System Design Study on a Sodium-Cooled Small-Scale Reactor; Study Result in JFY2002

Hori, Toru; Chikazawa, Yoshitaka  ; Kida, Masanori; Konomura, Mamoru

In the "Feasibility Studies on Commercialized Fast Reactor System", sodium-cooled small-scale reactor concepts have been studied fromstandpoints of economy, safety, and long lived core. And in JFY2002,based on study of technical issues, three concepts (electricity output of 150MWe) were designed with parameter of reactivity control and coolant circulation type. The above concepts had prospect to attain safety enhancement (avoiding core melt without SASS at ATWS) and long lived core (10 years). They could not satisfy cost target (350,000 yen/kWe), because the inherent and passive safe core was flat (phi3.3m x h0.6m),and upper reactor diameter increased by considering some space to take out EMP periodically. But forced circulation-type concepts had potential to decrease construction cost by adopting compact core with mitigation of coolant temperature reactivity coefficient and devising in-vessel EMP arrangement.Control rod system had merits about decreasing reactor diameter, utilizing relative displacement reactivity coefficient between reactor and control rod, and small technical issues, by comparing with reflector system. And EMP had no necessity to be taken out from reactor, except failure accidents, by considering EMP characteristic of Passive equipment and maintenance process. Based on these results, it was important that some attractive small-scale reactor concepts, which attained compact and high temperature reactor with control rod and forced circulation-type, would be proposed by aiming at "longer lived core (more than 10 years)", "simpler operation and maintenance" , and "diversified social needs (hydrogen production)".