Appendix CRF - Part 3 - Northamptonshire County Council

Radiological Assessment 0820-2
Version 2
For pathways involving drinking water or other transitory exposures such as
aerosols, it is assumed that dissolution is gradual and an annual release to
leachate is used to calculate releases and doses.
These pathways are distinguished because in the former case radionuclides will
accumulate in the soil and an assessment effectively based on a single year would not
be demonstrably conservative.
The closest analogue for landfill disposal is the trench disposals at the LLWR near
Drigg. A comparison of the annual discharges through the marine pipeline (BNFL
2002a) with estimates of the disposed inventory (BNFL 2002b) indicates that a factor
of at least 1x10 -3 year -1 should be applied to determining what fraction of the
inventory might be in leachate. Initial concentrations, and concentrations of more
insoluble radioelements, would probably be lower than this, but this factor has been
used in this assessment for all radionuclides as a conservative assumption.
3.3 Supplementary calculations
In addition to a radiological assessment based on the pathways and scenarios included
within the SNIFFER methodology, two supplementary calculations have been
undertaken. These relate to potential doses from the treatment and discharge of
leachate at an off-site water treatment plant, and to possible radiological effects on
wildlife.
The SNIFFER methodology includes a leachate spillage scenario, which is modelled
as a release of leachate to a water body (e.g., river, lake) that is then exploited as a
water resource (e.g., drinking, fishing). This scenario and modelling treatment is
intended to address accidental releases and not routine discharges. At the ENRMF,
leachate is collected and sent by tanker to a water treatment plant at Avonmouth.
Following treatment, water is then discharged to the Severn Estuary. Potential doses
arising from the leachate treatment and discharge are not included within the
SNIFFER methodology and have been separately assessed using the Environment
Agency’s Initial Radiological Assessment - Sewer methodology (Environment
Agency 2006a; 2006b).
Discharges and migration of radionuclides from a disposal facility might have a
detrimental effect on non-human species or more general environmental effects such
as damaging habitat quality. The guidance from the Environment Agencies includes a
requirement to ensure that all aspects of the accessible environment are protected:
The developer/operator should carry out an assessment to investigate the
radiological effects of a disposal facility on the accessible environment both
during the period of authorisation and afterwards with a view to showing that
all aspects of the accessible environment are adequately protected.
Although there is no specific evidence that there might be a threat to populations of
non-human species from the authorised release of radioactive substances if people are
protected, environmental damage might occur to areas and habitats that are not
extensively exploited by people. Furthermore, there is a specific need to be able to
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