Scram device having a multiplicity of neutron absorbing masses

Claim 1

In a liquid metal-cooled nuclear reactor, apparatus for holding, releasing, and resetting a multiplicity of neutron absorbing masses for the rapid shutdown of the reactor core, comprising: a. a safety duct vertically disposed within and in fixed relation to said reactor, said duct further having a substantially uniform cross-section extending from below said core to the top of said duct above said core; b. a hopper valve positioned at a predetermined location above said core on the vertical axis of said duct, said valve having an upper portion forming shoulder means; c. a plurality of trapdoors, each hinged at the same elevation to the inside of said duct for vertical movement such that when said valve is in said predetermined location said doors rest in a neutral position on said shoulder means whereby said doors and said valve block substantially the entire cross-section of said duct thereby providing support for said absorbing masses in the cocked position above said core; d. actuating means located within said duct for maintaining the predetermined location of said valve and for reciprocally moving said valve a predetermined distance sufficient for said trapdoors to lose contact with said shoulder means; e. a vertically moveable platform which blocks substantially the entire cross-section of the lower portion of said duct; and f. a first lifting means for vertically reciprocating said platform substantially between said hinges and below said reactor core.