The purpose of this contract is to project management "realize" the 11th tranche (TR11) of construction work for 2 lines of radioactive waste storage facilities of the Aube Storage Center (CSA). The project management service includes the following standardized missions with reference to the MOP LAW: ACT / DET / VISA / OPC / AOR. Andra also entrusts the prime contractor with a technical assistance mission as part of its discussions with the Nuclear Safety Authority (ASN) concerning the construction of storage facilities.

During the 10 successive phases of work that took place between 1989 and 2021 on the Aube Storage Centre (CSA), Andra operates 195 storage facilities in which packages of radioactive waste are stored. These parallelepiped reinforced concrete structures have the following dimensions:

— internal length 24,6 metres,

— internal width 20,4 metres for gravel structures (so-called 'OG' structures) and 20 metres for concrete structures ('OB' structures),

— variable height between 8.2 and 8.66 metres.

These structures are located in contiguous lines of 4 or 5 independent structures (for units 1 and 2) or monobloc (for units 3 to 10).

Each book consists of the following main elements:

— a reinforced concrete raft with a minimum thickness of 0,4 metres,

— peripheral sails whose thickness varies between 0,4 and 0,8 m for the sails of concrete structures (OB) and 0,4 m for the sails of gravel structures (OG),

— a reinforced concrete closing slab with a thickness of between 0.25 and 0.35 metres.

A movable frame houses the structure being filled, in order to protect the packages from rainwater. This frame is equipped with an overhead crane that allows loading operations to be carried out. Infill material (concrete injected by layer or gravel spilled once the structure is filled) is used to fill the interstitial voids between the packages.

The operation of the centre requires the use of six structures allowing the simultaneous operation of six lines of structures, taking into account the diversity of waste packages received (diversity in terms of geometry and/or nature).

After loading operations, each structure is closed by a reinforced concrete slab, itself covered with a temporary seal (polyurethane type with two sprayed components) which is intended to limit water infiltration.

The lines of works are located along the service road of the works (known as "track 2"); They are part of a mesh defined by the sills intended for moving the frames from line to line and the sills located along each line, between axes of 24 m.

An Underground Gravity Separative Network (RSGE) placed in underground galleries, arranged under or laterally to the structures, makes it possible to check the effectiveness of the sealing device, and to recover any water infiltrated into the structures.

Since the construction of the centre, the galleries under the structures or the lateral galleries located under the sills have been connected to the main gallery by means of special elements allowing their connection.

Subsequently, once all the structures have been built, operated and closed on the site, a probable permanent watertight cover will be built over the structures; This cover could be composed of a superposition of layers of materials with an average thickness of 4 meters. After complete operation and covering of the entire storage area by this cover, the CSA will enter a monitoring phase for a period of about 300 years.

To date, all the works carried out during tranches 1 to 7 have been consumed; Units 8, 9 and 10 are being filled. Given the forecasts of deliveries of waste packages, the 2 lines of works of the future unit 11 should be available for operation by the end of 2026.

The purpose of this contract is the project management mission "Realization Tranche 11" which includes the missions ACT / DET / VISA / OPC / AOR in application of the law of 12/07/1985 known as MOP LAW. Given that there are no changes to the design of the TR11 structures, the design and execution studies carried out during the TR10 are repeated identically for the work of the TR11.