A new detector to measure γ and β decay power from radionuclides

Neutron activation of structural materials gives rise to an energy release during the subsequent radioactive decay. In large devices for energy production like a fission reactor, the future proposed Energy Amplifier or a Fusion power plant, this energy release represents a source of heat, which although at a very much lower level than the heating during operations is of the order of MWs for large nuclear power plants. Accurate estimation of the decay power is essential for safety analyses of the power plant against loss of coolant accidents, etc. Some computer codes have been developed to predict the decay power, but validation of the computer codes through experimental measurements is essential. A new large, almost 4π detector, formed by coupling a well-type CsI scintillator and a small plastic β detector has been developed for accurate and efficient measurements of decay power from γ and β radiation. Preliminary measurements of decay power produced in neutron-activated tungsten are presented and compared with the predictions of the European Activation Code System, EASY-99.