Patent ID: 6865245

Claim:
A pebble-bed nuclear reactor comprising: a reactor core vessel suited for containing radioactive fuel pebbles; a guide ring mounted within the reactor core vessel and defining an inner volume within the ring and an outer annular volume outside the guide ring; a column of flowable reflector pebbles that are essentially free of fissionable radioactive material, wherein the reflector-pebble column extends beneath the inner volume defined by the guide ring; a column of flowable radioactive fuel pebbles containing fissionable radioactive material, wherein the fuel-pebble column extends beneath the outer annular volume defined by the guide ring, and surrounds and contacts the column of flowable reflector pebbles beneath the guide ring along an inner, vertically extending, annular surface of the fuel-pebble column, the guide ring extending within the vessel to provide an outer surface that fuel pebbles at a free surface atop the fuel-pebble column can contact and an inner surface that reflector pebbles at a free surface atop the reflector-pebble column can contact; at least one reflector-pebble conduit containing one or more of the reflector pebbles, wherein the reflector-pebble conduit includes an outlet above the column of reflector pebbles, enabling reflector pebbles that pass through the outlet to be guided through the inner volume defined by the guide ring to the column of reflector pebbles, and the reflector-pebble conduit defining at least a portion of a passage extending from a bottom end of the reactor core vessel to the outlet of the reflector-pebble conduit so as to enable reflector pebbles that exit from the bottom end of the reactor core vessel to flow through the reflector-pebble conduit and through the guide ring to the top of the reflector-pebble column; and at least one fuel-pebble conduit containing one or more of the fuel pebbles, wherein the fuel-pebble conduit includes an outlet at a position above the column of fuel pebbles, enabling fuel pebbles that pass through the outlet to be guided through the outer annular volume outside the guide ring to the column of fuel pebbles, and the fuel-pebble conduit defining at least a portion of a passage extending from a bottom end of the reactor core vessel so as to enable fuel pebbles that exit from the bottom end of the reactor core vessel to flow through the fuel-pebble conduit to the top of the fuel-pebble column.