Synthesis of 20 years Research, Development and Demonstration in Andra's Underground Research Laboratory in Bure for Cigéo

Read or download the research synthesis document here

 

Prior to the construction and later during the operation of the URL, geoscientific research programmes

have been carried out to provide data for regional geological and hydrogeological modelling. More than

fifty deep geological boreholes have been drilled. Most of them were cored and tested and logged.

From 2004 to 2019, 1700 m of scientific and technical drifts up to 9 m in diameter were excavated in

the URL (Figure 4). Four technical excavation means have been used (drill and blast, pneumatic hammer,

road header, and tunnel boring machine with segment erectors). Many techniques for lining and

supporting the drift walls have also been tested (steel arches, bolts, shotcrete with or without

reinforcement, and segments).

These drifts have three main purposes (i) circulation and access to experimental and technical zones, (ii)

technical areas (safety niches, power supply niche, cement preparation niche), and (iii) experimental

zones.

The main level of the URL is implemented in the middle of the Callovo-Oxfordian formation where the

clay content is at is maximum (55%). This level is also the level defined for the waste disposal vaults. In

the URL, the drift at 455m aimed at starting the experiment programme in the upper part of the layer

and allow the setting up of the REP experiment dealing with the host rock behaviour during shaft

excavation.

More than 850 boreholes have been drilled from the drifts providing 8000 m of core for geological survey

and laboratory analysis (58,000 samples). More than 10,000 sensors are monitored in real time on an

integrated data acquisition and management system (SAGD/DAS). The system displays and holds records

of all of the data acquired since the experimental drifts were put into service. It is also used for

monitoring the environmental parameters that may influence the phenomena observed (temperature,

hygrometry, effects of excavation in adjacent drifts, etc.).

Looking back over more than 25 years of URL construction and operation, three main phases can be

defined in close relation with the milestones of Cigéo project development plan. The first one that took

place from 2000 to 2005 is the confirmation of the intrinsic favourable properties of the Callovo-

Oxfordian clay to demonstrate the feasibility principal of Cigéo project, in particular for long term safety.

The second one from 2006 to 2010 was mainly focused on the deeper characterization of the disturbance

that would be generated by the repository on the Callovo-Oxfordian and the behaviour of engineering

components (steel, concrete, glass…). The third one from 2010 to 2015 consisted of firstly testing

construction and operation options in order to design a reversible repository that could be safely closed

and sealed at the end of a century long period of operation.

The current phase started in 2016 aims at providing additional scientific and technical evidence to

support the license application of Cigéo project, including its instruction.

This report proposes an overview of these 25 years of French URL development. It will present the drivers

of the scientific and technological R&D programmes and how these programmes were up-dated and set

up to accompany the development of Cigéo project. To illustrate the purpose of the report, the four R&D

investigation phases of the URL are described with selected example R&D key experiments designed,

implemented and performed.