Abstract: Both gadolinia nuclear fuel rods and urania fuel rods are non-destructively tested to determine the enrichment concentration of the fuel pellets therein by serially conveying the gadolinia rods and the urania rod along separate test channels through an active scanner where they are irradiated from a common neutron souce, and the neutron-induced gamma ray emissions are counted as a measure of the enrichment concentrations at a multiplicity of points distributed along the rod length. The enrichment counts are corrected for background radiation, variations in fuel density, and, in the case of gadolinia rods, for gadolinia content by passing these rods through a magnetometer.

Abstract: An improved passive cooling system for water cooled and moderated nuclear fission reaction plants provides means for enhancing the cooling arrangement for coping with loss of coolant accidents or removing decay heat during periods of reactor shutdown. The improvement comprises providing a measure consisting of a tubular sleeve, which encourages flow circulation within a pool of cooling water.

Abstract: The wetwell space in a suppression pool of a nuclear reactor containment is continuously ventilated by exhausting gas therefrom, while at the same time, during normal system operation atmospheric air from a source of same is admitted to the wetwell but such admission being blocked during a LOCA. All exhaust flow from the wetwell is conveyed through a conduit that outlets at a remote elevated location in the atmosphere. All exhaust flow through the conduit is before outletting therefrom passed through gas treatment operation wherein any particulates in the gas mixture are removed. Further treatment of the gas with charcoal to adsorb noble gases can be carried out. In normal reactor operation the ventilation flow rate is at minimal level. However on occurrence of a loss-of-coolant-accident, highly heated gases from the containment drywell are passed into the suppression pool where condensables condense while non-condensable gases are cooled and vent to the wetwell.

Abstract: A spacer with a spring construction for the fuel bundle having matrix of parallel side by side fuel rods supported within a fuel channel between a supporting lower tie plate and holding upper tie plate is illustrated. The spacers each have a corresponding matrix of individual ferrules each surrounding the discrete fuel rods to be spaced within the matrix of fuel rods at any given elevation within the fuel bundle. Each of the individual ferrules surrounding the individual fuel rods are provided with stops against which the fuel rods are biased to ensure the required side-by-side spacing. Each ferrules must have at least one spring for forcing the fuel rods against the stops of its spacer ferrules to enable the spacer to assure required side-by-side alignment of the fuel rod. The springs are provided with a continuously looping main body having protruding tabs on opposite sides of the springs.

Abstract: A quality assurance inspection system utilizes a plurality of ultrasonic transducers to probe an elongated tube for both dimensional and structural integrity. The transducers are pulsed in rapid succession, and echo signals are conducted over separate RF channels and through a multiplexor to a lesser number of detector signals channels, each including a discriminator. Inspection windows are opened in these discriminators to permit detection of echo signals and the generation of time mark signals for stopping a plurality of clocks which then register pulse-echo time intervals. These data are computer processed to provide tube dimension and flaw information.

Abstract: Flux-trap control rod flow diverters comprising a series of tabs formed along the length of one side of a hafnium neutron absorber tube, and bent inwards towards the opposing side so as to allow water in one side of the tube, and simultaneously divert internal water out of corresponding openings formed in the opposing side of the tube. In this way the internal water does not stay inside the control rod long enough to boil, and the water's effectiveness as a neutron moderator is assured.

Abstract: A boiling water nuclear fission reactor is disclosed with a unique steam-water separating system. The steam-water separation means comprises an assemblage of open troughs positioned above the fuel core which reduces the amount of steam recycled through the coolant circuit.

Abstract: A nuclear reactor system which includes a containment uses, upon loss-of-coolant event, an isolation condenser submerged in a large supply of water and elevated some distance above the system pressure vessel to effect both initial and decay heat dissipation cooling in the containment. The isolation condenser has inlet thereto communicated to an open entry conduit disposed in the containment so that steam and heated gasses in the containment space enter the isolation condenser and are cooled. Condensate resulting from the cooling is returned to an elevated system gravity coolant supply pool, which pool is used for replenishing coolant lost from the pressure vessel, the return being through a return conduit that has a lower end section configured with a water trap with non-condensable gasses present in the steam being separated from the condensate and vented to the suppression pool.

Abstract: A liquid metal cooled nuclear reactor having a passive cooling system for removing residual heat resulting from fuel decay during reactor shutdown. The passive cooling system comprises a plurality of partitions surrounding the reactor vessel in spaced apart relation forming intermediate areas for circulating heat transferring fluid which remove and carry away heat from the reactor vessel. The passive cooling system includes a closed primary fluid circuit through the partitions surrounding the reactor vessel and a partially adjoining secondary open fluid circuit for carrying transferred heat out into the atmosphere.

Abstract: An improved spacer and method of making a spacer is disclosed for use in a nuclear fuel bundle wherein a plurality of fuel rods enclosed within a channel are maintained in parallel side-by-side relation by a plurality of the spacers. Each spacer is placed within the fuel bundle at selected elevations between upper and lower tie plates. The improved spacer is a member of the class of spacers wherein solid strips of material are welded at interstitially placed tube members between the fuel rods to form the continuous spacer grid. The improvement constitutes forming separate upper and lower reduced section grids from separate, normally aligned, first and second parallel sets of grid members. One grid is formed for the top of the spacer; the remaining grid is formed for the bottom of the spacer. Tube members placed interstitially between the fuel rods are used to interconnect the grids.

Abstract: A vacuum system for cleaning the base of a control blade guide tube comprises a vacuum source and a novel vacuum head. The vacuum source includes a conventional vacuum pump and filter, for trapping matter entrained in water driven by the pump. The vacuum head is disk-shaped and has an off-axis vacuum port which can scan the guide tube base when the disk is rotated 360.degree.. Elongated slots in the disk admit water down through the disk. Guide fins separate the slots from the vacuum port. The guide fins are shaped to provide a clearance over the guide tube base, effecting a highventuri action which helps sweep up debris on the guide tube base. An annular ridge on the disk surrounds a similar annular ridge on the base, isolating a control rod drive tube housing below the base from the vacuum. This prevents control rod drive components from being disturbed by the vacuum.

Abstract: Apparatus for thermal sizing elongated, tubular channels of a square cross section includes a die having plural elongated die elements and an elongated mandrel having a frame mounting plural pairs of rollers distributed along its length on all four sides. The die is inserted in the channel with its die elements disposed adjacent the channel corners. The mandrel is then inserted with its roller pairs peripherally engaging the die elements, pressing them against the channel corners. The channel, die and mandrel are then heated to a hot-forming temperature, thermally expanding the mandrel frame into pressing engagement with the die elements in lieu of the rollers to plastically reform the channel to a stable shape free of geometric irregularities.

Abstract: The disclosed invention comprises a method for assembling fuel bundles for service in nuclear reactors which minimizes damage to the assembled components of a nature that renders the components susceptible to destructive corrosion in service, and the enhanced product of the improved method. The invention includes the utilization of a temporary protective barrier, such as water soluble sodium silicate or gelatin, intermediate the components during assembly.

Abstract: A fluid pressure actuated steam depressurization valve for nuclear reactor service. The valve is maintained closed retaining steam pressure within the system by the application of fluid pressure from an external source and control, and upon release of the applied fluid pressure steam pressure within the nuclear reactor system is vented to depressurize the system.

Abstract: A measure providing improved personnel safety in the operation of a steam producing, water cooled, boiling water nuclear fission reactor for generating electrical power is disclosed. The measure comprises utilizing catalytic oxidation to inhibit the escape of certain radioactive material from the reactor and its passage through the steam circuit.

Abstract: A liquid metal cooled nuclear reactor having a passive cooling system for removing residual heat resulting from fuel decay during reactor shutdown. The passive cooling system comprises a plurality of cooling medium flow circuits which cooperate to remove and carry heat away from the fuel core upon loss of the normal cooling flow circuit to areas external thereto.

Abstract: An electrical switching system comprising a relay having a photoelectric element comprising a photodiode, with first and second electrodes and a photosensitive portion. The photosensitive portion is responsive to optical stimulation for electrically coupling the first and second electrodes, permitting transmission of electrical current between them whereby the relay can be connected to a source of electrical power. The electrical switching system comprises a pair of such relays which cooperate through optical signals to operate the switch system. Also a part of the switching system is an optical rotary switch for controlling the operation of the switch system. A further aspect of the disclosed invention comprises a nuclear power generating apparatus including a monitoring arrangement operated by the electrical switching system of this invention.

Abstract: A monitor for detecting airborne radioactive particulates is disclosed. An elongate strip of filter paper is fed across first and second air inlet ports of a collection chamber. Ambient air is selectively drawn into the chamber through a selected one of the inlet ports and out an through outlet port. Particulates trapped on an area of the filter paper in alignment with the open inlet port are detected after advancing the strip area into alignment with the closed inlet port. A radiation detector mounted on a movable arm is selectively positioned over the closed inlet port to detect the trapped radioactive particulates, while a new sample is collected at the open inlet port. Exposure of the detector surface to corrosive materials is avoided and the detector can be positioned close to the filter strip to maximize counting efficiency and energy resolution. A microprocessor controls the functions of the monitor and allows continuous unattended operation.

Abstract: An improved channel is disclosed which has a reduced average thickness in its upper portion. The lesser average thickness corresponds to a lower pressure difference acting on the channel sides, over the upper portion of the channel. The reduction in average thickness is accomplished by cutting flow trippers into the inner surface of the channel walls and/or cutting grooves into the outer surface of the channel. The axial variation of channel average thickness increases water volume adjacent to the upper part of the channel to provide increased neutron moderation, to minimize the steam void reactivity coefficient, and to provide a greater cold shutdown margin. The material removed to produce the flow trippers increases the cross-sectional area inside the channel and reduces pressure drop in the upper portion of the channel. The flow trippers divert water flowing on the channel walls to the fuel rods adjacent to the channel walls, permitting higher reactor power operation.