Patent Number: 053435052
Section: summary

DESCRIPTION The invention relates to a recovery device for a nuclear reactor molten core. Certain accidents in the recent past have demonstrated that the molten core dropping onto the foundation or floor was able to have such an action thereon as to penetrate the same, so that the material might then spread in the neighbouring soil with difficulty forecastable consequences and only limited possibilities of reacting thereto. This is why a recovery device located under the core is proposed, which is designed in such a way as to vigorously cool the core when it has melted as a result of an accident and has dropped, while preventing the advance thereof towards the floor. In its most general form the device comprises vertical partitions defining separate volumes, certain of these volumes being empty, whereas the other volumes are filled with coolant. The latter volumes are surmounted by a refractory material layer. Therefore the molten material mass flows into the empty volumes, but the latter are sufficiently numerous and narrow to decelerate said flow, whose viscosity is also rapidly reduced by the coolant surrounding the empty volumes. The molten material is in heat exchange relationship with the coolant, from which it is only separated by the partitions, which conduct heat and are normally relatively thin. Therefore it is to be expected that the dropping of the molten core will be greatly slowed down and will be forced to solidify before reaching the actual floor. It is advantageous for the partitions to be parallel, so that the coolant-filled volumes form channels in which the coolant can effectively flow in a substantially horizontal direction. Under these conditions, the channels can extend between a slightly raised coolant source and a vaporized coolant outlet. Therefore the coolant replenishment is automatic and is due to the hydrostatic pressure as soon as the vaporization reduces the coolant height on one side of the channels. However, the channels can be separated from the source by a valve or any other isolating device, but a valve or automatic opening device is provided when the coolant is heated. It is also advantageous that the empty and the coolant-filled volumes are surmounted by a continuous heat absorption material layer, which surmounts the refractory material layer so as to reduce the mechanical and thermal shocks if an accident occurs. This avoids the risk of the destruction of the refractory material layer and the partitions by a core having an excessive temperature. It is pointed out in this connection that only the destruction of large portions of partitions could modify the process, but small size destructions during normal operation of the device would not have dangerous consequences, because the material which would penetrate the coolant-filled channels would be subject to an even more vigorous cooling and would therefore rapidly solidify.