Design study of medium size forced circulation 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 have been studied, in which lead-bismuth is one of the subject. In this study, design studies of medium size forced circulation (FC) reactor were carried out using newly proposed correlation in evaluation for clad outside surface corrosion and in restriction on the maximum clad outside surface temperature to 570C based on the design in JFY 2003. The influence of changes in foregoing design conditions on core performances of the FC reactor was smaller than that of natural circulation (NC) reactor, and consequently, design of the FC core (outputs were 1980MWt, 750MWe) was performed to meet demands for coolant velocity, bundle pressure loss and so on. The designed core was larger than that designed in JFY 2002 because of increase in fuel pin diameter and fuel pin pitch. The main specifications for the designed core were as follows; with no radial blanket, fuel pin diameter of 8.0mm, core height of 70cm, core equivalent diameter of 4.43m, envelope diameter of radial shielding region of 5.35m. The main core performances were as follows; operation period of 18 months, burn-up of over 150GWd/t, and breeding ratio of 1.10 for the breeding core and 1.04 for the break even core. They achieved the performance targets in the FS within the condition where envelope diameter of radial shielding region was less than 5.5m. Fast fluence was not restricted in anticipation of improvements on materials in the future. When it was restricted to the development target of ODS steel and PNC-FMS steel (510n/cm, E0.1Mev), the burn-up was about 125GWd/t. From these results, prospect of possibility of core manufacture was gained within the new design conditions of clad corrosion and temperature.