Unified control methods in dosimetry for high-activity irradiation facilities in Hungary

The increasing interest in the application of ionizing radiation raised not only the number but also the capacity of the facilities in Hungary, and presented the problem of measuring 10 to 100kGy/h dose rate, and doses in the range 50Gy to 1MGy. For the mapping of the exposure field of laboratory facilities the well-known and internationally-accepted Fricke dose meter was introduced. For the high dose rate and dose control different chemical dose meters were introduced, such as the ethanol-chlorobenzene dose meter. This method of evaluation turned out to be too slow for industrial processes and an evaluation method by oscillometry was developed. The ethanol-chlorobenzene dose meter became, for practical and industrial use, a simple, easily applicable method in several countries. Economy of mapping exposure fields is claimed for simple and rapid evaluation, thus computer programs were worked out using semiconductor rate meters for the determination of relative dose rates. All the methods applied and introduced in the Institute were compared with others introduced abroad in international cooperation. On the basis of the methods of dosimetry carried out in the Institute of Isotopes of the Hungarian Academy of Sciences unified control methods have been introduced in Hungary for high-activity cobalt-60 irradiation facilities and processes, such as preparation of exposure rate maps and tables, application of 'test dosimetry' in pilot and industrial irradiators, process control dosimetry, process control by semiconductors, and process control by dose indicators. (author)