Dosimetric characterization of dyed solid dosimeters for gamma radiation

Abstract

The solid dosimeters of dyed or undyed polymethylmethacrylate (PMMA), in the plate form, are often used for routine monitoring in high-dose radiation processes. Ionizing radiation induces changes in the absorption spectrum of some polymers at characteristic wavelength; these changes can be related to absorbed dose. The dosimetric properties of dyed polymethylmethacrylate plates of commercial use were studied to evaluate the viability to use this material in radiation dosimetry. For dosimetric characterization PMMA samples were irradiated with 60Co gamma radiation in the dose range between 0.5 and 100 kGy, using the facilities of the Centro de Tecnologia das Radiações of Ipen. For the samples preparation and spectrophotometric evaluations the facilities of the Centro de Metrologia das Radiações of Ipen were used. The samples (1 x 3 cm 2 ) were obtained from plates with original dimension of 120 x 60cm 2 ; the plates thickness varied between 2.1 and 2.5mm. The studied parameters were: batch homogeneity, ambient conditions sensibility and dose-response. The results were compared with the response of Red 4034 Perspex and Gammachrome YR dosimeters, developed by Harwell Dosimeters that show good performance in the quality control of the absorbed dose in the radiation processes. The evaluated samples present adequate properties to be used as control dosimeter in radiation process. They don't present significant variations with the ambient conditions and presents behavior similar to the comparative standards. Depending on the dyed used, the useful dose range can be between 5 and 100 kGy.