Abstract: A roof for a built structure is proposed, which is designed in the form of a hollow body structure. It possesses interconnected walls (18 and 19) of flexible and at least substantially air-impermeable material. These walls (18 and 19) constitute elongated chambers (22), which are arranged side by side in sequence and are alternatingly designed as vacuum chambers (24) and gage pressure chambers (23). It is in this manner that an extremely strong, free span roof is created.

Abstract: A pressurized water reactor residual heat extraction system uses the secondary cooling circuit to extract the residual heat in certain operating and malfunction conditions. A steam generator (D1) has a connection, located on the live-steam and feed-water side, to the secondary circuit side of a safety condenser (SK1). The tertiary circuit side of the safety condenser is fed from a water reservoir (B) located at a physically higher level. The steam generated is vented to the atmosphere through a blow-off line (b2) which may include a separator. A make-up feed device (E1) is connected to the secondary side of the steam generator. Because of the higher location of the safety condenser with respect to the steam generator, the heat energy in the secondary cooling circuit circulates by natural circulation.