Self-absorption of tritium betas in metal tritide particles

Inhaling metal tritide particles is a potential occupational hazard. The radiation dose to tissue from tritide particles depends on their solubility and retention in the body. In each tritide particle, a portion of the beta particles from decay of tritium is absorbed by the metal matrix and therefore cannot contribute to absorbed radiation dose to tissue. A theoretical model for estimating the self-absorption of tritium betas in spherical metal tritide particles is presented. Numerical calculations are made with this method for titanium, zirconium, and erbium particles from 0.5 to 50 microm in diameter. The tritium spectrum is divided into energy groups to facilitate estimation of the energy that escapes the particle for dose calculations. Our results show considerable absorption of beta particles and their energy, even for respirable particles smaller than 5 microm. Limited experimental data of self-absorption for titanium and zirconium tritides supported the theoretical calculation. It is concluded that the self-absorption factors should be required for counting tritide particle samples as well as for estimating absorbed radiation dose to tissue.