Uncertainties associated with 223Ra and 224Ra measurements in water via a Delayed Coincidence Counter (RaDeCC)

The short-lived radium isotopes, Ra-223 (T-1/2=11.4 days) and Ra-224 (T1/2 = 3.66 days), have been successfully used as tracers of several environmental processes, e.g., submarine groundwater discharge, coastal mixing processes, and water residence times. In this paper, the uncertainties associated with Ra-223. and Ra-224 measurements using a Radium Delayed Coincidence Counter are determined on a detailed error propagation basis with a confidence interval of 1 sigma. From the data analyses of several groups of coastal water samples, the calculated relative uncertainties averaged 12% for the R-223(a) and 7% for the Ra-224. These uncertainties can decrease for radium-enriched groundwater samples although asymptotic limits have been found at 7% relative uncertainty for Ra-223 and 4% for Ra-224. In this paper, the influence of sampling and measurement parameters on the final radium uncertainties is evaluated in order to provide guidance to optimize these factors and obtain more reliable results. (c) 2007 Elsevier B.V All rights reserved.