Steam generator for sodium-cooled reactors.

摘要

In a steam generator utilized with a liquid sodium cooled nuclear reactor to which it is coupled by an IHTS (intermediate heat transport system), provision is made to vent the violent sodium water reaction emanating from a tube rupture casualty. In the preferred embodiment, the steam generator is of the type combining a sodium expansion volume (C), an electromagnetic pump (Q min ) for circulating sodium, and a large number of helically coiled tubes (78) for generating steam. The invention is also applicable to helical coiled tube steam generators having other types of internal and/or external sodium pumps. The steam generator includes a sodium plenum (64) at the bottom thereof containing a conventional rupture disk (D) for venting sodium, steam, and reaction products including hydrogen immediately upon a tube rupture casualty. The invention includes providing an alternate concentric flow path (63) interior to the steam generator and parallel to the tube bundle. This alternate concentric flow path extends from the upper portion of the steam generator down into the lower head or plenum adjacent to the pressure relief diaphragm. This alternate path is partially filled with sodium (80) during normal reactor operation. In the event of a tube bundle break, the alternative flow path dumps its sodium through the conventional rupture disk and then provides an immediate alternate pressure release path in parallel with the tube bundle for steam and water flow from the tube rupture site to the rupture disk. This parallel flow path reduces the pressure differential from the water/steam flow through the tube bundle such that water/steam does not flow back through the IHTS (18/20) to the IHX intermediate heat exchanger in the reactor, where it would react with residual sodium and potentially damage the IHX tube bundle which is part of the reactor primary containment barrier.