Intrusion scenarios in radwaste repositories Jean de Mèredieu Risk management division / Post closure safety departement 26/09/2012 DMR/SAF/12-0018

1 – The French classification of radwaste and Andra’s sites locations 2 – Highlighting a few topics : French national guidance, safety case and safety functions, time-frames, contamination routes and depth parameter. 3 – Intrusion scenarios in Andra’s safety assessments 4 – Possible uses of intrusion scenarios results DMR/SAF/12-0018 26/09/2012

Waste classification and management channels DMR/SAF/12-0018 26/09/2012

Andra’s sites locations DMR/SAF/12-0018 26/09/2012

Guidance 1/2 French national guidance issued by ASN (Nuclear Safety Autority) LIL-SL Surface facilities RFS-I.2 (November 8th 1982, updated June 19th 1984) : safety objectives and design bases of surface facilities for the long term disposal of SL and/or IL radioactive waste of low specific activity, HIL-LL Deep geological repository Safety Guide Guide de Sûreté 2008 (formerly RFS-III.2.f) : objectives to be retained in the siting and study phases for the long term disposal of HL and IL-LL waste in deep geological formations in order to ensure safety after the operational phase of the repository. LL-LL Intermediate depth repository Safety Guide General safety guidance 2008 : guidances in the prospect of siting for a LL- LL repository. DMR/SAF/12-0018 26/09/2012

Guidance 2/2 Elements are given as regards : the types of intrusion scenarios that have to be analysed : for the surface facilities : road works within the repository footprint, residential area with permanent inhabitants on the site, “playground” scenario in the residential area. for the deep repository : the case of a drilling assumed to hit the repository has to be addressed. the timeframe for a possible intrusion : 300 years after closure in case of the CSFMA surface disposal. 500 years after closure for the deep geological repository. Regulatory Guidance let Andra free to describe the intrusion scenarios to be assessed with respect to the safety objectives. DMR/SAF/12-0018 26/09/2012

Human intrusion within the safety assessment Position of the intrusion scenarios in the safety case Strategy - Context Framework and Safety Strategy Regulatory framework/reference guidance Data input – Assessment basis Waste package characteristics Site Characteristics Technological knowledge Scientific knowledge Description / design of repository components Functional analysis (FA) Operational Post closure Operational safety / risk analsyis (RA) Post closure safety/analysis of uncertainties (QSA) Normal operation Incidental /accidental situations Normal Evolution Scenario Altered Evolution Scenarios Impact in normal operation (indicators) Impact of incidental / accidental scenarios ( indicators) Impact of normal and altered scenarios (indicators) Compliance of the safety level with the objectives (function of the stage of the project development) DMR/SAF/12-0018 26/09/2012

Safety functions Safety functions Repository safety functions are defined in order to meet the main fundamental objective : “protect humans and the environment from the dispersion of radionuclides”. After closure all function are safety functions, they must be fullfiled without any human intervention (“passive function”). Main after closure functions are (illustration) : Isolate the waste from human beings activities Prevent the circulation of water in the repository Limit the release of radionuclides and toxic chemicals and immobilise them in the repository Delay and reduce the migration of radionuclides released outside of the repository disposal cells. As regards human intrusion, the point is “How far the achievement of each safety functions could be degraded by an intrusion event hitting one or more components ?” DMR/SAF/12-0018 26/09/2012

Time-frames Multiple timeframes have to be considered : Radionuclides decay, and possibly appearance through radioactive chains Waste source-term (packages duration, waste matrix release ...) Geo-prospective aspects (uplifts, erosion processes, climate …) Institutional control and record keeping which define the earliest possible date for intrusion. Duration of the assessment (up to 1 My in the case of deep repository) (déchets vitrifiés) Radium bearing waste HL Waste radiological activity evolution over time Typical activity for a vitrified waste canister DMR/SAF/12-0018 26/09/2012

Possible routes for contamination Two routes for contamination Air pathway External irradiation through direct contact or vicinity with the waste. Internal irradiation through ingestion and inhalation of contaminated dust or inhalation of radioactive gases (Radon). Sources : cuttings from drilling, road works, houses construction. Main contributors : alpha decay radionuclides, radon ... Water pathway Through drinking water, livestock watering or irrigation : due to borehole drilling likely to shortcut the geological layers or engineered barriers. Main contributors : mobile beta-gamma decay radionuclides e.g. Cl-36, I-129 … Water pathways assessment needs are different : especially in terms of hydrogeological and transport modeling tools. DMR/SAF/12-0018 26/09/2012

The depth parameter Intrusion types Timeframes Waste content Water wells drilling Road works Houses construction Mining Timeframes Radionuclides decay rate Possible site erosion site stability Source term (packages duration, waste matrix release ...) Institutional control duration Waste content Radionuclides activity and decay rate Matrix form - primary package Mobility and sorption of radionuclides Toxic compounds content Site and repository design Host formation with suitable properties (hydraulic conductivity ...) No valuable resources in the subsoil Cells design / Dead end design Depth : Surface / Near surface or intermediate / Deep Pathways of contamination Air path (ingestion and inhalation) Water path (drinking water and other uses) Depth of repository DMR/SAF/12-0018 26/09/2012

Intrusion scenarios for the deep geological repository 1/2 Intrusion scenarios definition Types of intrusion Exploratory drilling passing trough the repository and continuing till the under-laying aquifer is reached (assumed target). Cores are brought to surface. The drilling is supposed abandoned without any plugging and keeps open. Time frames Direct impact to the driller : 500 years (loss of repository memory). Indirect consequences to the repository performances : continuous evaluation starting at 500 years. Assumption that all waste packages can be drilled. Locations of the hitting points in the repository, number of drillings IL waste tunnel, IL waste package, HL waste package, HL access tunnel ... One or two drillings at a time. Consideration is also given to potential indirect consequences of the drilling on other human groups. The fact of drilling a water well into a contaminated plume outside the repository footprint may rather be considered in the normal evolution scenario, except if the contamination is the consequence of an intrusion. DMR/SAF/12-0018 26/09/2012

Intrusion scenarios for the deep geological repository 2/2 The 2009 architecture IL waste area IL waste Sub-zone IL waste tunnel Shafts Non thermal HL waste area Main accesses Division module Slope access HL waste cell Division module HL waste sub-zone Thermal HL waste area DMR/SAF/12-0018 26/09/2012

Intrusion scenarios for the near-surface disposals Types of scenarios Related with a route of contamination trough the air : Road works, Residence building on site, Playground scenario. Related with a route of contamination trough ground water : A water well is dug within the repository footprint. The intrusion is assumed to take place at the moment and location of maximum impact for each radionuclide. CSFMA scheme DMR/SAF/12-0018 26/09/2012

Use of intrusion scenarios Even assumed that : an “non-interesting” site in terms of geological or surface resources has been chosen, the quantity of valuable material in the repository has been limited as far as possible; and future actions likely to make location and design records available as long as possible have been promoted, Intrusion risk can’t be excluded. Then the main purpose of the analysis is to make sure that an intrusion would not alter the safety functions in a way that would bring impact to an unacceptable level. In addition, intrusion scenarios may be used as a mean to improve and optimize the design in terms of robustness. If impact is slightly higher than acceptable : Define waste activity limits (total Bq or specific activity Bq/g) in order to achieve the protection goal (link with Waste Acceptance Criteria) Bring improvements to the repository design or possibly to the cell filing procedures in order to avoid “hot spots” (link with the design process) Improve the knowledge in order to reduce the calculation margins due to uncertainties (link with science and experiments) In any case, feedback is provided for the next safety assessment iteration: Identify the aspects that deserve improvement, Evaluate the interest of a better waste caracterisation and classification (if possible) in order to direct some of the waste categories towards better adapted facilities. DMR/SAF/12-0018 26/09/2012

DMR/SAF/12-0018 26/09/2012