are both advanced fuels for fast reactors. We got several designs which can be operated for more than 12 years without refueling with excess reactivity below 2% dk/k. The configuration with and without internal reflector is considered for radiation heat removal during depressurized accident considerations. The safety aspect is assessed by ultimate hypothetical accident, i.e., depressurized accident in which radiation becomes final heat removal after the reactor in passive shutdown condition.As one of the countries that prone to earthquake occurrences, it is important to conduct research on environmental geoscience in Indonesia with the goal to reduce loss of human lives and infrastructures during disaster. The present condition, as reported by Scopus database, suggested that ~60-70% of environmental geoscience research was done in the western Indonesia (Java and Sumatra), compare to ~30-40% research in the eastern region (Bali, Nusa Tenggara, Sulawesi). This is contradicts with the present tectonic condition of Indonesia, indicated by total number of earthquake occurred in the eastern region is greater the western one. Furthermore, the 2018 Lombok and Palu earthquakes occurred in the eastern region. The death tools of those earthquake reach ~2000 people, and also collapse of government office building, bridges, hotels and other important infrastructure during the events. The aim of this research is to investigates the relation between the Coulomb failure stress of the mainshock with the aftershocks sequence following the 2018 Palu-Donggala, Indonesia earthquake. We calculate the Coulomb failure stress using the available coseismic fault models, which had varied moment magnitudes between Mw 7.53 ~ 7.62. We find that only by conducting Coulomb failure stress analysis, we can not favour the preference of the coseismic fault which explains aftershock distribution. This investigation demonstrates that additional observational data from geological field surveys are required to identify the surface rupture in comparison with the coseismic fault model. We propose that the output of this research can be very useful to be used as an input for seismic hazard assessment conducted by the Government of Indonesia for hazard mitigation purposes, especially in the eastern region of Indonesia.