A Monte Carlo analysis of possible cell dose enhancement effects by uranium microparticles in photon fields.

Uranium microparticles (radii: 50 nm-1.25 μm) were modelled surrounded by tissue and exposed to natural background radiation, in order to investigate potential dose enhancements from photon interactions. Generally, the results depended on the microparticle size. For a 0.5 μm radius microparticle in an isotropic field, it was found that the combined photon/electron doses deposited in 1 and 10 μm radii shells around it were raised by factors of ∼3.8 and ∼1.1, respectively; for a typical background photon fluence rate, these would correspond to increased energy depositions of a few 10s and a few 100s of eV y(-1), which are far less than the likely deposition rate resulting from the radioactive decay of a (238)U microparticle. The health hazard from uranium microparticle interactions with background photons was concluded to be negligible.