Fission gas release restrictor for breached fuel rod

A sealed rod is described intended for vertical operation with closely spaced, vertically oriented rods in a liquid-metal-cooled nuclear reactor, during reactor operation the closely spaced rods having heat transfer liquid metal flowing upwardly therebetween and in contact therewith to remove generated heat therefrom; the rod comprising an outer elongated hollow continuous cladding member having the ends thereof sealed, pellet means positioned within the rod and operable during reactor operation to generate heat and fission gas, compression spring means within the rod to retain the pellet means in position within the rod prior to operation thereof, and space within the rod comprising elongated gas plenum means to receive fission gas which is evolved during reactor operation; elongated gas bottle means positioned within the elongated gas plenum means and occupying the substantial portion of the elongated gas plenum means, the gas bottle means having an elongated wall portion spaced from the interior surface of the hollow cladding member to permit the passage of fission gas therebetween, and substantially all of the gas bottle means being impervious to the passage of fission gas therethrough; gas pervious means provided through a small portion of the gas bottle means to permit fission gas introduced into the elongated gas plenum means during reactor operation to pass into the gas bottle means to equalize the fission gas pressure interiorly of and exteriorly of the gas bottle means