Criticality Safety for Final Disposal (CSFD)
Objectives
Explore the optimisation potential of the technical and administrative measures available for ensuring criticality safety in final disposal, attain an improved understanding of their methodological validation and experimental verification, and further consolidate the technical basis of the criticality safety argumentation for final disposal of fissile wastes.
Description of the WP
Ensuring criticality safety of final disposal facilities requires the development, optimisation and implementation of dedicated technical and administrative measures. The effectiveness and impact of these measures is evaluated in the criticality safety case of the disposal facility. For geological disposal concepts, the criticality safety assessments are carried out for time scales which are typically orders or magnitude larger than in any other area of the fuel cycle. Understanding, modelling and assessing the potential evolution of fissile waste packages over such long timescales represent a challenge that requires substantial new research, although there is a good knowledge base on which to build.
The results and conclusions of this research will be used to support optimisation of aspects of waste packaging and disposal concepts. While certain aspects of a PCCS assessment are intrinsically related to the particularities of each individual disposal concept, leading to differences in the way organisations derive and present PCCS arguments and address optimisation, many organisations face similar challenges. Research leading to advanced and innovative PCCS assessment methods will bring broad benefits to all project participants and their national programmes through activities focusing on:
- Validation of long-term evolution scenarios for PCCS assessments;
- Verification of calculation model implementation for PCCS assessments;
- Validation of depletion and criticality codes for PCCS assessments;
- Methodologies for post-closure criticality consequences assessments;
- Fissile waste package records as evidence supporting PCCS assessment assumptions;
- PCCS communication techniques.
Outcomes
- Improved understanding of long-term repository evolution processes relevant to PCCS and of the existing scientific data available to underpin criticality scenarios assessments. New methods and techniques for assessing the suitability of models, uncertainty treatment, and the impact of inherent modelling simplifications. Reductions in overly conservative assumptions. Support to optimisation of waste packaging and disposal concept designs.
(Scientific Insight, Implementation Safety, Innovation for Optimisation) - Improved understanding of data needs for PCCS assessments, especially for validation and verification of inventory prediction (depletion) and criticality codes. Insight into experimental gaps and definition of a new experimental programme focusing on PCCS assessment needs.
(Scientific Insight, Implementation Safety) - Innovative methodology to derive fissile material limits, such as spent fuel loading curves, based on PCCS considerations, that enables optimisation of waste packaging design.
(Implementation Safety, Innovation for Optimisation) - New methods to perform post-closure criticality consequences assessments to gain new scientific insight into how the repository barrier system can minimise the impacts of hypothetical criticality events.
(Scientific Insight, Implementation Safety, Innovation for Optimisation) - Improved understanding of information (data) needs for fissile waste and container properties as data supporting PCCS assessments. A novel data architecture concept as a basis for a waste package records database.
(Implementation Safety) - Innovative methods of scientific communication to express and present PCCS cases.
(Scientific Insight, Implementation Safety)
