INNOVATIVE APPROACH TO RELOADING AN INITIAL CYCLE

摘要

The objective of this paper is to present analyses of an innovative approach to reload an initial cycle loading pattern (LP) of a PWR by selecting the reload pattern fuel assemblies, FAs, based on their K_∞ rather than on their initial enrichment. In this new method, the FA K_∞ is the primary selection factor, i.e., the FAs having the lowest K_∞ are discarded after each cycle. However, it has been discovered that the sum of the ~(235)U and the ~(239)Pu nuclide's number densities are also very important factors when choosing the used FAs to be reloaded in cycle 2. The Haling Power Depletion (HPD) method has been extensively used to guide the design of the reload core. It was discovered that the first cycle has to be the highest possible leakage core because of the nature of the condition of the end-of-cycle FAs. The HPD acceptable reload design ended up with large loss in cycle length. In fact, the second cycle is also a relatively high leakage core. A more accurate step depletion calculation is implemented afterwards to verify the design. The simple relative fuel cost comparison made between the two methods for the first reload cycle must now be made for the second cycle. Studies will continue on reloading further cycles to obtain a long term understanding of minimizing the fuel cost.