Abstract
Characteristics for different moderation ratios are investigated with light water and heavy water coolant. Equilibrium state was implemented by four typical fuel cycles. Design parameters are the same for standard PWR design with different moderation ratios and different coolant as shown in table 1 Calculation method was performed by using ECICS (Equilibrium Cycle Iterative Calculation System) to get nuclide densities and uranium supply in equilibrium state and to estimate the required uranium enrichment to keep the reactor on the critical condition. Obtained results are shown in Fig.1 for both light water and heavy water coolant. In required uranium enrichment point of view the light water case has better performance than heavy water case, but in the lower moderator to fuel volume ratio the heavy water coolant has better conversion ratio than light water coolant.
