Apparatus for controlling nuclear core debris

A nuclear reactor including a pressure vessel having a lower plenum and structure therein for accommodating the flow of molten debris resulting from meltdown of the nuclear core cooled by a liquid coolant comprising:

• (a) means within said plenum adjacent said vessel for directing said debris radially and downwardly under circumstances of core meltdown, said means including a plurality of horizontal plates vertically spaced from one another, each said plate having a plurality of vertical openings therethrough with a depression peripherally thereabout, said depression shaped generally as the bottom half of a torus in horizontal position, and
• (b) cooling means within said vessel arranged to channel said coolant into contact with said debris such that said coolant absorbs heat energy from said debris and freely rises due to natural circulation, said cooling means including an annular region adjacent the walls of said vessel, said annular region being in direct fluid communication with the space below one of said horizontal plates, and inlet ports disposed below said core and above the uppermost of said horizontal plates for inletting said coolant from said vessel into said annular region such that coolant from said vessel enters said annular region, flows generally downward to said space below one of said horizontal plates, and rises through said openings in said one plate due to natural circulation .

Apparatus for controlling debris from meltdown of a nuclear reactor core normally cooled by a circulating liquid and disposed within a reactor vessel, said apparatus comprising at least an upper and a lower plate horizontally positioned in said vessel beneath said core and being ultimately affixed to said vessel, said plates disposed one atop another with a space therebetween, each said plate comprising a plurality of openings vertically therethrough with depressions about said openings, said openings spaced along said plates such that substantially all of said openings are vertically aligned above a depression in the successively lower plate, said plates each comprising a generally vertical section affixed about the periphery of said plates rising above the horizontal portion of said plates, said vertical secton of said lower plate section forming an outer annular-like region between said vessel and said vertical section and said vertical section of said upper plate forming an inner annular-like region between the vertical sections of said lower and upper plates, said vertical sections including inlet ports, said ports in the vertical section of said lower plate being at a higher elevation than said ports in the vertical section of said upper plate, at least one distributor having sides and a convex top, said distributor radially surrounded by said horizontal portions and affixed to said horizontal portions, said sides affixed to said vessel and having flow holes therethrough, at least a portion of said top being above the uppermost horizontal portion, and horizontal distributor plates affixed within said distributor including distributor openings with distributor depressions thereabout.

• whereby upon accidental meltdown of said core said debris falls generally downward through said liquid, some of said debris entering said annular-like regions through said ports and most of said debris falling onto said convex top and onto said uppermost horizontal portion being dispersed within said depressions until said depressions are filled, said debris then falling through said openings onto said depressions in the successively lower horizontal portion, said filling of depressions and falling through said openings continuing dependent upon the amount of said debris, and whereby due to the high temperature of said debris on said horizontal portions said liquid in said vessel circulates to cool said debris by natural circulation and convection, said liquid entering said ports, passing generally downward through said annular-like regions, and then generally upward through said openings in said horizontal portions and said distributor, and generally horizontally through said flow holes of said distributor, and whereby any chunks of debris entering said inner annulus tend to not enter said outer annulus, adjacent said vessel, due to said difference in elevation.