Abstract: The present invention is a detector assembly for a nuclear reactor which includes platinum detector segments (30-40) axially distributed end to end within a reactor assembly and vanadium detector segments (42-52) spatially congruent in the same assembly. The vanadium detectors calibrate the platinum detector signals to remove the flux contributions of fission products. A full length vanadium detector (62) and a full length platinum detector (90) can be substituted and used to determine the compensation for the platinum detector segments (30-40). The compensated platinum detector signals, wherein compensation consists of isolating that portion of the total platinum detector signal that is directly proportional to the current local heat deposition rate in the reactor fuel, can be used for reactor core protection purposes.

Abstract: A preferred embodiment of the present invention provides an incore instrumentation system for detecting conditions, e.g., neutron flux density, within the core of a pressurized water nuclear reactor (PWR). The instrumentation system includes a plurality of long straight thimbles (52), containing fixed incore detectors, which are inserted through the top closure head (18) of the PWR. The invention meets today's principal utility, EPRI, DOE and NRC requirements and preferences, including no bottom RV head penetrations and the use of fixed incore instrumentation. In addition, an instrumentation system according to the invention is mechanically simple with a straight core insertion/removal path that does not conflict with or add significant complexity to the reactor internals.

Abstract: A hydro-ball in-core instrumentation system employs detector strings each comprising a wire having radiation sensitive balls affixed diametrically at spaced positions therealong and opposite tip ends of which are transportable by fluid drag through interior passageways through which primary coolant is caused to flow selectively in first and second opposite directions for transporting the detector strings from stored positions in an exterior chamber to inserted positions within the instrumentation thimbles of the fuel rod assemblies of a pressure vessel, and for return. The coolant pressure within the detector passageways is the same as that within the vessel; face contact, disconnectable joints between sections of the interior passageways within the vessel facilitate assembly and disassembly of the vessel for refueling and routine maintenance operations.

Abstract: A hydro-ball in-core instrumentation system employs detector strings each comprising a wire having radiation sensitive balls affixed diametrically at spaced positions therealong and opposite tip ends of which are transportable by fluid drag through interior passageways. In the passageways primary coolant is caused to flow selectively in first and second opposite directions for transporting the detector strings from stored positions in an exterior chamber to inserted positions within the instrumentation thimbles of the fuel rod assemblies of a pressure vessel, and for return. The coolant pressure within the detector passageways is the same as that within the vessel; face contact, disconnectable joints between sections of the interior passageways within the vessel facilitate assembly and disassembly of the vessel for refueling and routine maintenance operations.

Abstract: A method of providing a nuclear steam supply system that is constructed to include a barge or flotation base as an integrated portion thereof. The system is tested for operability and safety at the factory and then towed along navigable coastal or inland waterways, or overseas to foreign locations, to a prepared foundation site at its point of use. The overall unit is so constructed and arranged as to permit the removal of top and side portions to permit passage under low bridges and through narrow locks without requiring disassembly of safety class piping and wiring. The method further provides for a complete nuclear power plant constructed on multiple barges at a separate factory site in parallel with plant site preparation, i.e., in estuaries or caves.

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: A nuclear reactor steam generating plant having a pressurized water reactor with a single discharge line to a steam generator, with the primary coolant passing through the steam generator tubes divided into two streams in the channel head outlet section that is divided into two subsections. Discharge nozzles on the outlet subsections direct the streams of coolant to hermetically sealed pumps directly attached to the discharge nozzles, with the pumps directing the cooled primary coolant back to the reactor vessel. A single removable closure is provided for access to both subsections of the outlet section of the channel head, with a removable portion provided on the divider plate that forms the subsections.

Abstract: A core support system for a core barrel of a nuclear reactor, which core barrel has a bottom core support plate wherein the core support plate has apertures therethrough about the periphery thereof which communicate with recesses in engagement means for the core support plate, and keys inserted into the core support plate apertures and secured thereto with the lower section of the key extending into the recess of the engagement means. The method of installation enables alignment and securement of the core barrel in the pressure vessel without need for an assembler to enter the area between the core barrel support plate and the bottom of the vessel.

Abstract: A fuel assembly for a pressurized water nuclear reactor incorporating fluid moderator spectral shift control means. During the first part of the fuel cycle when there is excess reactivity, neutron moderation may be decreased by replacing a portion of the water within the core with a less effective moderator such as heavy water. During the life of the fuel, the heavy water is gradually replaced with regular water. The fuel assembly incorporates the necessary means and apparatus to effectuate such control.

Abstract: Apparatus comprising a seal connector is disclosed for sealingly connecting flow channels in the core support plate with flow channels in fuel assemblies for use in a spectral shift pressurized water nuclear reactor. Spectral shift is obtained by displacing a portion of the light water in the core with deuterium oxide or a combination of deuterium oxide and light water or various gases such as helium during the initial state of reactor operation to harden the nuclear spectrum and thereby reduce excess reactivity and increase the production of fissile materials. The seal connectors provide a sealed flow channel for introducing the deuterium oxide into the core during the early stages of reactor operation and for reintroducing the light water into the core during the later stages of reactor operation.

Abstract: A pressurized nuclear water reactor has a substantially cylindrical flow liner with a cylindrical wall section and bottom and an open top. A barrel forms a riser chamber that contains the core in the flow liner. A pressure vessel contains the cylindrical flow liner to form a second annular chamber therebetween that contains a supplementary liquid coolant, with insulation means to provide a major portion of the supplementary liquid coolant at a first temperature and a minor portion thereof at a second higher temperature. Upon depressurization in the vessel, fluid communication means enable injection of supplementary liquid coolant from the second annular chamber into the core upon flashing of a minor portion to vapor. A further pool of water outside the pressure vessel, and insulation on the wall, maintain the desired temperature in the supplementary liquid coolant supply. Injection or removal of borated solution, as a chemistry control solution, into or from the supplementary liquid coolant is provided.

Abstract: A method and apparatus for extending the life of a core of a water moderated nuclear reactor by spectral shift comprising the displacement of a portion of the moderator in the core by a gas having a low neutron cross-section during the initial stage of the life of the core and displacing the gas and replacing it with moderator during the latter part of the life of the core.

Abstract: A fuel assembly for a nuclear reactor comprises a 5.times.5 array of guide tubes in a generally 20.times.20 array of fuel elements. The guide tubes are arranged to accommodate either control rods or water displacer rods. The fuel assembly also comprises a plurality of Inconel and Zircaloy grids arranged to provide stability of the fuel elements and guide tubes while allowing the flow of reactor coolant therebetween.

Abstract: A recirculation system for use in pressurized water nuclear reactors to increase the output temperature of the reactor coolant, thereby achieving a significant improvement in plant efficiency without exceeding current core design limits. A portion of the hot outlet coolant is recirculated to the inlets of the peripheral fuel assemblies which operate at relatively low power levels. The outlet temperature from these peripheral fuel assemblies is increased to a temperature above that of the average core outlet. The recirculation system uses external pumps and introduces the hot recirculation coolant to the free space between the core barrel and the core baffle, where it flows downward and inward to the inlets of the peripheral fuel assemblies. In the unlikely event of a loss of coolant accident, the recirculation system flow path through the free space and to the inlets of the fuel assemblies is utilized for the injection of emergency coolant to the lower vessel and core.

Abstract: A core cooling system is disclosed for a nuclear reactor of the type utilizing a liquid coolant with a cover gas above free surfaces of the coolant. The disclosed system provides for a large inventory of reactor coolant and a balanced low pressure cover gas arrangement. A flow restricting device disposed within a reactor vessel achieves a pressure of the cover gas in the reactor vessel lower than the pressure of the reactor coolant in the vessel. The low gas pressure is maintained over all free surfaces of the coolant in the cooling system including a coolant reservoir tank. Reactor coolant stored in the reservoir tank allows for the large reactor coolant inventory provided by this invention.