EMRAS II – Working Group 1 Reference Methodologies for Controlled Discharges

1. EMRAS II – Working Group 1Reference Methodologies for Controlled Discharges Justin Smith

2. Response to questions • 1 )Nuclear context: what types of facilities does your methodology cover? • Almost any type of facility where discharges occur to atmosphere, sea (European waters) or rivers and can be considered as continuous and constant. • 2) National Organisation: who is the authority in your country? What types of manufactures do you have? Who are the experts? • Environment Agency, SEPA. • Nuclear industry activities, NORM activities, radiopharmaceuticals. • Advice on Radiation Protection from HPA, EA, SEPA, FSA and NDAWG

3. Response to questions • 3) Do you use critical group concept? Or the new ICRP version of it? • We consider them to be the same in practice and we believe ICRP description is equivalent. However, because critical group terminology is still used in UK legislation we are still using it. We will move to representative person in due course so in state of transition. • 4) What are the regulatory limit values? Are they doses? Are they concentrations? Or other units? • Annual dose limit 1mSv from all sources, annual dose constraint 0.3 mSv for a single source, annual site constraint 0.5 mSv for a number of operations on a single site. • < 20 uSv annual (~ 1 e6 per year) is EA (Cm 2919 white paper) threshold of optimisation ie if BPM no further reduction need be sought. • Operator will seek an authorisation (under RSA 93) from EA or SEPA and discharge limits will be set on the basis that the practice has been optimised and no dose constraints or limits exceeded.

4. Response to questions • 5) What modelling approaches do you use? • Equilibrium models, compartmental models (marine, river, terrestrial food), Gaussian plume model (finite and semi-infinite cloud gamma models), empirical models for external exposure and resuspension. • Designed for continuous and constant discharges. • 5a) Do you transfer coefficients? (if so which ones?). • Yes. • Terrestrial activity concentration ratios between soil and plant, and between feed and meat, liver and milk. • For river and marine environments activity concentration ratios between filtered water and sediments and biota. • Sources include IAEA (Safety Series No 19, 2001 and TRS 364), NCRP (Screening models for releases of radionuclides to atmosphere, surface water, and ground. NCRP Report No 123I , 1996) and Coughtrey (Radionuclide distribution and transport in terrestrial and aquatic ecosystems. A compendium of data. 1985)

5. Response to questions • 5b) What type of atmospheric modelling do you use? • Gaussian plume model. • (Investigating use of NAME III) • 5c) Do you use site specific data? • Yes, but depends on the type and extent of the assessment eg for a large study looking at many sites generic habit data may be used. • Other issues: Collective dose, short term planned releases

6. PC-CREAM 08 • CEC report ‘Methodology for evaluating the radiological consequences of radioactive effluents release in normal operations’ (1979) • EC report ‘Methodology for assessing the radiological consequences of routine releases of radionuclides to the environment’ (1995) + PC-CREAM 98 • New methodology + PC-CREAM 08

7. Typical applications • Prospective assessments: • discharges from a single site at a constant annual release rate • for comparison of annual dose in e.g. 50th year, with dose limit and constraint • Retrospective assessments: • past or current doses from a single site if discharges can be approximated to a constant annual release rate • Calculation of collective doses for comparative purposes

8. Typical applications • Atmospheric • Inhalation of plume • External gamma and beta from cloud • External gamma and beta from ground • Inhalation of resuspended material • Ingestion of cow meat, cow liver, cow milk, sheep meat, sheep liver, green vegetables, root vegetables, fruit# and grain • Marine • Inhalation of seaspray# • External gamma and beta from sediments • External gamma and beta from fishing gear# • Ingestion of seaweed#, fish, molluscs and crustaceans • River# • External gamma and beta from sediments • Ingestion of fish and drinking water #Not available for collective dose assessments

9. Typical applications Habit data, Population and Agricultural production distributions Dose Coefficients Doses to people and populations Source of Radionuclides Transfer in in Environment Exposure pathways Discharge to atmosphere Pasture Cow Milk Human

10. Typical applications • PC CREAM uses effective dose • as defined in ICRP Publication 60 • dose coefficients from ICRP Publication 72 • committed to age 70 • 3 age groups • 1 year old infants • 10 year old children • Adults (For fetus advice given in Methodology report)

11. System structure Database User input Results GUI Input summary Fortran DLLs

12. Models Models Datasets Plume Farmland Granis Resus Cloud beta Ground beta Assessor – atmospheric individual and collective

13. Models • Plume – Gaussian plume model (R91): activity concentrations in air, deposition rates and cloud gamma dose rates for specified release rate. • Farmland – Compartmental model for soil, vegetation and animals: activity concentrations in foods per unit deposition rate. • Granis – Compartmental model for soil and gamma dose from infinite plane: time integrated ground gamma dose per unit deposition rate over one year. • Resus – Garland model for resuspension: time integrated activity concentration in air per unit deposition rate over one year. • Datasets – Cloud beta dose rates per unit air concentration (DOE/EH-0070) and ground beta dose rates per unit deposition (Holford 1989 Supplement…)

14. Models • Doris – Compartmental model for north European waters and Mediterranean Sea: activity concentrations in marine foods, water and sediments Doris Assessor – marine individual and collective

15. Models • Rivers – Screening dilution model or dynamic compartmental model: activity concentrations in fish, water and sediments River screening River dynamic Assessor – river individual only

16. Improvements and new features • Implementation of an extensive database to hold all data related to the dose assessment calculation. • Development of an improved graphical user interface. • The database includes an increased number of default sites • A comprehensive list of radionuclides. • Better treatment of progeny radionuclides.

17. Improvements and new features • PLUME – deposition of progeny which have a different deposition velocity to that of the parent; change the meteorological parameters; run for several stack heights at once. • GRANIS –It is easier to define the materials that comprise each soil layer and these can be stored for later use. • RESUS – includes contribution to the resuspended activity concentration in air from the first day after the initial deposition. • FARMLAND – includes review of model parameters and a revised fruit model.

18. Improvements and new features • Dynamic river model – revised to include transfer from filtered water to bed sediment. Includes default data describing some major European rivers. Review of water treatment values, Kd and CF values • DORIS – revised following the MARINA II study (EC, 2003); increases the extent of the region modelled; better represents the remobilisation process.

19. Improvements and new features • ASSESSOR, has been updated to make it easier to select the model results that will be used in the assessment and to provide greater flexibility when defining the habits of individuals. Radionuclide and pathway breakdowns are provided for all dose estimates including marine collective doses.

20. Progeny in models • In general the first radioactive progeny not in secular equilibrium (SE) on the timescales of interest is modelled although some parts of the system model the full radioactive decay chain. • Plume - first progeny not in SE over 3 minutes • Farmland – first progeny not in SE over 1 year • Granis – full chain • Resus – first progeny not in SE over 1 year • Doris – full chain • Rivers – no progeny

21. Progeny in Assessor • Aquatic external exposures • Fishing gear: uses mean gamma and beta energies which take account of progeny in SE • Ground shine from sediments: uses mean gamma energies and beta dose coefficients which take account of progeny in SE • Atmospheric external exposures • Cloud shine: uses binned gamma energies and beta dose coefficients for individual nuclides (exception where +d notation is used) • Ground shine: binned gamma energies for individual nuclides dose coefficients for deposited beta which include progeny • Inhalation dose coefficients include progeny, (progeny in SE in seaspray ignored) • Ingestion dose coefficients include progeny, (progeny in SE in food ignored)

22. Current status • Current version of PC-CREAM 08 (1.0.1.2/1.0.2) is complete • Updated version of methodology report (RP 72) to be published • Dedicated website under development • Training courses planned • Oct 27-28 2009 • provisionally Mar 2-3, Jun 29-30 and Oct 26-27 2010

23. The future Future development to the system may include: • Ability to use output from other atmospheric dispersion models • Inclusion of collective dose calculations for discharges to rivers • Inclusion of a sewers model • Revised population and agricultural production grids