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| Home > Publications database > Age-dating of environmental samples: a review and recent developments. |
| Conference Presentation (Other) | FZJ-2026-01259 |
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2025
Abstract: Mass spectrometric measurements on uranium samples taken in nuclear facilities and their surrounding environment can provide a wide range of important information about activities being carried out in these facilities. Not only the degree of uranium enrichment (235U/238U) can be determined, the 236U/238U isotopic ratio is a widely used tracer, which provides sensitive information on source identification for safeguard purposes, nuclear forensics studies and environmental monitoring [1]. An additional strong tool in nuclear forensics is the 230Th/234U chronometry. The method relies on the fact that uranium ore processing and further chemical purification of uranium (i.e. for enrichment) removes almost all impurities, including all radioactive decay products. In the case of the 230Th/234U chronometer the decay of 234U with a half-life of 245,500 years to 230Th is used for age determination. Measuring the parent-daughter ratio in the sample, and assuming a quantitative separation of impurities and daughter isotopes from the U-solution, the decay equations can be applied to calculate the time elapsed since the date of the last purification. This method was developed for the age-determination of samples with high 235U enrichment, and therefore comparably high 234U contents, and for large sample quantities of several milligrams [2].For the detection of undeclared activities in nuclear facilities, swipe and environmental samples are taken containing only traces of uranium bearing microparticles which can be analyzed for isotopic composition. In the case that undeclared activities are detected, the time when these activities have happened needs to be verified. Therefore, more sensitive analytical methods must be developed for a reliable 230Th/234U age-dating application [3]. Advanced mass spectrometry methods like SIMS with large-geometry instruments are considered the preferential analytical methods to determine the isotopic composition of these environmental samples with a very high precision [4]. The successful development and establishment of a method for age-dating application mainly relies on the accessibility of well-designed reference materials that are not only used for calibration of the analytical device, but also for the determination of important measurement parameters, such as the relative sensitivity factor.This presentation will provide some general background information about the analyses of microparticulate samples containing known uranium isotopic ratios and Th abundances with a focus on the development of reference particles with well-defined properties designed particularly for new age-determination applications.
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