Measurement control of NRC [Nuclear Regulatory Commission]-licensed facilities

Careful monitoring of measurement quality has been priority of the U.S. Nuclear Regulatory Commission (NRC) for over a decade. The NRC's comprehensive program for oversight of material control and accounting (MC ampersand A) at licensee facilities is evidence of its concern. The NRC expects the uncertainty of measurements involving significant quantities of material, which are performed by licensees, to at least match the target values established by international groups. The uncertainty of special nuclear material (SNM) measurements performed by NRC-licensed fuel manufacturing facilities is typically less than the published target values. Types of material measured by NRC-licensed facilities range from uranium feed materials through finished produce and uranium-bearing scrap and waste. Both element and fissile isotopes are measured. Chemical assay methods used for accounting purposes include gravimetry, titrimetry, spectrophotometry, laser fluorimetry, X-ray fluorescence, gas mass spectrometry, and thermal ionization mass spectrometry. Data have been collected from NRC-licensed fuel manufacturing facilities for the purpose of estimating typical uncertainties in the measurement of SNM. This paper reports the results of the data analysis, i.e., the state of the practice for chemical assay of uranium-bearing materials by NRC-licensed fuel manufacturing facilities