Independent Peer Review of - Low Level Waste Repository Ltd

Peer Review of LLWR Response to S9R2LLWR_2008-8-2Version 1Executive SummaryE1. The Low-Level Waste Repository (LLWR) has been the principal facility in theUK for the disposal of Low-Level Radioactive Waste (LLW) since 1959. Thesite is owned by the Nuclear Decommissioning Authority (NDA) and isoperated on behalf of the NDA by a Site Licence Company (SLC).E2. Disposals at the LLWR are authorised by the Environment Agency (EA) underthe Radioactive Substances Act 1993. Schedule 9 Requirement 2 of the LLWRAuthorisation requires that ‘The operator shall provide the Agency with a fullreport of a comprehensive review of national and international developments inbest practice for minimising the impacts from all waste disposals on the site.This shall include a comprehensive review of options for reducing the peak risksfrom deposit of solid waste on the site, where those risks arise from potentialsite termination events (e.g. costal erosion and glaciation) and future humanaction’.E3. This report records the comments of an independent peer review panel that wasasked by the SLC to review the submission made in response to Schedule 9Requirement 2.E4. The peer review panel considers that the submission made in response toRequirement 2 and provided to the EA on 1 May 2008 had improvedconsiderably in the time since the peer review panel reviewed the work in earlyApril 2008. Many of the changes and developments have resolved peer reviewcomments, and the SLC’s project team has acknowledged the benefit providedby the peer review. Inevitably and appropriately some peer review commentsand issues remain to be dealt with. The SLC is planning further work to addressthe remaining issues in the lead up to the next safety case.E5. The safety assessment work described within the submission has led to someimportant developments in terms of understanding how the site may evolve, andthe structure of the next safety case, but the peer review panel considers that forseveral reasons (uncertainty in which regulatory criteria apply, limited treatmentof uncertainty in the assessment calculations, limited traceability of assessmentdata, etc) it would be premature to draw any firm conclusions from comparisonsof the current assessment results (doses and conditional risks) with quantitativeregulatory criteria. The SLC acknowledges that the work does not represent afull safety assessment and that it includes only a limited treatment ofuncertainties.E6. The submission does not demonstrate that risks are as low as reasonablyachievable (ALARA), but it does indicate a firm commitment to the next safetycase and to making a robust ALARA demonstration. This seems appropriategiven the various uncertainties that exist.E7. The principal ‘threats’ to the safety performance of the LLWR have beenidentified as (i) facility destruction by coastal erosion, and (ii) inadvertentTerraSalus Limited i 2 September 2008

Peer Review of LLWR Response to S9R2LLWR_2008-8-2Version 1Contents1 Introduction ...........................................................................................11.1 Peer Review ................................................................................................11.2 Schedule 9 Requirement 2 and Peer Review Objectives ............................31.3 This Report..................................................................................................32 Peer Review Approach and Process ...................................................52.1 Approach.....................................................................................................52.2 Process ........................................................................................................63 Peer Review of the 2008 Performance Update....................................73.1 Assessment Context ....................................................................................73.1.1 Assessment Purpose and Philosophy ..............................................73.1.2 Regulatory Criteria and Assessment Endpoints..............................73.1.3 Assessment Timeframe ...................................................................93.2 Disposal System Description and Understanding.....................................103.2.1 Waste Inventory ............................................................................103.2.2 Engineered Facility .......................................................................113.2.3 Geology and Hydrogeology ..........................................................123.2.4 Site Evolution................................................................................143.3 Development and Justification of Scenarios.............................................153.3.1 Scenarios .......................................................................................153.3.2 Potentially Exposed Groups..........................................................163.4 Assessment Modelling ..............................................................................173.4.1 Engineering Performance..............................................................183.4.2 Source Term ..................................................................................193.4.3 Groundwater Flow ........................................................................193.4.4 Coastal Erosion .............................................................................213.4.5 Radon and Thoron Doses ..............................................................213.4.6 Human Intrusion............................................................................223.5 Quality Assurance and Use of Assessment Results..................................243.5.1 Quality Assurance .........................................................................243.5.2 Assessment Results .......................................................................253.5.3 Comparison with Regulatory Criteria ...........................................254 Peer Review of Options Analysis and Proposed Site Strategy .......264.1 Options Analysis – General Comments....................................................264.2 Proposed Site Strategy ..............................................................................274.2.1 Options for the Trenches...............................................................274.2.2 Institutional Control ......................................................................284.2.3 Coastal Defences...........................................................................294.2.4 Engineered Features ......................................................................294.2.5 Radiological Capacity and CFA of Waste ....................................305 Conclusions.........................................................................................315.1 Peer Review ..............................................................................................315.2 Addressing the Requirements ...................................................................31TerraSalus Limited iii 2 September 2008

Peer Review of LLWR Response to S9R2LLWR_2008-8-2Version 15.3 Proposed Strategy .....................................................................................315.4 Forward Programme .................................................................................326 References ...........................................................................................34Appendix 1 – The Peer Review Panel....................................................... A-1TerraSalus Limited iv 2 September 2008

Peer Review of LLWR Response to S9R2LLWR_2008-8-2Version 1Independent Peer Review of: LLWR Response toEnvironment Agency Schedule 9 Requirement 21 Introduction1. The Low-Level Waste Repository (LLWR) has been the principal facilityin the UK for the disposal of Low-Level Radioactive Waste (LLW) since1959. The site is owned by the Nuclear Decommissioning Authority(NDA) and is operated on behalf of the NDA by a Site Licence Company(SLC). United Kingdom Nuclear Waste Management (UKNWM) Ltd.holds a contract from the NDA for the management and operation of theLLWR, and shares in the SLC were transferred to UKNWM Ltd. on 1stApril 2008.2. Disposals at the LLWR are authorised by the Environment Agency (EA)under the Radioactive Substances Act 1993. The LLWR receives wastesfrom a range of consignors including nuclear power stations, fuel cyclefacilities, defence establishments, general industry, isotope manufacturingsites, hospitals, universities and from the clean-up of historicallycontaminated sites.3. In 2002, the previous operator of the site, British Nuclear Fuels plc(BNFL), provided the EA with environmental (operational and postclosure)safety cases for the facility (BNFL, 2002a; 2002b). These safetycases were reviewed by the EA (Environment Agency 2005a) and,following a period of consultation, a new authorisation was granted(Environment Agency, 2006a). The authorisation includes severalschedules, of which Schedule 9 is a list of improvements and additionalinformation that the operator must supply.4. Schedule 9 includes Requirement 2, which amongst other things (seebelow) requires, by May 2008, a comprehensive review of national andinternational developments in best practice for minimising the impactsfrom all waste disposals on the site. Requirement 2 is one of several thatmay be seen as important precursors to Requirement 6, which requires anupdate the environmental safety cases by May 2011.5. The SLC has initiated a programme of work – the LLWR LifetimeProgramme – to address the requirements of Schedule 9, and is subjectingthe work of the programme to independent peer review.1.1 Peer Review6. Peer review is a formally documented examination of a technicalprogramme or specific aspect of work by a suitably qualified expert orgroup of experts who have not been directly involved in the programme oraspect of work. The EA has indicated that it expects peer review to beused as one means of building confidence in the environmental safetyTerraSalus Limited 1 2 September 2008

Peer Review of LLWR Response to S9R2LLWR_2008-8-2Version 1cases, and has stated that such peer reviews should be fully documentedand provided to the EA (Environment Agency 2005a; EnvironmentAgency et al. 1997; 2008).7. In its review of the 2002 safety cases (Environment Agency, 2005a), theEA acknowledged that the previous operator, BNFL, had commissionedan independent peer review (Hill and Irvine 2002), but considered that thishad been done at too a late stage in the development of the safety casesand that, as a result, not all of the peer review comments had beenaddressed adequately when the safety cases were submitted. The EA,therefore, emphasised in its review the need for peer review to begin at anearly stage in the project and to be an active and continuous part of workleading to revision of the safety case.8. Fully recognising the need for peer review, the SLC has established a newindependent peer review panel, which is made up of six highly-qualifiedsenior specialists (Appendix 1). The peer review panel members wereselected by the SLC during early 2007, and collectively have considerableexpertise and experience in radioactive and conventional wastemanagement, and in environmental management more generally. Thepeer reviewers also have specific and detailed knowledge of the LLWRsite and facility. Importantly, the peer review panel members arecompletely independent of the team working on behalf of the SLC todevelop responses to the Schedule 9 requirements, including the safetycases.9. The remit of the peer review panel extends across the whole of theLifetime Programme and the Modular Vaults Project (MVP), whichincludes work on the design of the LLWR. The overall objectives of thepeer review panel are to:Provide timely independent review of key technical approaches,arguments, designs, assessments and safety cases being developedby the SLC’s project team.Work in such a way that it can be demonstrated to relevantstakeholders that a rigorous and effective process of review andscrutiny is operating.10. The peer review work is focusing on issues that are the most important tothe risks associated with the LLWR, and is assessing and commenting onwhether the work of the Lifetime Programme and Modular Vaults Projectare consistent with policy, regulation and best practice, so as to identifyareas where improvements may be made.TerraSalus Limited 2 2 September 2008

Peer Review of LLWR Response to S9R2LLWR_2008-8-2Version 11.2 Schedule 9 Requirement 2 and Peer Review Objectives11. Schedule 9 Requirement 2 states:‘The operator shall provide the Agency with a full report of acomprehensive review of national and international developments inbest practice for minimising the impacts from all waste disposals onthe site. This shall include a comprehensive review of options forreducing the peak risks from deposit of solid waste on the site,where those risks arise from potential site termination events (e.g.costal erosion and glaciation) and future human action.’12. The SLC is required to respond to this requirement on 1 May 2008 and ‘atsuch intervals thereafter as the Agency specifies in writing’.13. The most obvious objective of peer review for the S9R2 submissionwould be to consider whether the submission meets the Requirement asstated above. However, the wording of the Requirement is open to somedegree of interpretation, and the peer review panel understands that theEA’s expectations of the submission have been the subject of dialoguebetween the SLC and the EA, and have broadened since the date of theAuthorisation. The peer review panel has, therefore, reviewed thesubmission against its own objectives as stated in the submission.14. These wider objectives have included addressing two additional pointsgiven in the EA’s Decision Document (see page 54 of EA 2006b), whichsuggest that the submission should provide the EA with:‘…adequate information to allow the radiological capacity of thesite to be determined…’ , and‘…the outcome of a wide-ranging risk management study… …thatdemonstrates that future impacts will be As Low As ReasonablyAchievable…’15. The peer review panel notes that these points would logically be based ona full update to the 2002 safety cases, including a comprehensive safetyassessment (e.g., as will be developed to meet Schedule 9 Requirement 6).1.3 This Report16. This report records the comments of an independent peer review panelthat was asked by the SLC to review the submission made in response toSchedule 9 Requirement 2. The peer review panel has developed thisreport based primarily on the information provided in the five volumesthat comprise the submission (Table 1), but the panel has also reviewedsome of the documents that support the five volumes. The panel has alsoconsidered information provided by the SLC’s project team in response toinitial peer review comments, and during peer review meetings.TerraSalus Limited 3 2 September 2008

Peer Review of LLWR Response to S9R2LLWR_2008-8-2Version 1Table 1The main volumes comprising the submissionReference TitleLLWR(2008a)LLWR(2008b)LLWR(2008c)LLWR(2008d)LLWR(2008e)Managing Existing Liabilities and Future Disposals at theLLWR. Report No. 100001 LLWR LTP Volume 1, Issue 01.Assessment of Options for Reducing Future Impacts from theLLWR. Report No. 100002 LLWR LTP Volume 2, Issue 01.Inventory and Near field. Report No. 100003 LLWR LTPVolume 3, Issue 01.Site Understanding. Report No. 100004 LLWR LTP Volume4, Issue 01.Performance Update for the LLWR. Report No. 100005LLWR LTP Volume 5, Issue 01.17. In keeping with best practice in independent reviews (e.g., NEA 2005a),neither the SLC nor its contractors have commented on the technicalcontent of this report – the SLC has, however, had the opportunity tocheck for factual accuracy. The peer review panel has made its best effortto ensure that all information is accurate.18. The report is structured as follows:Section 2 gives a brief description of the peer review approach andprocesses that are being followed.Section 3 summarises the comments of the peer review panel onaspects of the Requirement 2 submission that relate to disposalfacility performance, i.e. the safety assessment. This section isstructured broadly following the IAEA ISAM methodology (IAEA2004).Section 4 summarises the comments of the peer review panel on theSLC’s review of options and proposed strategy for reducing thepeak risks from the LLWR. This section, thus, addresses some ofthe safety case arguments that go beyond the quantitative safetyassessment issues discussed in Section 3.Section 5 presents key conclusions from the peer review.Section 6 provides a list of references.Appendix 1 comprises brief CVs for the peer review panel.TerraSalus Limited 4 2 September 2008

Peer Review of LLWR Response to S9R2LLWR_2008-8-2Version 12 Peer Review Approach and Process2.1 Approach19. At the beginning of the peer review process it was agreed that:The peer review would be objective and undertaken to the higheststandards of probity, based on the principles of good science andengineering. The approach to the review would be consistent withrelevant international guidance on reviews of radioactive wastedisposal programmes (NEA 2005a, b; IAEA 2007).The review panel would be strictly independent of, and separatefrom, those involved in the work of the Lifetime Programme and/orthe MVP that are developing the safety cases for the LLWR.Formal methods would be used to ensure that a clear and traceablerecord is made of review comments and responses received.The review would be conducted so that, as far as possible, theoutput from the review panel would represent a consensus viewrather than a set of individual opinions. If there were significantun-resolvable differences of view amongst the review panel, thenthe different views would be recorded 1 .The peer review would be conducted in a practical way that fits inwith the schedules of the Lifetime Programme and the MVP, andenables them to respond and react appropriately to peer reviewcomments. Peer review activities would, thus, comprise twoprincipal activities: document reviews and peer review meetings.Key documents from the Lifetime Programme and MVP would beidentified for review. The peer review panel would not seek toreview all of the many deliverables that are being produced underthe Lifetime Programme and MVP, but would, instead, identify keyareas for review and select individual documents or related sets ofdocuments for review. In addition, it was envisaged that the SLCwould request peer reviews of particular documents.Documents would be reviewed by at least two members of the peerreview panel. Results from document reviews would be recorded inInterim Review Papers. These Interim Review Papers would beprovided to the SLC’s project team as they were produced, thusenabling early sight of the review comments and a chance to react asappropriate. The Interim Review Papers would form the basis forthe development of formal Review Reports (such as this report).1In practice this has not been necessary.TerraSalus Limited 5 2 September 2008

Peer Review of LLWR Response to S9R2LLWR_2008-8-2Version 1Formal Review Reports would be produced at key times in theschedule and would be provided to the regulators, together with theSLC’s responses to the peer review findings.2.2 Process20. The peer review panel met for the first time in September 2007 to discussits organisation and to receive presentations from the SLC’s project teamon on-going work, which included the development of the submissionmade in response to Requirement 2. During the latter part of 2007 andearly 2008 members of the peer review panel:Attended two meetings with stakeholders to assess managementoptions for the trenches (Bennett and Jones 2007; 2008)Briefly reviewed several draft contractor documents prior to theirdiscussion at the Lifetime Programme Technical Committee.Visited the LLWR site and met for a second time with the SLC’sproject team (Bennett 2008).21. At the latter meeting it was agreed that the peer review panel wouldreview drafts of the five volumes comprising the Requirement 2submission and that the review panel would record its peer reviewcomments on formal comment and response forms.22. In completing its submission made in response to Requirement 2, theSLC’s project team took account of the peer review panel’s comments,and recorded on the comment and response forms whether (and, if so,how) the peer review comments had been addressed. The peer reviewpanel then reviewed the responses to the comments and the final versionsof the volumes comprising the Requirement 2 submission.23. A series of peer review comments were developed on key aspects of theRequirement 2 submission and these are recorded in the followingsections of this report. The main peer review comments were presented tothe SLC’s project team at a meeting held on 2 July 2008 for theirinformation and with the aim of identifying any factual inaccuracies.TerraSalus Limited 6 2 September 2008

Peer Review of LLWR Response to S9R2LLWR_2008-8-2Version 13 Peer Review of the 2008 Performance Update3.1 Assessment Context3.1.1 Assessment Purpose and Philosophy24. Volume 5 of the submission (LLWR 2008e) addresses the post-closureradiological performance of the LLWR. LLWR (2008e) recognisesclearly that the volume ‘does not present a comprehensive post-closureperformance assessment’, and that ‘The uncertainties related to modelsand data are not fully explored as will be required within the 2011 PCSC;hence the results are to some extent interim’. The peer review panelacknowledges these caveats and notes that they must be borne in mindwhen considering the implications of the work.25. In many places LLWR (2008e) describes particular assumptions,modelling approaches or parameter values as ‘cautious’, meaning thatthey lead, in the SLC’s view, to an overestimate of dose or risk. The peerreview panel considers that there is a clear logic to most of the SLC’sstatements of this type (e.g., regarding the source term). However, thepeer review panel considers that there are also instances where thetreatment or omission from the assessment calculations of particular FEPs(Features, Events, Processes) means that it is not possible to be confidentthat the assessment is cautious in an overall sense. Such instances relate,for example, to the possible occurrence of further exposure pathwaysassociated with coastal erosion, to assumptions made in the engineeringperformance assessment, and to assumptions regarding the effectivenessof passive institutional controls. Our comments on these examples aredocumented more fully in the following sections. The review panelconsiders that a more thorough treatment of uncertainty will be necessaryfor the next safety case.3.1.2 Regulatory Criteria and Assessment Endpoints26. LLWR (2008e) presents arguments as to what are the appropriatereference levels to use when considering assessed doses and/or risksassociated with the LLWR trenches and vaults under differentcircumstances. A summary of the SLC’s position is given in Table 2.1 ofLLWR (2008e).27. First, LLWR (2008e) proposes that a dose rate of 10 mSv/year should beused as a reference level when considering the impacts from the trenches,however they arise (whether as a result of natural processes or as a resultof inadvertent human intrusion). The peer review panel notes that thisproposal is not consistent with the approach taken previously by the EA,which has argued that, at least for releases as a result of natural processes,the risks associated with the trenches should be considered together withthose from the rest of the site and should be compared to the GRA targetTerraSalus Limited 7 2 September 2008

Peer Review of LLWR Response to S9R2LLWR_2008-8-2Version 1for mean annual individual risk (Environment Agency et al. 1997;Environment Agency 2005a). The peer review panel understands thatsince 2005, there has been dialogue between the SLC and the EA on thisissue, and considers that the EA needs to clarify in a publically availabledocument exactly which regulatory criteria will be used when consideringthe LLWR trenches.28. Second, LLWR (2008e) proposes that a reference level dose rate of10 mSv/year should be used when considering impacts that may arise as aresult of inadvertent human intrusion (whether into the trenches or vaults).The SLC’s rationale for this is that this approach has been proposed inICRP Publication 81 (ICRP 2000). The peer review panel notes that theapproach of using a dose-based reference level for human intrusionscenarios (as opposed to a risk-based standard or level) has become morewidely accepted since 2000. However, the peer review panel notes that arange of views exists as to the dose rate at which the reference levelshould be set, for example:In its more recent publication (ICRP 2008) the ICRP has suggestedthat a figure of less than 1 mSv/year should be considered for publicexposures in planned situations (planned situations includeradioactive waste disposal), and that a band from 1 to 20 mSv/yearshould be considered for occupational exposures in plannedsituations, and for public exposure to radon in dwellings.EA (2008) suggests that the assessed effective dose rate to anyperson during and after the assumed intrusion should be consistentwith a dose guidance level in the range of around 3 mSv/year toaround 30 mSv/year, with values towards the lower end of thisrange applicable to assessed exposures continuing over a period ofyears (chronic exposures).HPA (2008) proposes that exposures resulting from inadvertenthuman intrusion and lasting more than five years should beconsidered using an annual dose guidance level of 3 mSv/year.29. The peer review panel considers that because of the uncertainty associatedwith the regulatory criteria to be applied to the LLWR, particularly inrespect of the trenches and inadvertent human intrusion, the SLC mayhave to revise its position on the appropriate reference levels.30. With regard to assessment endpoints, LLWR (2008e) presents selectedresults from calculations of dose and conditional risk to members of arange of potentially exposed groups. The peer review panel would haveliked to see a more comprehensive presentation of the assessmentcalculations and results, including results from all of the calculation cases,results for all of the identified potentially exposed groups (PEGs), andmore results for intermediate performance measures. The peer reviewpanel also notes that because of the limited treatment of uncertainty in theTerraSalus Limited 8 2 September 2008

Peer Review of LLWR Response to S9R2LLWR_2008-8-2Version 1assessment calculations, risk has not been evaluated in any sense thatcould properly be compared on a like-for-like basis with the mean annualindividual risk target in the GRA (Environment Agency et al. 1997).3.1.3 Assessment Timeframe31. A significant change to the safety assessment for the LLWR since the2002 PCSC (BNFL 2002b) has been to consider a much shorterassessment timescale (~5,000 years instead of ~60,000 years). In the 2002PCSC, facility destruction by coastal erosion was assessed as being‘likely’ (BNFL 2002b). This was interpreted by the EA (2005a) asmeaning that the probability of facility destruction by coastal erosion wasgreater than 0.5. The current assessment (LLWR 2002e) includes facilitydestruction by coastal erosion within the expected evolution scenario forthe site, reflecting the view of Thorne (2007) and Thorne and Kane (2007)that the LLWR will be eroded and completely destroyed by the sea in afairly well-defined timescale of less than 5,000 years, relatively soon afterrepository closure. That is, the probability of facility destruction bycoastal erosion is now believed to be essentially 1.0.32. This change to the assessment timeframe is one factor that contributes tothe assessed peak doses and risks being lower than they were in the 2002PCSC. This is because there is less time for in-growth of the daughters ofcertain long-lived radionuclides that contributed significantly to theexposures evaluated in the 2002 assessment. Other factors contributing tothe lessening of assessed peak doses and risks include the reducedimportance of the groundwater pathway (see paragraph 62), and the use ofa new model for assessing doses resulting from exposure to radon andthoron (see Section 3.4.5).33. The peer review panel’s comments on the underlying rationale for theshortened assessment timeframe are summarised in Section 3.2.4.Previously, review comments have suggested a need for the use of simplescoping calculations to address impacts after facility destruction(e.g., after glaciation of the site - see EA 2005a and references therein). Inthe present circumstances, where site destruction by erosion is nowbelieved to be essentially certain and the impacts of waste dispersal on theshore and into the sea have been assessed as part of the mainlineassessment, there seems to be little need for additional consideration oflonger timescales (as long as the mainline assessment calculationsproperly address all of the relevant exposure pathways and PEGs duringand after facility destruction e.g. in the lagoon system – see Sections 3.3.2and 3.4.4).TerraSalus Limited 9 2 September 2008

Peer Review of LLWR Response to S9R2LLWR_2008-8-2Version 13.2 Disposal System Description and Understanding3.2.1 Waste Inventory34. The SLC has commissioned several recent studies to refine the wasteinventory (e.g., Lennon et al. 2008; Wareing et al. 2008). These studieshave resulted in improved inventory estimates at a much greater level ofdetail than was available for the 2002 safety cases. The recent studieshave made a significant and positive contribution to risk management forthe site. The review panel has found that it is necessary to examine thereferences that underpin the five volumes comprising the submissionmade in response to Requirement 2 in order to properly understand theresults of the recent inventory work.35. There is now a much better understanding of the spatial distribution ofradionuclides in the trench wastes (see figures 1 and 2 of Lennon 2007).Lennon et al. (2008) shows that there are localised concentrations ofTh-232 in Trenches 2 and 3. Greater than 26% of the Th-232 occurs inless than 1% of the trench bays. In addition, one of the spatialconcentrations of Th-232 in Trench 2 coincides spatially with the mostsignificant concentration of Ra-226. Such localised concentrations ofradionuclides represent potential targets for intervention and should beassessed further as part of the work to determine whether localised wasteretrieval or some other type of intervention is justified (see Section 4.2.1).Localised volumes of waste possessing relatively higher concentrations ofradionuclides were described by the Environment Agency as ‘hot spots’(Environment Agency 2005a; 2006b).36. While much useful work has been done on mapping the spatialdistribution of radionuclides in the trenches, the peer review panelconsiders that further work remains to be done in the lead up to the nextsafety case in order to deal with some of the remaining uncertaintiesassociated with the trench waste inventory (e.g., those raised by localstakeholders at the BPEO workshops related to unrecorded disposals -Collier, 2008a).37. LLWR (2008c) indicates that compared to the inventory used in the 2002PCSC, the uranium content of the trenches is now believed to be lower bya factor of approximately two. Conversely, if as is assumed for theassessment calculations reported in LLWR (2008e), all of the wastestreams in the 2004 National Inventory for which the future disposal routeis declared as the LLWR were actually to be disposed of to the LLWR,then there would be some significant increases (as compared to the 2002PCSC inventory) in the amounts of long-lived radionuclides going into thevaults. For example, in the 2002 PCSC the Np-237 content of the futurevaults was estimated to be 0.01 TBq, whereas the current estimate is3.21 TBq - an increase of approximately 300 fold. This would mean thatthe future vaults would contain ~100 times as much Np-237 as the rest ofTerraSalus Limited 10 2 September 2008

Peer Review of LLWR Response to S9R2LLWR_2008-8-2Version 1the facility (trenches plus Vault 8). LLWR (2008c) indicates that thelargest increases in the inventory of long-lived nuclides (e.g., U, Np) areassociated with just a few waste streams, such as waste stream 2E101(Springfields decommissioning LLW).38. The current estimates of the inventory disposed of to date in the trenchesand in Vault 8 rely largely on declarations made at the time of disposal.For radionuclides of importance in the performance assessment, it wouldbe prudent to review knowledge of the waste producing processes, to seewhether significant additional undeclared amounts of the keyradionuclides could be present within major waste streams. For example,could Np-237 have been present in significant amounts in past disposalsof waste from Springfields?39. At the time of the last authorisation review, a key argument used in favourof allowing waste disposal to continue at the LLWR, was that futuredisposals would not appreciably increase peak annual risks and thatrestrictions on future disposals would have limited potential for reducinglong-term environmental impacts (see Environment Agency 2005b,para. 6.48). The review panel notes that the inventory estimates used inthe Requirement 2 submission mean that this argument would no longerhold.40. The submission made in response to Requirement 2 does not describepossible alternative assumptions about which wastes might come to theLLWR in future, but instead defers this topic to a separate UK LLWstrategy development process. Given this, we consider that the impactsfor the LLWR of accepting different type of waste might be explored inthe next safety case. The EA has asked for consideration of short-livedwastes (EA 2005a) and, in detail, various options might be possible. Thepeer review panel doubts that the LLWR should receive large amounts ofunprocessed soils and rubble from other decommissioning sites as issuggested might be the case by Figure 4.3 of LLWR (2008c).3.2.2 Engineered Facility41. The remit of the peer review panel includes the MVP and the design of theLLWR but, to-date, the panel has not had an opportunity to review thedesign in any great detail.42. The peer review panel acknowledges that facility design is not a primaryfocus of the submission made in response to Requirement 2, but considersthat the design could usefully have been described in more detail andshould have been presented more consistently across the five volumescomprising the submission.43. The submission does not describe the rationale for the design or itsjustification. The peer review panel notes that, consequently, it is difficultto assess design option choices.TerraSalus Limited 11 2 September 2008

Peer Review of LLWR Response to S9R2LLWR_2008-8-2Version 144. The peer review panel agrees that construction of a final cap is bestpractice in near-surface radioactive waste disposal and will be essential (tolimit infiltration and reduce the potential consequences of inadvertenthuman intrusion), but considers that further optimisation of the cap designmay be needed. For example, we are yet to be convinced that theproposed profile for the cap incorporating a central valley (see Figure 2.3of LLWR 2008c) is optimal, and we have concerns that it may berelatively more susceptible to cracking and failure due to differentialsettlement of the underlying waste than possible alternative designs.45. The peer review panel suggests that the SLC should consider a stagedprogramme of cap construction because this would provide an opportunityto trial and improve the cap construction process, to monitor capperformance, and to gather data on which to base models of capperformance.46. The peer review panel is not fully convinced by the justifications providedfor the vertical drains, the vault base liner, or the cut-off walls.Collectively these features (together with the cap) are designed to prevent‘bath-tubbing’ 2 and terrestrial discharge. The peer review panel considersthat the avoidance of bath-tubbing and terrestrial discharge should be akey design aim, but we are yet to be convinced that the proposed systemwill achieve this. For example, we are not convinced that with theircurrent proposed design, the vertical drains would continue to operate forthe required period and would not become clogged. The peer reviewpanel considers that a simpler facility design with a permeable vault basemight be better.47. We acknowledge that the SLC is planning further optimisation work onthe facility design and we support this. We would also encourage the SLCto review LLW disposal practices in other waste managementprogrammes (e.g., within Europe), with the aim of identifying examplesthat support the disposal practices and engineering measures beingproposed at the LLWR.3.2.3 Geology and Hydrogeology48. The geology and hydrogeology of the LLWR site and its immediatesurroundings are lithologically and spatially complex, and there have beenseveral attempts leading up to the 2002 PCSC and subsequently todevelop models of the geological structure and of groundwater andsurface water flows. Different modelling teams have had different viewson how the system should be represented and modelled, and over theyears, considerable resources have been put into the problem. LLWR(2008d) summarises the most recent work. However, some of the2Bath-tubbing is when the facility fills with water and this becomes contaminated and dischargesover the top of the facility walls into shallow groundwaters, the surrounding land or into streamsetc.TerraSalus Limited 12 2 September 2008

Peer Review of LLWR Response to S9R2LLWR_2008-8-2Version 1supporting reports, e.g., Arthur et al. (2008), were not available to the peerreview panel in time for this review.49. With regard to geology, the peer review panel considers that the changefrom the event-stratigraphy-based geological model used in the 2002PCSC to one based on lithological packages (LPs) gives the appearance ofbeing a sensible development. However, the LP model fails to deliver onits promises to better inform the modelled domain in any quantifiableway. This may be related to the particular LP approach adopted being toosimplified. In particular, the approach does not represent deterministicfeatures of sedimentological heterogeneity (e.g., interconnected sandylenses or channels such as those that may account for the groundwatertritium migration pattern). Consequently, there is some concern as to howmuch credence should be attached to the LP approach.50. With regard to hydrogeology, the peer review panel considers that theadoption of the LP approach has not significantly improved the linkbetween the geology and the hydrogeological interpretation and model.The credibility of the groundwater model, and its robustness, will need tobe improved, for example, by showing how well the model represents theeffects on groundwater movements of localised lithologicalheterogeneities, such as more permeable lenses and palaeochannels.Confidence that the groundwater model is fit for purpose also needs to beimproved by taking a more rigorous approach to model calibration(e.g., through the use of accuracy criteria), by explaining the reasons forany failure to achieve satisfactory model calibration against observed data,and possibly by testing transport predictions against the results ofmonitoring for tritium and other radionuclides in groundwater 3 .51. The peer review panel agrees that the evidence from piezometry and fromtritium migration studies indicates that the predominant pathway forleachate to enter groundwater is downwards to the deeper part of thegroundwater system. The tritium releases also identify certain pathwaysinto shallow groundwaters, which end up in various drains and streams(LLWR 2008d). We consider that the confidence in the groundwatermodel of these shallow pathways and of how they might evolve over timeneeds to be further enhanced.52. One aspect of this will be improvements in the diagrammatic presentationof information. For example, the peer review panel would have liked tohave seen: Better explanations of the particle tracking work (see figures 5.7-5.9of LLWR 2008d), which relies on the interaction of near-field andfar-field hydrogeology.3It is recognised that a fully quantitative model confirmation is not likely to be possible becauseof uncertainties in the magnitude and spatial distribution of the source term.TerraSalus Limited 13 2 September 2008

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

Peer Review of LLWR Response to S9R2LLWR_2008-8-2Version 1This was followed by global cooling under hyper-oceanic conditionsand repository disruption by valley glaciation in the period 20,000-40,000 years after present.BNFL’s regional glaciation variant was characterised by a period ofmild global warming during which the repository could be disruptedby coastal erosion in the period 2,000 and 5,000 years after present,followed by global cooling under relatively dry conditions. Grossdisruption by regional glaciation was projected in the period 60,000-100,000 years after present, under conditions of greatly reduced sealevel.62. The more recent work discussed in Section 3.2.4 (Thorne 2007; Thorneand Kane 2007) has led logically to the elimination of the glaciationvariants from the safety assessment, without the need for a new detailedscenario development process. The elimination of the glaciation variantshas the effect of greatly reducing the importance of the groundwaterpathway in the assessment because it was during the glaciation variantsthat there was the possibility of sea-level fall leading to exposures onemergent land to the south west of the facility. Overall, we consider thatthe changes since the 2002 PCSC are logical and help to increase focus onthe central issue of coastal erosion. The estimated timing and duration ofcoastal erosion have been refined, but are not significantly different fromthose assumed in the 2002 PCSC coastal erosion variant.63. Future human actions scenarios are discussed in Section 3.4.6. Commentson the inclusion or exclusion of certain potential exposure pathways in thesafety assessment scenarios are provided in Section 3.4.3.3.2 Potentially Exposed Groups64. Potentially exposed groups have been identified in a separate supportingstudy (Thorne 2007). Thorne (2007) describes changes to the approachadopted in the 2002 PCSC, referring specifically to comments made bythe EA on the treatment of PEGs in the 2002 assessment (EnvironmentAgency 2005a).65. The Thorne (2007) study appears to be quite comprehensive. The rangeof PEGs identified is adequate to cover the exposure scenarios that mayarise from either natural evolution or inadvertent human intrusionscenarios, and the key parameter values that would be used to relateconcentrations in environmental media to dose (occupancy times,inhalation and ingestion rates) are clearly described and appearreasonable.66. However, it is not clear from Volume 5 of the Requirement 2 submission(LLWR 2008e), that the PEGs as defined by Thorne (2007) have beencomprehensively considered in the assessment to date. For example:TerraSalus Limited 16 2 September 2008

Peer Review of LLWR Response to S9R2LLWR_2008-8-2Version 1Thorne (2007) correctly identifies ‘users of the estuary and lagoon’as a PEG, but it is not obvious from LLWR (2008e) that doses tothis PEG have been assessed.Agricultural smallholders making use of the cap area are identifiedas a PEG in Thorne (2007). LLWR (2008e) indicates that thepotential exposures of this PEG have been assessed for the cases ofinadvertent human intrusion and following releases of radionuclidesto the north-west gullies and ditches (LLWR 2008e, Table 4.3). Thepeer review panel, suggests, however, that this group might also beaffected via other pathways, such as gas release through defects inthe cap (in the absence of inadvertent human intrusion), or windblownmaterial arising from the advancing front of coastal erosion.Thorne (2007) notes current evidence of utilisation by local farmersof beach material for construction of roads and walls. Again, it isn’tclear whether this potential pathway of exposure is considered in thecoastal erosion scenarios described in LLWR (2008e).67. In summary, the PEGs as currently defined form a reasonable basis for theassessment, but more consideration is needed to ensure that all processesthat may contribute to their exposure and risk have been incorporated intothe assessment.3.4 Assessment Modelling68. The peer review panel has not undertaken a comprehensive, detailedreview of the assessment models used in developing the Requirement 2submission for the following main reasons:Many of the conceptual models are the same as those used in the2002 PCSC.The interim nature of the current assessment does not warrant such adetailed review at this stage.Documentation describing the models in detail has not always beenavailable, and there has been limited time for peer review work.69. In this section, therefore, we comment on selected parts of the assessmentmodels and focus largely on key assumptions, particularly where newapproaches have been adopted since the 2002 PCSC.70. More detailed review of the assessment models, parameter values andsupporting data, as well as of the accuracy and calibration of thesupporting models, and the use of the assessment models for uncertaintyand sensitivity analyses will need to be part of the programme leading tothe next safety cases.TerraSalus Limited 17 2 September 2008

Peer Review of LLWR Response to S9R2LLWR_2008-8-2Version 13.4.1 Engineering Performance71. Section 6 of LLWR (2008c) summarises the approach taken in Paksy(2008) to considering and quantifying water flows through the engineeredcomponents of the disposal facility. Water flows through the facility andits engineered features have been estimated using parameter values eitherderived from an expert elicitation or from the 2002 PCSC.72. The peer review panel considers that the engineering performanceassessment work conducted to date under the Lifetime Programme has notfully captured the uncertainties associated with how the facility mayactually perform and evolve over time. The SLC has been aware of ourconcerns for a relatively short time and has not had time yet to addressthem, but recognises this as an area for further work.73. Our concerns include:That the set of parameter values used in the engineeringperformance assessment do not form a coherent set. This has partlyarisen because after the elicitation workshop, the newly elicitedparameter values were put together with values from the 2002 PCSCthat had been derived on a different basis.That the recent elicitation process was not given sufficient time.That some rather optimistic assumptions were made, including:- that the vertical drains were assumed not to clog or fail;- that the permeability of the cap could be identified to within arather narrow range, that did not take account of the potentialfor cracking as a result of differential settlement; and- that waters flowing into the facility (e.g., into trench 6) wouldbe able to flow efficiently to the vertical drains on the otherside of the trenches.That there appears to be considerable uncertainty in the degree oflateral flows into the facility from the surrounding geology, andfrom the facility into adjacent drift groundwaters (e.g., along theNorth West perimeter of Vault 8).74. We are pleased, therefore, to see that the response made in submission toRequirement 2 recognises the need for optimisation of the repositorydesign, based on a better flow model for the engineered system. We notethat this model will need to link properly to the surrounding models ofgroundwater flow.TerraSalus Limited 18 2 September 2008

Peer Review of LLWR Response to S9R2LLWR_2008-8-2Version 13.4.2 Source Term75. The source-term model used in the current safety assessment is essentiallythe same as the one that was used in the 2002 PCSC (i.e., the DRINKbiogeochemistry model). The model is applied consistent with variousassumptions regarding the biogeochemical reactions that may occur in thedisposal system. For example, assumptions are made regarding whichsolid phases present in the near-field will control chemical conditions and,thereby, influence radionuclide dissolution and speciation. Assumptionsare also made regarding the production and ‘fate’ of gases. The peerreview panel considers that the model appears to provide a reasonablerepresentation of the aqueous chemistry of the system, but that furthersupport may be needed for certain assumptions made regarding thegaseous phases, carbon dioxide and methane.76. The main change in assumptions made since the 2002 PCSC has been as aresult of some excellent work on the nature of the uranium bearing wastesdisposed of to the trenches (Small et al. 2008). The peer review panelconsiders that this study has resulted in improved understanding of thenature of the wastes and their potential dissolution behaviour in thedisposal facility. The study is particularly commendable in that it hastaken the opportunity to access knowledge held by former staff of theSpringfields plant that were involved in the fuel manufacture processesthat led to generation of the wastes.77. The effect of the recent work (Small et al. 2008) is that much of theuranium in the trenches is now believed to be in a form that woulddissolve more slowly. The impact of the change to the uranium wastessource-term model is beneficial to (i.e., lowers) calculated doses and risksvia the groundwater pathway but, as noted above, this pathway is now lessimportant than it was believed to be in the 2002 PCSC. The impact of thechange to the uranium wastes source-term model on doses and risks viaother pathways should, of course, also be considered. It may mean, forexample, that some of the uranium wastes are less readily dissolved intocoastal waters following site destruction by coastal erosion.3.4.3 Groundwater Flow78. Section 4 of LLWR (2008e) describes a set of four different calculations(Cases A to D) undertaken to assess possible impacts from thegroundwater pathway (see Table 4.1 of LLWR 2008e).79. LLWR (2008e) recognises that, at this stage, not all conceptualuncertainties have been investigated, that an investigation of parameteruncertainties has not been carried out, and that although the calculationcases represent potential future conditions, they do not represent thepossible evolution of the system with time (e.g. the evolution of thecoastline).TerraSalus Limited 19 2 September 2008

Peer Review of LLWR Response to S9R2LLWR_2008-8-2Version 180. The peer review panel acknowledges these quite significant caveats andconsiders that further work will be necessary in the lead up to the nextsafety case. For the next safety case we suggest that it would be sensibleto focus in more detail on the following issues:Developing fully traceable documentation of the GoldSimassessment model, its testing and implementation.Describing how the GoldSim model is used in conjunction with thegroundwater flow and transport models.Developing clearer more consistent links between the detailedhydrogeological modelling and the calculation cases used in theassessment. For example, it is not completely clear how the fourcalculation cases described in LLWR (2008e) relate to the five‘future performance scenarios’ described in Section 5.1.2 of LLWR(2008d).Describing a realistic reference case. LLWR (2008e) focusesattention on Case A in which the engineering features are assumedto be performing as expected (no degradation) and which does notconsider sea-level rise or changes in recharge.Terrestrial discharge. The more detailed work summarised inLLWR (2008d) indicates the possibility under some circumstances(increased sea level) of terrestrial discharges close to the mean tideline, but it is not clear from the submission that this has beencaptured in the assessment modelling.Improving the clarity and basis for any arguments made relating tothe degree of hydrologic saturation in the near-field; the evidenceand reality regarding suggestions of unsaturated conditions andperched water in the shallow parts of the groundwater system arepresently vague.A better justification for the treatment of the water well. The peerreview panel considers that some aspects of the current treatment ofthe water well are clearly conservative (e.g., the assumed presenceand location of the well). However, we question whether it isreasonable to assume continuing regulatory control (e.g., under theWater Act 2003) over water abstraction after repository closure (seeSection 4.5.2 of LLWR 2008e). LLWR (2008e) suggests thatfurther work is needed to substantiate any claim that risks associatedwith the water well are consistent with the risk target, but it is notclear to the review panel what work is actually envisaged. Wewould caution against attempting to determine a quantitativeprobability for the drilling of a water abstraction well.TerraSalus Limited 20 2 September 2008

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

Peer Review of LLWR Response to S9R2LLWR_2008-8-2Version 1thoroughly peer reviewed. This is important because doses and risks dueto radon are the primary hazards between now and erosion of the site.87. The peer review panel notes that most of the large variation in radonlevels in dwellings (1 to 2 orders of magnitude) is not explained by thenew model. We consider, therefore, that the new radon model has a ratherlow predictive capability for any particular situation, and that it would benecessary for the next safety case to fully acknowledge and address theuncertainties inherent in its use.88. We note the SLC’s stated preference for an empirical model (LLWR2008e), but we consider that there may be benefit in making comparisonsbetween the empirical model and process type models, particularly withthe aim of allowing an analysis of uncertainties.89. We are also uneasy about the apparent extent of averaging in thederivation of the new radon and thoron model, and we suggest that in thenext safety case uncertainty should be assessed in a more explicit way;without this, further justification will be required for consideration only ofan average case.90. We also note that when applying the model to situations not involvinghuman intrusion, it has been assumed that the cap performs well and thatcracks do not allow more rapid release of radon from the waste.91. Overall, therefore, we regard the new radon and thoron dose model and itsresults as provisional. We agree that further development, as suggested inLLWR (2008e), would be necessary if the new radon and thoron model isto be taken forward to the next safety case.3.4.6 Human Intrusion92. The SLC’s approach to assessing human intrusion is summarised inSection 7 of LLWR (2008e). The human intrusion models used in thecurrent assessment are based on those used in the 2002 PCSC, but somedifferent assumptions and parameter values have been used in theircurrent implementation.93. The peer review panel supports the SLC’s view that events which involvedamage to the engineered barriers and/or penetration or excavation of thewaste represent intrusion, whereas the drilling of a water abstraction wellinto a plume of contaminated water outside of the facility does not (seefootnote 40 on page 84 of LLWR 2008e).94. In the 2002 PCSC, BNFL’s future human actions scenarios assumed thatinadvertent human intrusion could occur at any time after the withdrawalof active institutional controls (BNFL 2002b). In the current safetyassessment, various arguments are made regarding the probability ofinadvertent human intrusion, including an argument that the probabilityTerraSalus Limited 22 2 September 2008

Peer Review of LLWR Response to S9R2LLWR_2008-8-2Version 1will be reduced as a result of passive institutional controls (LLWR 2005e,page 86).95. While there is a reasonable logic for assuming that the probability ofinadvertent human intrusion can be assumed to be zero during the activeinstitutional control period, this is not the case for the period of passiveinstitutional control. For example, IAEA draft guidance is that althoughthe provision of passive institutional controls should be encouraged, safetyassessments should not assume that passive institutional controls will beeffective in preventing or reducing the probability of human intrusion(IAEA 2008). Consistent with draft IAEA guidance on safetyassessments (IAEA 2008), we consider that when assessing potentialdoses associated with radioactive waste repositories, inadvertent humanintrusion should be assumed to occur as soon as active institutionalcontrol ceases.96. We consider that a reasonable range of intrusion scenarios has beenidentified and assessed, but note that the impact of waste heterogeneityand the consequences of inadvertent intrusion into localised volumes ofwaste possessing relatively higher concentrations of long-livedradionuclides is more fully recognised and discussed more transparentlyin LLWR (2008a, b) than in LLWR (2008e).97. For example, LLWR (2008a, page 48) reports that ‘Intrusion into andthen building a dwelling on average waste from Trench 3 (the Trench withthe highest 226Ra inventory) would give a dose of 3 mSv yr -1 ; for theworst contiguous 20 bays the dose would be 38 mSv yr -1 . Higher radiationdoses could occur if the very highest concentration waste is built on. Weconsider, however, that such a case is very unlikely because of the size ofexcavation that is needed to penetrate to the waste depth, which impliesthat dilution and mixing is likely. It seems unlikely that an intrusion to 8mdepth for the purpose of road construction would remove a small volumeof waste to the surface and that a house would be constructed withoutsignificant mixing.’98. While it seems reasonable to take account of the thickness of the cap whenassessing the consequences of an inadvertent human intrusion, we differfrom the SLC’s project team over the presentation of some of thearguments made regarding the probability of the inadvertent humanintrusion event itself. We do not consider that quantitative credit shouldbe taken in the safety assessment for passive institutional controls, and wealso consider that it is too speculative to suggest a probability ofinadvertent human intrusion after the lapse of passive controls (see pages86 and 87 of LLWR 2008e). As noted by the ICRP (2000), there is noscientific basis for estimating the probabilities of future inadvertent humanintrusion events.99. LLWR (2008e) proposes that a reference level dose rate of 10 mSv/yearshould be used when considering impacts from inadvertent humanTerraSalus Limited 23 2 September 2008

Peer Review of LLWR Response to S9R2LLWR_2008-8-2Version 1intrusion. The peer review panel considers that if the consequences ofinadvertent human intrusion are to be compared against a dose-basedintervention criterion of this type, then it is a form of double counting alsoto make arguments as to the low probability of the intrusion event 4 .100. If arguments are to be made regarding the probability of inadvertenthuman intrusion, then logically the assessed risk from intrusion should becompared to a risk-based standard (e.g., the risk target).101. If calculated doses from inadvertent human intrusion are significant whencompared to the relevant dose-based intervention criterion, then a strongerargument would be made for or against waste retrieval by focussing on thecosts and other factors associated with retrieval, rather than by makingarguments about the probability of intrusion events.3.5 Quality Assurance and Use of Assessment Results3.5.1 Quality Assurance102. There is clear evidence that documents have been put through suitable QAprocesses, but some documents have been produced at too late a stage,and there has been little time for the SLC’s project team to draw togetherthe various different R&D and assessment studies into a coherentassessment to support the submission made in response to Requirement 2.103. For the next safety case, we believe that there will be a need for moredetailed documentation of safety assessment data and parameter values,and we recommend consideration of production of dedicated data reportssuch as SKB (2006).104. As an example of the need for further detailed documentation, we havenot seen detailed documentation of the GoldSim assessment model, orevidence of its verification or testing against the more detailed supportinghydrogeology models or against previous assessment models (e.g., thosefrom the 2002 PCSC).105. The peer review panel considers, therefore, that the safety assessmentwork could not be reproduced today by another suitably qualified teambased on the documentation provided.106. These issues are recognised by the SLC and will be taken into account inthe planning of the forward programme for development of the next safetycase. The issues are not significant for the submission made in responseto Requirement 2 because the submission is an interim deliverable, and4We note that judgement has to be exercised when developing human intrusion scenarios (e.g., sothat the illustrations considered are not wildly unrealistic), particularly those involvingsequences of events each with their own probabilities. However, in this case it does not seemunreasonable behaviour for people in the future to construct a house or houses on excavatedmaterials.TerraSalus Limited 24 2 September 2008

Peer Review of LLWR Response to S9R2LLWR_2008-8-2Version 1does not propose changes to the CFA, or come to firm decisions onfacility design or site remediation.3.5.2 Assessment Results107. The peer review panel considers that the current assessment results help toindicate, in a general sense, which scenarios and exposure pathways arethe most important and, therefore, where the emphasis for furtherassessment work should lie in the lead up to the next safety case.However, the limited range of uncertainty and sensitivity analyses carriedout mean that it is not possible to be particularly specific as to whereimprovements might be made.108. From a safety case perspective, the focus should probably be on ensuringthat a rigorous, ‘water-tight’ assessment is made of the coastal erosionpathways, and of inadvertent human intrusion, particularly into localisedvolumes of waste possessing relatively higher concentrations of long-livedradionuclides. There should also be further consideration of:Flows through the LLWR, taking account of facility degradation.The possibility of terrestrial discharge of contaminated groundwaternear the coast, especially under conditions of increased sea-level.Bath-tubbing and engineering measures to prevent this.109. We consider that it should be possible to make a reasonable qualitativeargument that the drilling of a water well between the LLWR and thecoast is unlikely.3.5.3 Comparison with Regulatory Criteria110. The safety assessment reported in LLWR (2008e) has led to someimportant developments in terms of understanding how the site mayevolve, and the structure of the next safety case, but the peer review panelconsiders that for several reasons (uncertainty in which regulatory criteriaapply, limited treatment of uncertainty in the assessment calculations,limited traceability of assessment data, etc) it would be premature to drawany firm conclusions from comparisons of the current assessment results(doses and conditional risks) with quantitative regulatory criteria.TerraSalus Limited 25 2 September 2008

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

Peer Review of LLWR Response to S9R2LLWR_2008-8-2Version 1particular localised volumes of waste possessing relatively higherconcentrations of long-lived radionuclides.4.2.1.4 In-situ Remediation120. For various reasons, including cost, the peer review panel agrees with theSLC’s assessment that the ‘In-Situ Remediation – Vitrification’ option isnot appropriate at the LLWR.121. We also agree that the ‘In-Situ Remediation – Grouting’ option wouldhave only a limited effect in reducing the impacts from human intrusion orcoastal erosion, and we consider some of the purported benefits of in-situgrouting (e.g., reducing radionuclide solubility – see page 68 of LLWR2008a) to be largely irrelevant in this context.122. In addition, we note that there might be difficulties in demonstratingeffective implementation of such in-situ remediation techniques.4.2.2 Institutional Control123. The IAEA defines LLW as ‘waste that is suitable for near-surfacedisposal’, and suggests that the concentrations of long-lived radionuclidesthat can be accepted in LLW are limited by the time period over whichnear-surface disposal can ensure the isolation of the wastes and canprevent inadvertent human intrusion.124. We consider that it would be sensible to aim to provide active institutionalcontrol for as long as possible given that 5 :The LLWR already contains relatively high levels of long-livedradionuclides as compared with wastes classified as LLWinternationally and in some other countries (and assuming that thesewastes are not retrieved for disposal elsewhere).Current plans are to continue to dispose of long-lived wastes in thevaults.125. Assuming that it ought to be possible in the UK to provide activeinstitutional control for at least 300 years, we agree with the SLC’sstatement that active institutional control should be provided for as long ascan reasonably be achieved (page 68 of LLWR 2008a).5Within the radioactive waste disposal literature, 300 years has often been suggested as areasonable estimate of the length of time for which it may be possible to rely on activeinstitutional controls. The period of 300 years coincides approximately with ten half lives of therelatively active, but short-lived radionuclides, Cs-137 and Sr-90. Thus, the provision of activeinstitutional controls for 300 years (which could be assumed to prevent inadvertent humanintrusion), enables the disposal of relatively active but short-lived wastes at or near the surface.TerraSalus Limited 28 2 September 2008

Peer Review of LLWR Response to S9R2LLWR_2008-8-2Version 14.2.3 Coastal Defences126. The peer review panel considers that the SLC is correct to conclude thatthe disposal facility should not be reliant on coastal defences forprotection from erosion in the long-term (i.e., for timescales relevant tolong-lived radionuclides). Unless sufficient funds were set aside by thepresent generation for use in the future, such reliance would place undueburdens on future generations who would have to pay to maintain thecoastal defences, but who would not have benefitted from the processesthat produced the wastes.127. In contrast, the peer review panel notes that the submission made inresponse to Requirement 2 is rather tentative regarding the possibility ofprotecting the site from inundation in the shorter-term (see page 66 ofLLWR 2008a); we consider that the possible need to prevent floodingshould be kept under active review.4.2.4 Engineered Features4.2.4.1 Cap128. The peer review panel considers that the SLC is correct to conclude thatconstruction of a final cap over the wastes is best practice in near-surfaceradioactive waste disposal, and should form part of the strategy for theLLWR.129. The peer review panel suggests that the SLC should consider a stagedprogramme of cap construction because this would provide an opportunityto trial and improve the cap construction process, to monitor capperformance, and to gather data on which to base models of capperformance.4.2.4.2 Other Engineered Features130. As discussed in Section 3.2.2, the peer review panel is not fully convincedby the justifications provided for the vertical drains, the vault base liner,or the cut-off walls. Collectively these features (together with the cap) aredesigned to prevent ‘bath-tubbing’ and terrestrial discharge.131. In terms of best practice, we note that the submission has not identified anexample of a near-surface radioactive waste disposal facility with animpermeable concrete vault base and liner. Also, the use of drains forimproving long-term performance appears novel – the text of LLWR(2008b) sometimes compares the vertical drains with the much morecommon operational drainage systems at other LLW disposal facilities,but this comparison can be misleading.132. The peer review panel considers that the avoidance of bath-tubbing andterrestrial discharge should be a key design aim, but we are yet to beTerraSalus Limited 29 2 September 2008

Peer Review of LLWR Response to S9R2LLWR_2008-8-2Version 1convinced that the proposed system will achieve this. For example, weare not convinced that with their current proposed design, the verticaldrains would continue to operate for the required period and would notbecome clogged. The peer review panel considers that a simpler facilitydesign with a permeable vault base might be better.4.2.5 Radiological Capacity and CFA of Waste133. Given the various uncertainties that exist (e.g., surrounding whichregulatory criteria to apply, the interim nature of the current safetyassessment, and the on-going LLW strategy development process), thepeer review panel agrees with the SLC that it is correct not to make firmdecisions at this time on the establishment of new radiological capacitylimits or conditions for waste acceptance of waste.TerraSalus Limited 30 2 September 2008

Peer Review of LLWR Response to S9R2LLWR_2008-8-2Version 15 Conclusions5.1 Peer Review134. The peer review panel considers that the submission made in response toRequirement 2 and provided to the EA on 1 May 2008 had improvedconsiderably in the time since the peer review panel reviewed the work inearly April 2008. Many of the changes and developments have resolvedpeer review comments, and the SLC’s project team has acknowledged thebenefit provided by the peer review.135. Inevitably and appropriately some peer review comments and issuesremain to be dealt with. The SLC has indicated that it is planning furtherwork to address the remaining issues in the lead up to the next safety case.136. Peer review is an ongoing process and will need to continue throughoutthe programme leading to the next safety case. Planning of peer reviewactivities needs to be an integral part of planning for the programmeleading to the next safety case.5.2 Addressing the Requirements137. The peer review panel considers that the submission has certainlyprovided a wide range of information that goes well beyond the originalwording of Requirement 2 as stated in the Authorisation.138. The submission includes the outcome of a wide-ranging risk managementstudy and addresses many issues relevant to the radiological capacity ofthe site. The submission does not demonstrate that risks are ALARA, butit does indicate a firm commitment to the next safety case and to making arobust ALARA demonstration. This seems appropriate given the variousuncertainties that exist.5.3 Proposed Strategy139. With regard to the strategy being proposed for the LLWR, the peer reviewpanel agrees with the SLC that:A final site cap will be essential.A period of active institutional control after waste disposals ceasewill be essential.Coastal defences cannot be relied on to protect the LLWR fromerosion in the long-term (i.e., for timescales relevant to long-livedradionuclides).TerraSalus Limited 31 2 September 2008

Peer Review of LLWR Response to S9R2LLWR_2008-8-2Version 1The pros and cons of retrieval from the trenches of localisedvolumes of waste possessing relatively higher concentrations oflong-lived radionuclides need further analysis.140. In April 2008, the peer review panel suggested that SLC should not bedefinite on the need for the vertical drains, the vault base liner, or the cutoffwalls – this is still our view. These features are still part of theproposed strategy, but the submission and the SLC recognise the need forfurther optimisation of the design, and we support this.141. Overall, therefore, the peer review panel is now more comfortable andable to support the main conclusions on strategy proposed in thesubmission.5.4 Forward Programme142. We have made various detailed technical suggestions in Section 3 and 4regarding issues that could be considered in the forward programmeleading to the next safety case. Here we highlight just a few key points:There is only a short period in which to develop the next safety case.Simply documenting the safety case might take a year towards theend of the period. Good planning will be essential if the variouscomponents of the safety case are to be brought together at the righttime and with appropriate levels of consistency, quality assuranceand peer review. It would seem sensible, therefore, for the SLC tomaintain the valuable momentum developed during recent months.The next safety case will need to include a safety assessment thatincludes a more comprehensive treatment of uncertainty. Planningthe approach to the treatment of uncertainty should probably be oneof the more strategic issues that should be considered at an earlystage.There is a need to better integrate the engineering design andoptimisation work with the safety case. Decisions on facilityoperation should be checked for consistency with the environmentalsafety cases.The risks from coastal erosion of the facility need to be assessed in athorough and robust way. A more convincing and well-supported understanding ofgroundwater movements and potential radionuclide transport shouldbe demonstrated in order to confirm that ground and surface waterpathways are now a less prominent issue in long-term performance.TerraSalus Limited 32 2 September 2008

Peer Review of LLWR Response to S9R2LLWR_2008-8-2Version 1The issue of localised waste retrieval needs to be assessed withmuch greater transparency, in order that risks can be shown to beALARA.The implications of coastal erosion for the suitability of the site fornear-surface radioactive waste disposal should be considered furtherwith regulators and stakeholders.TerraSalus Limited 33 2 September 2008

Peer Review of LLWR Response to S9R2LLWR_2008-8-2Version 16 References143. Amin, S., 2007. Management Options for the Optimisation of the LLWRat Drigg. Nexia Solutions Report No. 8842.144. Arthur, S., Sears, R. and Whitaker, D.A., 2008. LLWR Lifetime Project:Site-Scale Groundwater Flow and Transport Model. Version 2, NexiaSolutions Report No. (in prep).145. Bennett D.G. and Jones, S., 2007. Independent Peer Review Feedback on:LLWR BPEO Toolkit Workshop Thursday 6th December 2007. LLWRLifetime Programme Peer Review, Interim Review Paper IPR001. In:Collier, D., 2008a. Report of the [External Stakeholder] ToolkitWorkshop 6th December 2007. Faulkland Associates Report No.C2089 R08-2.146. Bennett D.G. and Jones, S., 2008. Independent Peer Review Feedback on:LLWR BPEO Toolkit Development Workshop Thursday 17th January2008. LLWR Lifetime Programme Peer Review, Interim Review PaperIPR002. In: Collier, D. 2008b. Report of the [External Stakeholder]Toolkit Workshop 12th January 2008. Faulkland Associates ReportNo. C2089 R15-2, January 2008.147. Bennett D.G., 2008. Independent Peer Review Meeting on: LLWRResponse to Schedule 9 Requirement 2, Wednesday 13th February 2008.LLWR Lifetime Programme Peer Review, Interim Review Paper IPR003,12 March 2008.148. BIOCLIM, 2004. Deliverable D10-12: Development and Application of aMethodology for Taking Climate-Driven Environmental Change intoaccount in Performance Assessments. ANDRA, Parc de la CroixBlanche, 1/7 rue Jean Monnet, 92298 Châtenay-Malabry, France.149. BNFL, 2002a. Drigg Operational Environmental Safety Case. BritishNuclear Fuels plc.150. BNFL, 2002b. Drigg Post-Closure Safety Case: Overview Report. BritishNuclear Fuels plc.151. BNFL, 2004. Preliminary Assessment of Options for the Management ofthe Impact of the Drigg Low Level Radioactive Waste Disposal Facility.BNFL Report No. NSTS(04)5092, 2004.152. Environment Agency, 2005a. The Environment Agency’s Assessment ofBNFL’s 2002 Environmental Safety Cases for the Low-Level RadioactiveWaste Repository at Drigg. Report No. NWAT/Drigg/05/001,Version 1.0.153. Environment Agency, 2005b. Explanatory Document to Assist PublicConsultation on Proposals for the Future Regulation of Disposals ofTerraSalus Limited 34 2 September 2008

Peer Review of LLWR Response to S9R2LLWR_2008-8-2Version 1Radioactive Waste on/from the Low-Level Waste Repository at Drigg,Cumbria Operated by British Nuclear Group Sellafield Ltd.154. Environment Agency, 2006a. Certificate of Authorisation andIntroductory Note, Disposal of Radioactive Waste from Nuclear SiteBritish Nuclear Group Sellafield Ltd., Low Level Waste Repository,Drigg, Cumbria, Authorisation Number BZ2508.155. Environment Agency, 2006b. Decision Document: Future Regulation ofDisposals of Radioactive Waste on/from the Low-Level Waste Repositoryat Drigg, Cumbria Operated by British Nuclear Group Sellafield Ltd.156. Environment Agency, Scottish Environment Protection Agency,Department of the Environment for Northern Ireland, 1997. RadioactiveSubstances Act 1993: Disposal Facilities on Land for Low andIntermediate Level Radioactive Wastes, Guidance on Requirements forAuthorisation.157. Environment Agency, Scottish Environment Protection Agency,Environment and Heritage Service Northern Ireland, 2008. Near-SurfaceDisposal Facilities on Land for Solid Radioactive Wastes: Guidance onRequirement for Authorisation. Draft for Public Consultation, 15 May2008.158. Halcrow, 2008. Cumbria Coastal Studies Stage 3 Conceptual Model,Nexia Solutions Report No. 8563.159. Hill M.D. and Irvine, T.J., 2002. Final Summary Report on theIndependent Peer Review of the 2002 Drigg Post Closure Safety Case.160. HPA, 2008. Consultation Document: HPA Advice on RadiologicalProtection Objectives for the Land-based Disposal of Solid RadioactiveWaste, Health Protection Agency.161. IAEA, 1994. IAEA Safety Standards Series, Near-Surface Disposal ofRadioactive Waste, Requirements No. WS-R-1, International AtomicEnergy Agency, Vienna.162. IAEA, 2004. Improved Safety Assessment Methodologies for NearSurface Disposal Facilities (ISAM), Vol. I – Review and Enhancement ofSafety Assessment Approaches and Tools; Vol. II – Tests Cases,International Atomic Energy Agency, Vienna.163. IAEA, 2007. Regulatory Review of Post-Closure Safety Assessments forRadioactive Waste Disposal Facilities. International Atomic EnergyAgency Safety Report, Vienna.164. IAEA, 2008. The Safety Case and Safety Assessment for RadioactiveWaste Disposal. International Atomic Energy Agency, Vienna.TerraSalus Limited 35 2 September 2008

Peer Review of LLWR Response to S9R2LLWR_2008-8-2Version 1165. ICRP, 2000. Radiation Protection Recommendations as Applied to theDisposal of Long-lived Solid Radioactive Waste, InternationalCommission on Radiological Protection Publication 81, Pergamon Press,Oxford and New York.166. ICRP, 2008. International Commission on Radiological ProtectionPublication 103: Recommendations of the ICRP, Annals of the ICRPVolume 37/2-4, ISBN-13: 978-0-7020-3048-2, ISBN-10: 0-7020-3048-1.167. Lennon, C.P., 2007. Interim Assessment of Heterogeneity of theDisposed Waste in the Trenches at the LLWR. Nexia Solutions ReportNo. 8221, Issue 02.168. Lennon, C.P., Jones, A., Eden, L. and Ball, M., 2008. Heterogeneity inthe Inventory of Past and Potential Future Disposals in the LLWR. NexiaSolutions Report No 9126.169. LLW Repository Limited, 2008a. Managing Existing Liabilities andFuture Disposals at the LLWR. Report No. 100001 LLWR LTPVolume 1, Issue 01.170. LLW Repository Limited, 2008b. Assessment of Options for ReducingFuture Impacts from the LLWR. Report No. 100002 LLWR LTPVolume 2, Issue 01.171. LLW Repository Limited, 2008c. Inventory and Near field. Report No.100003 LLWR LTP Volume 3, Issue 01.172. LLW Repository Limited, 2008d. Site Understanding. Report No.100004 LLWR LTP Volume 4, Issue 01.173. LLW Repository Limited, 2008e. Performance Update for the LLWR.Report No. 100005 LLWR LTP Volume 5, Issue 01.174. Mallants, D., Vermariën, E., Wilmot, R. and Cool, W., 2008. Selectionand Description of Scenarios for Long-Term Radiological SafetyAssessment. Project Near-Surface Disposal of Category A Waste atDessel. ONDRAF/NIRAS Report No. NIRAS-MP4-02, Version 1.175. NEA, 2005a. International Peer Reviews for Radioactive WasteManagement: General Information and Guidelines. Organisation forEconomic Co-operation and Development, Nuclear Energy AgencyReport No. NEA 6082.176. NEA, 2005b. International Peer Reviews in the Field of RadioactiveWaste: Questionnaire on Principles and Good Practice for Safety Cases.Organisation for Economic Co-operation and Development, NuclearEnergy Agency Report No. NEA/RWM/PEER(2005)2.TerraSalus Limited 36 2 September 2008

Peer Review of LLWR Response to S9R2LLWR_2008-8-2Version 1177. Paksy, A., 2008. LLWR Lifetime Project: Near-field EngineeringPerformance: Methods and Data. Nexia Solutions Report No. 9275.178. SKB, 2006. Data Report for the Safety Assessment SR-Can. SvenskKärnbränslehantering AB Report No. TR-06-25.179. Thorne, M.C. and Kane, P., 2007. LLWR Lifetime Project: Climate andLandscape Change Scenarios. Mike Thorne and Associates Ltd. ReportNo. MTA/P0022/2007-2: Issue 2, Nexia Solutions Report No. 8847.180. Thorne, M.C., 2007. LLWR Lifetime Project: R&D on Climate Changeand Site Evolution. Mike Thorne and Associates Ltd. Report No.MTA/P0022/2007-1: Issue 2.TerraSalus Limited 37 2 September 2008

Peer Review of LLWR Response to S9R2LLWR_2008-8-2Version 1Appendix 1 – The Peer Review PanelDr David Bennett181. Dr David Bennett (BSc., PhD., FGS) is Director of TerraSalus(EarthSafety) Limited. He has over 17 years experience in providingstrategic and technical consultancy advice on radioactive wastemanagement and its regulation. He is a geologist and geochemist, and hascontributed to over 60 published papers and reports in the area ofradioactive waste management.182. His specialities include disposal facility authorisation and licensing,regulatory review and interpretation, peer review, risk and safetyassessment, safety case development, engineered barrier systems,radioactive waste immobilization, and geochemical and radionuclidetransport modelling. He has also contributed to a range of consultativeBPEO studies and options appraisals on waste management and disposal.183. Dr Bennett has contributed to radiological assessments and nuclear wastemanagement programmes in Belgium, Finland, France, Germany, Japan,Sweden, the UK and the US, and has also contributed to severalinternational programmes run by the European Commission, theInternational Atomic Energy Agency (IAEA) and the OECD NuclearEnergy Agency (NEA).184. Dr Bennett currently chairs the independent peer review panel that isreviewing the development of new safety cases for the LLWR near Drigg.He is also secretary to the international BRITE group, which is reviewingnear-field aspects of the Swedish spent fuel disposal programme on behalfof the Swedish Radiation Safety Authority. Dr Bennett is lead consultantto the NEA for its Engineered Barrier System (EBS) project, and hasrecently contributed to an international peer review of the Electric PowerResearch Institute (EPRI)’s assessment capability for radioactive wastedisposal at Yucca Mountain in the US. Dr Bennett has also been assistingthe IAEA to develop a new Safety Guide on safety cases and safetyassessments for radioactive waste disposal.Dr Adrian Bath185. Dr Adrian Bath (BSc., PhD., CGeol) is Director of Intellisci Limited. Hehas over 33 years experience as research scientist in groundwaterchemistry, hydrogeology, and environmental chemistry, and 24 yearsexperience in applying geochemistry in radioactive waste management,the environmental behaviour of radionuclides, and safety assessment ofwaste repository sites. He is also a member of the US GeochemicalSociety, of the International Association of Hydrogeologists, and of theInternational Association of Geochemistry.TerraSalus Limited A-1 2 September 2008

Peer Review of LLWR Response to S9R2LLWR_2008-8-2Version 1186. He specialises in environmental geochemistry and contaminant chemistryin groundwaters, the surface environment and engineered systems, andprovides services for clients in radioactive waste management, hazardouswaste management, environmental remediation, water resources andenvironmental quality. He has authored many scientific publications andconsultancy reports on the applications of geochemistry in radioactivewaste management and in other areas of groundwater and environmentalscience.187. His experience includes:Providing scientific advice and services to European, American andJapanese radioactive waste management and nuclear regulatoryorganisations.Planning and interpretation of site investigations for repositories andunderground laboratories in crystalline rock and clay rock.Geochemical modelling of radionuclides in engineered barriers,groundwater systems around repositories, and in contaminatedconstruction materials.Specialist problem-solving for projects concerning hazardous wastemanagement, landfill disposal, groundwater contamination andgeotechnics.Scientific management and review activities in projects onhydrogeochemistry, isotope hydrology, groundwater flow, solutetransport, palaeohydrogeology and groundwater and soilcontamination.Prof. George Fleming188. Professor George Fleming (BSc., PhD., FREng., FICE., FCIWM., CEnv)is Managing Director of EnviroCentre Limited, and Emeritus Professor ofcivil engineering at Strathclyde University. His research publicationsinclude contributions to 15 books and over 250 publications in journals,keynote addresses, papers at conferences, reports, plus the production of 4video documentaries and a permanent exhibition.189. He specialises in environmental management, including hydrology andwater and soil resources engineering, where he has pioneered thedevelopment of computer aided design and simulation techniques. He hasundertaken research into the uses of dredged material, landfill hydrology,real-time drought and flood forecasting, river basin management, landuse,and river engineering for fishing improvements. He currently leads amajor trial to manage contaminated dredgings in the North Sea.TerraSalus Limited A-2 2 September 2008

Peer Review of LLWR Response to S9R2LLWR_2008-8-2Version 1190. Professor Fleming has acted as consultant to many national andinternational organisations, including the United Nations FAO, IAEA,ILO, WMO; agencies such as the Scottish Development Agency,Highland and Strathclyde Regions, Monklands, Inverclyde, Dundee,Clydebank, Lochaber, Glasgow and Annandale and Eskdale DistrictCouncils; the SSEB and CEGB; and a number of private companiesincluding Jacobs Babtie, Binnie & Partners, Mott MacDonald, EPDC,Bovis, Wimpey Waste, Clydeport Ltd, Patersons of Greenoakhill, PeelHoldings and Port of Tyne.191. Significant projects include dams in Kenya, Labuan and Brunei;Strathclyde Park; flooding in Sutherland; numerous landfill sites; GlasgowGarden Festival Project; Dinorwig Power Station Project; reservoirmanagement in the Alps; flood control in California, Chicago and Brazil.192. Professor Fleming was appointed to the DTi’s Overseas Projects Board inJune 1991, and to the Boards of the Scottish International ResourceProject and to the Scottish Exports Forum in 1996. Professor Flemingwas elected to the Council of the Royal Society of Edinburgh and servedas Convenor of the Royal Academy of Engineering in Scotland for eightyears. Professor Fleming was President of the Institution of CivilEngineers in 2000, and served on various boards and committees.Following the completion of his Presidency, he became Chairman of theICE Waste Management Board and is still heavily committed to EngineersAgainst Poverty (formerly The Telford Challenge).Dr Graham Garrard193. Dr Graham Garrard (BSc., MSc., PhD., CGeol) is an Associate Directorof Halcrow Group Limited. He has over 27 years experience inengineering geology and geotechnics, with extensive experience in themanagement of major projects in the UK and abroad, including riskassessments, feasibility studies and investigations for nuclear facilities,road and pipeline developments, waste disposal sites. His experienceincludes:Geotechnical Team Leader and Deputy Design Manager for theDounreay Shaft Isolation Project.Project Manager for several programmes involved with the designand assessment of engineered barriers for low-level nuclear waste.Team Leader responsible for geotechnical studies using systematicrisk assessment methodologies to help quantify the possible riskfrom barrier failure in low-level nuclear waste landfills and fromcavernous ground.Project and Resident Engineer for a seismic hazard assessment andgeotechnical studies for a nuclear power station, including designTerraSalus Limited A-3 2 September 2008

Peer Review of LLWR Response to S9R2LLWR_2008-8-2Version 1and supervision of a state of the art site investigation with a projectvalue of approximately £2.2 millionConducting independent technical assessments of site investigationson behalf of the Department of Environment (old limestone mines inthe West Midlands) and DML (Devonport nuclear submarine refitfacilities) and having designs audited by regulatory authorities.Dr David Holton194. Dr David Holton (BSc., PhD., FGS) is Manager of Serco Limited’s WasteManagement and Environment Business. He has over 18 years experiencein hydrogeology and mathematical modelling of contaminant andradionuclide transport. His key skills include:Project management and technical leadership of projects in thenuclear industry internationally.Overall management of the use of various software tools to evaluatethe impact of radioactive waste as part of site investigation andinterpretation work.National and international expert reviewer (on behalf of the IAEA,POSIVA, ANDRA, KAERI, State of Nevada, Mont TerriConsortium, member of the NERC Peer Review College). Developer of methodologies for the integration of siteunderstanding.Expert in hydrogeology, hydrogeological modelling (includinginterpretation of hydraulic testing, integration of BIPS and othergeological information, point dilution and testing tracer testing),environmental risk assessments, groundwater flow and radionuclidetransport.Experience of communicating technically complex issues to a verywide range of technical stakeholder groups from Universities,Agencies (Environment), Radioactive Waste ManagementAgencies, IAEA in a range of different forums, to workshops andinternational conferences.Expert technical author. He has produced over 100 technical reportsand peer reviewed papers.Prof. Steve Jones195. Professor Steve Jones (BA., PhD) is Principal Consultant at the WestlakesResearch Institute. He is also an Honorary Professor of Environmentaland Occupational Toxicology, at the University of Central Lancashire, andTerraSalus Limited A-4 2 September 2008

Peer Review of LLWR Response to S9R2LLWR_2008-8-2Version 1is a Visiting Professor at the Industrial Ecology Research Centre, at theUniversity of Liverpool. He has over 16 years experience at senior levelin industry and as a consultant, largely concerned with the assessment andmanagement of environmental issues and the interactions betweenbusiness needs, scientific issues and understanding, legislation andregulatory policy, public and political expectations.196. He is an invited independent member of the National Dose AssessmentWorking Group, concerned with methodologies for assessing doses to thepublic from radioactivity in the environment. He acts as peer reviewer formany scientific journals in the fields of radiation protection, dosimetry,radioecology and occupational medicine197. His experience includes:Direction of industrially focused R&D in the environmental and lifesciences.All aspects of practical health physics, including radioactivitymeasurement, dose assessment, environmental monitoring,occupational exposure control, discharge assessment and emergencypreparedness.Interpretation of occupational and environmental epidemiologicaldata. Preparing environmental assessments and working withenvironmental legislation and regulators to negotiate authorisationsand consents.Development of environmental policy and related environmentalmanagement systems, and conducting environmental liabilityreviews in relation to due diligence.Legally-related scientific work, both as scientific advisor and anexpert witness, in both civil and criminal proceedings, together withjudicial review and public inquiry work concerned withenvironmental impact issues.Participation in BPEO, MADA and related environmental decisionmakingprocesses, involving stakeholder dialogue and concernsabout environmental performance and safety.Acting as an expert for the FCO in relation to actions against the UKGovernment in respect of Sellafield’s discharges to the Irish Sea.Contributing to the development of integrated waste strategies fornuclear sites.TerraSalus Limited A-5 2 September 2008

Peer Review of LLWR Response to S9R2LLWR_2008-8-2Version 1Participating in collaborative European research projects onprotection of the environment from ionising radiation.TerraSalus Limited A-6 2 September 2008