Cellulose for high level dosimetry

The dosimetric material used for electron spin resonance (ESR) analysis for absorbed dose assessment has to be selected according to task-specific requirements. Environmental conditions such as high ambient temperature during the irradiation or high humidity during storage may be limiting factors for the applicability of detector materials. For routine measurements in non-specific fields, the material should be resistant to water penetration. This is not the case with most organic materials and sophisticated watertight encapsulation becomes necessary in practice. The natural polymer cellulose is known to be resistant in various environments. It is insoluble in water or other polar solvents. In cellulose quite a few stable radicals are formed by ionizing radiation. They were found to be protected against the access of water from the environment. The dosimetric properties of purified cellulose membrane were investigated. The response of the cellulose radicals in terms of absorbed dose in water was terminated in the dose range 1-500 kGy. The ESR spectra were analysed with respect to the radicals' stability under different temperature and humidity conditions. The spectra were divided into three subgroups resulting from different radicals. Possible radical structures are discussed. (author). 9 refs, 6 figs, 1 tab