Results of Old and Program of New Experiments on the Small-Sized Fast Multiplying Systems with HEU/LEU Fuel

Benchmark criticality experiments on small-sized fast multiplying systems were performed using the ^Giacint critical facility of the Joint Institute for Power and Nuclear Research - Sosny of the National Academy of Sciences of Belarus. The critical assemblies' cores comprised fuel assemblies with 19 HEU fuel rods. Three types of fuel assemblies with different contents of fuel rods were used. The side radial reflector comprises an inner layer of Be, and an outer layer of stainless steel. The top and bottom axial reflectors are stainless steel. The analysis of the experimental results obtained from these benchmark experiments by developing detailed calculation models and performing simulations for the different experiments is presented. The ^Giacint and ^Kristal critical facilities are being prepared for benchmark criticality experiments on multiplying systems, simulating physical features of the cores with LEU fuel to be uses at fast reactors with gaseous and liquid-metal coolants. The critical assemblies represent uniform hexagonal lattices of fuel assemblies, each of which consists of 7 fuel rods and have no cladding. Three types of fuel assemblies with different matrix material (air, aluminum and lead) were investigated. The side radial, top and bottom reflectors are Be (internal layer) and stainless steel (external layer). The description of the design and the composition of the critical assemblies and the results of calculation are presented. (author)