On feasibility of optimizing the neutronic parameters of a laser system pumped by a pulsed reactor

Abstract

The paper examines the calculated feasibility of improving the energy characteristics of power pulses in a system consisting of a reactor and a subcritical block. A BARS-type fast neutron reactor is used as a self-quenching pulsed reactor.The subcritical block is a cylindrical structure comprising laser-active elements, moderator components and two reflectors (internal and external). The internal reflector material is zirconium hydride, and the external reflector material is beryllium. The pumping area containing the laser-active elements consists of zirconium hydride moderator, aluminum and uranium–molybdenum fuel (95% enriched uranium).The system operates in a pulsed mode. Fast neutrons are generated in the nuclear reactor at the pulse moment, many of which are leakage neutrons entering the subcritical block, slowing down there and inducing fissions of uranium nuclei in the laser-active elements. After the pulse terminates, the reactor changes to a deeply subcritical state, and the laser pulse generation stops.The neutron kinetics in the system under consideration is modeled based on a modified integral model.The pulse maximum power and energy in the system's subcritical block, as well as its weight and energy-to-weight ratio are selected as functionals for the optimization. The fissile material and moderator weight and the thickness of the subcritical block's internal and external reflectors are adopted as variables.The calculations have shown that it is possible to improve the energy characteristics of a reactor-laser system by increasing the amount of the fissile material in the block, not using the moderator in the block and fixing the thickness of the internal zirconium hydride reflector at a level of 3.1cm. It has been shown that a change in the external beryllium reflector thickness leads to a highly multidirectional behavior of the functionals (energy and maximum power, as well as the block weight and energy-to-weight ratio).