Abstract
Concentrations of uranium were measured, by neutron activation analysis, in gypsum used in a plaster cast. The gypsum samples were powdered and mixed thoroughly using an agate mortar. Measurements of uranium were made by detecting γ-rays from 239U, since those from 239Np (a daughter nuclide of 239U) cannot be detected because of the high background of bremsstrahlungs due to β-rays from 32P produced by an (n, p) reaction of 32S in gypsum. The results of these measurements showed the concentration of uranium to be 0.0358±0.0030ppm, which was much lower than that in other samples such as CRT glass and concrete blocks measured previously. This lower concentration probably results from the fact that the gypsum used in the present study was manufactured as a by-product of phcsphatic fertilizer from phosphate rock.
