Design-basis justification for implementing targeted energy release in test objects of the impulse graphite reactor

Abstract

The article presents the approaches and technical solutions applied to assure preset axial and radial distribution of energy release in simulative fuel rods and fuel assemblies in the tests at the impulse graphite reactor. It considers the procedure for the design-basis justification of solutions that provide a given volume distribution of energy release in a test unit. The considerations are based on the example of heterogeneous fuel assemblies with the altitude separation of enriched fuel into two zones by a depleted uranium layer used to reproduce fissile material. The implementation of the procedure and making appropriate technical solutions made it possible to provide a targeted profile of the axial and radial distribution of energy release in a simulative fuel assembly at the design stage of an irradiation device. By the result of study, it is demonstrated that uniform radial energy release and targeted average energy release in upper and lower fission zones of experimental fuel assembly could be obtained at the level of 90.6 W/g (UO2) and 74 W/g (UO2), respectively. The measures include profiling of fuel pellets enrichment in fuel rods, using the pellets with an absorber at the zone ends, and a certain altitudinal positioning of the irradiation device in the reactor.