This practice may be used as part of a bioassay program for workers potentially exposed to nuclear material by measuring ²³⁷Np, ²³²Th and ²³⁵U and ²³⁸U in their urine samples. ICP-MS has been used to analyze for many actinides in high-level radioactive wastes (1)³ , in soils (2) as well as uranium in urine (C 1379). ²³⁷Np and ²³⁹Pu analysis by ICP-MS in bioassay samples has also been reported (3).

Several days counting times are required for alpha-particle analysis of ²³⁷Np, ²³²Th and ²³⁵U and ²³⁸U whereas ICP-MS requires only four minutes per sample. Alpha-particle counting methods for neptunium may also require the use of ²³⁹Pu as a radiotracer for determination of chemical yield.

ICP-MS sensitivity limits and isobaric interferences preclude accurate determination of ²³⁹Pu, ²⁴¹Am and ²³⁴U at levels present in the urine samples. ²³⁴U may be estimated from the ²³⁵U:²³⁸U ratio by inference.

1.1 This practice covers the separation and preconcentration of neptunium-237 (²³⁷Np), thorium-232 (²³²Th), uranium-235 (²³⁵U) and uranium-238 (²³⁸U) from urine followed by quantitation using ICP-MS.

1.2 This practice can be used to support routine bioassay programs. The minimum detectable concentrations (MDC) for this method, taking the preconcentration factor into account, are approximately 1E-2Bq for ²³⁷Np (0.38ng), 2E-6Bq for ²³²Th (0.50ng), 4E-5Bq for ²³⁵U (0.50ng) and 6E-6Bq for ²³⁸U (0.48ng).

1.3 This standard does not purport to address all of the safety problems, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.