3.4.1 Definition, scope and rationale
Definition – The future development of reactor, fuel cycle and waste management technologies and
policies will inevitably raise needs for changes and adaptations in the design and implementation of geological disposal. Some of the future likely trends are visible already now and may be reflected in flexible designs and implementation schemes. Since the added flexibility may increase costs, the design strategy has to be optimised between the potential but often uncertain benefits of increased flexibility, and the likely cost impacts of such flexibility. This Key Topic deals with the integration of new developments during the lifetime of a geological repository (construction and the operation time up to closure). A license would be issued for constructing and operating a geological repository on the basis of the available information at the time of the application. However, during the operational lifetime of a geological repository from its construction to its closure, new technologies, new scientific findings or improvements are likely to occur and can also be considered for the future closure, as well as for any reversibility and retrievability rationale.
Adaptation is on-going throughout the lifetime of the repository from the reference layout, design, adaptation to the site during construction and also during operation.
Objectives – The Key Topic aims to ensure that a higher level of safety, or at least the same level as
that demonstrated for the initial license, is achieved independent of the new developments related to the repository over time.
A geological repository should take account of new developments in order to adapt and to optimise its construction, operation and closure. Improving the industrial conditions is expected to simplify the work and to improve quality and safety and at the same time to reduce the costs.
Rationale and benefits – Development will incorporate adaptation that will consist of adjusting or
modifying the design of the repository and thus its construction and operation conditions. Optimisation would include improving the short-term as well as the long-term safety, whilst also improving the industrial conditions of construction and operation.
Improving the safety conditions and its demonstration will be beneficial to gain or to maintain confidence. A benefit from improving the industrial conditions could be a reduction in costs. Specific developments are also likely to occur in the fuel cycle (higher burn-ups, new reactors and fuels, new cycle options), which may call for adaptation of the design, construction and operation conditions. In this case, adapta- tion might be induced by changes in boundary conditions.
Finally the reversibility and retrievability questions will have to be dealt with, in the framework of the knowledge and situation of the repository at the time any decision is to be taken.
3.4.2 Importance for licensing, description and timing of work Medium importance and urgency Topics
Topic 1. Improved methodologies for developing strategies and approaches for adaptation and optimisa- tion – in order to proceed to the construction of a geological repository, license applications will need to specify how any adaptation and optimisation in design, construction and operations would be managed during the lifetime of the project. For example, it is important that strategies for considering evolutions are anticipated and clearly acknowledged from the initial licensing stage. In addition, interaction with safety authorities and their Technical Safety Organisations (TSOs) is needed in order to specify the type of requirements at the time of initial license application which will allow further improvements. It is also useful to generate guidelines on assessing the consequences of any change on the overall disposal system, including those related with reversibility and retrievability. As a matter of priority, a methodology will be discussed for the future integration of adaptations. The focus of such a methodology would be to explore the possibility of defining adaptation trends and intensity as early as the initial operations license to allow further possibilities of improvement and adaptations. The methodology will be based on the following steps:
• Identification of the different types of evolution.
• Indication of changes to expected boundary conditions for each type of evolution. • Description of design adaptation suited for taking account of the evolutions.
• Preliminary assessment of the consequences of adaptations on the overall safety of the geological repository system, including all relevant sensitivity analyses.
The urgency and importance of performing further studies of the above mentioned Topics for Key Topic 4 are shown in Figure 3.4.1.
Figure 3.4.1. Urgency and importance for “Development strategy of the repository” Topics (Key Topic 4). The numbering of Topics is according to Section 3.4.2. 2012-14 2018 2025 Time Importance for receiving a license High Medium Low Key topic 4: Development strategy of the repository 1
3.4.3 On-going work and considerations for the Deployment Plan
Topic 1. A development strategy is required at each stage of the repository development starting from the refinement of conceptual designs into site specific designs. When creating such strategies the accumulation of site specific knowledge, boundary conditions and changes in design basis and evolv- ing regulations over time related to deep geological disposal as well as after the start of the repository operations should be taken into consideration. A topical working group’s first task could be to identify those components of the repository system that through adaptation and optimisation would potentially reduce over-conservatism, improving quality and simplifying the design, construction and operations. A general programme of work needed would be the first deliverable from which further work would be developed.