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

SSEM/2011/4730 June 2011The number of finds classified as Beta-rich has continued to decrease (despite an overallincrease in the total number of finds) which suggests that this category of activeparticles/stones is being removed (by the monitoring/retrieval programme) faster than theyare becoming available in the beach environment.The introduction of Synergy enhanced the ability to detect lower energy gamma radiation,which includes 241 Amand consequently finds characterised as Alpha-rich. 2010/11 was thefirst year where the Synergy detection system was used for the entire annual programme.This resulted in a much higher find rate compared to the last two monitoring years. Withsufficient monitoring, the Alpha-rich find rate may also start to decrease (similar to the patternfor Beta-rich finds) as they are removed via the monitoring/retrieval programme.HPA have published its detailed risk assessment and have confirmed that the adviceprovided in 2009 remains valid (Cooper, 2009), they advise that:3.2 Find Analysis and Statistics3.2.1 IntroductionParticles and stones recovered from beaches as part of the monitoring/retrievals programmeare sent to the Sellafield Analytical Service for an initial estimate of the activity of gammaemitting radionuclides. A high resolution gamma scan technique is used on the 'as received'beach finds and activities for 60 Co, 106 Ru, 125 Sb, 134 Cs, 137 Cs and 241 Am radionuclides arereported. The analysis report includes these radionuclides, even if they are at the limit ofdetection, plus any other significant gammas detected. Alpha-rich finds with significant 241 Amactivity can undergo further assessment for Plutonium isotope activities. This data providesconfirmation of the find category, which is provisionally allocated using the monitoringdata.To allow further find characterisation, a series of external analysis contracts have beenplaced with Serco, starting in December 2007 and continuing to date. A total of 123 findshave been analysed via these contracts, with work on find tranche 1 and 2 complete and findtranche 3 ongoing. The finds selected for these contracts were judged to give arepresentative sample of those recovered at the time of contract placement. The analysesselected for the contracts focus on identifying public risk, origins of finds and determination ofthe best practicable means (BPM) methodology for beach monitoring. Serco employed theNational Physical Laboratory (NPL) to undertake the main analysis work and the HealthProtection Agency (HPA) to undertake intestinal absorptions studies, on a selection ofalpha-rich finds.The sequence of the analyses is carefully designed with hold points at critical stages (e.g.hold for SL and EA approval before starting on destructive analyses etc.). The analysessteps are as follows:i) Drying, separation and washing.ii)iii)Scaled colour photography.Estimated activity in 'as received' finds, 'separated' finds and residues using highresolution gamma spectroscopy calibrated to give limits of detection (LODs) for134 Cs in the range of 1E+00 Bq to 1E+03 Bq, for 237 U, 238 Pu and 239 Pu (in the© Nuclear Decommissioning Authority 2011. 33