Abstract: A mixer grid for a nuclear reactor fuel assembly has a plurality of strips arranged in interlocking rows and columns defining a plurality of cells. A stopper is fixed to each corner of each cell for both directing coolant flow, providing coolant mixing and providing a smooth contact surface for the fuel rod. The stopper is either cone-shaped or cylindrical for directing and channeling coolant flow. The stopper also has a smooth, flat chamfered surface for contacting the fuel rod and minimizing damage upon the shifting of the fuel rod. The grid is attached to the nuclear reactor fuel assembly by using guide cells comprising a plurality of support arches for welding to the nuclear reactor fuel assembly.

Abstract: A radiation gauge is provided which comprises a casing having an evacuated inside, a pair of electrode plates contained within the casing, and an insulating material of aluminum oxide disposed between the pair of electrode plates, the insulating material undergoing an induced conduction phenomenon when ionizing radiation is illuminated thereon, whereby intensity of ionizing radiation can be measured based on the induced conduction phenomenon of the insulating material.

Abstract: Apparatus for sensing and transmitting a signal indicative of the position of a movable ferromagnetic member relative to a fixed structure within which the member moves. The apparatus includes a plurality of magnetic circuit arrangements arranged uniformly along the outside of the fixed structure. Each magnetic circuit arrangement includes a pair of magnets and a pair of arcuate-shaped magnetic path elements extending circumferentially about the fixed structure. A plurality of magnetic field responsive position transmitters are positioned adjacent the magnetic circuit arrangements for sensing the presence of the movable ferromagnetic member at predetermined positions within the fixed structure. The apparatus is particularly useful for monitoring the position of control rods in a nuclear reactor because the monitoring is done from outside the sealed structure.

Abstract: Certain of the nuclear fuel assemblies contained in a fast neutron nuclear reactor core have an integrated passive safety device.More specifically, said device is constituted by an annular block (48) forming at least the lower part of the upper neutron protection (42) of the assembly. The block (48) is formed by elements (50) of a neutron-absorbing material, embedded in a matrix (52) meltable at a temperature above the temperature of the sodium during the normal operation of the reactor. A perforated, inner envelope (54) mechanically secures the block (48), whilst enabling the elements (50) to drop in the assembly following the melting of the matrix (52).

Abstract: A nozzle dam has a valve controlled passage through the nozzle dam wall for releasing trapped gas from the nozzle in the region below the nozzle dam. The gas is released while the reactor coolant system water general level is above the level of the nozzle dam.

Abstract: Nuclear fuel rod tubes of zirconium alloy are heat treated in an induction furnace to produce a protective oxide coating two to fifteen microns in thickness. The furnace is only slightly larger than the tubes and receives the endmost eight inches of the tube. The furnace is controllable in zones along the tube. To calibrate the furnace to produce the desired temperature profile, typically a flat profile at a temperature between 650.degree. and 750.degree. C..+-.1.5.degree. C., a temperature calibration probe is provided with spaced thermocouples for sensing the temperature developed in the probe at each of the zones when heated. The probe is made of inconel 600 stainless or the like, and is dimensioned and shaped to correspond closely to the dimensions of the fuel rod tubes, including having a closed chamfered end. At the opposite end the probe protrudes from the furnace, where the thermocouple leads are terminated. The leads pass through a potting compound in the probe, such as magnesium oxide.

Abstract: A nozzle dam automatically latches on an annular ledge surrounding the nozzle opening. A pivotal latch arm on the dam, biased to the locked position is forced toward the unlocked position by a cam on the ledge as the nozzle is pressed on the ledge, and snaps into engagement with the ledge when the dam is fully seated over the opening. A bias arm may be operated by a wrench to pivot the latch arm toward the unlocked position until a detent locks the latch arm in the unlocked position.

Abstract: A boiling water reactor control rod drive housing support bars having wing assemblies to limit the travel of a control rod in the event that a control rod housing is ruptured. The wing assemblies are placed on support bars located in rows on opposing sides of the control rod drives. Each wing on the wing assemblies supports a quadrant of a control rod drive. The wing assemblies may be rotated from an operation position to a service position to allow replacement of the control rod drives.

Abstract: A fuel assembly for a boiling water nuclear reactor contains a plurality of vertical fuel rods, which are arranged between a bottom-tie plate and a top-tie plate (12) in a surrounding vertical casing part. The fuel rods extend through a number of spacers which are arranged in a spaced relationship in the vertical direction and which together with the bottom-tie plate and the top-tie plate retain the fuel rods in a spaced relationship in the lateral direction. The fuel assembly is designed for conducting water in through the bottom-tie plate, through the space between the fuel rods in the vertical casing part, and out through the top-tie plate.

Abstract: A nuclear reactor containment arrangement has a permanent seal ring across the thermal expansion gap defined by the reactor vessel wall and the containment wall. The seal ring allows for lateral translation of the reactor vessel, in addition to radial and axial expansion and contraction. The seal ring features an outer attachment arrangement characterized by a radially corrugated cylinder extending vertically between two annular Belleville plates having different diameters. The corrugations of the cylinder extend longitudinally between the cylinder edges, and flex during lateral movement of the reactor vessel relative to the containment wall. The Belleville plates accommodate axial expansion and contraction of the vessel, and an inner attachment arrangement accommodates radial expansion and contraction.

Abstract: In order to reduce the time and difficulty of disassembling a seal arrangement which includes a Grayloc flange, in a cramped radioactive environment, the Grayloc hub is modified to include a step bore which receives a seal arrangement and a retaining nut which presses the seal into engagement with an inner wall portion of the hub and outer wall portion of an ICI (in core instrument) supporting column. A loading ring is threaded onto a portion of the column. Bolts associated with the ring are screwed down onto a belleville washer which is disposed between the loading ring and the top of the retaining nut for maintaining a desired amount of load on the seals irrespective of thermal variations.

Abstract: A boiling water reactor control rod drive housing support bars having radiation shields to limit the travel of a control rod in the event that a control rod housing is ruptured and protect persons working under the reactor vessel from radiation exposure. The radiation shield includes radiation shield cups for surrounding the bottom portion of a control rod drive. The radiation shield cups are placed on support bars located in rows on opposing sides of the control rod drives. The radiation shield may be easily raised and lowered automatically by the control rod drive installation/removal machine.

Abstract: The spent nuclear fuel rods stored in a wet pit are extracted dry and transported dry to a transport container for dry transportation to a storage area or treatment center. The spent nuclear fuel rods are withdrawn from the wet pit, held within a cask that may be selectively closed at the bottom and transferred while the rod is dry after it is removed from the wet pit and then positioned over a dry container with an open top for a dry transfer of each of the rods to the container. Between the container and the cask is a closure that includes a shield plug and a shielding base that supports the shield plug and allows the shield plug to be moved on guide rails to the position above the open top of the container where the shield plug may then be raised allowing the shielding base to be moved out of position on the rails and the shield plug lowered to close off the container.

Abstract: Calibration arrangement and method for calibrating an inspection instrument, such as an ultrasonic inspection instrument of the kind typically used to inspect nuclear reactor pressure vessels. The calibration arrangement comprises a frame, the frame having a slot therethrough for receiving a sonic coupling medium therein. A plurality of channels extend through the frame and are in communication with the slot. A plurality of solid reflector rods matingly extend through respective ones of the channels and into the slot for reflecting sonic energy produced by a pulsed ultrasonic transducer mounted on the frame and spanning the slot. A pulser stimulates the transducer so that the transducer transmits pulsed sonic energy through the coupling medium which resides in the slot. The sonic energy is reflected by the rods that pass through the slot. The reflected sonic energy or echoes are received by the transducer, which generates transducer output signals that are received by a receiver.

Abstract: This invention relates to a method for protecting the integrity of the reactor container base in nuclear power plants, and a device for implementing the method.The proposed method and device are applicable to all reactor types (PWR or pressurized water reactor, BWR or boiling water reactor, HWR or heavy water reactor, etc.) and to all types of containing system (large dry type, steam suppression type, condensation on ice type, subatmospheric type etc.), although for simplicity the present text will describe only their application to a PWR with a steam suppression and large dry containing system.

Abstract: An apparatus for attaching a key member to a nuclear fuel assembly grid and detaching the same therefrom is disclosed. The apparatus includes a supply and recovery mechanism, an inserting and removing mechanism, and a rotating mechanism. The supply and recovery mechanism operates to supply the key member to a prescribed position adjacent to the grid and recover the same. The inserting and removing mechanism is disposed between the supply and recovery mechanism and the grid, and operates to insert the key member supplied from the supply and recovery mechanism into the grid and remove the key member from the grid to recover the same to the supply and recovery mechanism. The rotating mechanism is disposed adjacent to the inserting and removing mechanism, and operates to rotate the key member inserted in the grid in a prescribed direction about the longitudinal axis to attach the same to the grid and rotate the same in a direction opposite to the prescribed direction to detach the same from the grid.

Abstract: An integrated information system is provided for a plant with interactive processes running in functional equipment subsets, such as a nuclear power generation plant. Sensors are operatively coupled to monitor processes and equipment in the plant, collecting sample data for assessing operational conditions and for predicting maintenance requirements based on loading of the equipment. One or more processors access the sample data and compares present conditions to diagnostic specifications, technical specifications and historical data stored in memory and indexed to equipment subsets and functional operating groups. The processor(s) generate prioritized reports to alert users to potential operational and/or maintenance problems. In addition to the prioritized reports, the processor accesses and outputs to the users reports of the diagnostic and technical specifications applicable to the process parameters exhibiting the potential problems.

Abstract: An automated monitoring system and method of operation is provided for a nuclear reactor having a pressure vessel containing a reactor core for boiling water to generate steam. A plurality of monitors provide signals for respective monitoring parameters for monitoring operation of the reactor, and a computer includes a database therein containing predetermined setpoints for the monitoring parameters. The computer identifies abnormal and normal behavior of the monitoring parameters based on the database, and determines cause of abnormal behavior of the monitoring parameters using artificial intelligence. A warning i also provided to identify the cause of the monitoring parameter abnormal behavior. And, automatic mitigation action may also be effected.

Abstract: A throttle valve having defined characteristics controls flow of gas from a gas heater to a turbine in a closed cycle gas turbine system. The gas heater may be a nuclear reactor fueled by fission material preferably having a negative temperature coefficient of reactivity whereby the reactor automatically ceases heat production upon closing of the throttle valve.

Abstract: In a fuel assembly, lower end pieces of fuel rods, guide tubes and coolant pipes, etc., are inserted and/or screwed into a base plate and secured against lifting by a bolt. In the case of fuel rods, in particular fuel rods which do not extend over the entire length of normal rods, the bolt is screwed onto connecting parts in such a way that a releasable bayonet closure is produced. In the case of coolant pipes of boiling water reactors, there is provided in particular a screw connection which is irreleasably secured against torsion by the bolt.