Calculational and experimental studies of thermal-hydraulic conditions of the BOR-60 fuel assembly operation

The results of calculational and experimental investigations of temperature fields of heat-generating assemblies (HGA) of BOR-60 reactor under real operation conditions are given. Essential non-uniformities of sodium temperature distribution along the assembly cross section are found in experiments on standard HGA. Radial temperature nonuniformity in assembly approaches 80-100 deg C, and temperature non-uniformity by azimuth of fuel element shells and assembly casings 35-50 deg C. It is shown, that level and distribution of heat carrier temperatures in HGA are determined by real geometry of fuel element lattice and nonadiabaticity of assembly boundaries, connected with interpacket sodium passages and different nonuniformities in the zone (channels of control and protection systems, experimental assemblies and assemblies of reproduction zone. It is noted, that nonuniformity of temperature distribution increases at the expense of power generation nonuniformity by the radius of reactor active zone, heat losses in interpackage gaps and HGA heat exchange with cold channels, particularly, cases of rods of control and protection systems and assemblies of side screen. It is concluded, that nonuniformity of temperature distribution in HGA should be necessarily taken into account during interpreting the results of fuel element radiation tests, conducted at BOR-60 reactor