Conceptual design study of helium cooled fast reactor in the "feasibility study" in Japan

None

岡野 靖; 永沼 正行  ; 池田 博嗣; 水野 朋保; 此村 守

Okano, Yasushi; Naganuma, Masayuki; Ikeda, Hirotsugu; Mizuno, Tomoyasu; Konomura, Mamoru

ガス冷却高速炉の炉心概念として有望な3形態:被覆粒子型横方向流冷却概念,被覆粒子ブロック型概念、及び、ピン型概念について、炉心設計および過渡解析を実施し、その炉心特性及び安全特性を比較した。被覆粒子型概念は炉心特性と安全特性を両立し得る概念であり、ピン型概念は安全性確保に技術課題を有するものの非常に優れた炉心特性を示す。

Conceptual design of gas-cooled fast reactor (GFR) have been studied for selecting applicable combinations of coolant, fuel material and configuration, and, balance of plant, as a part of feasibility study in Japan. Large-scale He-cooled GFR, employing mixed nitride fuel and achieving a high core outlet temperature of 850C, is recognized to achieve attractive features as a future nuclear reactor system. Three fuel configurations are considered and compared in their core and safety performances; one is horizontal-flow cooling fuel assembly (F/A), another is hexagonal matrix block F/A, and the last one is sealed pin bundle F/A. The horizontal-flow and matrix block F/A cores show nearly the same neutronics performances on discharge burnup around 120GWd/ton, breeding ratio above 1.1, and, core cooling performances under depressurization condition without control rod scram or auxiliary core cooling system (ACCS) actuations; whereas around 30% smaller quantity of fissile Pu required is a merit for matrix concept. The sealed pin bundle F/A core potentially shows attractive neutronics performances on discharge burnup about 141GWd/ton with breeding ratio of 1.27, although rapid control rod scram and ACCS actuations are indispensable for core cooling under depressurization accident conditions.