Terrestrial Assessment

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Terrestrial Assessment

• Comparison of human and non human dose
  assessments for prospective new nuclear power
  stations

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Outline

• Background
• Human assessment (assumptions)
• Non-human assessment (assumptions)
• Comparison of the results from the two
  assessments
• Discussion of results?
• Summary/Issues for PROTECT

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• Background

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Background

• Assessment loosely based on proposed build of new
  nuclear power stations (AGR and PWR types)
• Terrestrial assessment looking at exposure to
• humans via foodstuff/living nearby
• Non-human species living in a (protected) Natura
  2000 site at approximately the same distance as
  that for humans
• Uses probable permitted discharge limits as input
• Single source of radioactivity to assessment
  assumed

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Map of proposed facility
Agricultural land used for food crops/milk
production 500m from aerial discharge
Humans living at 100m from site
Facility with sea discharge
Terrestrial Natura 2000 site 500m from aerial
discharge
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Permitted discharge limits

• In TBq per year

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• Human assessment

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Approach

• Modelled using the Environment Agency Initial
  Radiological Assessment Tool
• Prospective assessment
• Simple spreadsheet tool

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Assumptions

• Assumes a ground level release uniform
  windrose
• Exposure to humans is at 100m from discharge
  point assumed to be consuming high levels of
  locally sourced foods such as milk, beef, lamb,
  offal, green vegetables, root vegetables and
  fruit (sourced 500m from discharge point)
• Other beta modelled as I-131
• Noble gases modelled as C-14 (not available in
  ERICA)
• No direct shine assessment included (cant do it
  for non-human species yet)

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• Non-human assessment

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Assumptions

• Modelled terrestrial input concentrations through
  IAEA SRS19 transfer model
• Assumed ground level release
• Distance to receptor 500m
• Used ERICA tool Tier 2, assuming reference
  organisms in the assessment and using all default
  concentration ratios, occupancy factors, etc for
  terrestrial environment
• Other beta modelled as I-131
• Noble gases modelled as C-14

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AGR - Screened against 10 µGy/h
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PWR - Screened against 10 µGy/h
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• Results comparison

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Predicted dose rates - human
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Predicted dose rates - human
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Non- human results total doses µGy/h
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Non- human results total doses µGy/h
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Non- human results total doses µGy/h
C-14 is the main contributor
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Risk Quotients

• Human results compared to 1mSv/y
• Biota results compared to 10 and 40 µGy/h
• (EA uses 40 as action value currently)

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Risk Quotients

• Human
• AGR RQ of 3
• PWR RQ of 14
• Biota v 10 µGy/h (using reptile as most affected)
• AGR RQ of 0.14
• PWR RQ of 0.64
• Biota v 40 µGy/h (using reptile as most affected)
• AGR RQ of 0.035
• PWR RQ of 0.16

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Risk Quotients

• Human
• AGR RQ of 3 0.36 (using Ar-41 not C-14)
• PWR RQ of 14 0.23 (using Ar-41 not C-14)
• Biota v 10 µGy/h (using reptile as most affected)
• AGR RQ of 0.14
• PWR RQ of 0.64
• Biota v 40 µGy/h (using reptile as most affected)
• AGR RQ of 0.035
• PWR RQ of 0.16

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• Open discussion of results

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• Summary/Issues for PROTECT

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Issues/Future

• Include noble gases in the non-human assessments
  (unsure of actual dose predictions)
• However human and biota results should change
  proportionally if/when noble gases are included
  in biota assessments
• This is a simple terrestrial only assessment
  (note in EWs no terrestrial habitat assessments
  ever triggered at Stage 2)
• Need to expand evaluation for purposes of ICRP
  Committee 4 (include ICRP approach in
  assessment?)
• Combine terrestrial and aquatic assessments