Environmental Assessments On Radioactive Material Discharged Into City Sewers

1
Environmental Assessments On Radioactive Material
Discharged Into City Sewers

• ???????????????

???
2
Where does the radioactivity in sewer coming from
naturally occurring radionuclides
Radium-226
liquid radioactive wastes from these non-nuclear
establishments to the public sewer systems are
permitted in the UK under authorisations issued
by the Environment Agency (England and Wales) or
the Scottish Environmental Protection Agency
under the provisions of Radioactive Substances
Act 1993
hospitals
Iodine-131
university laboratories
Carbon-14
pharmaceutical industry
Tritium
research facilities
Americium-241
3
Most common radionuclides found in the sewage
treatment work (STW)
4
Sewage Treatment Model - Conceptual model
5
Sewage Treatment Model - Conceptual model
Surface run-off
bypass STW
river
overflow
Preliminary screening
Tertiary micro-straining etc
Primary sedimentation
Secondary percolating/activated
Public sewer system
effluent
sea
clean waste
Radionuclides partition onto sludge
Landfill
Effluent treatment
Imported sludge
Sludge treatment
Sludge mixing
Initial processing thickening
non-radioactive
Stabilisation digestion, composting
radioactive
De-watering drying
De-watering drying
Incineration multiple hearth or fluidized bed
slurry
air
sludge
cake/pellet
ash
landfill
agricultural land
6
Radionuclide transport in the environment and
human exposure pathways
7
Sewer model and other model involved

• Sewer treatment work (STW) model

• River model
• Farmland model
• Plume transport model (incineration)
• Marine model
• Landfill model (including geosphere transport
  model)
• Sludge spread model (arable land and pasture)

8
Sewer model interface
9
Some illustrative calculation
Workers dose at recovery stage
10
Some illustrative calculation
Public dose raised from effluent and sludge
disposa
11
Summary
A model has been developed to assess doses
arising from authorised disposals of
radionuclides to sewers. Dose to workers and
member of the public can be calculated, it can be
used for normal assessment and assessment at
emergency situation. Work shows that the dose are
well below the maximum public dose constraint of
300 mSv y-1 for a single practice.