Abstract: An apparatus for simulating special nuclear material is provided. The apparatus typically contains a small quantity of special nuclear material (SNM) in a configuration that simulates a much larger quantity of SNM. Generally the apparatus includes a spherical shell that is formed from an alloy containing a small quantity of highly enriched uranium. Also typically provided is a core of depleted uranium. A spacer, typically aluminum, may be used to separate the depleted uranium from the shell of uranium alloy. A cladding, typically made of titanium, is provided to seal the source. Methods are provided to simulate SNM for testing radiation monitoring portals. Typically the methods use at least one primary SNM spectral line and exclude at least one secondary SNM spectral line.

Abstract: A system for inspecting nuclear fuel pellets is provided. The inspection system is configured to use X-ray radiation at one or more energies to probe nuclear fuel pellets disposed within a nuclear fuel rod for nuclear fuel pellet defects. In some implementations of the inspection system, a nuclear fuel rod manufacturing facility may be able to integrate the inspection system for fully or partially automated inspection of all fuel rods produced within the facility.

Abstract: A tool for use in servicing an LPRM assembly of a nuclear reactor vessel includes a structural member having a first bore that is structured to receive an LPRM device associated with the LPRM assembly, a headpiece provided at a first end of the structural member, and a nut engaging assembly slideably mounted on the structural member. The headpiece has a plurality of projections structured to mate with a plurality of bores provided in a seal of the LPRM assembly to enable the seal to be removed, and the nut engaging assembly has a housing that defines a second bore and that has first and second nut engaging portions. The nut engaging assembly is free to slide along the structural member and over the headpiece to a position wherein the engaging portions extend beyond the headpiece so that they may be used to remove the assembly nut.

Abstract: The original image composed of pixels representing a sample of the alloy, the hydrides being represented by groupings of pixels (21), the method comprises steps of processing the image (1, 2, 3, 4, 5) to obtain the skeleton of the groupings of pixels (21?) contained in the image, the skeletonization step (5) being followed by a step (6, 10) of analysis pertaining to the groupings thus skeletonised. The analysis step allows the determination of the hydrogen content as well as the morphological study of the hydrides so as to determine their danger.

Abstract: A system for inspecting nuclear fuel pellets is provided. The inspection system is configured to use X-ray radiation at one or more energies to probe nuclear fuel pellets disposed within a nuclear fuel rod for nuclear fuel pellet defects. In some implementations of the inspection system, a nuclear fuel rod manufacturing facility may be able to integrate the inspection system for fully or partially automated inspection of all fuel rods produced within the facility.

Abstract: A system for detecting and containing a breach in a container. The container wall includes containment layers and a sensor layer sandwiched between the containment layers. The sensor layer contains a signal path that can be carried by a signal cable such as fiber optic or wire cable. The containment layers contain shards of material. When the wall of the container is compromised, the signal in the sensor layer is altered by the disturbed shards cutting the signal cable, thus allowing for the detection of a rupture, vandalism or an unauthorized access attempt, The containment layers may be composed of a gel or rubber material to slow leakage.

Abstract: The invention relates to a method of determining at least one technological uncertainty factor in respect of nuclear fuel elements (23) as a function of variations in the production parameters of the elements (23) in relation to nominal values. The inventive method comprises a step involving the use, for at least one production parameter, of a collective variation in said parameter in relation to the nominal value within a batch of produced elements (23). The invention can be used, for example, to design, produce and check pellets for light water reactors.

Abstract: A seal arrangement for providing a seal between a nuclear reactor in-core instrument housing and an instrument contained within the housing includes a lower seal assembly surrounding an outer portion of the in-core instrument housing, an upper seal assembly surrounding an outer portion of the in-core instrument, a seal housing enclosing the lower and upper seal assemblies, and lower and upper compression assemblies positioned on respective ends of the seal housing. The compression assemblies each include a drive nut and a compression collar. The compression collars engage and apply an axial load on the seal assemblies to maintain a reliable seal between the seal housing and the outer portion of the in-core instrument housing, and between the seal housing and the outer portion of the in-core instrument.

Abstract: The contents of a container 1 are non-intrusively monitored by probing the container with an ultrasonic signal, and measuring changes in the ultrasound signature of the received signal after the signal has passed through the contents of the container.

Abstract: A seal arrangement for providing a seal between a nuclear reactor in-core instrument housing and an instrument contained within the housing includes a lower seal assembly surrounding an outer portion of the in-core instrument housing, an upper seal assembly surrounding an outer portion of the in-core instrument, a seal housing enclosing the lower and upper seal assemblies, and lower and upper compression assemblies positioned on respective ends of the seal housing. The compression assemblies each include a drive nut and a compression collar. The compression collars engage and apply an axial load on the seal assemblies to maintain a reliable seal between the seal housing and the outer portion of the in-core instrument housing, and between the seal housing and the outer portion of the in-core instrument.

Abstract: Apparatus for the determination of radiation induced growth due to burnup of a nuclear reactor fuel assembly in a reactor core.

Abstract: A capsule containing a tag gas in a zircaloy body portion having a hemispical top curved toward the bottom of the body portion. The hemispherical top has a rupturable portion upon exposure to elevated gas pressure and the capsule is positioned within a fuel element in a nuclear reactor.

Abstract: In order to avoid uncontrolled secondary damage to a fuel rod, in particular a fuel rod being formed of Zircaloy and having a liner on the inside, in which the secondary damage may be generated by coolant that enters the fuel rod in the event of primary damage, a nucleus is deliberately provided in a cladding tube. The nucleus, although passivated in an undamaged fuel rod and not impeding the serviceability of the fuel rod, is activated by coolant which enters the fuel rod in the event of primary damage or by hydrogen or other reaction products produced in reactions of the coolant in the interior of the fuel rod and results in a small-area perforation. This prevents an aggressive atmosphere, which may result in unintentional large-area secondary damage at other points, from accumulating in the cladding tube after primary damage.

Abstract: A method and system for providing nuclear fuel rods with a configuration of isotopic gas tags. The method includes selecting a true location of a first gas tag node, selecting initial locations for the remaining n-1 nodes using target gas tag compositions, generating a set of random gene pools with L nodes, applying a Hopfield network for computing on energy, or cost, for each of the L gene pools and using selected constraints to establish minimum energy states to identify optimal gas tag nodes with each energy compared to a convergence threshold and then upon identifying the gas tag node continuing this procedure until establishing the next gas tag node until all remaining n nodes have been established.

Abstract: The device includes a first tubular support (11) carrying on its outside surface means for fixing to a handling tool, a second tubular support (18) mounted coaxially inside the first support (11) for rotation about its axis. A flexible strip (55) carrying a monitoring probe at one of its ends is engaged in a slideway support carried by the second support (18) and including an end part (65) mounted to pivot about an axis which is perpendicular to the axis (25) of the second support (18). The strip (55) is moved translationally along the axial direction (25) by a conveyor bolt (53). The inside surface of the tubular piece (3) is monitored by moving the probe fixed to the end of the flexible strip (55) rotationally about the axis (25) and in axial translation, inside the annular space (8) between the sleeve (5) and the tubular piece (3).

Abstract: For use in the manufacture of gas tags such as employed in a nuclear reactor gas tagging failure detection system, a method for designing gas tagging compositions utilizes an analytical approach wherein the final composition of a first canister of tag gas as measured by a mass spectrometer is designated as node #1. Lattice locations of tag nodes in multi-dimensional space are then used in calculating the compositions of a node #2 and each subsequent node so as to maximize the distance of each node from any combination of tag components which might be indistinguishable from another tag composition in a reactor fuel assembly. Alternatively, the measured compositions of tag gas numbers 1 and 2 may be used to fix the locations of nodes 1 and 2, with the locations of nodes 3-N then calculated for optimum tag gas composition.

Abstract: Gamma radiation leaving the surface of a radioactive materials storage vessel is measured and monitored using a plurality of gamma ray absorbing calorimeters. The gamma ray energy absorbed is converted into heat and such heat is measured or indicated for the purpose of monitoring expected radioactive decay processes of the stored radioactive materials. Material leakage or removal from storage is detected and defined by deviations from the normal expected decay in gamma radiation. Such deviation or lack of deviation, as the case may be, provide the desired accountability of the radioactive materials. Since there can be several bands of gamma ray radiation, both flux and its energy level may be determined by using different gamma absorbing materials in the calorimeters selected for the known possible energy levels of the decaying radioactive material.

Abstract: A method and apparatus for providing a permanent identification of reactor fuel assemblies with an in-reactor remote readout capability. A bar code type code assemblage is permanently coupled with the upper portion of the fuel assembly which is comprised of alternating components of magnetic and non-magnetic metal such as stainless steel. An active sensor including a magnetic core, excitation winding, and sensor or pick-up winding is employed to interact with the individual code components of the bar code assembly. The latter assembly may be formed as a sequence of rings through which the sensor is passed during a grappling procedure or as a sequence of vertically-oriented bar segments positioned outwardly of the fuel assembly and readable by rotating the fuel assembly before the active sensor.

Abstract: A light water nuclear reactor test assembly for emulating the performance of a nuclear boiling water reactor fuel bundle and measuring the subchannel void fraction in the two-phase region of the emulated fuel bundle by gamma ray attenuation is disclosed. The emulated fuel bundle has individual emulated nuclear fuel rods typically heated by individual electrical currents instead of nuclear reaction and are cylindrically hollow. A gamma-emitting source is placed on a probe and mounted for vertical excursion inside a selected emulated hollow fuel rod. A detector, typically a Geiger-Muller counter, is placed for corresponding vertical excursion inside another and preferably adjacent fuel rod. Gamma radiation from the source to the detector through the walls of the emulated fuel rods is measured. Preferably, both detector and source are collimated so that the detector does not receive gamma ray scattering from the interior of the test assembly.

Abstract: An inspection apparatus and method for testing nuclear fuel rods for helium leaks includes the basic operative steps of constantly leaking helium at a predetermined known value into a test chamber containing a fuel rod to be tested, and sampling the atmosphere within the chamber and measuring the helium in the atmosphere. A measured helium value below a preset minimum helium value indicates a malfunction in the inspection apparatus, whereas a measured helium value above a preset maximum helium value indicates the existence of a helium leak from the fuel rods. On the other hand, a measured helium value between the minimum and maximum helium values indicates the absence of a helium leak from the fuel rod.

Abstract: A nuclear fuel assembly has mechanical elements which constrain the flux thimble tube within the instrumentation tube to maintain physical contact with the interior surface of the instrumentation tube at a plurality of points staggered on a single-diametral plane and spaced substantially throughout the length of the instrumentation tube. The staggered mechanical elements induce a controlled elastic sinuous deflection of the inner thimble tube. The mechanical elements can take several different forms, for example, dimples or cantilevered spring fingers formed in the wall of the instrumentation tube and projecting radially inwardly therefrom.

Abstract: An insert for providing a reduced inside diameter for a structural tube, specifically an instrumentation guide tube, of a nuclear fuel assembly. The insert has forming lobes which coact with the structural tube to plastically deform the structural tube and mechanically lock it with respect to grid straps of a grid assembly. The insert also has centering lobes to prevent it from being expanded in other than a coaxial alignment with the structural tube. An expansion tool is provided for sequentially registering with and expanding sequential forming lobes in a simplified manner whereby all of the operations necessary to assemble the structural tube in the fuel assembly can be easily and accurately performed.

Abstract: In a nuclear fuel rod identification system, indicia is provided on a nuclear fuel rod in two stages. In the first stage, by use of a laser beam a bar code is applied directly on the fuel rod cladding tube prior to loading it with nuclear fuel and attaching plugs to opposite ends thereof to provide an assembled fuel rod. In the second stage, after loading nuclear fuel into and attaching end plugs to opposite ends of the fuel rod cladding tube with the applied bar code to provide an assembled fuel rod, by use of a laser beam, identification and enrichment symbologies are applied respectively to the side and end of one of the end plugs of the assembled fuel rod.

Abstract: An insert for providing a reduced inside diameter for a structural tube, specifically an instrumentation guide tube, of a nuclear fuel assembly. The insert has forming lobes which coact with the structural tube to plastically deform the structural tube and mechanically lock it with respect to grid straps of a grid assembly. The insert also has centering lobes to prevent it from being expanded in other than a coaxial alignment with the structural tube. An expansion tool is provided for sequentially registering with and expanding sequential forming lobes in a simplified manner whereby all of the operations necessary to assemble the structural tube in the fuel assembly can be easily and accurately performed.

Abstract: A method of repairing under water a boiling water reactor-fuel assembly having a fuel assembly channel and an upper grid plate by means of a channel stripping machine, disassembling the upper grid plate, determining a damaged fuel rod and exchanging the damaged fuel rod for another fuel rod by means of a fuel rod exchanging device, which includes, after stripping off the fuel assembly channel and disassembling the upper grid plate at the location thereof in the channel stripping machine, placing on the fuel assembly a guide box with which the fuel rods of the fuel assembly are centered, then placing thereon an indicator plate and determining the varying growth of the fuel rods, and replacing the indicator plate by a centering plate to which the fuel rod-exchanging device is coupled and a device for carrying out the method.

Abstract: An end cap with a tag gas capsule adapted to close an end of a cladding tube of a nuclear fuel element and to introduce a tag gas into the fuel element. The end cap is fixed to the tag gas capsule to form a unitary structure. The end cap has a specific shape or description on its outer surface corresponding to information concerning the specific tag gas and the capsule, so that the description or shape of the end cap can identify the specific capsule and the tag gas contained in the capsule.

Abstract: A solid tag material which generates stable detectable, identifiable, and measurable isotopic gases on exposure to a neutron flux to be placed in a nuclear reactor component, particularly a fuel element, in order to identify the reactor component in event of its failure. Several tag materials consisting of salts which generate a multiplicity of gaseous isotopes in predetermined ratios are used to identify different reactor components.

Abstract: A measuring head suitable for determining the pressure of fission gases released inside non-instrumented bars of nuclear fuel (which have reached high irradiation levels), and for connection to said bars by a method which allows no escape of said active gases and does not cause appreciable disturbance either to the fuel or to the released fission gases.

Abstract: A tagging gas releasing element which is contained in a nuclear fuel rod to release a tagging gas for detecting a failed fuel. The element comprises an inorganic solid material holding the tagging gas therein. The tagging gas is composed of a rare gas, and is held in the inorganic solid material in an injected or adsorbed state.

Abstract: This invention teaches improved apparatus for the method of detecting a breach in cladded fuel used in a nuclear reactor. The detector apparatus uses a separate bypass loop for conveying part of the reactor coolant away from the core, and at least three separate delayed-neutron detectors mounted proximate this detector loop. The detectors are spaced apart so that the coolant flow time from the core to each detector is different, and these differences are known. The delayed-neutron activity at the detectors is a function of the dealy time after the reaction in the fuel until the coolant carrying the delayed-neutron emitter passes the respective detector. This time delay is broken down into separate components including an isotopic holdup time required for the emitter to move through the fuel from the reaction to the coolant at the breach, and two transit times required for the emitter now in the coolant to flow from the breach to the detector loop and then via the loop to the detector.

Abstract: A method for testing the clad integrity of a nuclear fuel rod, comprising the first step of fabricating a sealed fuel rod with a wad of electrically conducting material mounted therein. The material is of a type that undergoes a permanent change in electrical conductivity when exposed to water. The next step is to establish an eddy current signal characteristic of the moisture-free rod. The rod is then loaded into the core as part of a fuel assembly. After the producing power, the assembly is removed for inspection, and an eddy current signal is again obtained from the rod. The eddy current signals are compared to determine whether inleakage of moisture has oxidized or otherwise altered the conductivity of the wad enough to significantly change the characteristic signal.

Abstract: The present invention relates to a standard fission product emission device, for detecting failed fuel elements in a nuclear reactor of the type cooled by pressurized water, said reactor comprising a pressure-resistant vessel and a core constituted by fuel element assemblies, wherein said device comprises a hollow rod, adapted to be inserted into said vessel and defining a chamber divided into a first chamber and a second chamber located at the end of the rod by a constriction creating a first drop in pressure, said second chamber comprising on its wall a deposit or a metal plate of radioactive material and communicating with the vessel of the reactor, when said device is in position, by a nozzle creating a second drop in pressure greater than the one created by said constriction, a first tube disposed in said rod and opening out at the end of the first chamber remote from the second chamber, said first tube being adapted to be connected to a source of pressurized water at a pressure greater than that of the

Abstract: In a nuclear reactor comprising control rods, nuclear fuel elements each having a cladding and pellets inserted therein, and a recirculation system, the reactor raises its power at least once by withdrawal of the control rods above a pellet-cladding interaction starting power (kw/ft) of the fuel element in a burnup range below the burnup at which the maximum pellet-cladding interaction starting power appears.

Abstract: A nuclear fuel rod, which comprises:a cladding tube filled with an inert gas or liquid metal and sealed at both ends in airtightness; anda plurality of nuclear fuel pellets piled one atop another in the cladding tube,and wherein an adsorbent carrying a tag gas for monitoring a nuclear fuel rod failure is received in the inner space of the cladding tube defined at least above or below the nuclear fuel pellet pile.

Abstract: A fuel element contains a tag gas serving to detect breakage of a cladding tube. Pellets of a fuel material and a metal foil having a tag gas implanted thereinto by ion implantation method are loaded in a cladding tube.

Abstract: A fuel pin for a liquid metal nuclear reactor is provided. The fuel pin includes a generally cylindrical cladding member with metallic fuel material disposed therein. At least a portion of the fuel material extends radially outwardly to the inner diameter of the cladding member to promote efficient transfer of heat to the reactor coolant system. The fuel material defines at least one void space therein to facilitate swelling of the fuel material during fission.