[ RadSafe ] Rn-222 from Depleted Uranium

[Andrew McGechaen]

Dear Sir/Madam,

My building stores about 300kg of depleted uranium. I have read that the indoor radon hazard in buildings originates from decay products of uranium in soil. Checking the Radium Series, I noted U-234 (245500a) -> Th-230 (75380a) -> Ra-226 (1602a) -> Rn-222 (3.8235d), with the attached half-lives. Fetter and von Hippel (1997) give U-234 at a concentration of 7 ppm in DU.

Is it safe to ignore the decay chain of U-238 to U-234, and consider only the initial concentration of U-234 ?

Is it realistic to assume that the residue of Ra-226 in the DU would be zero after chemical refinement?

I assume the U was depleted and chemically refined years or decades ago. What activity of Rn-222 would exist now?

Might radon escape through cracks or communicating voids in the metallic uranium?

Might any appreciable quantity of radon escape from the uranium metal by Fickian diffusion?