EXPERIMENTS ON INVESTIGATION INTO PLUTONIUM TEMPERATURE EFFECT IN PLUTONIUM MULTIPLYING SYSTEMS WITHOUT REFLECTOR

The article presents the investigation into reactivity and critical parameters affected by temperature changes in cylindrical and spherical space-effective multiplying systems (MS) of plutonium in α-phase without reflector during integral critical experiments. The experiments were performed in “Zababakhin All-Russia Research Institute of Technical Physics” on a critical assembly stand FKBN-2. Brief description of the experimental set up is provided. During the experiments, the multiplication factors and decay constant of the prompt neutrons were determined at a fixed gap between MS parts and different MS temperatures. Values of MS critical gap at different MS temperatures were established experimentally. The change in MS reactivity is initiated by energy release under the plutonium isotopes alpha-decay. As a result, the change in MS temperature during the experiments without its forced regulation may reach ~40 °C. It is proposed to consider this temperature effect when specifying experimental results including error estimation. The obtained experimental data were used to estimate the temperature coefficients of reactivity. The work results are applied to create benchmark models of the multiplying systems.