Abstract: A spent fuel rack for storing fresh fuel assemblies, or spent fuel assemblies removed from a nuclear reactor, which includes a base plate having multiple cells of modular construction welded at their bottom ends to the plate. The cells are formed of L-shaped sections having walls which support neutron absorbing material, and the walls of one cell are common to the adjacent cells. The base plate includes openings primarily for receiving the bottom nozzle of a fuel assembly, but they further serve as access openings for apparatus used for leveling the base plate and for lifting and transferring the base plate with or without cells thereon, to a different area.

Abstract: A method of making a rack for storing a maximum number of fuel assemblies in spent-fuel storage locations in a minimum space. The rack has locations each formed by bending a stainless-steel sheet into a hollow body of the generally rectangular cross section and with each side shaped so that the apices of the body project outwardly. Except for bodies along the outer periphery of the rack, the apex of each body is contiguous to the apex of an adjacent body. These contiguous apices are joined by spaced welds longitudinally along the bodies. The welds are spaced so as to maximize the resistance of the rack to seismic acceleration and spent-fuel storage locations are thus formed. Four storage locations extend radially from the apices of each location. A wrapper plate is secured to each side of each of these four locations providing a pocket for neutron-absorbing material. An additional storage location is formed having pockets in common with the locations which bound it.

Abstract: The zirconium cladding of a coolant-displacement rod of a nuclear reactor is precollapsed in the zirconium oxide stack of pellets which supports the cladding. Current is conducted through the cladding in an atmosphere at reduced pressure containing residual oxygen, to heat the cladding to a temperature at which its yield strength is reduced. Then, while the rod remains at this temperature, it is subjected to isostatic pressure which collapses the cladding uniformly. The formation, by reason of exposure to neutron flux, of a long unsupported gap in the cladding which might be collapsed under the pressure of the coolant is precluded. In addition, the rod retains its symmetry. The outer surface of the cladding is oxidized, facilitating the movement of the rod into its thimbles of the core and improving the resistances of the cladding to reaction with the coolant.

Abstract: Refueling apparatus for a nuclear reactor including a bridge and a trolley. The bridge is moveable in tracks along the containment of the pit in which the reactor is immersed in water and the trolley moveable in tracks on the bridge at right angles to the tracks on the bridge. The trolley carries a mast assembly for engaging, raising, and lowering a nuclear-reactor component assembly involved in the refueling. The mast includes an elongated member for engaging control-rod and thimble plug assembly and a gripper for raising fuel assemblies. The elongated member is moveable upwardly or downwardly.A TV camera and a light source and reflector are mounted on the gripper assembly at the lower end of the mast assembly. The source and reflector illuminate a selected part of the fuel assembly which is to be transferred and the camera is directed to this part so as to pick up an image of this part. The cooperative TV-receiver monitor on the console on the trolley is provided with cross hairs.

Abstract: Refueling apparatus for a nuclear reactor including a bridge and a trolley movable at right angles to each other over a pit. The trolley carries a mast assembly for engaging, raising, lowering reactor component assemblies.The mast assembly carries electric cables and compressed air hoses from electric and air driven components on the mast and is rotatable relative to the trolley. The cables and hoses are passed from the mast assembly through a flexible cable tray which is oriented with its cable-carrying slot vertically in the configuration generally of an S. The cable tray is connected to the mast at one of its ends, is partly wound around the mast from that end and departs from the mast a predetermined distance at the opposite end. The tray remains fixed at the opposite end as it is wound on or unwound from the mast, so that the cables and hoses as they pass from the opposite end to electrical and air terminals as the trolley remains anchored at the opposite end.

Abstract: The endwise resistance welding of a weld coupling to a plate. The weld coupling is mounted in a collet which is mounted slideably in a cavity in a block of conducting material. In the standby condition of the apparatus the collet is urged outwardly of the cavity by a spring between the block and the collet. The end of the block at the entrance to the cavity and the outward end of the collet have frustro-conical or tapered surfaces tapered at the same angle to the common axis of the block and collet. The surfaces are face-to-face. This assembly including the weld coupling is mounted on the movable electrode of the welder. During welding this electrode is moved towards the cooperative electrode, on which the plate is mounted, compressing the weld coupling against the plate. Under the reactive forces from the coupling and plate, the collet is moved inwardly of the block causing the tapered surface of the collet to slide with a cam-like motion along the tapered surface of the block.

Abstract: Refueling apparatus for a nuclear reactor including a bridge and a trolley. The bridge is moveable in tracks along the containment of the pit in which the reactor is immersed in water and the trolley moveable in tracks on the bridge at right angles to the tracks on the bridge. The trolley carries a mast assembly for engaging, raising, lowering a nuclear-reactor component assembly involved in refueling. The mast includes an elongated member for engaging control-rod and thimble plug assembly and a gripper for raising fuel assemblies. The elongated member is moveable upwardly or downwardly.The bridge, trolley and mast assembly each has a pulse generator which produces pulses in accordance with the movement of each. The number of pulses produced when the bridge, trolley or elongated member move to a position at a predetermined distance from a reference position is a measure of the new position of each.

Abstract: A nuclear reactor having a remotely removable and replaceable thermal insulating shield for the head. Access permitting removal and replacement of the head is thus afforded.The thermal insulating shield includes a vertical frame of insulating material of polygonal transverse cross section encircling the head. A top panel of insulating material is mounted on the top of the frame pivotal by remote actuation between a horizontal position and a retracted position which may be vertical. In the horizontal position, the panels mate to provide thermal shielding for the head.

Abstract: A calandria for use in conducting the hot coolant of a nuclear reactor transversely. The calandria includes an upper plate and a lower plate which support tubes. The plates and tubes are enclosed in a shell which extends above the upper plate and has a supporting flange. The lower plate has holes for transmitting coolant into the region between the plates. The shell has openings whose boundaries mate with the outlet nozzles of the reactor. The tubes are of stainless steel and are dimensioned so that they have mass, stiffness and strength such that they are not subject to failure by the transverse flow of the coolant even at a high velocity.

Abstract: Disclosed is a reactor internals hold down spring and upper head region cooling passage. The hold down spring utilizes a plurality of stacks of Belleville spring washers to provide spring load and deflection capability to hold down the reactor vessel internals. Each spring assembly includes a generally leak tight means for passing an adjustable coolant flow to the upper reactor vessel head region in order to maintain that region at inlet coolant temperature. The spring assemblies are angularly spaced about a core barrel support flange to cooperate with coolant flow passage formed therein.

Abstract: Power supply apparatus including a generator of electrical energy, such as fuel cells, solar cells, MHD generators or the like, in which a storage battery is connected to the generator and to the load for supplementing the generator when the load exceeds its output or for storing energy from the generator when the generator output exceeds the load. A differentially rated, current-sourced, dual converter is interfaced between the storage battery and the generator for controlling the flow of power into or out of the battery.

Abstract: A method of air recirculation and air makeup for a nuclear reactor control room practiced with air supply apparatus having an alternate purification loop (84) in parallel with a portion of the recirculation loop (26). In the alternate purification mode of operation of the system a predetermined portion of the recirculated air is drawn through the purification loop (84) in parallel with a flow of the remainder of the recirculated air through the normal parallel recirculation flow path (86). The volume of air drawn through the purification path (84) is established to maintain the purification loop operating at its maximum efficiency. A makeup air supply loop (24) having a normal flow path (42) and an alternate, parallel filtration flow path (50), communicates with the recirculation loop (26).

Abstract: A coolant-displacement rod for a nuclear reactor including a stack of zirconium-oxide pellets in cladding of ZIRCALOY-4 alloy. The outer surfaces of certain of the pellets spaced at intervals along the stack are depressed. The cladding grows permanently when exposed to neutron flux but the zirconium oxide is dimensionally stable. Under the hoop stress impressed by the coolant on the cladding, the part of the cladding encircling each of the pellets with the depressed outer surface engages the outer surface compartmentalizing the pellets into sub-stacks. The formation of a long unsupported gap under the cladding which might collapse under the pressure and at the temperature coolant is prevented by forming a plurality of short unsupported gaps instead of one long gap.

Abstract: The guide tube is disconnected and removed from the upper internals of the reactor to a work station in a pool of borated water. The work station includes a clamp-and-index tool, a metal-disintegration-machining (MDM) tool, pick-and-put tool, a brush tool, a nut hopper, a pin-insertion/torque tool, and a crimping tool. These tools are hydraulically operable. The clamp-and-index tool positions and, by repeated centering maintains the guide tube in precise position for removal and replacement of its split pins, the MDM burns through an old pin-and-nut assembly severing it into readily removeable fragments. This pin fragment is removed by an expeller on the clamp-and-index tool. This pick-and-put tool removes the burned nut fragment and replaces it with the new nut. The pin-insertion/torque tool inserts the new pin and torques the new nut onto the new pin. The crimping tool crimps a locking cap secured to the nut onto the pin. The tools are controlled from a command center external to the pool.

Abstract: A method of crimping a locking cap secured to the nut of a new split-pin assembly to the new split-pin to preclude turning of the nut and pin relative to each other. The method is practiced with apparatus including a crimping mechanism including crimping jaws having crimping pins face-to-face near one end. The jaws have external cam surfaces. The crimping pins are retracted and brought into crimping engagement with the cap to be crimped by cam followers which traverse the cam surfaces when actuated hydraulically through a C-frame connected to the cam followers. The crimping mechanism is mounted on a support which is moveable by a hydraulic cylinder between a retracted setting, where it is latched generally vertically, and an operating setting where it is positioned generally horizontally.

Abstract: The overflow in the secondary of a steam generator of a nuclear-reactor plant, which occurs when one or more primary tubes conducting the coolant are ruptured, is controlled. The secondary of the steam generator, which contains the water that is converted to steam, is connected through valves to the pressurizer relief tank. The level of the liquid in the shell is monitored. An alarm is sounded when the level of the liquid in the generator reaches a predetermined height alerting the operator. When the level reaches a greater height, the valves are opened and the liquid in the shell is discharged into the pressurizer relief tank. The liquid in the tank is discharged into the containment sump when a disc is ruptured. The time taken after the rupture is 30 minutes as mandated by safety regulations. If, after the liquid in the shell reaches the level at which the valves are opened, the level drops to a height at which steam may be injected into the pressurizer relief tank, the valves are automatically closed.

Abstract: Apparatus for processing the damaged tubes of a steam generator. This apparatus includes a sleeving tool for inserting sleeves in the tubes, a high-roller tool for rolling the sleeves at their upper ends where they have been expanded, and a low-roller tool for rolling the sleeves at their lower ends in the tube sheet. Each tool is provided with locking pins which engage tubes adjacent to a tube to be processed and suspend the tool in processing position. The sleeves are inserted in the tubes and are rolled by rolls driven by a hydraulic motor. For sleeve insertion and for high and low rolling, the motor is controlled by a servo control valve. The feedback signal to this valve is derived from a flow transducer in the feed line for the motor. The feedback for the force of sleeve insertion is the pressure across the motor derived from pressure transducers in the conductors through which the motor is supplied. For insertion speed and for rolling speed, the feedback is derived from a fluid-flow transducer.

Abstract: The old split-pin assemblies of the lower guide tube of a nuclear reactor are replaced by new split-pin assemblies in a robotic work station under a pool of water. The work station includes a plurality of robotic tools which are remotely actuable from a robotic command center outside of the pool to position the guide tube precisely for a replacement operation, to fragment the old split-pin assemblies and dispose of the fragments under water, and to install a new split-pin assembly. The lower-guide-tube positioning means has a hydraulic cylinder, also remotely actuable externally to the pool, for rotating the guide tube so that it may be oriented properly to be processed by different tools in succession and also so that both split-pin assemblies in each guide tube may be replaced by the same set of tools.

Abstract: To limit the exposure of personnel to radioactivity within the channel head of a steam generator of a nuclear-reactor plant a cartridge sleeve-blank loader for automatically sleeving a plurality of tubes without the intervention of personnel is provided. The cartridge loader includes a turret or drum which carries a plurality of sleeve blanks around its periphery. A lifter engages the bottom of each sleeve bank in its turn at a sleeve insertion position of the turret and inserts the sleeve blank into a tube. Successive sleeve blanks are indexed to the insertion position for insertion into tubes. The sleeve blanks are slightly bowed or curved so that when a sleeve blank is inserted as a sleeve into a tube, the sleeve, since the tube is linear, exerts a restoring force on the wall of a tube which holds the sleeve in the tube when the lifter is retracted. In inserting the sleeve blank, the lifter moves at a low speed until the leading end of the sleeve enters a tube. Then the speed of insertion is increased.