Abstract: An enclosed reservoir is sized and located in relation to the steam generator of a pressurized water nuclear reactor power plant so that upon a loss of feedwater flow to the steam generator, a gravity induced supplementary flow into the steam generator is automatically initiated to dissipate the residual heat generated in the reactor. The height of the reservoir is the same as the distance between upper and lower design limits on steam generator feedwater level. The top of the steam generator is fluidly connected to the top of the reservoir to equalize the pressure therebetween. The gravity induced flow from the reservoir to the steam generator produces a water level in the steam generator that stays within the upper and lower design limits.

Abstract: A bottom loaded filter assembly for filtering radioactive liquids through a replaceable cartridge filter. The filter assembly includes a lead-filled jacket enveloping a housing having a chamber therein for the filter cartridge. A track arrangement carries a hatch for sealing the chamber. A spacer plug supports the cartridge within guide means associated with the inlet conduit in the chamber. The plug and cartridge drop out of the chamber when the hatch is unbolted and move laterally of the chamber. During cartridge replacement, a new plug and cartridge are supported in the guide means by a spacer bar inserted across the track means under the chamber. The hatch is then slid under the chamber and bolted to the vessel, engaging an O-ring to seal the chamber.

Abstract: An arrangement for temporarily sealing the space between two substantially parallel, adjacent plates in which a flexible, partially inflatable seal is located between the plates to effect primary and secondary sealing interfaces along the upper and lower edges of the plates, respectively. The seal has a wedged-shaped upper portion, a tubular lower portion and a substantially solid intermediate shank. The tubular end of the seal is inflated so that it expands into contact with the lower edges of the plates, drawing the wedge-shaped upper portion of the seal toward the tubular portion, thereby forming primary sealing interfaces between the wedged-shaped portion and the upper edges of the plates. The contact of the inflated tubular portion with the lower edges of the plates forms secondary seal interfaces. The effectiveness of the seal can be tested by measuring the pressure in the chambers formed between each set of primary and secondary sealing interfaces.

Abstract: A self-actuated mechanism within a safety assembly in a liquid metal nuclear reactor comprising sensor fuel pins located in a reactor coolant flow path, a sensor bulb containing NaK located near the upper end of the sensor fuel pins and in the reactor coolant flow path, and a sensor tube connecting the sensor bulb to a metal bellows and push rod. The motion of the push rod resulting from the temperature dependent change in the NaK volume actuates a safety rod release mechanism when a predetermined coolant temperature is reached.

Abstract: A poison bundle release mechanism within a safety assembly of a liquid metal nuclear reactor. A baffle consisting of a plate with recesses in fluid communication with low pressure coolant is formed in the upper portion of the safety assembly. A plug attached to the upper end of the poison bundle fits snugly against the recesses and is held up against the plate by the coolant pressure difference acting on the lower and upper sides of the plug. A conduit and valve arrangement is provided within the plug whereby the actuation of the valve permits high pressure coolant to enter the recessed region, reducing the pressure difference across the plug and producing rapid disengagement thereof from the plate.

Abstract: A nuclear reactor control rod containing a stack of B.sub.4 C absorber pellets in which the pellets in the lower end have a radius smaller than that of the other pellets and are wrapped with a sleeve having a linear compressibility sufficient to accommodate exposure-induced radial expansion of the end pellets without producing excessive clad strain and having a thermal conductivity sufficient to keep the centerline temperature of the end pellets below the melting point of B.sub.4 C. One such sleeve material is a type 347 stainless steel having 22.5% theoretical density.

Abstract: A sensor chamber having one cavity containing coolant separated by a diaphragm from another cavity containing a fixed mass of inert gas is located within a safety assembly of a liquid metal-cooled nuclear reactor. The liquid cavity is in fluid communication with the coolant outside the chamber through a flow limiting orifice. An actuating bellows in fluid communication with the gas cavity is in contact with coolant outside the chamber and is connected to a push rod, which serves as a trigger for a poison bundle release mechanism. During slow changes in reactor coolant pressure experienced under normal operation, the diaphragm moves to equalize the gas cavity and liquid cavity pressures with the coolant pressure outside the chamber. The actuating bellows does not move because it is biased so that a threshold pressure difference is required before it will expand.

Abstract: An apparatus for holding, releasing, and resetting a multiplicity of neutron absorbing balls within a safety assembly of a liquid metal nuclear reactor comprising vertically hinged trap doors resting on the shoulders of a generally cylindrical release valve, the actuation of which disengages the doors, permitting the poison balls above the doors to drop into the core. In the reset mode of operation a platform is raised, lifting the balls from the bottom of the core and swinging the trap doors upward until the balls are above the door hinges. The release valve is reset and the platform is lowered to reset the doors against the valve shoulders. In the disclosed embodiment, the valve is operated by a self-actuated, temperature responsive scram mechanism.

Abstract: A lock down device for restraining a nuclear fuel assembly against hydraulic flow forces having cantilever leaf springs on the fuel assembly lower end fitting which lock into recesses in the fuel alignment pins located on the core support plate.

Abstract: An apparatus for the safe and compact storage of nuclear fuel assemblies in an array of discrete open-ended neutron absorbing shields for which the theoretical minimum safe separation distance and cell pitch are known. Open-ended stainless steel end fittings are welded to each end of each shield and the end fittings are welded to each other in side-by-side relation, thereby reducing the cell pitch tolerance due to fabrication uncertainties. In addition, a multiplicity of ridges on the sides of each shield having a height equal to one half the theoretical minimum safe separation distance further reduce shield bowing tolerances. The net tolerance reduction permits a significant increase in the number of fuel assemblies that can be safely contained in a storage area of fixed size.