5.1 It is common practice within the nuclear industry for internal dose assessment to be made as part of a bioassay program for nuclear facility workers. For indirect bioassay of workers that may be exposed to uranium at enrichments that may differ from natural then the ²³⁵U concentration must be measured in addition to the total uranium isotopes so that an estimate of uranium enrichment may be made for use in the dose assessment.

5.2 The enrichment measurement may also be of value in tracing the source of uranium exposure should significant uranium levels be detected in a sample.

5.3 A modern, quadrupole ICPMS should be capable of delivering performance characteristics close to those claimed in this test method; however, older models or those where performance has deteriorated over time may be unable to do so. It is the responsibility of the user to validate the performance of their equipment.

1.1 This test method covers the determination of uranium in urine by Inductively Coupled Plasma Mass Spectrometry (ICP-MS) after dilution in nitric acid. The method is presented in two parts. Part A describes a method for determination of total uranium in urine that does not distinguish between uranium isotopes. Part B describes a method that determines the ratio of ²³⁵U to ²³⁸U (the enrichment) in samples that Part A has shown to contain levels of uranium that the user of the data considers to be significant. The measurement in Part B may be combined with the measurement in Part A to calculate a ²³⁵U concentration. The enrichment measurement may in turn be used to estimate levels of minor uranium isotopes, in particular ²³⁴U, that are important for calculating the internal radiation dose received by an individual exposed to uranium. The estimation of minor isotope concentrations and the calculation of internal dose does not form part of this standard.

1.2 Units—The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.

1.3 This standard does not purport to address all of the safety concerns, 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.