Design study of medium size lead-bismuth cooled core

Yamashita, Takumi; Sanda, Toshio; Mizuno, Tomoyasu

In "Feasibility Studies on Commercialized Fast Breeder Reactor Cycle System(FS)", various types of fast breeder reactor using different coolant are studied, in which lead-bismuth is one of the subject. In JFY 2003 study of FS phase-II, design studies of medium scale forced /natural circulation nitride fuel core (FC/NC core) were carried out considering DDI (duct-duct interaction) which was not considered in JFY 2001 studies. The prospect of satisfying a design target of the core performance was acquired by improved design. By comparing properties of FC core (750MWe) and NC core (550MWe), we recommended the FC core as a hopeful one to design. The FC core was superior to the NC core in the following points, (1)Larger average burn-up (core and blanket) (2)Less Pu-fissile loaded weight (3)Smaller core equivalent diameter in spite of larger generating power (4)The NC core has much problems from the viewpoint of earthquake-resistant design. A design target of high burn-up of 150 GWd/t was satisfied, but fast fluence on clad is over the development target of ODS steel and PNC-FMS stee1 (5 10n/cm, E0.1Mev). Cores in which fast fluence was restricted to less than the target were also designed. MOX fuel and metal fuel cores were studied, and the effect of composition of TRU fuel recovered from LWR to core performance was also investigated to show flexibility and diversity in the lead-bismuth cooled core. In recent studies, it is becoming clear that the present evaluation for the clad corrosion in lead-bismuth gives non-conservative result and lowering the highest clad temperature will be required in core design. The lowering of temperature was permissible according to preliminary analysis using the present corrosion correlation.