Temperature regime of the reactor graphite structure at the Bilibin nuclear heat and power plant

Calculational and experimental data on temperature distributions in the graphite structure in different elements of the Bilibin nuclear heat and power plant (BNHPP) reactor cores are presented. The reactor design features effecting the temperature profiles of the graphite structure are considered. The temperature field in a fuel channel is discussed. The approach is described for choosing gas gaps in the fuel channel design which govern mainly the graphite temperature. The presence in the reactor core of control elements brings about the reduction in the maximum graphite temperature by about 70 deg C. In the centre and at the outskirts of the core the graphite temperatures are practically equal. The BNHPP reactor graphite temperature peaks in the core equals to 510 deg C at nominal reactor power. The peaking temperature calculated for the gas gaps is about by 50 deg C higher. The calculated temperature fields in the lateral reflectors are also presented. It is noted, that in calculating the graphite structure temperature fields one is to take into account an increase of the thermal conductivity of the gas gaps owing to touching of some structure elements