Absorbed dose rate produced by natural uranium as a function of depth in tissue

Slabs of natural and depleted uranium are used routinely to calibrate personal dosimeters and radiation survey instruments for beta radiation. However, little information is available on the absorbed dose rate produced by a uranium slab as a function of depth in matter. In this study, an extrapolation chamber was used to measure the dose rate produced by natural uranium at a variety of depths in a tissue-equivalent material (Mylar). The dose rate decreases from 11,900 mrad h-1 at the surface of the uranium to 229 mrad h-1 at a depth of 7 mg cm-2 and to about 60 mrad h-1 at a depth of about 250 mg cm-2. (author)