Andra Research on the Geological Disposal of High-Level Long-Lived Radioactive Waste

Andra research on the geological disposal of high-level long-lived radioactive waste

> Detailed knowledge Experimental drift (-445 m) of the Meuse/Haute-Marne underground research laboratory of the waste to be managed

A national mission Andra has compiled an inventory of the waste and assessed its future production by current facilities he high-level long-lived radioactive National Review Board, an independent th based on four scenarios defined waste (HLLL) resulting from authority created by the December 30 with waste producers (EDF, Tnuclear power plants, spent fuel 1991 Waste Act, and constitute the basis AREVA, CEA) and representative of reprocessing, research and defence of the parliamentary debate scheduled possible strategies for spent fuel activities is currently stored safely and for 2006. reprocessing (from continuation to temporarily in industrial facilities. complete interruption). The French Waste Act dated 30th December 1991 initiated a research There are two types of waste: programme to define methods for the > C waste: high-level waste (1% long-term management of this waste. of the total volume and 96% of It has entrusted Andra, the French National the radioactivity) resulting from Radioactive Waste Management Agency, spent fuel reprocessing, confined with the task of assessing the feasibility in a glass matrix and poured into of deep geological disposal of this waste,

1.34 m 1.34 stainless steel drums. This type a solution also considered by various of waste gives off large amounts other countries (Finland, Sweden, of heat. Belgium, Switzerland, United States) and deemed particularly robust with regard Picture > B waste: long-lived intermediate- to safety by international authorities such of an R7T7 vitrified C level waste (the most abundant as the IAEA1. The results of this research waste primary in terms of volume) compacted are regularly assessed by the French package or conditioned in bitumen or concrete matrixes and then pla- 0.43 m ced in concrete or steel drums. The radioactivity of the waste decreases over time.

consists of a series The studies have encompassed the > A repository system possibility of the disposal of non- of elementary cavities (disposal cells) excavated in the rock (host reprocessed spent fuel, although formation). These disposal cells are grouped into large sets (modules) spent fuel is not today considered and receive the waste packages. The modules are connected as waste and is planned for repro- by drifts, themselves serviced by access paths connected to the cessing in the next years. surface via shafts.

1 International Atomic Energy Agency > Granite medium Since Andra does not have available an underground laboratory in a French granite formation, its research teams have partici- Clay and granite: pated in experiments conducted in Sweden (Äspö), Switzerland (Grimsel), Canada (Lac Two research du Bonnet) and Finland (Olkiluoto). These studies were not intended to assess the programmes feasibility of a repository designed according to the specific characteristics of a parti- Andra has studied the feasibility of an referred to as the Callovo-Oxfordian for- cular site. Their purpose was to assess the HLLL waste repository in French clay mation. Since 1994, Andra has drilled 27 interest of the granite medium and to pro- and granite formations. The results of deep boreholes meaning over 15 km of pose generic concepts capable of meeting this research are presented in the drilled formations, cored 2.3 km of the long-term safety objectives within the Dossier "2005 Argile" (clay) and Dossier argillite from these boreholes, and French geological context. In the same "2005 Granite". taken over 30 000 samples. Direct sur- manner, the safety analysis is not intended The studies covered four complementary vey of the Callovo-Oxfordian and in situ to produce specific conclusions regarding aspects: experiments are pursued since 2004 in the performance of the system considered the shafts and in nearly 100 metres of > Acquisition of data concerning the with respect to quantified radiological drifts. The Mont Terri laboratory in protection objectives. Its purpose is to waste packages, material behaviour Switzerland is also an essential resour- and clay and granite mediums. identify and handle essential issues and ce, with clay similar to that of the Bure to verify that none of the problem areas > Repository design: waste conditioning, site. examined rules out feasibility. repository architecture and integration in a geological site, operating modes SURFACE GEOLOGY Ornain river and reversibility. Alluviums or Ligny-en-Barrois Plio-Quaternary Research laboratory Callovo-Oxfordian Lower Cretaceous Saulx river Gondrecourt graben > Analysis of the long-term behaviour of Tithonian formation and its the repository and modelling of its Kimmeridgian Marne graben Gondrecourt le Château surrounding layers Oxfordian Joinville thermal, mechanical, chemical and limestone Savonnières-en-Perthois syncline hydraulic evolution. Marne river > Long-term safety analyses.

> Clay medium

n Andra has conducted studies in ia its Meuse/Haute-Marne underground research laboratory, created by the o-Oxford

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a decree of August 1999 and located at a C LITHOLOGICAL CROSS SECTION Limestone depth of 490 m in a stiff argillaceous Poissons Marls and clays fault rock (argillite) 155 million years old, Sandstone and evaporites (Trias) Scale : Sandstone and clays (Permian) 0 5 km Vertical exaggeration : 4x Undifferentiated basement

with the scientific community in France and abroad. Over 100 laboratories > International cooperation (French Geological Survey BRGM, throughout the world have participated. and review Atomic Energy Commission CEA, In addition, Andra submits its research French National Centre for Scientific for international review. In 2003, a Andra has conducted these two Research CNRS, French Petroleum group of international experts under the research programmes in collaboration Institute IFP, National Institute for aegis of the OECD/NEA examined the with foreign counterparts (Nagra in Industrial Environment & Risks INERIS, synthesis report on clay produced in 2001 Switzerland, Enresa in Spain, BGR in National Polytechnic Institute of and considered the results obtained as Germany, Ondraf in Belgium, etc.) and Lorraine INPL, School of Mines, etc.) positive. Meuse/Haute-Marne site > An argillaceous Other characteristics are: very low formation favourable water flow, little deformation, good response to the perturbations due for waste disposal to mining excavation work and to the After 10 years of research, Andra has thermal and chemical impact of the acquired sufficient data to consider that waste and repository materials (thus the Callovo-Oxfordian formation of the preserving its confinement properties Meuse/Haute-Marne site has favourable over very long periods of time), stable properties for an HLLL waste repository. geological environment. As well, surrounding formations presents This argillaceous formation with very low permeability and slow water flow. low permeability and homogeneous These favourable characteristics are over a large area, located at an average found throughout a 200 km2 area north depth of 500 metres, is unaffected by and west of the laboratory. faults and presents very low seismic risk. Since deep enough, future climatic changes (erosion) will not impact it. Meuse/Haute-Marne research laboratory Repository architectures in an argillaceous formation

> Robust options and placed in concrete containers (B waste) formation, then later to limiting and or steel containers (C waste and spent delaying the release and migration of modular system fuel). The repository is located on a sin- radioactive elements. specialized according gle level in the middle of the Callovo- to waste type Oxfordian and organised into distinct zones (according to package type) > Reversibility In order to dispose of and manage the separated by 250 metres of argillite and guaranteed for at various types of waste packages (B, C, subdivided into modules. least three centuries and possibly spent fuel) in a safe and The generally circular profile of the engi- reversible manner, Andra has adopted neered structures, their dimensioning, Integrated as of the repository design simple and robust options, proposing a their dead-end arrangement, their closure phase, the reversibility requirement modular and flexible architecture with low-permeability seals, the back- leads to privileging durable materials consisting of elementary components filling of the drifts at the end of the ope- and to the implementation of systems (repository modules). rating phase and the choice of materials for package retrieval. Waste package In order to simplify operation and increase (concrete, steel, clay) all contribute at retrieval is possible through simple its robustness, the waste packages first to reducing perturbations and mini- inversion of the emplacement process manufactured by waste producers are mising water flow in the geological over various centuries.

The B waste disposal cell has a useful lenght of 250 m, an excavated diameter of 12 m, and is equipped with concrete lining. The waste disposal packages, wich contain primary packages, are manufactured in concrete and stacked in several layers in the disposal cell.

Two basic guidelines Three major functions

Surface Basic layout of the installations Long-term safety and reversibility geological repository are the guiding principles for repository design The purpose of a geological repository is to protect man and environment from the possible impact of radioactive waste by interposing various barriers Shafts capable of confining the radioactivity for Zone B Zone C0 several hundreds of thousands of years 500 m (packages containing the waste, repository installations, geological medium). Zone C The safety approach adopted therefore takes into account very long periods of Underground installations time and privileges the most robust Disposal solutions so as to ensure the three cells major functions of the repository: These functions are ensured by barriers packages and as well to intervene in > Limiting the release of radioactive and various redundant components. the disposal process and to modify the elements and immobilising them in The approach to reversibility proposed repository design. An observation the repository by Andra consists of allowing the flexible programme has been developed to ensure the technical feasibility of the > Delaying and reducing the migra- and step-wise management of the repository. The objective is to leave backward process. The studies have tion of radioactive elements beyond shown that reversibility could be ensured the repository future generations the freedom to make decisions concerning repository mana- for a minimum period of two to three > Preventing water circulation (which gement. The modular repository design centuries, with no intervention other can degrade the waste packages and is intended to offer the widest possible than standard maintenance and monito- favour the migration of the radionu- range of choices. Reversibility means ring operations. clides contained therein) the possibility to retrieve emplaced > Granite medium: Interesting properties

In the absence of a specifically site, the design principles adopted by Andra are based on research conducted in foreign laboratories and on a typological analysis of 78 granitic zones of over 20 km2 located in the Massif Central and Massif Armoricain formations, quite apart from large faults. The architectures proposed are adapted to granite fracturing and rely on the very low permeability and high Äspö laboratory (Sweden) resistance of the non-fractured rock. Various options have been transposed from the repository studies concerning Safety assessment the clay medium: overpacking, separa- tion of packages into specialized zones > Demonstration of the millisievert in normal situations (i.e., 1/4 and modules, modular operation and robustness of the repo- the dose due to non-natural exposure cur- closure, sealing and backfilling of sitory concept in an rently admitted for the public and approxi- engineered structures, measures mately 1/10 the annual dose due to natu- favouring reversibility. argillaceous formation ral radioactivity). This impact has been In the absence of a specific site, subsequently calculated based on To verify the robustness of the solutions the safety analysis has not estimated models. Andra has extended its calcula- proposed, Andra has simulated the the impact of the repository in terms of tions to one million years, in accordance repository evolution in the very long the dose to which the public may be with international practice. term through a phenomenological ana- exposed. It has been used to determine lysis of repository situations (PARS) and The analysis shows that for all the situa- the role and performance of the reposi- then tested the limits of validity of this tions considered, normal or altered, the tory components with regard to the representation via a safety analysis. This proposed system ensures the three main safety functions, and to identify and safety analysis defines the simplified safety functions without excessively handle uncertainties. It stresses the history of repository evolution (normal depending on any of its components (each relevance of the architecture adopted evolution scenario). It covers the full component contributes to the overall safe- (adapted to granite fracturing) and the range of possible situations through ty of the system in a significant but non- efficiency of the engineered compo- very cautious choices. Andra has also preponderant manner). The Callovo- nents. A strong uncertainty remains examined scenarios entailing highly Oxfordian formation plays a major role in regarding the possibility of finding sites unlikely events (intrusion, failure of safety immobilising the radionuclides and in with sound granite blocks of sufficient functions). delaying and limiting their migration into size outside the fracture network. > Calculations projected the environment in all situations. The repository performance meets the over a period of dose objectives recommended by Basic 1 million years safety rule III.2.f in all the scenarios considered, whether accidental or According to the methodological guide altered, and with significant margins. > Conclusion published by the Nuclear Safety Authority The repository represents therefore a Based on the research completed, (Basic Safety Rule RFS.III.2.f), the impact robust disposal concept, including in the basic feasibility of geological of the repository on man and the envi- rather unlikely situations with concurrent ronment must amount to less than 0.25 penalizing circumstances. disposal in an argillaceous formation appears to be achieved.

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