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U Age Dating - Determination of the production date of a uranium certified test sample.


Publication date
28 June 2013


U Age Dating - Determination of the production date of a uranium certified test sample.

REIMEP-22* was an inter-laboratory comparison opened to all laboratories, whose aim was to determine the production date of a uranium material (i.e. the last chemical separation date of this material) based either on the disequilibrium between the 230Th-234U (compulsory) or between the 231Pa-235U (optional).

Participants in REIMEP-22 received either a 20 mg (for mass spectrometry) or/and a 50 mg (for alpha-spectrometry) of low-enriched uranium sample (3.6 % 235U) in solid uranyl-nitrate form.

The participation fee for REIMEP-22 was € 1000 per sample (including sample dispatch).

Registrations were done using the IRMM online registration system for the two comparisons on a 20 mg uranium sample (comparison 1121) and on a 50 mg uranium sample (comparison 1122).

Prior to the shipment of the REIMEP-22 samples from the EC-JRC-IRMM, each participant had to fill in the Declaration of Licensing and the End-User Statement.

The laboratories were asked to measure, using their lab's routine procedure, the isotope amount ratio n(230Th)/n(234U) (in 20 mg uranium sample) or activity ratio A(230Th)/A(234U) (in 50 mg U sample). In the same way as for Th/U, they could as well measure the isotope amount ratio n(231Pa)/n(235U) for the 20 mg uranium sample or the activity ratio A(231Pa)/A(235U) for the 50 mg U sample.

The measurement results were evaluated against the reference value for the production date of the certified test sample by means of zeta scores in compliance with ISO 13528:2005. Full confidentiality was guaranteed with respect to the link between measurement results and the participants’ identity.

The REIMEP-22 report with the results of this inter-laboratory comparison was sent to each participant and will be available for download in PDF format from this website.

In addition, each participant received as well an individual certificate with their reported results, the REIMEP-22 reference value and their laboratory performances.

The certified test sample used for REIMEP-22 has been certified according to ISO Guide 34:2009 and is now available as IRMM-1000a (20 mg U sample) and IRMM-1000b (50 mg U sample).

For more information on REIMEP-22, please contact:

For more information on CRMs, please visit our on-line catalogue.

*Regular European Interlaboratory Measurement Evaluation Programme (REIMEP)

Reporting of results:Closed
Sample dispatch:December 2013-January 2014
Year:2013-01-01 00:00:00


(26.98 MB - PDF)