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

likely to be extremely limited.Therefore, a cautious, but reasonable basis forassessment is to use the initial Ra-226 inventory as a basis for calculation.Inventory of Ra-226 in the Trenches and VaultsRa-226 activity in the trenches is not uniformly distributed. For example, of the total0.29 TBq of Ra-226 in the trenches, over 95% of that activity is in Trenches 2 and 3 (Ballet al., 2008). These two trenches contain between 1 and 10% of the total Ra-226 activityanticipated to be disposed of at the LLWR, i.e. accounting for future Ra-226 arisings inthe vaults (Wareing et al., 2008).There is considerable uncertainty over future arisings of Ra-226 LLW that mightpotentially be acceptable for disposal at LLWR, although based on current information(Harper, 2011) much of the Ra-226 inventory in the vaults is expected to arise fromwaste generated during land remediation. The Ra-226 inventory data from Serco(2011) is given in Table 2-1, from which it is clear that, based upon the assumptionsused in deriving the inventory, a large proportion of the total projected future Ra-226inventory is currently anticipated to be disposed of in Vault 8 (84% of the total Ra-226inventory); a plan of the LLWR layout is given in Figure 2-2.Figure 2-2: Plan View of the Cap Design (6 April 2010; adapted from Paulley andEgan, 2010)6