Independent Peer Review of - Low Level Waste Repository Ltd

Peer Review of LLWR Response to S9R2LLWR_2008-8-2Version 13.4.4 Coastal Erosion81. LLWR (2008e) describes the approach taken for assessing the impactsresulting after erosion of the LLWR. The approach is a simplified one,which involves continuous erosion along a straight line ‘erosion front’parallel to the present day cliff. Calculated doses rely on the exposureassumptions.82. The peer review panel considers that to support the identification ofexposure pathways, there is a need for a better geomorphologicaldescription of the coast during possible erosion processes. As a result ofdeveloping such a description of how erosion might actually proceed, it ispossible that additional exposure pathways may be identified that need tobe assessed. For example, there might be periods of sea-level stability, ortemporary sea-level falls, within the overall trend of increasing sea level,during which exposures might occur.83. The peer review panel has also identified some aspects of the currentassessment that appear optimistic, e.g:The structure of model compartments may be too coarse toadequately represent radionuclide uptake by organisms in theintertidal zone.The assumption that exposures in buildings constructed on the shorecan be ruled out appears optimistic. We note that there is a need toassess potential exposures in buildings constructed by a lagoon (seefigure 4.2 in LLWR 2008d).The assumption that the recovery and re-use of waste materialswould not lead to further exposures appears optimistic.84. LLWR (2008e) acknowledges the fact that uncertainties exist, andindicates that further work will be conducted for the next safety case. Thepeer review panel supports this intention.3.4.5 Radon and Thoron Doses85. The safety assessment described in the submission made in response toRequirement 2 includes a new model for estimating doses from radon andthoron. This new model replaces the model used in the 2002 PCSC. Thenew model is best documented in Appendix B of LLWR (2008e).86. Although the problems with the 2002 PCSC model are more clearlyexplained in the final version of the Requirement 2 submission than theywere in earlier drafts, and the description of the background to the newmodel is generally good, it is not entirely clear how the present model hasbeen derived from the data. The peer review panel considers that the newmodel needs to be fully and traceably documented so that it can beTerraSalus Limited 21 2 September 2008