Precise assay of weight per cent sodium in high-level processed nuclear tank waste using a 252Cf neutron source

A basis for production assessment of the vitrification of Hanford nuclear fuel reprocessing wastes will be high precision measurements of the elemental sodium content. However, the chemical analysis of both radioactive and non-radioactive components in nuclear waste can be challenged by high radiation dose rates. In many cases, reduction of dose rates through dilution compromises the precision and sensitivity for certain key components. The use of neutron activation analysis provides a method of analysis which avoids the need for dilutions or extensive sample preparation. The recently developed analysis process is traced with iron-manganese wire referenced to weight per cent sodium standards. The procedure uses a nominal 80 mg 252Cf neutron source to activate the natural sodium to 24Na, followed by gamma-energy analysis. Assay of direct waste samples containing weight per cent sodium has shown precision of less than one per cent standard deviation of total propagated uncertainty.