Abstract: A vault system is disclosed herein for the disposal of hazardous waste formed from vault cells, each of which has a liquid collection and monitoring system. Each vault cell comprises a liquid impermeable floor slab having a drainage channel for collecting liquids, a wall assembly disposed around the periphery of the floor slab, a ceiling slab overlying the wall upper edge of the assembly, and a monitoring and inspection aisleway disposed between the wall assembly and radioactive waste stacked within the vault cell that encompasses the drainage channel to render it both observable and accessible. The floor slab includes a plurality of feeder channels arranged in a rectangular grid pattern that ultimately drain into the drainage channel and are arranged such that each feeder channel collects liquid from a different rectangular zone within the floor slab so that the location of a leakage condition may be generally determined by observing which feeder channel conveys liquid to the drainage channel.

Abstract: The overflow line for the reactor vessel of a liquid-metal-cooled nuclear reactor includes means for establishing and maintaining a continuous bleed flow of coolant amounting to 5 to 10% of the total coolant flow through the overflow line to prevent thermal shock to the overflow line when the reactor is restarted following a trip. Preferably a tube is disposed concentrically just inside the overflow line extending from a point just inside the reactor vessel to an overflow tank and a suction line is provided opening into the body of liquid metal in the reactor vessel and into the annulus between the overflow line and the inner tube.