Standard Test Method for Uranium and Plutonium Concentrations and Isotopic Abundances

1.1 This test method is applicable to the determination of uranium (U) and plutonium (Pu) concentrations and their isotopic abundances (Note 1) in solutions which result from the dissolution of nuclear reactor fuels either before or after irradiation. A minimum sample size of 50 [mu]g of irradiated U will contain sufficient Pu for measurement and will minimize the effects of cross contamination by environment U.

Note 1—The isotopic abundance of Pu can be determined by this test method; however, interference from U may be encountered. This interference may be due to (1) inadequate chemical separation of uranium and plutonium, (2) uranium contamination within the mass spectrometer, and (3) uranium contamination in the filament. One indication of uranium contamination is a changing 238/239 ratio during the mass spectrometer run, in which case, a meaningful Pu analysis cannot be obtained on that run. If inadequate separation is the problem, a second pass through the separation may remove the uranium. If contamination in the mass spectrometer or on the filaments is the problem, use of a larger sample, for example, 1 μg, on the filament may ease the problem. A recommended alternative method of determining Pu isotopic abundance without U interference is alpha spectroscopy using Practice D3084. The Pu abundance should be obtained by determining the ratio of alpha particle activity of Pu to the sum of the activities of Pu and Pu. (1) The contribution of Pu and Pu to the alpha activity differs from their isotopic abundances due to different specific activities.

1.2 The procedure is applicable to dissolver solutions of uranium fuels containing plutonium, aluminum, stainless steel, or zirconium. Interference from other alloying constituents has not been investigated and no provision has been made in the test method for fuels used in the Th U fuel cycle.

1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.