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 Agency’s 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

5. 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

8. 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

9. Example model – release to air

10. 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

11. Initial Radiological Assessment Tool

12. Initial source assessment - simple & cautious assessment of critical group dose Step by step method Critical group <0.02 mSv/yr Critical group >0.3 mSv/yr Critical group >0.02 & <0.3 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 <0.02 mSv/yr Critical group >0.02 & <0.3 mSv/yr Critical group >0.3 mSv/yr Further refinements or site specific assessment Permit unlikely to be acceptable on RP grounds Permit may be acceptable on RP grounds. Critical group >0.02 & <0.3 mSv/yr

13. Limitations • Inflexible - fixed locations and critical groups • Conservative approach – overestimation • Not suitable for < 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

14. Answers to questions that I haven’t 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

15. Thank you Laura.Newsome@environment-agency.gov.uk John.Titley@environment-agency.gov.uk