Biosphere impact models

Compliance with basic radiation protection rules requires the assessment of the radiological exposure resulting from planned activities, historical pollution or accidents, or the dose reduction following the application of countermeasures. Therefore, models and model codes are developed (BIOSPHERE, DosDiM, DosDiMEco) to predict the dispersion of radionuclides in the biosphere and the resulting radiological exposure to man and environment.

• Impact assessment of routine and accidental discharges on man and environment

We participated in the EU BioMoSa project which objectives were to implement the reference biosphere methodology developed in the IAEA program BioMAss (Biosphere Modelling and Assessment methods). We used this methodology in order to increase the transparency of biosphere modelling, evaluate the importance of the different radionuclides and pathways, and enhance public confidence in the assessment of potential radiological dose to future population groups.

We contributed to the IAEA-EMRAS program on model validation for radionuclide transport in the aquatic systems.

• Contribution to the performance assessment for the disposal of radioactive waste

For demonstrating compliance of nuclear waste disposal with current radiation protection standards, the radiological impact due to hypothetical releases of radionuclides into the biosphere is the principal safety indicator. However the assessment of the radiological impact to future exposure groups is associated with inherent uncertainties.
The reference biosphere concept has been developed and is adjusted where and when required. There is a continuous effort in determination of the assessment context, the description of biosphere system and exposure groups, the identification of applicable Features Events and Processes (FEPs) in the determination/quantification of selected FEPs. The BIOSPHERE code is adapted accordingly and the biosphere parameters data base (DCFs) is updated. These activities are carried out both for the high level waste and low level waste disposal programme of NIRAS/ONDRAF in collaboration with our colleagues of Performance Assessment.

• Development of methods for the evaluation of remediation options for contaminated sites

SCK•CEN has been involved in an international comparison exercise under the IAEA EMRAS programme where the radiological impact of a hypothetical NORM waste dump site and the effect of corrective actions had to be assessed. The outcome of different radiological assessment models was compared.

The importance of this work is two-fold:

• Remediation of sites contaminated by NORM is a current issue in many countries world wide. In recent years, new radiation protection legislation, growing awareness of radiation risks at some sites have created the necessity to develop remediation strategies for those sites. These strategies can be based on the exploration of hypothetical scenarios, where different exposure pathways are screened as was the objective of the IAEA-exercise.
• Secondly, by participation in these model comparison exercises, we test the reliability of our assessment models.

People: Olyslaegers Geert, Sweeck Lieve