THE MAYAK WORKER DOSIMETRY SYSTEM (MWDS-2013) FOR INTERNALLY DEPOSITED PLUTONIUM: AN OVERVIEW.

The Mayak Worker Dosimetry System (MWDS-2013) is a system for interpreting measurement data from Mayak workers from both internal and external sources. This paper is concerned with the calculation of annual organ doses for Mayak workers exposed to plutonium aerosols, where the measurement data consists mainly of activity of plutonium in urine samples. The system utilises the latest biokinetic and dosimetric models, and unlike its predecessors, takes explicit account of uncertainties in both the measurement data and model parameters. The aim of this paper is to describe the complete MWDS-2013 system (including model parameter values and their uncertainties) and the methodology used (including all the relevant equations) and the assumptions made. Where necessary, Supplementary papers which justify speci fi c assumptions are cited. The calculation of organ doses from measurements of activity in urine (and occasionally from autopsy samples for Mayak workers) involves four distinct steps. The value air measurements. The lognormal distribution variable median M GSD of six based on one derived Puncher (16) from an analysis of historical personal air sampler data relat-ing to plutonium and uranium concentrations in for- mer workplaces of the UK Atomic Energy Authority. That paper also includes a sensitivity ana- lysis on M to lung dose; it was found a 10-fold change in M gave a 2-fold change in lung dose, indicating that dose estimates are not overly sensitive to the choice of the value of M. This is also likely to be A full description of the re-analysis of the beagle dog data is given in this special edition (27) . The analysis was performed using two different representations of particle transport from deep lungs: one based on a dog model similar to the ICRP Publication 66 model, and one based on the MWDS-2013 model. The results yielded best estimates of 0.2% and 0.8% for f b , respect-ively. For the model based on the ICRP Publication 66 structure, the model could not be explained without the presence of a bound state. For the model based on the MWDS-2013 structure, the model could be made to fi t the data, but only by reducing particle transport rates to an implausible level. Taken together, the results give very strong evidence to support the presence of a bound fraction.