Limer LMC and Thorne MC, Assessment Calculations for Radon for ...

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Table 8-3: Biosphere and Exposure FEPs for Rn-222 AssessmentFEP ID FEP Name Included intheAssessmentModel?CommentGAS_Rn_B_RBEM_01 Release to open air No Exposure to radon inoutdoor air is notconsidered due to therelatively lowconcentrations, andnegligible doses,anticipated (e.g. Sumerling,2008).GAS_Rn_B_RBEM_02Entry and accumulationin buildingsYesGAS_Rn_B_RBEM_03 Empirical relationships YesGAS_Rn_B_RBEM_04GAS_Rn_B_RBEM_05Occupancy and humanhabitsDose factors for radonand radon daughterexposureYesNoGAS_Rn_B_RBEM_06 Other sources of radon NoOccupancy treated as adeterministic parameterImplicit in Rn-222 dosefactorReferencesLean C and Willans M (2010). A Features, Events and Processes and UncertaintyTracking System to support the 2011 ESC. National Nuclear Laboratory Reportprepared for LLW Repository Ltd, NNL (09) 10762, Issue 1.1, March 2010.72
QRS-1443ZG-1, Version 3.0Appendix B: Comparison with Previous LLWRAssessment ResultsThere are a range of differences between the assumptions made in the 2011 ESC andthose made for previous LLWR assessment calculations (McGarry, 2003; Ball et al.,2008; Sumerling, 2008). Differences include, for example, the inventory and itsdistribution, the volume of the regions of the facility, the diffusion coefficient of radon,the path length from the waste to the surface.In the 2002 ESC gas pathway assessment (McGarry, 2003), the diffusion path lengthsassociated with the trenches and vaults were 6.5 and 4.9 m respectively. In all casesconsidered in the 2002 ESC, the highest calculated peak exposure from the indoorinhalation of Rn-222 13 was associated with Vault 8. For the best estimate calculation,using an Rn-222 diffusion coefficient of 5.0E-7 m 2 s -1 (Lee, 2002), the peak exposurearising from indoor inhalation of Rn-222 over Vault 8 was calculated to be 8.33E-3 mSv.Increasing the diffusion coefficient to 1.0E-6 m 2 s -1 resulted in the calculated peakexposure over Vault 8 increasing to 8.00E-2 mSv. Decreasing the path length to 1 m,but keeping the diffusion coefficient as the best estimate case, lead to the calculatedpeak exposure over Vault 8 increasing to 1.23E-1 mSv. That this calculated exposure islower than that calculated in the 2011 ESC can be explained by the difference ininventory assumed for Vault 8 (2.3E-1 TBq was assumed for Vault 8 in 2002) and thediffusion coefficients assumed (1E-5 m 2 s -1 in the 2011 ESC, as compared to 5.0E-7 m 2 s -1in 2002).In the 2008 R2S9 Submission, for the situation of the engineered cap remaining intact,the level of release of radon gas from the LLWR was expected to be very low, such thatdoses would be imperceptible above the natural levels of radon in outdoor air locally(Ball et al., 2008; Sumerling, 2008). This has also been demonstrated in the 2011 ESCcalculations.For human intrusion, three possible cases were assumed whereby a building wasconstructed on the cap, which varied in their assumptions as to the potential source ofRn-222 entering the building. Exposure from the inhalation of both Rn-222 and Rn-220were considered; the calculated annual exposures are given in Error! Reference sourcenot found.. These results agree within a factor of five with the 2011 ESC reference caseresults. As with the 2011 ESC, their most cautious case leads to the calculated dosefrom Rn-222 being greater than 3 mSv also.13 This exposure pathway was considered for the local resource dominated PEG.73
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The estimates of Rn-222 concentrati
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References 65Appendix A FEP Audit o
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This assessment provides the basis
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Section 2 describes the current kno
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likely to be extremely limited.Ther
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2.2 The Relationship of Rn-222 Conc
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Rearranging:C1 = 8 ⋅C− 2. 8 ⋅
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Table 2-2: Radon Measurements from
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Table 2-3: Radon Measurements from
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Figure 2-4: Spatial Distribution of
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The Rad 7 is a portable electronic
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Probe 1.6Probe 4.6Probe 4.12Probe 4
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Page 34 and 35: shown in Figure 2-8. Rn-222 concent
Page 37 and 38: QRS-1443ZG-1, Version 3.0ProbeTable
Page 39: QRS-1443ZG-1, Version 3.0would be e
Page 42 and 43: Probe 1.3Probe 2.3Probe 3.4Probe 2.
Page 44 and 45: 3 Radon Migration Processes through
Page 46 and 47: 3.2.1 Rn-222 Fluxes to the Ground S
Page 48 and 49: If there were a pathway comprising
Page 50 and 51: In addition, it is relevant to note
Page 52 and 53: 4 Indoor Concentration of Rn-222In
Page 54 and 55: GM indoor radon Bq m-34003503002502
Page 56 and 57: The analysis of UK data by BGS/HPA
Page 58 and 59: concentration is 39 Bq m -3 and the
Page 60 and 61: SummaryThe values obtained from the
Page 62 and 63: dose per unit EEC of 12.5 nSv per B
Page 64 and 65: 6 Summary of Assessment Assumptions
Page 66 and 67: A case is identified that assesses
Page 68 and 69: constitutes an unquantified conserv
Page 70 and 71: Table 7-3: Potential Annual Effecti
Page 72 and 73: Table 7-5: Potential Annual Effecti
Page 74 and 75: 8 Conclusions and SummaryThe assess
Page 76 and 77: Drever J I (1997). The Geochemistry
Page 78 and 79: McGarry R G (2003). Gas Pathway Res
Page 80 and 81: Appendix AFEP Audit of LLWR 2011 ES
Page 84: Table 8-4: 2008 R2S9 Submission - C
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Limer LMC and Thorne MC, Assessment Calculations for Radon for ...

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