Study on reactor core and fuel design of sodium-cooled fast reactor (Metal fuel core); Results in JFY 2005

Oki, Shigeo ; Sugino, Kazuteru; Ogawa, Takashi; Aida, Tatsuya*; Hayashi, Hideyuki

Core and fuel design study of was performed. The reference specification of the large-scale (1,500 MWe) and the middle-scale (750 MWe) cores were proposed as a final result of . Since the local conversion ratio of any of the core points is made close to unity with single Pu enrichment, it is possible to minimize the necessary coolant flow rate for the core region and then, accept high reactor outlet temperature of 550C. By the rationalization of hot spot factors, the coolant flow distribution design can be optimized to 5 regions for the large-scale core and 8 regions for the middle-scale core, respectively. It was also confirmed that the core specification met the criteria of fuel-assembly integrity, as well as those of shielding design. For further improvement on the reactor outlet temperature condition, the reduction of the maximum cladding inner-wall temperature was investigated with the reflection of the actual control rod insertion depth and the rationalization of the excess-reactivity uncertainty. An alternative core design was investigated by adopting the PNC-FMS steel as the cladding material instead of the ODS steel. As a result of the investigation of extending the control rod lifetime, three-cycle lifetime (which is the same as fuel assemblies) could be possible by means of the reductions in B enrichment and BC pellet diameter.