Appendix CRF - Part 3 - Northamptonshire County Council

Radiological Assessment 0820-2
Version 2
site workers, using mechanical handling to emplace the waste packages and soil cover
or working near-by, may be exposed. Occupational dose assessments will be made
separately from this report.
4.1.6 Leachate collection and management procedures
Leachate levels at the ENRMF are maintained by pumping excess leachate to tankers
and transporting this leachate to a water treatment plant at Avonmouth. There may be
periods when this route is unavailable – leachate could be re-circulated to the upper
parts of the site but leachate would not be used for dust suppression or other processes
that could lead to aerosol formation at the site.
The radiological assessment includes two scenarios that could result in doses to offsite
exposed groups:
Tanker accident resulting in spillage of leachate and contamination of a water
resource.
Routine treatment of leachate and discharge of treated water to an estuary.
The first of these scenarios has been considered using the SNIFFER methodology as
discussed below. The second of the leachate scenarios has been considered by means
of supplementary calculations described in Section 4.4.
4.1.7 Leachate spillage
Notwithstanding any radioactive components, landfill leachate poses a hazard to the
environment if spilt and any road accident involving loss of an entire load would be
subject to mitigation measures. Leachate that did enter water resources would also
become diluted. For this assessment, it is conservatively assumed that an entire
tanker load of leachate (30 m 3 of leachate) reaches a small reservoir (2 x 10 6 m 3 ) that
is used for drinking water, irrigation and fishing.
The dissolved radionuclide concentration, CRn,leachate (Bq m -3 ) in the leachate
associated with an inventory ARn (Bq), is given by:
C Rn,
leachate
V
ARn
Df
Galson Sciences Limited 32 14 July 2009
landfill
where Vlandfill is the volume of the waste (m 3 ).
Df is the dissolution factor (-).
waste is the porosity of the waste (dimensionless).
is the degree of saturation of the waste (dimensionless).
Parameter values used in the calculation of radionuclide concentrations in leachate are
listed in Table 4.2.
waste
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