Dose to lung from inhaled tritiated particles

Tritiated particulate materials are of potential hazard in fission, fusion, and other tritium handling facilities. The absorbed fractions (fraction of energy emitted that is absorbed by the target region) are calculated for t ritiated particles deposited in the alveolar-interstitial (AI) region of th e respiratory tract. The energy absorbed by radiologically sensitive tissue irradiated by tritiated particles, in regions of the lung other than in th e Al region, is negligible. The ICRP Publication 71 assumes the absorbed fr action is unity for tritium deposited in the Al region. We employed Monte C arlo methods in a model to evaluate the energy deposition in the wall of th e alveolar sac from particles of tritiated beryllium, tritiated graphite, t itanium tritide, tritiated iron hydroxide and zirconium tritide. For the fi ve materials examined, the absorbed fraction in alveolar tissue ranged from 0.31 to 0.61 for particles of 1 mum physical diameter and 0.07 to 0.21 for 5 mum diameter particles. The dose to alveolar tissue, for an acute inhala tion of tritiated particles by an adult male worker, was calculated based o n the ICRP 66 lung model and the particle dissolution model of Mercer (1967 ). For particles of 5 mum activity median aerodynamic diameter (AMAD), the committed equivalent dose to alveolar tissue, calculated for the five mater ials, ranged from 32-42%, respectively, of the committed equivalent dose de rived assuming the absorbed fractions were unity.