Architecture and management of a geological repository - Andra

11 – Operational Safety11.5.2 ConclusionDuring the transfer phase between the surface installations and the disposal cells, the fire on a transfercask transport vehicle would not have any thermomechanical consequences capable of affecting theintegrity of the transfered waste packages, which have a two-fold protection: the transfer transfer cask,with one of its components serving as a thermal shield, and the disposal package.Nevertheless, it would be necessary before any action required as a result of the accident is taken thatthe level of radiological protection ensured by the transfer transfer cask be checked. In case this levelis insufficient, it might be necessary, for example, to use movable radiological protections.11.6 Study of the consequences of a fire on the emplacement vehicle (forklift) of B waste disposal packagesIn the surface installations, the B waste disposal packages 177 are placed in the transfer transfer cask byan electric powered handling vehicle, or fork lift. These packages are then moved in this transfer caskup to the disposal cell where they are handled by the same type of vehicle to emplace them in a cell.In addition to the usual consequences resulting from a fire (temperature increase, smoke, …), if thishandling vehicle of the B waste disposal packages is on fire inside the disposal cell, it could haveradiological consequences if the fire affects the function of maintaining the containment of the primarypackage.The purpose of this section is to estimate by means of simulation studies [107] whether radiologicalconsequences may result and propose, if necessary, additional measures to prevent this risk or protectagainst it.11.6.1 Assessment of the thermomechanical consequences of a fire on the waste disposalpackage and the primary packages contained in itThis assessment is based on the assumption of a fire breaking out in a waste disposal package handlingvehicle despite the preventive measures taken (cf. section 11.4). The characteristics of the wastedisposal package were previously described in Table 11.5.1.11.6.1.1 Definition of the fire scenarioThe retained scenario is the scenario which would take place while handling the type B2 wastepackages because the bituminised matrix of the wastes for this type of package is the most sensitive toa temperature rise. On the other hand, the case of the fire on the underground vehicle waspreferentially studied because this vehicle appears to have a higher heat potential than the surfacevehicle.The fork lift (emplacement vehicle) used to transfer the disposal packages from their transfer cask totheir final emplacement in a disposal cell would be a self-propelled electric vehicle on rails. The fireconsidered would occur during the transfer of the disposal package between the cell’s entrance and thealready disposed of packages. The fire would be electrically caused and would imply the vehicle’sbatteries and motors as the origin. The scenario takes into account the installation of a 2 cm thickthermal shield between the vehicle’s motor section and the handling section.The fire’s characteristics were defined based on the vehicle’s characteristics ; the fire corresponds to aheat rating of 3 MW for a half hour duration. This fire breaks out in a cell where the ventilation rate ison the order of 3 m 3 /s.177 This illustrative case doesn’t concern the C and CU waste packages directly emplaced from the transfer cask into their cells withoutrequiring the use of an additional vehicle.DOSSIER 2005 ARGILE -ARCHITECTURE AND MANAGEMENT OF A GEOLOGICAL DISPOSAL SYSTEM469/495