Abstract: Apparatus for the underwater loading of nuclear materials into concrete containers employing heat removal systems includes a holding vessel and a cover. The holding vessel has a metal bottom and a metal outside wall which define an upwardly open cavity dimensioned to accommodate the concrete container while leaving a gap between the container and the outside wall. A cover covers this gap, while allowing access to the central open cavity of the container. Fasteners and seals fasten and seal the cover to the container and the holding vessel. A method for loading nuclear materials into such concrete containers, utilizing the apparatus of the subject invention, includes the steps of lifting the container into the steel vessel, lowering the cover into place, fastening and sealing the cover onto the container and vessel, and then lowering the container and vessel assembly into the water storage pool.

Abstract: A tool for protecting a boiling water reactor component against damage by a shroud repair assembly suspended from a cable and lowered into the downcomer annulus. The tool has a roller with an outer surface made of a material which will not scratch the surface of a tie rod of the shroud repair assembly as the latter is lowered relative to the roller. The tool has sets of opposing grippers made of aluminum alloy which are pressed against opposing surfaces of the shroud and the reactor pressure vessel with sufficient force to clamp the tool in the annulus. The pressing force is generated by air-actuated cylinders which are actuated remotely. In one embodiment, the roller is fixed and acts as a stop to limit tangential travel of the suspended assembly. In another embodiment, the roller is displaceable in a tangential direction in response to remote actuation of a pair of air-actuated positioning cylinders.

Abstract: A fuel bundle assembly for a nuclear reactor includes a lower tie plate; a transition piece underlying the lower tie plate; a plurality of fuel rods and at least one water rod seated on the lower tie plate and extending in substantially parallel relationship toward an upper end of the fuel bundle assembly, wherein a fuel bundle assembly lifting load is carried by load bearing members including certain of the fuel rods or by the at least one water rod; a plurality of spacers axially spaced along the at least one water rod and including means for laterally supporting each of the fuel rods; and a handle bar assembly at the upper end of the fuel bundle assembly connected to the load bearing members such that the plurality of non-load bearing fuel rods are supported only by the lower tie plate and the plurality of spacers.

Abstract: The performance of a compact heat exchanger in which a flow of air is employed to cool a flow of water can be enhanced by spraying water as a fine mist into the stream of coolant air. The water droplets, preferably less than 100 microns in diameter, coat the heat exchanger surface on the air side of the heat exchanger and provide evaporative cooling. The preferred form of heat exchange surface has strip fins.

Abstract: An automatic refueling apparatus has a travel carriage, a traverse carriage and a fuel assembly grappling apparatus composed of a grapple, an extension pipe and a hoist. The automatic refueling apparatus also includes a system for controlling automatic fuel transferring operations, in which a calculation unit and a control unit are provided. After the positions of a start point and a target terminal point of a fuel assembly transfer are input through an input device, the calculation unit determines the shortest route from the start point to the terminal point in a preset fuel transferring permitted region, and the control unit generates driving command signals for moving the fuel assembly grappling apparatus along the obtained shortest route through a simultaneous control along X, Y, Z (Z: an elevation direction vertical to a X-Y horizontal plane of the grapple) and .theta. (a rotation direction in a X-Y horizontal plane of the grapple) axes.

Abstract: A light water reactor, in particular a boiling water reactor, includes a reactor pressure vessel having an interior, a core disposed in a lower half of the pressure vessel, fuel assemblies disposed in the core, and a column of water covering the core and acting as a coolant and a moderator. The column has an initial level range during normal operation. A passively operating safety device is provided. Fluid lines are connected between the safety device and the interior of the pressure vessel. The fluid lines automatically transmit an actuation criterion to the safety device, with at least a drop of a level in the pressure vessel to a value below the initial level range serving as the actuation criterion.

Abstract: A uranium-containing nuclear-fuel sintered pellet containing UO.sub.2, (U, Pu)O.sub.2, (U, Th)O.sub.2, (U, RE)O.sub.2, (U, Pu, Th)O.sub.2, (U, Pu, RE)O.sub.2, (U, Th, RE)O.sub.2 or (U, Pu, Th, RE)O.sub.2, wherein RE=rare earth, has a sintered-pellet surface layer being formed of at least 80% by volume of a chemical boron compound UB.sub.x or (U, . . . )B.sub.x, wherein x=2;4;6 or 12, and a remainder of the sintered pellet containing at most 5% by volume of the chemical boron compound. A nuclear-reactor fuel assembly has a fuel rod containing such a uranium-containing nuclear-fuel sintered pellet in a cladding tube with the boron as a burnable absorber for thermal neutrons. The surface layer having the chemical boron compound is obtained by treating the nuclear-fuel sintered pellet with boron or a boron-containing chemical compound at an appropriately high treatment temperature.

Abstract: A probe delivery system for delivering a bendable probe into a tube bundle is provided. The system uses an elongated guide which is insertable into the tube bundle via the access opening. The guide has a channel for directing the probe therealong and several pivotable port devices spaced along the length of the guide, operable to selectively direct the probe either farther along the guide, or outwardly and away from the guide and into the tube bundle. Actuators operate the port devices, and may be pneumatic, for example. A base is mountable on the shell which surrounds the tube bundle, and a servomotor is mounted on the base to move the guide in and out of the tube bundle. A rotation drive servomotor preferably is mounted on the base for rotating the guide about its central axis. Preferably, the system includes a spool drive for the probe itself, having a rotatable substantially circular spool around which the probe may be wound for feeding into and retracting from the tube bundle.

Abstract: The present invention relates to a technique for estimating core performance which includes the steps of: dividing a reactor core into a plurality of core portions, each consisting of at least one fuel assembly, then further dividing each of the core portions into segments by planes perpendicular to the axis thereof and allocating a parallel processing apparatus having a plurality of arithmetic processing units, a memory for storing processing data of the arithmetic processing units, and communications circuitry for transferring data with respect to the arithmetic processing units, in a manner such that the arithmetic processing units correspond to the segments of the core. Data on the power distribution for the entire core portion to which a corresponding segment belongs is transferred to each arithmetic processing unit, before each of the arithmetic processing units performs thermal hydraulic calculations.

Abstract: A nuclear containment arrangement has a permanent pool cavity seal extending across an annular gap between a reactor pressure vessel and a refueling pool wall to provide a water tight seal therebetween. A seal plate has a support ring with a cylindrical section weldedly connected to an outer seal ring on an embedded ring. A J-shaped flexible ring attached to the seal plate allows axial and radial movement of the reactor vessel during thermal expansion and contraction. The inner portion of the seal plate overhangs the J-shaped flexible ring thereby to protect it from damage resulting from an object dropped thereon. Cooperating access holes and access hole covers in the seal plate provide access to the refueling pool cavity. Support arms underneath the seal plate are provided. Each support arm may have leveling screws to adjust the level of the seal plate.

Abstract: A dry transfer system for spent nuclear fuel (SNF) assemblies includes a transfer container with a sliding sleeve for vertical translation therein. The sliding sleeve includes a number of compartments for receiving a corresponding number of fuel assemblies. The container includes an integral and remotely controllable hoist with a number of individually actuated grapples for latching onto a corresponding number of fuel assemblies. The system further includes a loading stand with an elevator for raising and lowering a fuel basket that also includes a number of compartments for moving fuel assemblies up to and in alignment with the sleeve of the transfer container that is landed on the loading stand.

Abstract: A metal cutting motor driven saw blade carried by a housing structure for anchoring inside the fuel storage cell forms part of apparatus that is used in method to reduce the volume of radiologically contaminated metal racks after use for storing nuclear fuel assemblies under water in a storage pool. The motor driven saw is supported by a linear bearing that can be displaced by an actuator laterally with respect to a housing structure which is provided with piston and cylinder assemblies on two adjacent side walls to serve as releasable anchors. The linear actuator presses the saw blade against a side wall of a fuel storage cell causing part of a blade segment to penetrate the side wall. Thereafter, a drive shaft supported by bearings in the housing structure is rotated to displace the motor driven saw about a radial path of travel for severing the remaining portions of the wall of the fuel cell.

Abstract: In an initial core constituted by various kinds of fuel assemblies having a different average enrichment of uranium 235 four fuel assemblies having the lowest average enrichment constitute a square shaped cell. Three fuel assemblies having the highest average enrichment constitute an L-shaped cell, and the L-shaped cell is arranged at corners of the square shaped cells, whereby each assembly of the L-shaped cell adjoins a square shaped cell. The ratio of the number of assemblies of the L-shaped cell to the total number of fuel assemblies in the core is 10% or more.

Abstract: A pressurized water reactor (PWR) is protected from departure from nucleate boiling and from hot leg boiling by generating a segmented delta temperature trip function having a first line segment which closely follows the departure from nucleate boiling core limit line and a second segment closely following the hot leg boiling core limit line. Each line segment is a function of the average core temperature and coolant pressure with the departure from nucleate boiling segment further adjusted for axial power distribution. The two set points are continuously compared to actual delta temperature in four independent channels. If either set point is exceeded in at least two channels, the reactor is tripped.

Abstract: A maintenance cover for use in a nuclear reactor including a pump deck having at least one pump diffuser opening is described. The cover includes, in one embodiment, a substantially cylindrical member having a first end and a second end. The first end has a diameter larger than the diameter of the pump diffuser opening. The substantially cylindrical member includes a substantially cylindrical frame having a plurality of window openings formed therein. Grating is secured to the frame and extends over the window openings. The cover further includes an end member secured to and positioned over the second end of the substantially cylindrical member. The end member also includes grating. A handle is secured to the substantially cylindrical member.

Abstract: A storage tank for radioactive fissile material solutions. The tank comprises at least one cell containing a radioactive solution and a solid neutron-absorbing material while preventing any risk of criticality. A network of substantially vertical tubes is arranged within said cell and metal walls completely separate the radioactive solution from the solid neutron absorbing material. Said tubes contain the neutron absorbing material and are located in compartments defined by the metal walls throughout the radioactive solution. Said tank occupies a reduced floor space.

Abstract: A nuclear fuel assembly for a boiling water reactor, comprising an outer channel having a substantially square cross-sectional area, and fuel rods arranged with a predetermined pitch in an array of 10.times.12 where the centers of the fuel rods are located at the vertices of equilateral triangles.

Abstract: A fuel assembly for a nuclear reactor vessel includes a plurality of fuel rods, at least one coolant rod, a lower tie plate supporting the fuel rods and coolant rod, and a channel surrounding the fuel rods, coolant rod and tie plate. The lower tie plate is supported by the channel such that the channel carries a load of the fuel assembly. In one aspect of the invention, an upper tie plate includes two spring loaded latch pins engageable with corresponding apertures in the channel. A transition member supports the lower tie plate and is rigidly secured to the channel. Thus, when lifting the fuel assembly from the reactor, the channel bears the load of the fuel assembly. End gussets or clips are welded to the channel and inserted into the transition member, which serve as a secondary support for the transition member in the event that its primary connection to the channel fails. A channel guide member is secured to the, upper tie plate and includes two ears that are received in ear apertures in the channel.

Abstract: A pre-oxidation treatment for decreasing the amount of chromium deposited on out-of-core surfaces such as the internal surfaces of recirculation piping. Hydrogen peroxide is injected into the reactor coolant through the recirculation line during reactor shutdown after H.sub.2 addition has been terminated. A dilute acid solution (e.g., nitric acid) is also injected into the loop to serve as a catalyst to accelerate the oxidation reactions. An appropriate water pH (e.g., in the range of 5-6) is maintained by acid injection. The coolant temperature during shutdown is maintained at approximately 150.degree. C. or lower. The peroxide concentration in the recirculation piping is maintained at approximately 1 ppm or higher as needed. The oxidation process should be allowed to take effect in the proposed temperature range with the recirculation pump in operation for at least a few hours to 24 hours, depending on the temperature and the oxide film thickness.

Abstract: A tool for lifting a tie rod off of the refueling floor and lowering the tie rod into the downcomer annulus of a boiling water reactor during a shroud repair operation. The tie rod lifting tool can be attached to the end of a strongback suspended from a hoisting cable or to the end of the cable itself. One embodiment of the tie rod lifting tool has redundant locking pins which interlock with corresponding holes formed in the end of the tie rod. The locking pins are moved out of locking engagement in response to actuation of respective pneumatic cylinders. The locking pins are latched so that the tie rod cannot be disengaged from the lifting tool unless the latches are first manually released by an operator using a handling pole.