Limer LMC, Assessment Calculations for C-14 Labelled Gas and ...

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Figure 1-1: Schematic of the LLWR with Extended Disposal Area2
QRS-1443ZH-1, Version 3.02 Summary of Fundamental AssessmentAssumptions and Models UsedIn order to evaluate the potential impacts of C-14 and Rn-222 labelled gas releasedfrom wastes disposed of at the LLWR, it is necessary to consider how these gases mightreach the soil zone and above-ground atmosphere for any impacts to occur. Thus,consideration needs to be given to the following aspects of the system:The source term of gas released from the wastes;Transport through the cap to the soil zone and above-ground atmosphere; andImpacts of that gas in the biosphere.Full details of assumptions made for these aspects of the system were given in theequivalent RDA assessment reports (Limer et al., 2011; Limer and Thorne, 2011). Thefollowing subsections provide a summary of important aspects of the system identifiedin those RDA assessments.2.1 Source Term2.1.1 C-14C-14 is present in the LLWR inventory in a variety of waste streams (Wareing, 2009),with the majority in the form of an activation product from the irradiation of materials.These materials include metals, concrete and graphite, and all are likely to offer somedegree of retention of the C-14 during leaching by groundwater. Other LLW materialsinclude cellulose and organic materials.A key assumption made in the 2002 post-closure safety case (PCSC) was that the C-14inventory was assumed to be released from all waste materials at the same rate and itwas further assumed that the C-14 was present in the most reactive cellulose-typematerial (BNFL, 2002; Graham et al., 2003). The 2011 ESC uses updated assumptionsabout the dynamics of C-14 in the near-field (Baker et al., 2008; Small et al., 2008). Oncereleased from the waste-forms in to the near-field, the C-14 is assumed to be fullyavailable for and subject to the full range of biogeochemical processes that can affectthe subsequent reactions of the C-14 and partitioning between mobile (aqueous andgas) and immobile (carbonate minerals and microbial biomass) phases.In the near-field modelling, the C-14 labelled gas released is in the form of methaneand carbon dioxide (Small et al., 2011a). In these calculations, it is assumed that the3
Page 3: Les thèmes du portail Leçon 3Néa
Page 7: QRS-1443ZH-1, Version 3.0SummaryThe
Page 11: QRS-1443ZH-1, Version 3.01 Introduc
Page 15 and 16: QRS-1443ZH-1, Version 3.0case, it i
Page 17 and 18: QRS-1443ZH-1, Version 3.0consumed d
Page 19 and 20: QRS-1443ZH-1, Version 3.0relation t
Page 21 and 22: QRS-1443ZH-1, Version 3.0In the RDA
Page 24 and 25: Table 3-2: Rn-222 Inventory Informa
Page 26 and 27: Please see Table 5-1 of Limer et al
Page 28 and 29: contribute substantially to the tot
Page 30 and 31: Calculated Effective Ingestion Dose
Page 32 and 33: (a)Annual Effective IngestionExposu
Page 34 and 35: calculated annual ingestion dose fo
Page 36 and 37: Figure 5-7: Average Decay Corrected
Page 38 and 39: Figure 5-9: Calculated Effective An
Page 40 and 41: Table 5-5: Calculated Annual Effect
Page 42 and 43: Table 5-7: Calculated Annual Effect
Page 44 and 45: Table 5-9: Calculated Effective Inh
Page 46 and 47: Table 5-11: Calculated Effective In
Page 48 and 49: throughout. The reference case is h
Page 50 and 51: EDAVaults_NoCap@10000y and Vaults15
Page 52 and 53: area of the cap over vault 8 were t
Page 54: the Nuclear Decommissioning Authori

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