Development of a Spectrometer to Measure Photon and Electron Decay Heat from Radionuclides

Abstract

Neutron activation of elements gives rise to an energy release during the subsequent radioactive decay. This paper deals with the development of a large, almost 4π, spectrometer for accurate and efficient measurements of photon and electron decay heat of neutron activated elements. The spectrometer consists of a well-type 22.8 x 22.8 cm cylindrical CsI(Tl) scintillator (for photon detection) and a small plastic electron detector inserted in the well. The spectrometer was designed to have many excellent features such as the possibility to measure simultaneously the total activity of the sample and its electron and photon decay heat separately with high sensitivity and wide dynamic range. To demonstrate the feasibility of decay heat measurements with our spectrometer, we have irradiated twelve samples of different materials using the 14 MeV neutron generator FNG. The measurements have been compared with the prediction of the activation system EASY-99 and the results in term of the C/E (calculation vs. experiment) are presented. While most of the C/E values are, within the uncertainties, equal to one, discrepancies for one radionuclide was found and are discussed in the paper.