Thermoluminescence Dosimetry at High Temperature and High Doses

The increasingly wide spread use of electronuclear energy has led to the need for an improved knowledge of the radiation doses received by various structural materials. Dose rates are particularly high in regions in the vicinity of the core of a reactor, steam generators and the pool in which spent fuel elements are stored; high dose rates will also be encountered at high-level waste disposal sites. In most, involving gamma radiations resulting from the de-activation of fission products, thermal conditions can be problematic: temperatures as high as 300 oC can be reached inside the core or steam generators. Preliminary tests performed in high-level waste disposal environments suggest that similar temperatures are likely to be reached. Thermoluminescence (TL) dosimetry can be employed if certain conditions are satisfied: the TL products must possess at least one deep trap and must also be sensitive over a sufficiently wide dynamic range. The following materials have been investigated for this purpose: dysprosium doped calcium sulphate powder, alumina and cerium doped ceramic glasses. The maximum dose measurable depends on the material employed and ranges from a fraction of a kilogray for alumina, to a few kilograys for calcium sulphate and cerium doped glasses. A comparative study of the various available products has been performed in order to define the limits and to optimise their use.