engleski

Calibration of an optoelectronic reader for chemical radiation dosimetry system

Some form of personal accident dosimetry is unavoidable in attempts to reconstruct massive irradiation and/or contamination accidents. Dosimeters for this purpose must be sensitive to penetrating (gamma+n) radiations and not expensive because of a large number needed. Chemical radiation dosimetry system consisting of chlorobenzene - ethanol - trimethylpentane (CET) dosimeters with an optoelectronic reader offers a possible solution. The system described here was especially designed for accident dosimetry ; it covers doses in the range 0.2-15.0 Gy and enables electronic processing of data. The most important dosimetric properties of the CET system are its linear response with dose, independence of the dose rate and quality of the incident radiation, and the approximately equal response to gamma rays and neutrons for the same dose in tissue. The optoelectronic reader was designed as a hand-held instrument for readout of dosimeters based on a spectrophotometric method. It operates fully automatically and enables the storage of more than one thousand data, which can be directly transmitted to and processed by a PC. Low cost makes it suitable for mass use. In our previous paper [1] the results of the “ relative” calibration of the optoelectronic reader were shown – CET dosimeters were irradiated with known doses and the calibration curve was constructed. In this work, the method of “ absolute” calibration is described. For this purpose, special colour standards were prepared with the same composition as the dosimeter solution, omitting chlorobenzene, so that standards are stable to irradiation. The absorbance of each colour standard was adjusted by mixing the appropriate amounts of the acid form of thymolsulphonphthalein (red) and alizarine solutions (yellow). The absorbance of each standard corresponds to the absorbance of a dosimeter that had been irradiated to a certain dose.

Chemical dosimetry system; radiation accidents; optoelectronic reader

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