Baldwin TD and Hicks TW, Assessment Calculations for Human ...

0977-6Version 10.000160.000140.00012Dose (mSv)0.000100.000080.00006TotalExternalIngestionInhalation0.000040.000020.000002000 3000 4000 5000 6000 7000Year (CE)Figure 6.6Dose from different exposure pathways for drilling intrusion (B1a) atgrid cell C10 (Vault 15) (Case A).6.1.2 B1b – Geotechnical Investigations: Trial Pit ExcavationsFigure 6.7 and Figure 6.8 show the total dose to a worker during a trial pit intrusion atdifferent locations across the facility at the year 2230 and at the year 7000,respectively.The assumed depth of the trial pit (4.5 m) results in intrusion into all vaults. Themaximum calculated dose resulting from trial pit excavation at 2230 is 1.5 x 10 -5 mSvand occurs in grid cell E11 (Vault 20). As shown in Figure 6.9 and Figure 6.10, afterdecay of 137 Cs, the dose to the intruder occurs primarily from 94 Nb via externalirradiation, and from 239 Pu via the dust inhalation exposure pathway.As discussed in Sections 2 and 5.2, it has been assumed that an engineer could beinvolved in excavating 20 trial pits at the site. If the 20 trial pits were excavated intoVault 20 at 2230, the dose received by the worker would be about 3.0 x 10 -4 mSv.However, if the trial pit locations were randomly selected across the site, the totaldose received would be lower – the calculated dose received by a worker at differentlocations across the EDA at 2230 ranges from 7.3 x 10 -6 mSv in grid cell E10(Vault 17) to 1.5 x 10 -5 mSv in grid cell E11 (Vault 20). By the year 7000, thecalculated dose received at any location is less than about 3 x 10 -6 mSv.Galson Sciences Ltd 25 21 March 2011