Patent Number: 046559981
Section: claims

1. A liquid metal cooled nuclear reactor comprising a nuclear fuel assembly housed in a coolant-containing primary vessel which is housed within a concrete containment vault and having thermal insulation interposed between the vessel and the vault, the improvement comprising: said thermal insulation consisting of a plurality of adjoining units, metal structure secured to and projecting from the concrete of the vault and from which each thermal insulation unit is hung, each said unit including a pack of thermal insulating material, each unit also including a contained void co-extensive with said pack, said void being situated between said pack of thermal insulating material and the concrete, and means connecting the void of each unit to the void of at least one adjoining unit so as to form continuous ducting for a fluid coolant. 2. A nuclear reactor according to claim 1, wherein adjoining units have interleaving means for presenting a barrier to radiation and for minimising leakage of fluid coolant from said ducting. 3. A nuclear reactor according to claim 1, wherein the said metal structure is formed so that the said units are themselves spaced from the concrete of the vault to form with the concrete a volume of generally static environmental atmosphere to assist in thermally insulating the concrete. 4. A nuclear reactor according to claim 1, wherein the said metal structure comprises spaced pads embedded in the concrete of the vault, stanchions secured to said pads, and pegs projecting from the stanchions at spaced positions, said units being hung from the pegs with keyhole engagement. 5. A nuclear reactor according to claim 2, wherein each unit is constructed from sheet metal and defines said void, with said pack of thermal insulating material mounted on that void boundary which is remote from the concrete, said interleaving means being provided at the edges of both the metal sheets defining the void and the thermal insulation pack. 6. A nuclear reactor as claimed in claim 3 wherein said volume between the units and the concrete contains a generally static gas. 7. A nuclear reactor as claimed in claim 1 wherein said fluid coolant in said ducting is other than liquid metal coolant. 8. A nuclear reactor as claimed in claim 7 wherein said fluid coolant in said ducting is a gas.