Safety analysis of compacted spent fuel with natural convection flow

Abstract

Among the advanced methods of increasing the spent fuel storage capacity, there is a method so called rod consolidation method which disassemble the spent fuel assembly and rearrange the fuel rods in the more compacted state. A key element in the new design of underwater storage systems is intended to make sure removal of heat generated in the spent fuel by radioactive decay. When the abnormal conditions or the accidents occur, the analysis of the natural convection flow in the pool is very important subject. Three-dimensional analysis of axial convection is studied by numerical simulation. The numerical technique developed by using ADI scheme is based on the coupled conservation equations of mass, momentum, and energy for the typical fuel element. The spent fuel heat generation rate calculation is accomplished by the ANS Standard method. The nonuniform surface heat flux condition is assumed with a chopped since curve for the spent fuel decay heat generation. Computations are performed by varying the affecting parameters, i.e. spacing ratio, decay heat generation, Prandtl number, and radius of the spent fuel rod. The numerical results show that the natural convection flow through compacted spent fuel bundles provides safe and effective temperature control after the appropriate cooling time, and the limiting criteria for rearranging the spent fuel rods was found.