Harmonisation of internal dose assessment practices
Workers in the nuclear power industry and in the production/use of radiopharmaceuticals are exposed to a broad range of radioactive materials. Due to the stringent control measures, minimisation of doses from intakes of radionuclides is assured in these workplaces. Yet, radiation doses of individual workers are directly measured, recorded and assessed on a periodic basis. Unlike this, calculation of doses from radioactive materials inside the body are estimated with the aid of biokinetic models that describe the behaviour of a radionuclide. Both biokinetic and dosimetric models published by the International Commission on Radiological Protection (ICRP) are commonly used and regularly updated. In order to assess the effective dose of an individual, several assumptions are made including the route of intake, its time pattern, and the physico-chemical form of the material. In cases where more than one measurement is taken, weighting factors for each constitute another potential source of variation in the estimates of intake and dose. The most recent intercomparison exercise on internal dose assessment revealed the need for development of agreed guidelines for internal dose evaluation procedures. Such guidelines are expected to enable harmonisation of assessments between organisations and countries and hence, improve the quality of radiation protection. Urged by this the IDEAS project developed a set of general guidelines for internal dose assessment, whose adoption would allow derivation of standard estimates for any given set of data. On the grounds of a general philosophy on four-levelled tasks structure, the developed general guidelines offer background information on the biokinetic models and the corresponding bioassay functions. Detailed information on special aspects of the dose assessment practice is also provided including the handling of the monitoring data, extended exposures and the number and type of data required. Potential end-users include health physicists, national/international authorities, and expert groups engaged in the development of guidance/standards, such as members of the ICRP task group on internal dosimetry.
