Investigation of different methods to design the start-up core of the canadian SCWR

The Canadian concept of Super-Critical-Water reactor is a three-batch refuelling core with target exit burnup of 40 MWd/kg. It uses a mixture of plutonium and thorium oxides as fuel. The equilibrium cores as well as the refuelling scheme of this concept have been proposed by CNL (formerly AECL). The equilibrium core is the core which will be reached after refuelling the start-up core with the same fuel for a number of times in a three-batch operation. The goal of this work is to design the start-up core which will allow reaching a specific equilibrium core when refuelled with the nominal fuel enrichment using the proposed refuelling scheme. This start-up core will be designed using a set of different fuel enrichments. Different methods to select these enrichments have been investigated. Results of each method, including the cycle length, cycle burnup, maximum power and power peaking factor of each cycle, are presented in this paper. Keywords: SCWR, Start-up, Linear reactivity model, Cycle length.