Design of highly moderated pressurized water reactor based on critical heat flux considerations

The difficulty of applying the existing critical heat flux correlations to the design of a modified 100% mixed plutonium uranium oxide fuelled assembly are outlined. A core with increased moderating ratio (RMA) was designed. The purpose of this design modification is to permit the consumption of large amounts of plutonium which cannot be burned in a conventional pressurized water reactor (PWR) owing to safety considerations. The design criteria required that the minimum departure from nucleate boiling ratio (DNBR) in the modified fuel does not exceed the value of the standard N4 PWR, which served the basis for the design. The desired conditions were achieved by reducing the fuel pin diameter to increase the moderating ratio and increasing the number of grids with mixing vanes to improve the minimum DNBR in the modified assembly. The design methodology and some of the proposed design options are presented.