Architecture and management of a geological repository - Andra

9 – Nuclear operating resources in the repository• Choice of the principle for handling the packagesThree principles, illustrated by Figure 9.3.9, have beenidentified for the transfer of the disposal package:- a air transport robot using the air cushion principle,- a self-propelled transporter robot,- a self-propelled pusher robot.The "air cushion" principle on a circular support has beenthe subject of two conclusive feasibility tests. One wasconducted by Andra (case of type CU1 spent fuels) and theother by the Swedish agency SKB (case of a supercontainer).However, these tests were conducted on a loadwith a much greater diameter (1.80 m and 1.25 m) than thatof type C disposal packages (0.60 m) so that they cannot beconsidered to be readily transposable. The diameter of Cpackages is in fact too small to be able to use standard aircushion cells. The thickness of the structure bearing the aircushions (about 5 cm) imposes a relatively large functionalclearance compared to the diameter of the cell (0.60 m).The principle of the transporter robot consists of lifting thedisposal package in a position jutting out in front, by a selfpropelledrobot. This robot has a counterweight to balancethe weight of the package. The combined package and robottherefore constitutes a rigid block whose length requires alarge clearance between the packages and the sleeve.Figure 9.3.9 Illustration of theenvisaged handling principlesThe principle of lifting in an offset position requires compensation by the weight of the robot, leadingto a rather long machine. This factor therefore leads to an increase in the size and weight of theprotective transfer cask.The principle of the pusher robot with step-by-step jacks consists of pushing the package by simplesliding on the cell sleeve. The push is exerted by an axial hydraulic jack. The robot buttresses itselfusing radial jacks that push on the sleeve. The robot advances by retracting the push jack.At this stage of the studies, the push option by a jack was preferred to the other options. This principleof pushing by sliding, benefits from the experience gained in two trials conducted, one by ONDRAFand the other by Andra. These tests showed that the key factor is the nature of the contact between thepackages and the sleeve. In particular, contacts of the "metal on metal" type are not allowed. The useof stainless steel is a factor that would be liable to seize the system as shown by the test conducted byONDRAF.Taking into account this difficulty has led us to envisage using ceramic sliding runners included on thepackages.9.3.3.2 Description of the equipment used for installing C waste disposal packagesThe equipment studied, complying with the principle described above, consists of three parts: a mobilerobot, fixed equipment mounted on the chassis of the protective transfer cask and fixed equipmentinstalled at head of the cell.The robot is connected to the fixed equipment of the transfer cask by means of an umbilical cable. Thefixed equipment at the head of the cell contributes with the transfer cask to the radiological protectionof personnel.DOSSIER 2005 ARGILE -ARCHITECTURE AND MANAGEMENT OF A GEOLOGICAL DISPOSAL SYSTEM353/495