Dynamics of variation in WWR-K reactoroperationalparameters under gradual replacement of waterreflector by beryllium one

The WWR-K research reactor operates with low-enriched uranium (LEU) fuel beginning with 2016. In view of keeping high levels of the generated power in the core and the reactivity margin sufficient for the 21-day work cycle, side water reflector of neutrons gradually, as fuel burns out, is replaced by beryllium one such way that the reactor operational characteristics are not getting worse. The object of the study is the core of the WWR-K research reactor with low-enriched fuel. The aim of the work is to substantiate the procedure for the transition from a water reflector to a beryllium reflector during the operation of the reactor, which allows not only preserving, but also improving the neutron characteristics of the core, as well as analysing the changes in the main neutron-physical characteristics of the core, obtained both by calculation and experimentally during the three-year operation of the reactor. The main tool for computational studies is the computer code MCNP6. Experimental data - the operating characteristics of the WWR-K reactor generated during its operation. A cycle of computational studies was carried out with modelling the core of the WWR-K reactor in the MCNP environment and determining the dynamics of changes in the neutron flux density, reactivity, efficiency of the control and protection system working elements and kinetic parameters important for ensuring the safe operation of the reactor. The calculated dependences of the main operational characteristics of the WWR-K reactor are presented and analysed from the point of view of their use for scientific research, as well as their impact on the safety of the reactor operation.

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