Appendix CRF - Part 3 - Northamptonshire County Council

2 RADIATION RISKS FROM NORMAL OPERATIONS
2.1 RADIATION DOSE RATES AND EXTERNAL RADIATION RISKS
2.1.1 Augean employees engaged in the LLW operation
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VERSION 3, 14 July 2009
The radiation dose rates from a range of radionuclides have been calculated as part of the
supporting documents to the RSA93 application. Extracts from these documents, relevant to
the estimation of external dose, are reproduced in Appendix 1.
For all external dose scenarios, cobalt-60 is the limiting radionuclide (i.e. it gives rise to the
highest dose rates). For the purpose of this risk assessment, the following representative
dose rates, working patterns and estimated doses are used.
Work activity
Receipt of waste
consignments, including QA
and monitoring, etc.
Dose rate
(Sv/h)
10
2
Occupancy
(hours/year)
50
100
Estimated
annual dose
(mSv)
Transfer and placement of
waste in landfill. 2 100 0.2
Occupancy of covered waste
area
Summary
0.5
0.2
2 100 0.2
TOTAL ESTIMATED ANNUAL DOSE 1.1 mSv
The above estimates are likely to be conservative, and it is unlikely that the same
person(s) will be exposed during all the work activities listed above. Nevertheless, it
is reasonable to assume, for planning purposes, that annual external doses of the
order of 1 mSv per year might be associated with the LLW operation.
2.1.2 External radiation risks to other persons
Such persons might include other employees (i.e. not involved in the LLW operation), visitors
to site, etc. Such persons would be unlikely to be exposed to dose rates above 1 μSv/h, and
exposure times would be expected to be short. Consequently, it is expected that external
doses to such persons should be negligible.
External doses to members of the public (during and after the LLW operation) were
estimated in the RSA93 application, and are a small fraction of the 20 μSv/y dose constraint.
2.2 CONTAMINATION LEVELS AND INTERNAL RADIATION RISKS
The waste will be in closed containers (either steel drums or bulk bags) throughout the LLW
operation. Furthermore, waste consigners will be required to demonstrate that the external
surfaces of these containers are effectively free of loose contamination. Consequently,
contamination levels, and hence internal radiation doses, during normal operations are
expected to be negligible.
There is the potential for contamination and internal exposures arising from accidents, in
particular a damaged container. This is considered in the Section 3.
WS010001/ENRMF/CONSAPPCRF 645