A bioassay method for ²³⁷ Np in fecal samples

Fecal radiobioassay is a crucial and sensitive tool for estimating internal exposure and intake of actinides following radioactive or nuclear incidents. This study developed an analytical method to determine²³⁷Np in feces, utilizing TEVA resin for separation and purification, followed by detection with inductively coupled plasma mass spectrometry. By introducing²⁴²Pu as a chemical homologue tracer, which shares similar chemical behaviour with²³⁷Np in the tetravalent state, we effectively monitored the chemical recovery of the target nuclide. We systematically optimised sample pretreatment steps, such as calcination temperature and redox conditions, along with key parameters in the TEVA resin separation process, including sample acidity and elution volume, significantly enhancing the separation and purification efficiency of²³⁷Np. Experimental results indicated average chemical recoveries of 79% for²³⁷Np and 82% for²⁴²Pu. Furthermore, multiple repeated experiments effectively verified the method's accuracy and reliability. The established analytical procedure is practical and yields stable results, providing robust technical support for accurately quantifying²³⁷Np in feces, with significant applications in radiation protection and public health monitoring.