Independent Peer Review of - Low Level Waste Repository Ltd

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Peer Review of LLWR Response to S9R2LLWR_2008-8-2Version 14 Peer Review of Options Analysis and Proposed Site Strategy4.1 Options Analysis – General Comments111. The peer review panel considers that the SLC has carried out a usefulstudy of options for future management of the trenches. One of the mostpositive aspects of the recent study, particularly as compared withprevious studies (e.g., BNFL 2004), was the inclusion of local and otherstakeholders in the process. This is an aspect that should be continued,not least because some of the local stakeholders may hold importantinformation on waste disposals to the trenches.112. Initially, the recent options study probably went into too much detail onremediation technologies (e.g., Amin 2007) and the ‘toolkit’, thusdeveloped, was not sharply enough focused on the issues requiringmanagement at the LLWR.113. The ‘threats’ to the safety performance of the LLWR were identified as (i)facility destruction by coastal erosion, (ii) inadvertent human intrusion,(iii) releases via groundwater, and (iv) releases via gas. These threatswere reviewed and discussed with stakeholders, and in doing so weregiven roughly equal emphasis by the SLC’s project team. Localstakeholders tended to focus on the threat of ‘leaks’ via groundwater.This raises the question of how well stakeholders understood the natureand relative importance of the different pathways leading to risk, andwhether adequate information was provided. In our view, the greatestemphasis should have been placed on the first two threats, i.e., coastalerosion and inadvertent human intrusion.114. A reasonable set of options was considered in the study (see Section 4.2),but there was a lack of clarity over the definition of some of the optionsand this was particularly the case for the ‘Bulk or Local [waste] Retrieval’option. The lack of clarity over the waste retrieval options could havebeen resolved by using some of the detailed information on the spatialheterogeneity of the wastes in the trenches to define the scale of wasteretrieval envisaged. In particular, it would be possible to identifyparticular localised volumes of waste in the trenches possessing relativelyhigher concentrations of long-lived radionuclides (see figures 1 and 2 ofLennon 2007), and examine the pros and cons of different options for theirmanagement.115. The recent options analysis study did not include a quantitative scoring ofthe options against defined attributes. Currently, the peer review panelconsiders that the basis for implementing some options while rejectingothers needs to be further clarified and strengthened. While we recognisethat quantitative scoring can only provide a guide to decision-making, weconsider that, in order to demonstrate that risks are ALARA, there needsto be a new quantitative evaluation of the costs and benefits (e.g., in termsTerraSalus Limited 26 2 September 2008
Peer Review of LLWR Response to S9R2LLWR_2008-8-2Version 1of risk reduction) of options defined using the latest information on thespatial distributions of wastes in the trenches.116. The financial cost of an option, in particular, will depend on the scale atwhich it is applied and, for example, retrieval or in situ remediation of asmall amount of waste will likely be cheaper than for a larger amount. Atpresent it is not clear how the risk reduction benefits of groundwater cutoffwalls and vertical drains, compare to those of localised waste retrievaland, therefore, why cut-off walls and vertical drains are considered a‘better buy’ than selective waste retrieval.4.2 Proposed Site Strategy4.2.1 Options for the Trenches4.2.1.1 Retrieval of all Trench Wastes117. The peer review panel considers that the SLC is correct to conclude thatretrieval of all of the trench wastes for re-disposal elsewhere would be acostly exercise. We also recognise that this would pose a major issue fornational LLW management strategy.4.2.1.2 Retrieval of Wastes to Reduce Average Specific Activity118. The peer review panel considers that the option of attempting to retrievesome of the wastes from across each of the trenches in order to reduce theaverage specific activity of the remaining wastes (see Section 7.2 ofLLWR (2008a) is a rather hypothetical one. The peer review panel is notaware of any regulatory or other pressure to consider such an option. Thepeer review panel also notes that long-lived radionuclides, which are theparents of radon and thoron, are widely distributed within the trenches,such that it would not be easy to selectively remove all of the long-livedradionuclides. We agree, therefore, that such options should not form partof the strategy for the LLWR.4.2.1.3 Retrieval of Localised Wastes119. We agree with the SLC that further analysis is required to determinewhere the balance lies between the pros and cons of retrieving certainlocalised volumes of waste in the trenches possessing relatively higherconcentrations of long-lived radionuclides. Although there areuncertainties in the dose assessments, it seems that some relatively smallvolumes of waste in the trenches could give rise to calculated doses ofseveral tens of mSv and possibly more than 100 mSv under somescenarios. There are also further considerable uncertainties related to theregulatory criteria, and to the costs and risks of waste retrieval. In ourview, the issue of localised waste retrieval needs to be assessed in moredetail, with much greater transparency, and with specific reference toTerraSalus Limited 27 2 September 2008
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Independent Peer Review of - Low Level Waste Repository Ltd

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