Synthesis and integration in performance assessment (RTDC5)
In evaluating the overall performance of a geological repository for the disposal of radioactive waste, very long timescales have to be considered. Over such timescales, the disposal system will evolve due to interactions between the different near-field components as well as with the host rock. Also, the relative importance and impact of dominant processes controlling the evolution of the disposal system determine will advance with time. NF-PRO’s RTD Component 5 integrates information from the investigation of detailed processes and individual near-field components into assessments of the overall performance of the near-field system.
The Integrated Project NF-PRO investigates key processes influencing the isolation of nuclear waste in geological repository systems for the disposal of high-level vitrified waste and spent fuel. Work performed under NF-PRO includes experimental and modelling studies investigating detailed processes taking place in the near-field of the disposal system. The main objective of NF-PRO’s RTD Component 5 is to build confidence in the capacity of the near-field components to fulfil their assigned safety functions. To this end, information derived from detailed process investigations is applied and integrated in studies allowing for the quantitative assessment of the long-term behaviour of the overall near-field system
NF-PRO performs an integrated analysis of the evolution of the near-field and its influence on radionuclide release and transport in the near-field of different European geological disposal concepts. This includes also the assessment of overall mass balances and mass and energy flows into and from the near-field. Also, a synthesis of the outcomes of the whole Integrated Project will be made. Conclusions will be drawn from it especially in terms of the influence of key processes and their couplings on the performance and safety functions of Engineered Barrier System components. In doing so, NF‑PRO represents a major step forward in the establishing of the scientific and technical basis for geological disposal and the safe management of radioactive wastes.
As part of NF-PRO’s RTD Component 5, a number of topical are drafted. The first report of this type planned concerns hydrogen production and transport from the near-field for various disposal systems. The pressure of hydrogen as a function of time is relevant to chemical processes such as spent fuel dissolution. Another report is planned on the topic of sensitivity analyses for radionuclide release from the near-field. A report on the key radionuclides and the way in which the near-field safety functions (containment, waste form dissolution, retention in precipitates (solubility control) and sorption and diffusion in buffer) play a role in delaying the release of these radionuclides will be developed based on work in various studies.
Further cross-cutting areas in which reports are to be developed are:
- Gradients of pH in the near field (alkaline plume effects);
- Coupled chemical and THM processes (effect of chemical processes on THM, such as corrosion product volume changes and neo-mineral formation due to buffer alteration)
- Saturation processes
- RN transport in the EDZ for different disposal systems