Abstract: A nuclear reactor including a vertically extending reactor vessel containing a number of reactor components and located within a cavity defined by a vertically extending, circumferential cavity wall assembly is disclosed herein. The reactor also includes a particularly designed guard vessel arrangement including a guard vessel located around and spaced from the reactor vessel between the latter and the cavity wall assembly. The guard vessel is supported by means in the shape of an inverted frustum which not only serves as a support but which also acts as a means to provide a uniform temperature gradient between the guard vessel and cavity wall assembly and provides for ready access into the space between the two vessels by suitable equipment for providing in-service inspection of the vessel walls defining this space.

Abstract: A pool type nuclear reactor including a number of reactor components located within a vertically extending cavity which is located under a reactor deck arrangement and which is defined by a circumferential cavity wall assembly is disclosed herein. The reactor also includes a reactor vessel separate and distinct from the deck arrangement and the cavity wall assembly for containing the reactor components just recited. This vessel includes a main body located within the cavity and an upper circumferential rim forming a support flange located and interlocked between the deck arrangement and an upper section of the cavity wall assembly whereby to support the vessel body in place.

Abstract: A nuclear reactor having an inherently safe automatic shutdown capability comprising a pressure vessel, a core located within the vessel and containing a sufficient amount of fissionable material to establish and sustain a chain-type fission reaction, and a plurality of elongated conduits disposed in a regular arrangement within the vessel. Each of the conduits defines a fluid flow path and comprises a first section located within and extending through the core, and a second section located exteriorly of the core and positioned above the first section. Each of the conduits contains a plurality of substantially spherical bodies in a sufficient quantity to substantially fill the first section of each of the conduits. The conduits are provided with a first fluid connection to a lower part of the first section and a second fluid connection to an upper part of the second section for the passage of a pressurized fluid therethrough while maintaining the reactor in operation.