The UK Approach the Initial Radiological Assessment Methodology

1
The UK Approach - the Initial Radiological
Assessment Methodology

• Laura Newsome
• Scientist Environment Agency
• September 2009

2
Structure

• Background to UK situation
• The Environment Agencys responsibilities
• Summary of Initial Radiological Assessment
  Methodology
• Answers to questions

3
Who does what in the UK?
4
Legislation for UK regulation

• Radioactive Substances Act 1993
• Euratom Basic Safety Standards Directive 1996
• Ionising Radiation Regulations 1999
• Radioactive Substances (Basic Safety Standards)
  (England and Wales) Direction 2000
• Principles document 2002

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Summary of criteria for public exposure
6
Who do we regulate?
7
How do we regulate discharges?

• Use of permit system under RSA 93. Part of
  permit determination involves radiological
  assessment
• Initial Radiological Assessment Methodology is
  used to complete prospective assessments and set
  authorisation limits
• Spreadsheet based tool
• Easy to use
• Cautious but consistent assumptions
• PC CREAM used for detailed site assessments

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Initial Radiological Assessment Methodology

• 100 radionuclides
• Critical Group members of the public
• Seven different groups of the public
• Four age groups (offspring, infant, child, adult)
• Releases via air, estuary/coastal water,
  river/stream, public sewer

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Example model release to air
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Initial Radiological Assessment Methodology

• Dose Per Unit Release (DPUR)
• Assessment of continuous uniform releases
• Dose assessed in 50th year of release
• Ingrowth of progeny included if significant
  ingrowth likely to occur in 50 year period
• Also includes assessment to non-human biota

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Initial Radiological Assessment Tool
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Step by step method
Initial source assessment - simple cautious
assessment of critical group dose
Critical group lt0.02 mSv/yr
Critical group gt0.02 lt0.3 mSv/yr
Critical group gt0.3 mSv/yr
Refine assessment or undertake site specific
assessment
Refine assessment more realistic by using scaling
factors and habits data
No further assessment required on Radiation
Protection grounds. Permit likely to be
acceptable.
Critical group lt0.02 mSv/yr
Critical group gt0.02 lt0.3 mSv/yr
Critical group gt0.3 mSv/yr
Further refinements or site specific assessment
Permit may be acceptable on RP grounds.
Permit unlikely to be acceptable on RP grounds
Critical group gt0.02 lt0.3 mSv/yr
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Limitations

• Inflexible - fixed locations and critical groups
• Conservative approach overestimation
• Not suitable for lt 1yr releases
• Does not apply to the disposal of radioactive
  waste to land or discharge to lakes
• Dose Per Unit Release factors are not appropriate
  for the direct external radiation dose pathway

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Answers to questions that I havent yet covered

• Transfer co-efficients
• Databases of PC CREAM
• Standard compilations such as IAEA TRS ICRP
  publications
• Other robust compilations
• Scaling, analogues, one-off analytical
  calculations
• Atmospheric modelling
• DPUR for atmosphere derived using PC CREAM
• Gaussian plume model
• Most parameters fixed

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Thank you Laura.Newsome_at_environment-agency.gov
.uk John.Titley_at_environment-agency.gov.uk