<p>Environmental radioactivity arises from natural and anthropogenic sources: 238U, 232Th and their decay products, and 40K in differing concentrations in rocks and soils; natural materials transformed by industrial processes to enhance the concentrations of some radioactive\ud isotopes; materials discharged from some nuclear processes; fallout from nuclear accidents and weapons testing; radioactive sources that may have been lost or stolen; and radiation shine from sites using nuclear technology. Mobile gamma spectrometry provides powerful methods of measuring the distribution of radioactivity in the environment; airborne platforms allow the rapid survey of large areas, and ground based platforms more detailed surveys of smaller areas.</p>\ud \ud <p>Airborne surveys in 1990 (conducted to produce a baseline data set for the Sellafield site) and 2000 (as part of a large study on spatial and temporal aspects of airborne measurements) showed several radiometric features along the coast, including elevated 137Cs activity along a beach in West Cumbria between St Bees and Nethertown, in an environment comprising pebbles and gravel where this was unexpected. An additional short survey of this area was\ud conducted during the 2000 survey, at reduced ground clearance and speed, to verify the existence of these unexpected signals. With increased interest in the search and recovery of particulate activity from the beaches in the vicinity of Sellafield, this data was reviewed in 2008 to illustrate the use of airborne methods in locating potential particulate activity on beaches and to aid in the planning of further ground based investigations. SUERC conducted an exploratory ground based survey in June 2010; to investigate whether the features observed in the airborne surveys were still present, to define the spatial distribution of activity more precisely, and to attempt to assess the form of the activity and whether it had been redistributed since 2000. This report presents the 2000 airborne measurements reviewed in 2008, with the results of the June 2010 survey.</p>\ud \ud <p>A portable gamma spectrometry system has been developed at SUERC. This consists of a 3x3” NaI(Tl) detector with digital spectrometer, a GPS receiver and netbook computer. The system is lightweight, easy to use and can be carried over terrain that would be inaccessible to vehicular systems. By holding the detector close to the ground the extent of any observed enhanced activity feature can be determined more precisely. Two of these systems have been\ud field tested on the 22-23rd June 2010 along this beach.</p>\ud \ud <p>The exploratory survey has clearly demonstrated the utility of the SUERC backpack system in producing detailed maps of the distribution of radioactive materials in the environment. A survey using two systems successfully mapped an area of approximately 50x200m with very high density measurements in a period of approximately 2h.</p>\ud \ud <p>It has shown that the enhanced 137Cs activity is still present on the beach, in locations that are consistent with the earlier airborne measurements. The more detailed survey shows a pattern of patches of enhanced 137Cs activity. Samples collected from some of these had concentrations of 50 Bq kg-1, which would account for the observed 137Cs count rate. The nature of the material that carries this activity is at present unknown.</p
To submit an update or takedown request for this paper, please submit an Update/Correction/Removal Request.