The dose conversion factors for thoron decay products exposure

The dose evaluation of 220Rn exposure in environment is one of the hottest discussed issues in the field of radiation protection. One focused point of this issue is the change of the dose conversion factor of 220Rn exposure. This paper reviews the recent domestic and foreign research results related to this problem and calculates the dose conversion factor of 220Rn progeny, especially taking into count of the affect of the size distribution of attached 220Rn progeny and the unattached fraction. The results show that the dose conversion factor changes with the size distribution of attached 220Rn progeny, as it grows, first grows down then grows up. The dose conversion factor increases linearly with the unattached fraction. In typical environment, the effective dose conversion factor of 220Rn progeny exposure would be 95.95 nSv·(Bq·h·m-3)-1, with a varing range of 90.60-101.28 nSv·(Bq·h·m-3)-1. (authors)