Annual Report for 2010/11 and Forward Programme - Sellafield Ltd

Figure 2.3: Ratio of counts in the 137 Cs window (IW) to counts above this window (AW), fordata collected by Nuvia Ltd from the beach at St Bees between May 2007 and October 2008.2.2 Point Source SimulationsData specifying the date, location, depth and activity of all finds to date was supplied for usein this project. These data are tabulated in Appendix A. The distribution of the depths atwhich the finds have been recovered is shown in Figure 2.4. It can be seen that there are veryfew finds recovered from below 20cm depth, with the majority being recovered from the top10cm of the beach. Simulations of sources at depths that reasonably approximate therecovered finds are needed to simulate the response of the airborne detector to such sources.The first stage of this work simulated sources on the surface and at 10cm depth. In this stageof the work additional simulated spectra have also been produced for depths of 5cm, 15cmand 20cm, with the simulations for each range of recovered depth as given in Table 2.1.5