Physics of Graphite Lattices with Plutonium Bearing Fuels

The economics of a nuclear power plant highly depend on the fuel utilization. It is necessary to predict with great accuracy the burn-up level at which the fuels have to be rejected, the maximum irradiation level, in order to achieve the best fuel management (radial or axial shuffling, unloading, type of fuel to be reloaded, etc...). Thus one must be able to compute, under all conditions encountered in the reactor life, the various physical phenomena varying with the fuel composition: plutonium build-up, isotopic changes, depletion of the uranium 235, fission product formation, variation of the neutron spectrum and of the effective cross sections of the various present nuclei, variation of the total reactivity, variation of temperature coefficient.