The relative sensitivity of thermoluminescent material to neutrons: a review of available data

The review is intended as the basis for establishing the response of thermoluminescent (TL) materials to neutrons so that these materials can be used in the assessment of the gamma-ray dose in mixed neutron and gamma-ray fields. The relative tissue-kerma sensitivity, k, is defined as the ratio of the measured response of the TL material to neutrons to the measured response to 60Co gamma radiation relative to the tissue kerma for neutrons and gamma radiation, respectively. There are many factors which effect k including the TL material itself (its composition, dimensions and surrounding material), the characteristics of the TL reader, the irradiation conditions, batch to batch variations and environmental conditions such as temperature, humidity, UV light and irradiation history. None of the data in the literature is produced under standard conditions and so a true comparison is not possible. However, it has been possible to eliminate the kerma dependent factors from k and so demonstrate that the efficiency of TL materials for detecting neutrons, etasub(n), relative to that for detecting 60Co gamma rays, etasub(s), is essentially constant for a given material for neutron energies from thermal to about 10 MeV. Above this energy, etasub(n)/etasub(s) increases significantly. The increase can be accounted for qualitatively by a reduction in LET at higher energies. There are large uncertainties in the data which could be reduced if standard conditions could be agreed internationally. However, following this Symposium, a full report of this study will be published by CENDOS with any more information that may be forthcoming