Abstract: Method and apparatus for maintaining a water level which immerses heat exchanger tubes, containing radioactive emitting material, within an inner shell of a steam generator while permitting space between the inner shell and a coaxial outer shell to be free of water during operations performed by workmen in such space after the apparatus is installed thereby reducing exposure of the workmen to harmful radiation. Seal support segments are installed around the inner shell at the lower end of the space and in engagement with the inner and outer shells. A pair of inflatable tubes are placed end-to-end on the support segments so as to encircle the inner shell. Seal retention segments which, together, form a ring around the inner shell are placed on the inflatable tubes and the latter tubes are inflated to form a water tight seal between the shells.

Abstract: In a nozzle dam assembly wherein a circular dam faces into a nozzle adjacent its opening and a support frame abuts the backside of the dam and is removably affixed across a ring encircling the opening, apparatus for selectively locating the dam at its optimum sealing position within the nozzle notwithstanding the particular longitudinal profile of the nozzle or eccentricity of the ring-relative to the nozzle opening comprising apparatus for adjusting the dam relative to the frame along the nozzle axis and also vertically and horizontally perpendicular to the nozzle axis.

Abstract: In a nozzle dam assembly wherein a flange ring is affixed around a circular nozzle opening in a chamber wall, a support frame spans and is in non-threaded connection with the ring by releasable pins which carry under tension any load on the frame directed axially out of the nozzle into the chamber, and a circular dam with a sealing diaphragm disposed over it is attachable to the frame with its rim within the nozzle so that inflatable peripheral sealing means on the diaphragm effect the desired seal of the nozzle independent of the aforementioned axial load.

Abstract: In a nozzle dam assembly wherein a flange ring is affixed around a circular nozzle opening in a chamber wall, a support frame spans and is in non-threaded connection with the ring by releasable pins which carry under tension any load on the frame directed axially out of the nozzle into the chamber, and a circular dam with a sealing diaphragm disposed over it is attachable to the frame with its rim within the nozzle so that inflatable peripheral sealing means on the diaphragm effect the desired seal of the nozzle independent of the aforementioned axial load.

Abstract: A canister for holding loose nuclear fuel rods for containment within a cell of a pool storage rack. The canister is designed with lateral restraints at both its bottom and its top to substantially prevent impact with the sides of the cell during an earthquake.

Abstract: High storage density for spent nuclear fuel assemblies in a pool achieved by positioning fuel storage cells of high thermal neutron absorption materials in an upright configuration in a rack. The rack holds the cells at required pitch. Each cell carries an internal fuel assembly support, and most cells are vertically movable in the rack so that they rest on the pool bottom. Pool water circulation through the cells and around the fuel assemblies is permitted by circulation openings at the top and bottom of the cells above and below the fuel assemblies.