An Investigation on the control rod homogenization method for next-generation fast reactor cores

次世代高速炉の核設計における制御棒均質化法の検討

滝野 一夫 ; 杉野 和輝; 大木 繁夫 

Takino, Kazuo; Sugino, Kazuteru; Oki, Shigeo

A Japanese next-generation fast reactor core design adopts the reaction rate ratio preservation (RRRP) method for control rod homogenization with a super-cell model in which a control rod is surrounded by fuel assemblies. An earlier study showed that the RRRP method with the conventional super-cell model could estimate the control rod worth (CRW) of a 750-MWe large fast reactor core within the analytical uncertainty of 1.5%. The estimation of radial power distribution (RPD) tends to have relatively large analytical uncertainty especially for large fast reactor cores with the control rods inserted. In order to eliminate the radially-dependent analytical uncertainty of CRW and RPD, this study evaluated and refined the surrounding fuel assemblies of the super-cell model for all control rods in the RRRP method. This refinement significantly decreased the radially-dependent analytical uncertainty: the analytical uncertainty of CRW and RPD were reduced to less than 0.13% and 0.35%, respectively.