Measurements of photon spectra in mixed fields at a nuclear installation

This paper describes the measurements of photon spectra in mixed neutron/photon radiation fields at a few locations in a nuclear reactor. The measurements were performed inside the containment of reactor 4 at the Swedish reactor site Ringhals, with a Ge-detector (4%). The measurements were carried out as a part of a EURADOS project in co-operation with the Swedish authorities and the reactor operating company. The measurements showed that a large fraction of the photons are high-energy photons (up to 7.6 MeV). This implies that GM-based photon detectors will overread in these fields since this type of detector generally overestimates the ambient dose equivalent in 6–7 MeV photon fields. The measurements also indicated that the photon field was almost isotropic, which in turn implies that the effective dose as well as the personal dose equivalent will be lower than the ambient dose equivalent.