Abstract: There is proposed a plastic closure which serves to close a container (3) with a mouth region (5). The closure (1) has a lid (7) allocated to the container mouth (5) and an annular side wall (9) connected with this. On the inner surface (15) of the side wall (9) there are provided fastening means (16) which coact with corresponding fastening means (14) on the outer surface (11) of the container (3) and are constructed, for example, as screw threads. The closure has, finally, also a sealing means. It is distinguished in that the sealing means (11) has a circumferential pivotable sealing lip (9) projecting from a support (15), which lip coacts with a side wall (25) surrounding the container mouth (21) of the container (19), which in the closing of the container is swung out of a rest position into a sealing position and which in its sealing position is clamped between support and side wall of the container so that it is subjected to a compression.

Abstract: A gas-coolant nuclear breeder reactor includes a core enclosed by a pressure vessel having a bottom beneath the core potentially capable of burning through if the core melts due to excessive operating temperatures. A basin is positioned beneath the core, either outside or inside of the pressure vessel, to intercept the melted core. The heat of the melted core must be dissipated rapidly because the reactor is enclosed by a steel containment vessel which might be unable to resist the internal pressure that would otherwise result from the heat. Therefore, means are provided for conducting a fluid coolant cooling the metal core, in the basin, from the latter to an extended area of the inside of the steel containment vessel which, being of relatively high heat conductivity, conducts the heat from the coolant to the atmosphere outside of the containment vessel. Cooling water may be sprayed on the outside of this containment vessel to assist in the dissipation of the heat.