Use of group monitoring data in lung dose estimation for intakes of uranium

This paper describes an internal dosimetry program developed for Canadian uranium processing facilities. The recently adopted recommendations of ICRP Publication 60 have made it extremely difficult to detect intakes of insoluble forms of natural uranium by in vivo methods (lung counting). A type S intake of UO2 corresponding to a 20 mSv effective dose has a lung burden that is a factor of 2-3 lower than the MDA, 6 months after the intake occurred. A new methodology, approved in principle by the Canadian Nuclear Safety Commission, has been designed to overcome this problem by summing sequential, but separate, lung counts for an individual, or summing lung counts from a group of workers performing similar tasks. This summing technique effectively increases the counting time and, therefore, reduces the MDA to a value below the dose limit. Doses will be assigned to the individual or work group based on the average lung burden.