Appendix CRF - Part 3 - Northamptonshire County Council

point source with a 10 microSv/hr doserate at 1 metre, assuming that the
member of the public is located 50 metres from the waste. The doserate at 50
metres can be estimated from:
D1=D2 (X2 2 /X1 2 )
Where, D1 and D2 = doserate at positions 1 and 2
X1 and X2 = the distance from the source at positions 1 and 2
This gives an estimated maximum doserate at 50 metres of 4E-3 microSv/hr. If
the person stands in that location for 8 hours per day and there is waste at the
maximum level in that location every day then the person would receive 12
microSv per year. This is based on conservative assumptions and is within the
20 microSv per year lower bound dose criterion.
Under the same assumptions but with a 100 metre distance to the person, the
maximum estimated dose would be 3 microSv/yr.
These calculations do not take into account the significant shielding afforded by
the soil screen bund at the boundary of the site.
8.2 Pre-Closure – expected to occur
Exposure from Gas Generation from the Landfill
8.2.1 The dose criteria are the legal limit to workers of 20 mSv/yr, the site criterion of 1
mSv/yr for workers, the dose guidance level of 0.02 mSv/yr for the public and the
dose constraint for the public of 0.3 mSv/yr.
8.2.2 The impacted groups during the pre-closure phase are the public and workers.
8.2.3 The assessment is contained within Annex B, section 5.5.
8.2.4 The scenario is radioactive gas release from the landfill in the pre-closure phase.
Annex B indicates that the worst case is for Ra-226 in both the case of the
worker and the public. For this worst case and using a worker dose criterion of 1
mSv/yr the capacity of the landfill to take only Ra-226 would be 8.4E9 MBq (42
million tonnes at 200 Bq/g). For this worst case and using a public dose criterion
of 0.02 mSv/yr the capacity of the landfill to take only Ra-226 would be 81E6
MBq (403 thousand tonnes at 200 Bq/g).
8.2.5 This scenario has the potential to constrain landfill capacity for the public
exposure case but not for the worker case (because the landfill is physically
smaller than the radiological capacity).
Application for disposal of LLW including HV-VLLW under RSA 1993,
for the East Northants Resource Management Facility:
Supporting Information
July 2009
61
WS010001/ENRMF/CONSAPPCRF 380