The role of trace impurities in classification of in-core reactor components

Low-level radioactive waste is classified into three distinct categories under Title 10 of the Code of Federal Regulations Part 61 (10CFR61). These categories, Class A, B, and C, are determined by the concentrations of specified radionuclides, with Class C being the most restrictive. Waste which is determined to exceed the Class C limits is referred to as Greater Than Class C (GTCC) and is generally deemed to be unacceptable for disposal in a shallow land burial site. Under the Low-Level Waste Policy Act Amendments of 1985 (Public Law 99-240), the responsibility for disposal of waste classified as GTCC rests with the US government. To provide a better understanding of the elemental constituents that are present in nuclear fuel related materials, 41 samples of unirradiated materials used in the manufacture of fuel assembly hardware and nonfuel assembly components were obtained and analyzed. Particular emphasis was placed on evaluating the concentration of niobium in Zircaloy. The results of this work indicate that insignificant amounts of niobium are found in the current generation of Zircaloy. However, the reason for the inconsistency between the trace amounts of elemental niobium (<10 ppM) observed in the current analysis and the significant amounts (>100 ppM) that were observed in the previous analysis has not been identified