[en] Gamma radiation fields from fission product mixtures are experimentally and theoretically investigated in order to determine the exposure rate and its temporal changes. Properties of gamma radiation emitted from a fission product mixture depend on the energy distribution function of the source strength. Results of measurements using a model fission product mixture obtained from momentary fission of ²³⁵U are in agreement with values cited in the literature. Measurements of the temporal behaviour of the exposure rate confirmed former results