The UK Approach - the Initial Radiological Assessment Methodology Laura Newsome Scientist – Environment Agency September 2009

Structure Background to UK situation The Environment Agency’s responsibilities Summary of Initial Radiological Assessment Methodology Answers to questions

Who does what in the UK?

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

Summary of criteria for public exposure Public dose limit future and historical discharges and future direct radiation from the site and other sources excluding medical and natural 1.0 mSv/yr Site constraint future discharges from a site with more than one operator 0.5 mSv/yr Source constraint future discharges and future direct radiation from a facility or group of facilities 0.3 mSv/yr Threshold of optimisation future discharges and future direct radiation from a facility 0.02 mSv/yr Potentially of no regulatory concern future discharges and future direct radiation from a facility <0.01 mSv/yr

Who do we regulate?

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

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

Example model – release to air Exposure Group Exposure PathwaysDefault model assumptions Release to air Local resident family Inhalation of radionuclides in the effluent plume Release at ground level Local resident is located 100m from the release point Food is produced at a distance of 500m from the release point External irradiation from radionuclides in the effluent plume and deposited on the ground Consumption of terrestrial food incorporating radionuclides deposited to the ground

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

Initial Radiological Assessment Tool

Critical group <0.02 mSv/yr Critical group >0.02 & <0.3 mSv/yr Critical group <0.02 mSv/yr Critical group >0.02 & <0.3 mSv/yr Critical group >0.3 mSv/yr Step by step method Refine assessment or undertake site specific assessment Further refinements or site specific assessment Initial source assessment - simple & cautious assessment of critical group dose Refine assessment more realistic by using scaling factors and habits data Permit may be acceptable on RP grounds. Permit unlikely to be acceptable on RP grounds Critical group >0.3 mSv/yr No further assessment required on Radiation Protection grounds. Permit likely to be acceptable. Critical group >0.02 & <0.3 mSv/yr

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

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

Thank you