A measurement control (MC) program should be an integral part of every nondestructive assay measurement system used for the assay of special nuclear materials. This report describes an MC program for plutonium isotopic composition measurements using high-resolution gamma-ray spectroscopy. This MC program emphasizes the standardization of data collection procedures along with the implementation of internal and external measurement control checks to provide the requisite measurement quality assurance. This report also describes the implementation of the MC program in the isotopic analysis code GRPAUT. Recommendations are given concerning the importance and frequency of the various MC checks in order to ensure a successful implementation of the MC procedures for the user's application.

We discuss the general approach, computerized data analysis methods, and results of measurements used to determine the isotopic composition of plutonium by gamma-ray spectroscopy. The simple techniques are designed to be applicable to samples of arbitrary size, geometry, age, chemical, and isotopic composition. The combination of the gamma spectroscopic measurement of isotopic composition coupled with calorimetric measurement of total sample power is shown to give a totally nondestructive determination of sample plutonium mass with a precision of 0.6% for 1000-g samples of PuO2 with 12% 24°Pu content. The precision of isotopic measurements depends upon many factors, including sample size, sample geometry, and isotopic content. Typical ranges are found to be 238Pu, 1 to 10%; 239Pu, 0.1 to 0.5%; 24°Pu, 2 to 5%; 241Pu, 0.3 to 0.7%; 242Pu (determined by isotopic correlation); and 241Am, 0.2 to 10%.

Measurement of various U and Pu samples by gamma-ray spectrometry were performed at the Institute of Physics and Power Engineering to support physical-inventory-taking activities under the Joint US-Russian MPC and A Program. The resulting data was analyzed by several different methods which included Canberra's MGA9.63 (Pu and MOX analysis) and MGAU (U analysis), EG and G Ortec's MGA++ (Pu and MOX analysis) and U235 (U analysis), and FRAM v2.2 (U and Pu analysis) provided by Los Alamos. The results indicate that all of these codes are capable of performing the isotopic analysis adequately. However, some additional modifications may be required to permit better measurement of some of the more unusual components in the Institute of Physics and Power Engineering (IPPE) inventory to meet the demands of inventory-taking activities.