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Development of an Ultra-Pure, Carrier-Free 209Po Solution Standard



Ronald Colle, Ryan P. Fitzgerald, Lizbeth Laureano-Perez


Ultra-pure, carrier-free 209Po solution standards have been prepared and standardized for their massic alpha-particle emission rate. The standards, which will be disseminated by the National Institute of Standards and Technology (NIST) as Standard Reference Material SRM 4326a, have a mean mass of (5.169  0.003) g of a solution of polonium in nominal 2.0 mol▪L-1 HCl (having a solution density of (1.032  0.002) g▪ mL-1 at 20 C) that are contained in 5-mL, flame-sealed, borosilicate glass ampoules. They are certified to contain a 209Po massic alpha-particle emission rate of (39.01  0.18) s-1▪g-1 as of a reference time of 1200 EST, 01 December 2013. This new standard series replaces SRM 4326 that was issued by NIST in 1994. The standardization was based on 4 liquid scintillation (LS) spectrometry with two different LS counting systems and under wide variations in measurement and counting source conditions. The methodology for the standardization, with corrections for detection of the low-energy conversion electrons from the delayed 2-keV isomeric state in 205Pb and for the radiations accompanying the small 0.45 % electron-capture branch to 209Bi, involves a unique spectral analysis procedure that is specific for the case of 209Po decay. It is similar, but revised and improved from that used for SRM 4326. Spectroscopic impurity analyses reveled that no photon-emitting or alpha-emitting radionuclidic impurities were detected. The most common impurity associated with 209Po is 208Po and the activity ratio of 208Po/ 209Po was
Journal of Research (NIST JRES) -


alpha counting, lead-205, liquid scintillation (LS), measurements, polonium-209, radioactivity, standards.


Colle, R. , Fitzgerald, R. and Laureano-Perez, L. (2015), Development of an Ultra-Pure, Carrier-Free 209Po Solution Standard, Journal of Research (NIST JRES), National Institute of Standards and Technology, Gaithersburg, MD, [online], (Accessed February 28, 2024)
Created July 23, 2015, Updated November 10, 2018