Experience of Operating VVR-K with a Beryllium Reflector and Low-Enriched Uranium Fuel

The VVR-K research reactor has been converted to fuel with reduced-enrichment uranium in keeping with the concept of minimizing the use of high-enriched uranium. Operation of the reactor with low-enriched fuel began in September 2016. The initial configuration of the core had a water lateral reflector, and as the fuel burned up it was gradually replaced with a beryllium reflector. A phased assembly of a beryllium reflector commenced at the end of 2016. The beryllium reflector made it possible to maintain the radial dimensions of the core and to increase the neutron flux density in peripheral irradiation channels. The complete beryllium side reflector was formed after 270 eff. days of reactor operation. The results of the operation of the VVR-K research reactor on low-enriched fuel in 2016–2019 are presented and the procedure for transitioning from a water reflector to a beryllium reflector is described.