A case study of environmental gamma radiation measurements: West Kirby Beach, River Dee Estuary

The current on-site evaluation of environmental contamination is examined. This is achieved by using soil samples taken from three points at West Kirby beach in the River Dee Estuary. This site is chosen because it is a tidal area in close proximity to the nuclear facilities at Sellafield, Windscale, and Calder Hall (which are all near Seascale, Cumbria). Sellafield is a former nuclear power station that closed in 2004 and now a nuclear reprocessing site, whilst Windscale and Calder Hall are both nuclear power plants undergoing decommissioning. This case study examines whether there is evidence to show that possible wash off of radioactive substances via the neighbouring rivers Calder and Ehen enter the sea and may then be washed along the nearby coastline. The samples collected were analysed with the aid of gamma spectrometry using high purity germanium (HPGe) detectors, this included both BEGe, and N-type detectors. Two natural occurring decay chains were observed, Th-232 and the U-238 series. Observed radionuclides included Ac-228, Pb-212, Bi-212 and Tl-208 and Pb-214, Th-234 and Bi214 for Th-232 and U-238 respectively, although with a very low activity level in both cases which might not be unconnected to their short half-lives that are either in days or in minutes. Two artificial radionuclides (Am-241 and Cs-137) were detected in some of the collected samples. Am-241 was present in only a few of the samples and with very low activities of ≤ 0.023Bq/kg. Cs-137 was present in almost all of the samples irrespective of the depth or point of collection, also with a low level of activity of ≤0.029Bq/kg. The most obvious activity detected was that of the naturally occurring radionuclide K- 40, with a recorded activity level of about 0.4Bq/kg. The discovery of K-40 may be due to its presence in rocks and from the use of fertilizers by farmers, which could have subsequently washed off into the river system. However, there are also other radionuclides detected which include, Eu-152 with half-life 13.537 years, Y-88 with half-life of 106.65 days, etc., Eu-152 is a member of the lanthanide series which are rare earth metals that can be found in exploitable ore deposit whilst the Y-88 is the most stable radioisotope of natural Yttrium with Y-89 being the only isotope, though in their lowest activity levels.