Indirect determination of plutonium at trace levels by use of gamma- and L X-ray spectroscopy

A nuclear counting method was developed to accurately determine 239Pu in aqueous samples at concentration levels as low as 10-11 M. The method utilizes the UL X-rays following the decay of other Pu isotopes (i.e., 238Pu, 242Pu) also present in small quantities in the 239Pu solution. Possible contributions to the L X-rays from the decays of other radionuclides are accounted for by measuring the low-energy gamma ray spectra individually to establish a specific gamma/L X-ray ratio. This ratio is then used in the analytical measurements to correct the total L X-ray count. Gamma-ray/L X-ray ratios were established for U(234,235,237,248), 241Am, and Th(231,234), known to be possible contaminants. This nondestructive technique can replace both traditional labor-intensive radiochemical separation techniques and elaborate activation analytical methods in determining low concentrations in Pu solubility studies