Experiments on HTR criticality parameters at the ASTRA facility of the Kurchatov Institute

The 'zero' power ASTRA critical facility at the Kurchatov Institute is intended for experimental investigation of neutronics of HTGR reactors. Spherical graphite elements with multilayer coated fuel particles inside, along with pure graphite and absorber containing spherical elements can be used in different configurations of cores. Reactor-grade graphite blocks are used in the structures of bottom, side, top, and/or internal reflectors. Hardware capabilities of the facility allow creation of the critical assemblies with the outer diameter and height of the side reflector of up to 3.8 and 4.6 m, respectively. The ASTRA critical facility was used to simulate the HTGR reactors earlier designed in Russia, PBMR reactor (being developed in RSA) and is going to be used under the international GT-MHR project (France, Japan, Russia, USA) mainly for the purpose of obtaining experimental benchmark data for computer code validations. Brief description of the ASTRA facility characteristics, investigated core configurations, experimental methods, and results is given in the paper