Study of materials for mixed field dosimetry by EPR spectroscopy.
ML Hervé, F. Trompier, D.D Tikunov, V. Amouroux, I Clairand, 14th International Conference on solid state dosimetry, 27/06-02/07/2004, Yale, USA.
The EPR dose reconstruction after accidental photon exposure based on materials irradiated in the vicinity of the victim (sucrose, medicine,..) was successfully used in several cases referenced in the literature. However, accidental exposure may also occur with a neutron component such as the Tokai Mura criticality accident. The aim of this work is to investigate the potentiality of EPR dosimetry for mixed photon and neutron field exposure with different organic materials already used for photon exposure (sucrose) or with potential dosimetric properties. For this study, ascorbic acid, sorbitol, glucose, galactose, fructose, lactose, sucrose, and mannose were chosen. In a first time, optimisation of spectrometer registration parameters, micro-wave power and amplitude modulation, was performed for each material. The materials were then exposed to Co-60 photons in order to study the fading and the time dependence of the spectrum shape following irradiation, and to determine the sensitivity to Co-60 photons. To assess the fission neutron sensitivity, the materials were exposed to a mixed radiation field of an experimental reactor with different neutron to photon ratios. The reactor reference dosimetry was performed with thermoluminescent detectors for the photon component, and with silicon diodes for the neutron component. The sensitivity of each material to fission neutrons was then estimated relatively to photon sensitivity and to the reactor reference dosimetry expressed in tissue kerma using the formula given in the ICRP 26 report. The relative neutron sensitivity was found to range from 15 % to 50 % according to the materials. The potentiality of these materials for mixed field EPR dosimetry is discussed.