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Masui, Akihiro; Nakamura, Makoto; Watanabe, Kazuhito; Someya, Yoji; Tanigawa, Hisashi; Tobita, Kenji
no journal, ,
When a pipe of tokamak cooling system breaks outside of vacuum vessel, it is necessary to keep integrity of buildings to prevent that tritium and ACP contained in coolant are released to environment. A load to buildings is affected by plant design parameters, for example mass of coolant, pipe diameter and volume of buildings. The impacts of these parameters on the load to buildings are shown based on thermal hydraulic analyses.
Watanabe, Kazuhito; Nakamura, Makoto; Someya, Yoji; Masui, Akihiro; Katayama, Kazunari*; Hayashi, Takumi; Yanagihara, Satoshi*; Konishi, Satoshi*; Yokomine, Takehiko*; Torikai, Yuji*; et al.
no journal, ,
In the DEMO design, the blanket primary cooling system involves high temperature pressurized water (~300
C). This means the temperature of blanket structural material is higher than that of ITER. This increases tritium permeation ratio from the fusion plasma and blanket breeder to the primary cooling water. Therefore, we need to consider installation of a water detritiation system. In this study, we estimate the demand of water detritiation system from the view point of the amount of tritium permeated to primary cooling water that assumed conservatively. We also organize the issues for management of tritiated water from the other point of view based on the characteristic of the fusion DEMO reactor. The result shows that the existing facilities can be adopted to the DEMO if we can control the tritium ratio of primary cooling water as same as that of CANDU reactor.
Nakamura, Makoto; Tobita, Kenji; Tanigawa, Hisashi; Someya, Yoji; Masui, Akihiro; Watanabe, Kazuhito; Konishi, Satoshi*; Torikai, Yuji*
no journal, ,
Tritium is major radioactive material in a fusion reactor. Evaluation of the dose due to the tritium is essential to understand environmental consequences of incidental or accidental conditions postulated in the fusion reactor. A purpose of this study is to identify issues to apply UFOTRI, a code of tritium dose analysis being used for the ITER safety assessment, the Japanese environmental conditions. Extensive scans of UFOTRI calculation runs were performed in various meteorological and release conditions. The scans show that the contribution of the secondary tritium release is more significant in the cases of lower release height, lesser stable atmosphere or more distant conditions. The analysis, thus, suggests that it is important to take into account the contribution of the secondarily released tritium in evaluating the early dose to the public due to the tritium release.
Tanigawa, Hisashi; Nakamura, Makoto; Someya, Yoji; Masui, Akihiro; Watanabe, Kazuhito
no journal, ,
Blanket in fusion nuclear reactor has three functions such as neutron shielding, heat recovery and tritium breeding. The blanket in ITER is called as Shielding blanket because it has only a function of neutron shielding. The blanket with heat recovery and tritium breeding functions will be equipped with fusion DEMO reactor for the first time. Therefore it is important to study event sequences and their effects related to the blanket for understandings of safety characteristics in DEMO plants. For both of ITER and DEMO, it is the same that a vacuum vessel is treated as the first container against radioactive materials. Safety-related events including in-vessel LOCA and in-box LOCA are analyzed and their effects on the vacuum vessel are assessed.