Architecture and management of a geological repository - Andra

11 – Operational Safety11.6.1.2 Assumptions related to the simulation studiesThe methodology used is similar to that indicated for the fire during a transfer of packages (cf.11.5.1.2). The only difference is due to the fact that the disposal package is located laterally withrespect to the fire source located at the vehicle batteries. Under these conditions, it is assumed that theradiant rating applied to the package side corresponds to half the total radiant rating and that 50 % ofthis rating is distributed over the side surface directly attacked by the fire and 50 % over the fouradjacent sides.11.6.1.3 Thermal behaviour of the disposal package and the primary package of bituminisedsludge B2 during the fireTable 11.6.1 gives the results of the simulation with the estimations of temperatures which would bereached at the various surfaces of the disposal package and at the primary packages during the fire. Italso indicates the time required from the outbreak of the fire to reach the maximum temperature.Table 11.6.1Temperatures estimated at the disposal package and the packages ofbituminised sludge obtained by digital simulation of fire conditionsMaximumtemperaturereached (°C)Time to reachT max from theoutbreak of the fireSide surface, from side521 ~ 30 minof the fire sourceDisposal packageAdjacent surfaces 319 ~ 30 minOpposite side 134 ~ 30 minPrimary packages located Container body 98 ~ 4 hon the side of the firesource Wastes 66 to 97 ~ 3 hThe simulations show that there isn’t any risk of igniting the wastes because of the protection offeredby the concrete envelope of the disposal package, which prevents any direct contact by a flame withthe bituminised matrix. Spontaneous combustion of the bituminised matrix, which requires atemperature on the order of 350°C, is also impossible. The only consequence of the fire on the wasteswould be a softening of the bituminised matrix related to its heating. Additional protection measuressuch as the shutdown or reduction of the ventilation flow in a cell (fire shut-off valve) could also beretained to isolate that cell and reduce the fire’s intensity.The primary packages would be subjected to temperature levels less than 100°C for the two mostexposed packages on the fire side, which would not damage their metallic envelope and would notaffect the contained bituminised wastes. Their average temperature would be around forty degrees (cf.Figure 11.6.1.The concrete envelope of the disposal package would be subjected to temperatures on the order of500°C, which should not affect its integrity. On the contrary, its mechanical properties may be alteredand a scaling phenomenon is liable to occur on its surface 178 .In any case, the results obtained refute the assumption of a deterioration of the package of bituminisedsludge provoking radiological consequences.178 Tests showed that fibre concrete packages of comparable thickness subjected to an average temperature of 800°C for 30 min couldundergo superficial scaling phenomena on the surface in contact with the flame, but without the concrete bursting.DOSSIER 2005 ARGILE -ARCHITECTURE AND MANAGEMENT OF A GEOLOGICAL DISPOSAL SYSTEM470/495