Nondestructive measurement of combustible waste containing uranium in a B-25 box

The Oak Ridge K-25 Site is a shutdown uranium enrichment facility which processes and stores a large variety of radioactive wastes. Measurements to identify and quantify radioisotopes present in this waste are performed using nondestructive assay techniques. A measurement substation, consisting of four sodium iodide γ-ray detectors, is used for measurement of low to medium-density waste contained in B-25 boxes [a strong, tight container]. Regions of interests are defined and used for quantification of 235U and 238U as well as the identification of 137Cs and 237Np. A software program (GAMMAEFF) was developed to estimate the overall detection efficiency, including effects from B-25 box walls, waste matrix, item size, and detector positioning. Items which exceed a preset threshold are also measured using a high-resolution γ-ray detection system to determine enrichment and to estimate the relative amounts of non-uranium radionuclides. Results indicate that the target measurement sensitivity of 32 ρCi/g of waste is achievable in most 900-sec measurements for most items