Evaluation for Influence of New Volcanic Eruption on Geological Disposal Site
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Evaluation for Influence of New Volcanic Eruption on Geological Disposal Site Taro Shimada1, Seiji Takeda1, Ryutaro Sakai2, Kazuya Takubo1 and Tadao Tanaka1 1 Nuclear Safety Research Center, Japan Atomic Energy Agency, 2-4 Shirakata, Tokai-mura, Ibaraki, 3191195, JAPAN. 2 OYO Corporation, 1-66-2 Miyahara, Kita-ku, Saitama City, Saitama, 3310812, JAPAN ABSTRACT There are some regions where it is difficult to exclude the possibility of appearance of new volcanic activity on the site even if the geological disposal site is located far from existing volcanos in Japan. In order to identify the influence of volcanic eruption at the site to the public if it occurs, public exposure doses were evaluated based on the two scenarios considering types of eruption at new volcanic activity in Japan. One is the exposure by volcanic ash widespread by Strombolian eruption and deposited on the ground surface, including radionuclides from vitrified waste forms after a volcanic conduit penetrated the repository. The other is that by waste forms appeared at the ground surface by Merapi type pyroclastic flow. Exposure doses of the residents living on the volcanic ash do not exceed 1mSv/y even when the eruption occurs at 1,000 years after closure of disposal site. Exposure dose rate for the volcanic researchers temporarily approaching naked waste forms without realizing radioactive wastes is 0.8mSv/h when the eruption occurs 100,000 years after. It indicated that attention should be paid to the influence by Merapi type pyroclastic flow on researchers approaching waste forms appeared rather than that by Strombolian eruption on residents living on the volcanic ash widespread. INTRODUCTION Japan is located at one of the world’s most volcanically-active areas and has 110 active volcanoes, 7% of those in the world. However, it is possible to select the location of a geological disposal site for high-level radioactive wastes far from the existing volcanoes, because the active volcanoes depend on the regional location in Japanese islands [1]. It is required that the disposal site should be located far from the existing volcanos. On the other hand, there are regions where it is difficult to exclude the possibility of appearance of new volcanic activity on the site even if the site is located far from the existing volcanos. Since the disposal site has not yet been decided at the moment, it is important to evaluate the radiological impact that a volcanic conduit penetrates the repository and radioactivity appears on the ground surface at the site where is located at the area impossible to exclude the possibility as a rare natural event scenario. The influence on the geological disposal system impacted directly by the volcanic activity is supposed to be significantly larger. However, there is no precedent for a quantitative evaluation of the influence on volcanic activity to the system in Japan. This paper focuses on the evaluation of the influence that a volcanic conduit penetrates the repository and the radioactive wastes appear at atmosphere or th
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