Reactor Physics Calculations on Close-Packed Pressurized Water Reactor Lattices

The recycling of plutonium in close-packed pressurized water reactor (PWR) lattices, leading to a higher conversion ratio than recycling in a normal lattice, has been studied by calculations. These calculations were performed with the multigroup cell and assembly transport theory code CASMO. This code, widely used for normal light water reactor (LWR) lattices, was tested for close-packed ones by calculations on experiments. The outcome of these tests was reasonably good for the parameters of greatest importance in close-packed plutonium-recycle lattices. Subsequently, the code was applied to an LWR system containing PWRs with such lattices. The emphasis in this application was on the net consumption of natural uranium and separative work. In an asymptotic (steady-state) situation for the close-packed lattice case, these amounts turned out to be ∼35% below the corresponding ones for plutonium recycling in a normal lattice.