Appendix CRF - Part 3 - Northamptonshire County Council

Radiological Assessment 0820-2
Version 2
There is potential, during leachate management or spillage, for the production of
aerosols which could lead to doses via the inhalation pathway. Other pathways, such
as external irradiation from deposited aerosols or ingestion of foodstuffs contaminated
by aerosols would give specific doses that are comparable to or less than the
inhalation pathway.
The concentration of aerosols at time t, CRn,air,aero(t) (Bq m -3 ), created during leachate
management or spillage is assumed to be equivalent to the concentration of the
leachate diluted by the aerosol load:
aerosol
t)
C
1000
CRn, air,
aero ( Rn,
leachate
where aerosol is the aerosol concentration (kg m -3 of air).
CRn,leachate is the activity of radionuclide, Rn, in the leachate at time t (Bq m -3 ).
1000 is the density of water (kg m -3 ).
The above equation cautiously assumes that the aerosols are non-depleting during
passage towards the exposed individual. An aerosol concentration of 0.001 kg m -3 of
air is assumed.
Exposure to aerosols at the ENRMF or during a tanker accident will be abnormal and
short-lived. An initial assessment of the potential impacts from routine, off-site
leachate management has been made using the Environment Agency’s methodology
and the assumption that doses from water treatment would be similar to doses from
sewage treatment.
The Environment Agency’s methodology allows for a range of exposure groups
affected by releases to a public sewer, depending on the discharge route for treated
effluent. For this assessment, only the groups associated directly with operation of
the treatment plant, farming of land conditioned by sludge or using the estuary are
considered. These groups and the relevant exposure pathways are:
Sewage treatment workers (adults only)
Galson Sciences Limited 34 14 July 2009
( t)
External irradiation from radionuclides in raw sewage and sludge
Inadvertent inhalation and ingestion of raw sewage and sludge containing
radionuclides
Farming family living on land conditioned with sewage sludge
Consumption of food produced on land conditioned with sludge and
incorporating radionuclides
External irradiation from radionuclides in sludge conditioned soil
Inadvertent inhalation and ingestion of sludge conditioned soil
Fisherman family (estuary/coastal water receives treated effluent from sewage
works, typically via a river)
WS010001/ENRMF/CONSAPPCRF 584