Abstract
The paper describes the preparation and production of the reference materials, IRMM-1000a and IRMM-1000b, certified for the production date based on the 230Th/234U radiochronometer in compliance with ISO Guide 34:2009. The production date of the reference materials corresponds to the last separation of 230Th from 234U, i.e. when the initial daughter nuclide content in the material was finally removed. For the preparation low-enriched uranium was used, which was purified using a unique methodology to guarantee high U recovery and Th separation efficiency. The CRM is intended for calibration, quality control, and assessment of method performance in nuclear forensics and safeguards.
Highlights
In order to avoid the malicious use of nuclear materials, an international safeguards system directed by the International Atomic Energy Agency (IAEA) has been set up to verify the correctness and completeness of states’
The quality assurance in nuclear forensic investigations is of primary importance, currently no uranium reference material (RM) with certified production date is available to assure the confidence in the quality of results for the age measurement in nuclear forensics [19]
Since 230Th is present at trace-level in the nuclear materials, the Th/U measurements are still challenging for most nuclear forensic laboratories despite of the availability of state-of-the-art analytical techniques
Summary
In order to avoid the malicious use of nuclear materials, an international safeguards system directed by the International Atomic Energy Agency (IAEA) has been set up to verify the correctness and completeness of states’. Assigning a consensus or agreed value for a uranium age dating certified reference material by an inter-laboratory comparison bears the risk that proper accuracy and traceability of this value cannot be achieved It would be a lengthy exercise and requires combining results which could have a significant bias and large uncertainties. As the 230Th/234U method is highly sensitive to the initial purity of the material, a very high degree of separation (more than 107) has to be achieved for this chronometer to eliminate the positive bias caused by residual 230Th in the material (i.e. incomplete zeroing) This high separation factor was not accomplished in the past for several uranium isotopic standards, and a discrepancy was found between the measured production dates and the known archive date of the material preparation [23].
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