Monitoring strategy for a reversible waste disposal facility (Cigéo)

Transcription

1 Monitoring strategy for a reversible waste disposal facility (Cigéo) S. Buschaert MoDeRn Int. Conf. and Workshop

2 Cigeo repository project Paris basin

3 Motivations for monitoring Andra developed a combined strategy of waste controls and monitoring to provide needed knowledge, which includes: The controls of waste packages (for compliance to specifications before acceptance), as well as their monitoring in disposal Surveillance for operational security and nuclear safety Monitoring as an input to reversibility management and long term safety assessment Monitoring of the environment This strategy responds to several demands expressed in, among others: The 2006 planning acts on management of radioactive waste and on transparency and security The 2008 Safety Guide for disposal (formerly RFS III.2.f) The Environmental Code, requiring to establish an environmental reference state consistent with the dimension of the industrial project The Public Debate, in venues discussing reversibility

4 Motivations for monitoring Given the specific character and the length of operations of the installations, Andra develop a further approach of monitoring completing the considerations on operational safety (surveillance) Emphasis of monitoring is specifically placed on verifying process evolutions in support of: A consolidation of knowledge used to evaluate long term safety A periodic re-evaluation of the repository safety and of its reversibility conditions An appreciation of initial design based margins with a view to optimizing the design of future construction stages This must contribute to knowledge and understanding With an aim to address the overall functioning of the underground structures, and more specifically the interactions between structures or groups of structures, as well as the host formation.

5 Motivations for monitoring Substantial upstream knowledge (data, modeling, experience gained in Bure URL) Chaleur Hydrogène Air (O 2 ) 1. Feedback from monitoring and technology inventory Eau Phenomenological Analysis of disposal situations H 2 O 2. R&D monitoring Disposal design (based on reversibility and long term safety) Identify processes to monitor Technical monitoring objectives & parameters Design of monitoring system 3. Qualification In a laboratory At the surface In the URL Metrology Hardening Monitor T-H-M-C-R An iterative process

6 Strategy for the monitoring system To optimize the spreading of monitoring systems in the repository, make use of Sets of identical structures/components/cells The homogeneity of host formation properties We propose amongst all disposal cells to select : Instrumentation density decrease Heavily instrumented reference structures ( Witness structures - Level 1 of instrumentation) Fulfill all technical monitoring goals Selected amongst the first structures built Current instrumented structures (level 2) Less instrumented Main monitoring goals Monitored by comparison with a witness structure Standard structures (level 3) not instrumented. only contain essential equipment for the operating safety with ongoing monitoring by occasional inspection and control (by mobile system) The possibility of other reference disposal cells is foreseen in the event of new type or design

7 Strategy for the monitoring system We also plan demonstrator structures (Level 0) «Sacrificial» structure HLW (Real withdrawal tests of HL wastes) Provide the possibility to carry out visual inspection, destructive analyses and samplings on construction materials Planned to be dismantled because of the potential disturbance of their component performances from the testing process Test structure ILLW ILLW disposal cells with unreal waste A seal of surface-to-depth infrastructure and a gallery seal Constructed as early as possible With a fast resaturation and subject to hydraulic pressure to allow monitoring its evolution during repository operations

8 Design of the monitoring system (ILLW cell level 1) longbasedfieldextensome ter IPC Reference for WVS Reference OFS (T M) T-H-M-C monitoring 10m; 5 measuring points OFS (T, M) Temperature probe Level 1 cell representative of others ILLW cells Identical constructing methods Real waste packages WVS Same diameter / length TDR (H) In addition, a ILLW test structure (level 0) will be a representative but an inactive cell based on the same design principles of disposal cells in order to give the possibility of : samplings, complementary measurements visual observations

9 Design of HLW monitoring system (level 1) Associated monitoring systems : Parallel boreholes (rock behavior) Metallic liner instrumentation Technology lack : Corrosion rate (waste packages and liner) Associated parameter of corrosion (hygrometry, O 2, Water, ph, Eh, etc.) Need some «sacrificial» cells in addition, to be able to periodically open them in order to test retrievability and to verify corrosion rates and the associated parameters by gas sampling lines.

10 Principles for a suitable monitoring Monitoring data must be representative of the overall repository behavior and its spatial variability valuable for verifying the hypotheses of the safety case and reversibility performance Conception of: an adapted density of embedded sensors in these chosen instrumented cells Methodology for selecting high priority parameters whose monitoring would be realized in instrumented structures identification of long-term safety and reversibility requirements and the process parameters a reasonable density of instrumented cells within the repository Methodology for distributing instrumented structures within the repository

11 Methodology for selecting parameters (reversibility) Failure Modes, Effects and Criticality Analysis (FMECA) methodology Evaluating the factors that could hinder waste package removal Characterizing (n/5) their probability of occurrence : P seriousness (levels of difficulty regarding package removal): S ability to detect the event (before it happens): D D1 : detection by embedded devices in cells D2 : detection by mobile devices / periodic inspection Criticality : maximum, significant, moderate, low DRD/OS/ Audition CNE-Andra 13 juin 2012

12 Methodology for selecting parameters (reversibility) Example of HLW packages recovery Failure factor P x S Monitoring method envisaged PxDxS D1 D2 Presence of water in the cell 16 Sampling lines Presence of H 2 in the cell 16 Sampling lines Accumulation of corrosion products 12 Sacrificial cell Blocking of the hatch be a foreign body (pad 10 Sacrificial cell fragment or corrosion products) Loss of means of environment monitoring (taps) 8 Maintenance of sampling lines Presence of H 2 in the head of the cell 10 Sampling lines Deformation of the gallery with respect to the insert potential misalignment of the cover bracket on the insert (monitoring reference) 10 Submerged extensometers Parameters will be completely monitored in the HLW cells of level 1 of instrumentation But in level 2 HLW cells, only the parameters whose importance remain significant or moderate (after detection D)

13 Overall distribution of instrumented cells (HLW cells) 70 C 40 C DRD/OS/ Audition CNE-Andra 13 juin 2012

14 Design of the monitoring system HLW ILLW At cell scale, monitoring systems are distributed to yield a 3D representation of its evolutions. Visual inspections They will combines : Sampling Non destructive methods In-situ instrumentation Constraints to take into account No access to monitoring systems (in disposal cells) Either maintenance free or robotized systems prior to sealing Discretion : No degradation of conditions favorable to long term safety Locally aggressive environmental conditions (temperature, pressure, chemistry, irradiation )

15 Design of the monitoring system For each in situ technology, seek redundancy and complementarities Proven (Experience) / Innovative (qualification in progress), Localized/Spatially continuous Direct/Indirect measurements Reference measurements («isolated» sensors/ metrological standards) TDR Vibrating wire extensometer Optical fiber sensors: T - ε

16 Design of the monitoring system Selection of setups / reference instruments and qualification of monitoring technology based on 4-step process Chamoise (inspired from Qualification guide FD CEN/TR Non-destructive testing ) Selection and in-depth understanding of sensor (material ) Tests in laboratory under controlled conditions Qualification and long term tests of monitoring systems In construction sites with surface tests on real structures In the URL, i.e. in the target environment (host formation, concrete)» Structures demonstrators (see Farhoud et al., this meeting) Hardening (irradiation) + Metrology complement each qualification steps.

17 Design of the monitoring system Overview of progress on technology R&D R The different types of technology C H TM T Mobile system ph Mobile system corrosion Rock gas Concrete 0 Selection based on prior experience Upstream R&D (Adapting) 1 Tests in laboratory 2 In situ and large scale tests 3 Hardening 4

18 Conclusions and Outlook An illustration of the strategy adopted for monitoring parameter selection and the distribution of instrumentation in repository The results derived from few years of Andra s R&D monitoring program allow main comments : Ensure that representative information could be provided by monitoring for performance confirmation By a distribution of instrumented structures over the entire repository, With increasing knowledge Decrease of instrumentation density Current limits of monitoring technologies requires Development of strategic solutions to bypass them, with the concept of sacrificial cell a R&D program for adapted measurements technology : Available technology often only provides a partial match with repository requirements