AN INTERNAL DOSIMETRY INTERCOMPARISON STUDY

Pacific Northwest Laboratory performed a study to evaluate the consist ency of internal dosimetry assessments. A total of eleven laboratories , including DOE sites and NRC licensees, participated in this intercom parison study. Participants were asked to respond to five actual expos ure scenarios, previously used in a similar European study. The partic ipating dosimetrists assessed the data of the test scenarios and calcu lated results in terms of estimated radionuclide intake and the result ing internal doses. To maintain confidentiality, results are given wit hout identifying any site. Except for one scenario, the results showed that the standard deviation of the final results on committed effecti ve dose equivalent for each exposure scenario was about 30-50% of the mean value, giving a consistency slightly greater variant than that of the European study. The discrepancies can be attributed to variations in 1) the interpretation and statistical treatment of the bioassay da ta; 2) the biokinetic models applied; and 3) the computational tools u sed. This represents a preliminary study; further intercomparison test ing is needed to fully evaluate the problem of dose-assessment inconsi stency.