Preliminary Computations for the Pulsed Reactor IBR-4. Optimization of the Neutron Flux

Abstract

The IBR-4 pulsed reactor with a power of 4 MW and a pulse repetition frequency of 10 1/s is considered as a pulsed neutron source to replace the IBR-2M reactor, which will be decommissioned by the end of the 2030s. The IBR-4 design is based on the MBIR reactor implementing the principles of continuity of succesful solutions used in the IBR-2 and IBR-2M reactors. The IBR-4 core ensures the nuclear safety of the reactor and minimizes low-frequency fluctuations in pulse energy. The IBR-4 design is a development of the basic design of the core with the addition of beryllium reflectors and small-volume water moderators. The IBR-4 reactor makes it possible to obtain thermal neutron flux densities on the surface of the water moderator for the extracted neutron beams at a level of 1.2 × 10¹⁴ n/(cm² s), and, in the region close to the surface of the moderator, 3.0 × 10¹⁴ n/(cm² s). Thus, IBR-4 is a powerful pulsed source of thermal neutrons.