Preparation of Mn-fiber standards for the efficiency calibration of the delayed coincidence counting system (RaDeCC)
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2010-04Author
Scholten, Jan C.
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Pham, Mai Khanh
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Blinova, Oxana
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Charette, Matthew A.
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Dulaiova, Henrieta
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Eriksson, Mats
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https://hdl.handle.net/1912/4396As published
https://doi.org/10.1016/j.marchem.2010.04.009Abstract
Precise measurements of the short lived radium isotopes 223Ra and 224Ra by means of the delayed
coincidence counting system (RaDeCC) rely on an efficiency calibration of this system using
Mn-fiber standards for which radium activities are exactly known. We prepared seventeen
different standards by placing Mn-fibers in seawater spiked with various amounts of 227Ac (with
223Ra in radioactive equilibrium), 228Th (in radioactive equilibrium with 232Th and 224Ra) and
226Ra. We tested for quantitative adsorption of 227Ac and 228Th on the Mn-fibers by: (1)
measuring 227Ac and 232Th in the residual solutions after preparing the Mn-fiber standards and
(2) monitoring their 223Ra and 224Ra activities over a period of ~100 days. In the residual
solutions, the activities of 227Ac and 232Th were < 1.0 % and < 5.3 %, respectively, of the
activities initially added to the Mn-fibers. Our results indicate that Milli-Q water washing of the
Mn-fibers is the major source of our observed losses of thorium. Measurements of 227Ac
standards over 1½ years indicate a significant decrease of measurable 223Ra with time prohibiting
the long-term use of 227Ac Mn-fiber standards. We found the 224Ra efficiency to be independent
of the range of 227Ac, 228Th and 226Ra activities on the Mn-fibers standards used. The efficiency
determination for 223Ra, however, may be biased in the case of relatively high 224Ra activities
due to insufficient correction of chance of coincidence. Thus we suggest using a single 227Ac
Mn-fiber standard for the efficiency determination for 223Ra.
Description
Author Posting. © The Author(s), 2010. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Marine Chemistry 121 (2010): 206-214, doi:10.1016/j.marchem.2010.04.009.
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Suggested Citation
Preprint: Scholten, Jan C., Pham, Mai Khanh, Blinova, Oxana, Charette, Matthew A., Dulaiova, Henrieta, Eriksson, Mats, "Preparation of Mn-fiber standards for the efficiency calibration of the delayed coincidence counting system (RaDeCC)", 2010-04, https://doi.org/10.1016/j.marchem.2010.04.009, https://hdl.handle.net/1912/4396Related items
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