Conceptual Design Study of Small Sized Sodium Cooled Reactor

None

臼井 伸一; 近澤 佳隆  ; 此村 守; 田中 俊彦; 堀 徹*; 大久保 俊之*

Usui, Shinichi; Chikazawa, Yoshitaka; Konomura, Mamoru; Tanaka, Toshihiko; Hori, Toru*; Ohkubo, Toshiyuki*

実用化戦略調査研究フェーズIIの小型炉設計研究では、電源以外の多目的利用を幅広く想定して、経済性、安全性などの要求条件を満たすナトリウム冷却小型炉の検討を進めており、平成15年度の成果として経済性の向上を目指した出力165MWeで,原子炉出口温度550、燃料交換期間20年を同時に達成したナトリウム冷却小型炉プラントの概念を構築した。炉心はZr含有率3領域単一Pu富化度炉心を採用し、万一のATWS発生時にもSASS挿入に期待しないで高温整定する見通しを明らかにした。冷却系は、一体型の環状IHX及びEMPを原子炉容器内に収納した強制循環冷却式のタンク型炉で2次冷却系は1ループとし、崩壊熱除去系は自然冷却方式を採用することでシステムの簡素化を図った。経済性は、NOAKで建設単価の基準値(35万円/kWe)を満足することを確認した。

The Japan Nuclear Cycle Development Institute and the Electric Utilities have been studying for concepts of commercialized FBR plant system. In this study, a small sized sodium cooled reactor has been studied from standpoints of having a potential to use a power source applicable to diversified social needs and reduced capital risks. The concept is pursued to satisfy various requirements: economical competitiveness, reactor safety, very long lived core, etc. The electrical power is set to 165 MWe based on previous studies of small sized sodium cooled reactor which was aim of cost reduction of the plant pursued. A three regional Zr concentration with one Pu enrichment core has been designed. The burn-up reactivity is kept 1.17% dk/k and the core refueling occurs after 20 years operation with 77,000 MWd/t average burn-up. The reactor system is enhanced a passive safety to avoid a core melt even an ATWS and the design has possible capability to withstand UTOP and ULOHS events, although it requires reactor shutdown action by operator within a certain time. Tank-type primary system has been designed. A circular type IHX and a primary EMP are located in series inside of the reactor vessel. The steam generator and the secondary EMP are located outside of the reactor vessel and connected to the IHX by piping. A diameter of the core is minimized in order to reduce a reactor vessel size. Two PRACS driven by natural circulation is chosen as a decay heat removal system in order to satisfy a heat removal condition of Category IV in Japanese standard.The construction cost of the whole plant evaluates to be achieved an economical goal considering a mass production.