Computational-theoretical model of a wave multiplying pulsed reactor

Abstract

A computational-theoretical model is proposed for an innovative "zero" power wave multiplying pulsed reactor (WMPR) for studying the development of a nuclear fission chain reaction near the upper critical state of the system, i.e., in the region where calculations are difficult to perform and on which nuclear explosion-safety of critical systems depends. A scenario of possible accidents is presented. The novelty and special features of the physical scheme of the WMPR required the use of new computational methods. These methods can be used, for example, to calculate conventional pulsed nuclear reactors.A wave multiplying pulsed reactor (WMPR) differs from classical reactors in that the excess reactivity arises in it as a result of the passage of a short acoustic plane wave of compression through a cylindrical core along the axis of the cylinder. The compression wave is generated by detonating a thin layer of explosive with a mass of several grams. For such a small quantity of explosives, the structural materials remain whole, which ensures that the experiments are ecologically clean and that the core can be reused. Another special feature of the reactor is that the energy released corresponds to the heating of the core from microdegrees up to several degrees celsius. This is actually a detonation-free fission chain reaction, which has no effect on the mechanics and kinetics of reactor operation.To implement this operating regime, before the explosives are detonated the reactor must be under control in a critical testing stand, which is part of the reactor construction, and must be brought close to its upper critical state so that even a weak acoustic wave of compression can transfer the reactor for a short time into a subcritical (with respect to spontaneous neutrons) state and the number of fissions required for the investigations can accumulate in the system. In addition, by the moment of startup the reactor must be started up on delayed fission neutrons up to ~10 11 fissions/sec. Such power is needed for recording confidently the development of a fission chain reaction in the system. Thus, it is important to know the neutron parameters of the reactor in order to describe the operation of the WMPR and to adjust the reactor prior to the experiment. Such calculations can be performed in two dimensions using the Loma-3 mathematical program, which is part of the Saturn-3 program system [1]. The critical state of the reactor was used as a reference point in the calculations. This methodological device makes it possible to prevent many uncertainties, which are associated with the neutron constants of the structural materials, the energy spectrum of the neutrons in the system, the angular distribution of the neutrons, the adopted spatial grid, and other factors, from affecting the computational results. Such unavoidable uncertainties make it impossible to use the conventional direct methods for calculating the system parameters with the accuracy required for WMPR (10 -4 in units of K eff ) because the system is extreme...