The disposal project is broken down into a number of consecutive phases, of which the planning is described here below. Apart from the initial phase, the planning is determined by the underground activities in the repository.
Site preparation phase
The disposal project is assumed to start from the moment of the granting of License 1, at time T0. The
current R&D planning at ONDRAF/NIRAS foresees the year 2025 for this. Nevertheless, based on previous experience with nuclear waste management projects and on discussions with the main waste producers, the present cost analysis has relaxed this date by 7 years. Hence, the year 2032 is taken as starting point T0.
The first phase is the site preparation. First, the site terrain is purchased. Then the site surface is leveled and cleared of vegetation where necessary. The site is provided with a sewage system, roads and a utility distribution system. A security system, complete with fence is installed around the site perimeter.
For this phase, a fixed time duration is taken.
Repository construction phases
The construction of the first repository section, dedicated to the disposal of cat.B waste, starts right after the site preparation phase.
The construction of the second (and last) repository section, dedicated to the disposal of cat.C waste, is scheduled with the objective to be finished by the time the 3rd Disposal Campaign is scheduled to start. The time duration of a repository construction phase is determined by the following sequence of activities:
1. Parallel construction of:
• Personnel shaft, followed by construction of Access Gallery • Waste Shaft (if applicable)
2. Construction of the disposal galleries, incl. end plugs and crossing with the Access Gallery
3. Construction of the shaft buildings and outfitting of the repository (transportation system, ventilation and lighting)
The duration of the construction phase of a repository section is therefore calculated as follows: It is the sum of:
o the longest of:
- the duration of the construction of the Waste Shaft (if applicable), or
- the duration of the construction of the Personnel Shaft and the Access Gallery
o the construction of the disposal galleries, including the crossings with the Access Gallery
o the construction of the shaft buildings and installation of equipment in the shafts
The construction of the associated Post-Conditioning building(s) and support installations is planned so that these are ready for operation by the same time the repository section is ready.
Disposal Campaigns
Disposal Campaign 1 starts right after the construction phase of the cat.B section of the repository.
Disposal Campaign 2 starts as soon as possible after Disposal Campaign 1, but should not be finished earlier then the fixed point in time linked with the disposability of the last CSD-C (see §5.3.2).
Disposal Campaign 3 is scheduled with the objective to be finished at the fixed point in time linked with the disposability of the last CSD-V (see §5.3.2).
The duration of each of the disposal campaigns is a fixed time input, based on estimation. At the current level of R&D, a more specific calculation would not be justified.
Inter-Campaign phases
An inter-campaign phase is a waiting time between two Disposal Campaigns of the same repository section. The planning should be made such that any inter-campaign phase is a virtual phase, i.e. that its duration is reduced to zero years. A non-zero inter-campaign phase would indicate a planning inefficiency.
Inter-campaign phase 1-2 is the waiting time between Disposal Campaign 1 and Disposal Campaign 2, which are both executed in the cat.B repository section. In the cat.C repository section, there is only Disposal Campaign 3. In the present cost evaluation (Appendix 1 and Appendix 2), the time of the end of Disposal Campaign 1 plus the duration of Disposal Campaign 2 largely surpasses the “no earlier than” limit of the end of Disposal Campaign 2. This means that Inter-campaign phase 1-2, the single inter-campaign phase featuring in the present cost evaluation, is effectively a virtual one.
Monitoring phases
The AFCN/FANC guidance note 007-020-F [12] prescribes that a certain time period should be observed between the end of a waste disposal phase and the closure of the associated part of the repository. This period is intended to be dedicated to “monitoring”, i.e. the observation of the evolution of the repository after all waste has been emplaced. The monitoring period should contribute to the establishment of a sufficient confidence level that the disposal project has been progressing as foreseen in the original license (License 1) and that there are no indications of future safety threats. This is a prerequisite to continue with the next phase of the disposal process, i.e. the closure of the associated repository section, for which a license needs to be granted.
In view of the “open wound” principle (see §5.1) and also for economic reasons (maintaining underground installations is relatively expensive), ONDRAF/NIRAS deems that in a geological repository the duration of a monitoring phase should be restrained to a limited number of years. Consequently, the objectives of monitoring in this phase should be mainly to confirm the geomechanical stability of the repository after waste emplacement and the absence of any indications of short-term failure of waste confinement.
The time frame of the monitoring phase is by definition long enough to cover at least the licensing process, which includes the collection of supporting evidence, redaction of reports, license application, and the review and approval process with the safety authorities ultimately resulting in a formal license granting.
The decommissioning and dismantling of the Post-Conditioning building(s) and support installations is not depending on the license to close the associated repository section and is therefore assumed to start already at the beginning of the monitoring phase. For reasons of simplification, these activities, which are purely surface activities, are taken to be part of the monitoring phase. This means that the duration of the monitoring phase is considered to be sufficiently long to cover at least the bulk of the dismantling activities. For the cat.B section of the repository, a (reasonable) minimum value of 3 years is assumed for the associated phase. The end of this monitoring phase is marked by the granting of the license to close the cat.B repository section (i.e. License 2).
For the cat.C repository section of the repository, which by definition contains heat-emitting waste, it is considered that the peak of the heat-up of the surrounding host rock should be awaited before the geomechanical stability of the repository can be confirmed. Based on thermal analyses by the SCK.CEN (see curves 7 and 8 on Fig 40 of report SCK.CEN-R-4277 [49]), the thermal peak in the clay surrounding the disposal galleries comes 10 to 15 years after the disposal of the vitrified HLW (with preceding cool-off time of 60 years). Taking the duration of the disposal campaign into account (say 10 years) and considering that at the time of disposal, the majority of the CSD-V’s will already have cooled-off longer than 60 years, it is taken that the thermal peak comes within 5 years after the end of the disposal campaign. On this basis,
5 years is assumed for the duration of the monitoring phase for the cat.C repository section. The end of this
monitoring phase is marked by the granting of the license to close the cat.C section and the remainder of the repository (i.e. License 3).
Repository closure phases
A repository closure phase starts right after the monitoring phase, when the associated Closure License has been obtained.
The duration of the closure phase of a repository section is the sum of: • the duration of the sealing and backfilling of the Access Gallery • the duration of the longest of:
o the duration of the sealing and backfilling of the Personnel Shaft, or
o the duration of the sealing and backfilling of the Waste Shaft (if applicable),
The site restoration activities, featuring the dismantling of the Administration building and support buildings and the clearance of roads and parking lots, are planned to be carried out towards the end of the closure phase of the last repository section, i.e. the cat.C repository section.
Dormant phase(s)
In general, a dormant phase is a waiting time between the closure of a repository section and the start of construction of the next repository section. The occurrence of a dormant phases is a consequence of the “Disposal as Soon as Reasonably Possible” principle (§5.1) in the context of a nuclear industry that is long- standing and/or a generator of waste that requires long surface storage times before disposal.
The dormant phase between the closure of the cat.B repository section and the construction of the cat.C repository section in the present cost evaluation is in essence generated by the needed 60 years cool-off time before disposal of newly generated CSD-V’s.