Burnup and feasibility study of low power density PWR's

Operational and safety problems of current Pressurized Water Reactors are often associated with the high power density level of the cores. An alternate use of current-design cores is proposed by reducing the power density.The effects should be improved safety, improved ore utilization, and improved operational characteristics. A scoping study is performed in order to define core parameters suitable for optimization under the low power density characteristics, while minimizing redesign requirements. A neutronic optimization study of the reactor cores is performed by systematic changes in the fuel lattice pitch. A new core burnup computational model (CRIBUR) is developed, which allows calculation of the burnup and isotopic analysis of a multi-batch core in its equilibrium cycle with a moderate computational and human effort. CRIBUR provides better accuracy and sensitivity than other known existing models of comparable scope, with a moderate computational effort. The code is benchmarked against actual core data and against multi-dimensional diffusion theory core calculations, and its sensitivity to several of the calculational parameters is also tested. The thermal-hydraulic behavior of the low-power cores is compared to that of the standard reactors, and their enhanced safety margins are clearly demonstrated. The low-power cores yield higher burnup levels than the standard reactors. Ore utilization is also improved in a once-through fuel management policy. Isotopic comparisons are presented. Core cycles are drastically increased. Plant availability and capacity factors are also increased as a result of both the reduced impact of refueling downtimes and the reduced forced outage time resulting from the improvement of operational characteristics