Independent Peer Review of - Low Level Waste Repository Ltd

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Peer Review of LLWR Response to S9R2LLWR_2008-8-2Version 1Additional results from the flow models (e.g., flow patterns, relativeflows in drift and underlying sandstones) to complement the particletracking results presented in LLWR (2008d).53. Other aspects relating to hydrogeology and the understanding of thepotential for radionuclide transport that may need to be improved for thenext safety case include:Additional hydrogeological data between the site and the coast (it isunderstood that the SLC has this in its plans for future work).Confidence in the transport and retention modelling of the keyradionuclides in both shallow and deeper groundwater pathways,using monitoring data for confirmatory testing as far as is possible.54. Given the difficulties in modelling the hydrogeology of the site, the peerreview panel considers that it will be important for the next safety case toinclude an adequate range of sensitivity studies that provide confidencethat the risks associated with the groundwater pathway have at least beenbounded.55. We acknowledge that the submission made in response to Requirement 2recognises that the hydrogeological models should be seen as ‘work inprogress’ and that the models will be further developed prior to the nextsafety case (LLWR 2008d). We consider that the aim of suchdevelopment work should be models that are only as detailed asnecessary, consistent with the reduced importance of the groundwaterpathway in the safety assessment (see para 62).3.2.4 Site Evolution56. Over the next few thousand years, coastal erosion and climate will be themain drivers of environmental change at the LLWR (LLWR 2008e). Thepeer review panel considers that the SLC has undertaken a thoroughexamination of the various factors that may influence the climate (Thorne2007; Thorne and Kane 2007). These references have suggested thatBIOCLIM scenarios B3 and B4 (BIOCLIM 2004) can be used in thesafety assessment to capture the likely range of effects on climate of fossilfuel utilisation. We note that other near-surface radioactive waste disposalprogrammes (e.g., Mallants et al. 2008) have also come to similarconclusions regarding the representation of climate in safety assessments,i.e., by using BIOCLIM scenarios B3 and B4.57. These scenarios are expected to involve significant sea-level rise and tocause erosion of the coastline, which will reach the LLWR on a timescaleof 750 to 2,500 years from now (Thorne 2007). Even if sea-level rise isdisregarded, it is concluded that coastal erosion will affect the LLWR inseveral thousand years (Table 6.1, LLWR 2008e). Halcrow (2008)suggests that the sea may flood and inundate the eastern parts of theTerraSalus Limited 14 2 September 2008
Peer Review of LLWR Response to S9R2LLWR_2008-8-2Version 1LLWR site, but not the capped area, even earlier than this (100-1,000years) due to a combination of increasing sea level and high tides. Whilstwe have found no obvious flaws in the link between the climate scenariosand facility destruction by erosion, we suggest that the link might besubjected to further scrutiny.58. The peer review panel believes that the high probability and shorttimescales for inundation and erosion of the facility raise questionsregarding the suitability of the site for near-surface radioactive wastedisposal, particularly those containing long-lived radionuclides. Forexample, IAEA Safety Requirement WS-R-1 on Near-Surface Disposal ofRadioactive Waste states ‘The frequency and intensity of processesaffecting the stability of land forms such as flooding, erosion, landslidingor weathering shall be such that they would not significantly affect theability of the disposal system to isolate the radioactive waste’ (IAEA1994).59. This site suitability issue is not directly addressed in the submission madein response to Requirement 2, but the peer review panel considers that thejustification for continued disposals at the site (i.e., to the vaults),particularly of long-lived wastes, needs to be tackled head-on.60. We understand that the SLC regards consideration of whether the LLWRfacility should continue to receive waste for disposal, given the threat ofcoastal erosion, to be part of the on-going UK LLW management strategydevelopment process. We note that the issue is also central to the safetycase for the LLWR and that, logically, there should be a two way transferof information between the LLWR safety case and the LLW managementstrategy.3.3 Development and Justification of Scenarios3.3.1 Scenarios61. For the 2002 PCSC, BNFL undertook a formal scenario developmentprocess, including an extensive analysis of FEPs. BNFL (2002b)identified a Central Projection Scenario and scenarios involving futurehuman actions. BNFL (2002b) distinguished three variants of the CentralProjection Scenario according to whether they ended with destruction ofthe repository by coastal erosion, valley glaciation or regional glaciation.BNFL’s coastal erosion variant was characterised by a period ofintensifying enhanced global warming and progressive sea-levelrise. This resulted in gross disruption of the repository by coastalerosion in the period 500-1,000 years after present.BNFL’s valley glaciation variant was characterised by a period ofmild global warming during which the repository could be disruptedby coastal erosion in the period 2,000-5,000 years after present.TerraSalus Limited 15 2 September 2008
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Independent Peer Review of - Low Level Waste Repository Ltd

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