R01037: Uncertainties in assessing doses to members of the public due to radioactive discharges to the marine environment
Wednesday 3 September 2003
This research project aims to improve the accuracy and precision of dose assessments by investigating uncertainty in the process.
Study Duration: April 2000 to December 2001
Contractor: The Centre for Environment, Fisheries and Aquaculture Science (CEFAS)
Background
This work aimed to provide an appreciation of the uncertainties involved in the assessment of doses from the discharge of radioactive waste to the marine environment. Sensitivity analyses of these uncertainties would indicate their influence on dose outputs. Further research could target areas of greatest uncertainty. The ultimate achievement would be an improvement in the accuracy and precision of assessments.
Research Approach
The system of modelling dispersion, uptake and dosimetry was broken down into the following components: the underlying assumptions of the CEFAS models (WAT and ADO); assumptions and uncertainties about the discharged effluent; the uncertainty of the values of the parameters that feed the models; uncertainties in the habits and consumption data obtained from surveys of the local people. These were investigated through either desk study or sensitivity analysis of the model to input parameters. The likely range of parameter values was established through consultation with experts at CEFAS.
Results and findings
Sediment parameters can introduce a very large uncertainty into model predictions with respect to particle-reactive radionuclides. With radionuclides that have a low affinity for sediment, variation in concentration factors appears to contribute the greatest uncertainty. A significant uncertainty is introduced from the International Commission on Radiological Protection (ICRP) data used for internal dosimetry. Calculations of radiological concentrations are sensitive to the residual velocity of the body of water, and to mean depth for the advection-diffusion model. The tidal excursion (for both water concentration models), discharge start/end times (advection-diffusion model) and mean depth (single compartment model) are all relatively insensitive to variation in their values. The report may be used to determine where effort could be most effectively spent for specific discharge sites and scenarios. However, it is recommended that a probabilistic assessment be made to quantify the distribution of parameter values. This project complements project R01036: a probabilistic modelling suite for the marine environment.
Dissemination information
Final report is available from the FSA Library and Information centre. To obtain a copy, please contact the Enquiry Desk, Dr. Elsie Widdowson Library and Information Services, Food Standards Agency (020 7276 8181/8182 or at library&info@foodstandards.gsi.gov.uk).
Contact: David Webbe-Wood
Tel: 020 7276 8742 (Intl. +44 (0) 20 7276 8742)
Email: david.webbe-wood@foodstandards.gsi.gov.uk