Static Thermal Design Analyses of Supercritical Water-Cooled Fast Reactor

Subchannel analyses have been carried out for SWFR. PCST difference arising from sub-channel heterogeneity has been calculated by using the improved sub-channel analysis code STARS and that was evaluated to be about 18 deg. C. Several suggestions have been also made for reducing the PCST difference arising from channel heterogeneity. Effect of local power peaking on deflection of cladding surface temperature is explained with actual pin power distribution taken from core depletion calculation in this paper. Maximum cladding surface temperature at nominal condition is evaluated to be 645.3 deg. C over the cycle. Statistical thermal design uncertainty associated with PCST calculation is evaluated by Monte-Carlo sampling technique combined with sub-channel analysis code. Maximum design uncertainty of PCST is calculated to be 51 deg C and is in a good agreement with that from RTDP method. Influence of downward flow in seed region on system sensitivity is investigated by improved Monte-Carlo thermal design procedure. Static thermal design limit of MCST is 701 deg. C (650 deg. C for nominal + 51 deg. C) within 95/95 limit for SWFR. (authors)