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

SSEM/2011/4730 June 2011Recommendations12 Consideration to be given to maximise the use ofspatial methods of analysis and mapping.13 Evaluation of trends in finds is time series shouldbe carried out, but first the series need to beadjusted for monitoring effort (seerecommendations 3, 5, & 11). Statistical modelsshould then be used to account for seasonalityand for possible autocorrelations. In the firstinstance, regression type models would beappropriate, (such as ARIMA) models to explorechanges over the monitoring period.14 Multivariate statistical techniques includingcluster and discriminant analysis could be usedto explore these features further, and todistinguish possibly distinct populations of finds.SL initial responseTo be considered for inclusion into statisticswork programme.To be considered for inclusion into statisticswork programme.To be considered for inclusion into statisticswork programme.Table 3.18. Statistical sampling report recommendationsRecommendations1 Consideration should be given to whether thecurrent categorisation of particles also reflectsdifferences in other risk related properties, i.e.properties which may affect their longevity inthe environment and solubility within thehuman stomach.2 An assessment as to whether particles behavein a similar manner to the sediment withinwhich they are found. Simply, does the hostsediment have similar size and densitycharacteristics to particle.3 Full and quantified specification of objectiveswithregard to area, probability of detection forspecific radionuclides and to an appropriatedepth to be agreed. The depth should reflecthabit information and the temporal and spatialdynamic of the beach.4 Following an assessment of beach dynamics,particle abundances, beach users’ habits etc,the regulator and other agencies should specify(in consultation with other parties) a minimumbeach coverage, frequency and detectioncapabilities - depth and activity (which shouldbe reviewed regularly).SL initial responseIt is judged that the categorisation of finds ishelpful in assessing risk to the critical group. Forexample, significant effort that been expended inmeasuring the parameters of alpha-rich finds(i.e. the high risk group). Consideration is givento the relative risks of sub-groups as new databecomes available (e.g. Magnox vs Oxidesubgroups etc.).The variation in sand characteristics issignificant over the range of beaches monitoredand within individual beaches. To overcome thisproblem consideration is being given to thecharacterisation of sand in a pocket around thefind. This would give information on thesimilarities between the find and local sand andthe variation in sand between different locations.The objectives are reviewed before setting eachyear's monitoring programme, taking account oftechnical issues and learning from experience.Explicit analysis and statistical objectives will beconsidered when developing future workprogrammes and will be incorporated into themonitoring programme review.The regulator and other stakeholders require SLto propose a monitoring programme thatincorporates the minimum beach coverage,frequency, and detection capabilities - depth andactivity. Where possible this should be based ona statistical analysis but the statistical samplingreport recognises that there are limitations tothis approach. The 2011/12 repeat visits willallow further refinement to future monitoringprogrammes.© Nuclear Decommissioning Authority 2011. 62