ABSTRACT: Statistical analysis has been performed on the gross alpha- and beta-activity measurements of surface waters collected at
the Atomic Weapons Establishment at Aldermaston (UK) during the period January 2002–September 2005. The results have been
found to follow a lognormal distribution and this has important applications when considering gross activity exemption thresholds.
This implies that the gross activity is the multiplicative product of many small independent factors, such as meteorology,
flow conditions and site operations. The influence of meteorological parameters has been investigated using linear regression,
and some correlation has been identified between gross beta-activity and parameters indicative of fine weather. Variations
in gross activity have been considered on monthly, weekly and daily timescales and characterised using the geometric mean
and geometric standard deviation in accordance with the properties of the lognormal probability density function.
KeywordsGross activity–Surface waters–Radioactivity
Journal of Radioanalytical and Nuclear Chemistry 04/2012; 289(2):389-394. · 1.52 Impact Factor
ABSTRACT: A novel technique has been developed for determining the (212)Pb activity of fresh waters. This is of interest to environmental monitoring programmes that utilise gross α-activity methods to screen for anthropogenic radionuclides. The contribution from (212)Pb varies, and is difficult to experimentally measure due to its relatively short half-life (t(½) = 10.6 h) and low environmental activity (<0.1 Bq l(-1)). The use of a three-stage technique that encompasses a unique form of pre-concentration, separation and analysis by liquid scintillation counting allows a lower detection limit of 0.006 Bq l(-1) with a chemical yield of 92.5 ± 5.6%. The measurement can be obtained within 7 h of sample collection, and is calculated using the radioactive decay of (212)Bi. Other naturally occurring radionuclides may also be extracted using the pre-concentration stage of the technique, with efficiencies above 90% at a range of pH values.
Journal of environmental radioactivity 02/2011; 102(4):326-30. · 1.47 Impact Factor
ABSTRACT: Sudden increases in the background gamma-radiation dose may occur due to the removal of (222)Rn and (220)Rn progeny from the atmosphere by wet deposition mechanisms. This contribution has been measured using a Geiger-Muller detector at the Atomic Weapons Establishment (Aldermaston, UK) during July 2005-April 2006. The results are approximated by a log-normal distribution and there were nine separate occurrences of the gamma-radiation dose exceeding 125% of the geometric mean value. The increases were associated with periods of heavy rainfall, although no correlation was evident between the dose rate and the amount of rainfall, as increased rainfall dilutes the activity further rather than increasing its atmospheric removal. The events were preceded by periods of fine weather and atmospheric stability that allow for the build-up of (222)Rn and (220)Rn progeny. Similar increases in gamma-radiation dose have been measured at a nearby monitoring station situated approximately 11 miles from Aldermaston. Increases in gamma-radiation dose during heavy rainfall have also been observed throughout the UK, that followed the trajectory of an air mass. All events decreased to typical values within 1-2 h as the water permeated into the ground below and the radioactivity decayed away.
Journal of Radiological Protection 09/2010; 30(3):525-33. · 1.39 Impact Factor