Abstract: Automated inspection assemblies for scanning pipes of a nuclear reactor are described. In one embodiment, the assembly includes a mounting subassembly and a scanning subassembly. The mounting subassembly includes a clamp configured to be mounted to selected pipes in a nuclear reactor pressure vessel, and the scanning subassembly is movably coupled to the mounting subassembly. The scanning assembly includes a scanning head configured to scan at least a portion of the circumference of the pipe to be inspected, and the scanning head includes a substantially "U" shaped transducer support assembly sized to receive the pipe. Transducer elements are coupled to the transducer support assembly legs, and the transducer support assembly is configured to rotate about the pipe to inspect the pipe.

Abstract: The present invention relates to a method and portable apparatus which is used to detect substances, such as explosives and drugs, by neutron irradiation. The apparatus has a portable neutron generating probe and corresponding controllers and data collection computers. The probe emits neutrons in order to interrogate an object. The probe also contains gamma ray detectors for the collection of gamma rays from fast neutron, thermal neutron and neutron activation reactions. Data collected from these detectors is sent to the computer for data de-convolution then object identification in order to determine whether the object being interrogated contains explosives or illicit contraband.

Abstract: A transiently unstable state of a boiling-water reactor is damped by measuring the oscillating neutron flux and, after a first threshold value is exceeded over a plurality of oscillation periods, the rate of increase of the oscillation is determined. Depending on the slope of the increase, and after a further threshold value (in particular one dependent on the rate of increase) for the oscillating flux is exceeded, a selection is made which one of various stabilization strategies for damping the oscillation should be triggered before a SCRAM becomes necessary. A hierarchy of stabilization strategies is available: blocking a power increase, for instance, in the control system, controlled slow reduction of the power, or rapid power reduction by a "partial SCRAM". The monitoring of the unstable state is effected with a system of sensors strategically distributed throughout the core and which redundantly measure the flux in one region of the core.

Abstract: A wedge locking support apparatus that applies a downward preload force to a jet pump inlet mixer gravity wedge and is remotely installable without disassembly of the jet pumps is described. The downward force supplied by the wedge locking support apparatus supplements the force supplied by the weight of the gravity wedge and improves the lateral support provided to the inlet mixer by the gravity wedge. The wedge locking support apparatus includes an upper leaf spring assembly configured to engage the gravity wedge bracket, a lower leaf spring assembly slidably coupled to the upper leaf spring assembly and configured to engage the top of the wedge, and a jack bolt coupled to the upper and lower assemblies.

Abstract: The invention relates to a pebble bed reactor comprising a core cavity filled with spherical fuel elements and bounded by reflector material. Spherical fuel elements pass through the core cavity under the effect of gravity. Coolant gas flows through the core cavity in a descending or ascending stream. The coolant-gas lines provided for the purpose discharge laterally above the base of the cavity bottom. In the reactor according to the invention, coolant gas can be conveyed through the pile of fuel elements without problems over long operating times.

Abstract: A method of producing mixed oxide fuel pellets. The method uses oxides of at least two fissile elements and includes a mixing, milling, spheroidising and sintering step to produce a fuel pellet incorporating a neutron poison.

Abstract: The invention is directed to a high-density dispersion nuclear fuel having spherical particles of an uranium alloy dispersed in a nonfissionable matrix. The alloy includes uranium and 4-9 wt % Q, wherein Q is selected from the group consisting of Mo, Nb, and Zr. A process of manufacturing the spherical particles is also disclosed.

Abstract: The length gauge includes an elongated standards rod, an indicator location block carrying a gauge and an indicator set block. The set block is applied to the location block and the gauge is zeroed out at a known distance between the movable element on the gauge and a reference surface. Water rods are assembled to a tie plate and the gauge is used to measure the length of the adjustable length water rods. The location block receives in a recess a portion of the tie bar of the water rod. The standards rod engages the tie plate and the gauge pin engages the opposite end of the standards rod. Any deviation in the length of the water rod from a designed length is indicated on the gauge.

Abstract: An apparatus for the creation and detection of high velocity alpha particles accompanied by one or two captured electrons. The apparatus is a modification of the well-known Cockcroft and Walton experiment used to disintegrate lithium-7 into high energy alpha particles by bombarding the lithium with high energy protons. The resulting alpha particles with captured electrons cannot be detected by normal helium absorption spectrum techniques and have other unique attributes.

Abstract: A method for disposing of a component located in a reactor pressure vessel of a nuclear reactor plant. The component is, in particular, a lower core structure of a pressurized water reactor plant. An upper part of a container provided for further transport is disposed above an opened and flooded reactor pressure vessel. The upper part is provided with a lower orifice. The component is raised through the orifice into the upper part of the container and is subsequently transported to an upwardly open lower part of the container. The upper part is assembled together with the lower part to form the container, so that the component is enclosed and shielded in the container.

Abstract: This invention relates to a method for the destruction of plutonium (Pu) by irradiation in a light water reactor (LWR). According to the invention Pu is mixed with highly enriched uranium (U) in roughly equal weight proportion rates. This mixture is embedded in an inert matrix of a material whose components have an atomic number significantly lower than 92. LWR fuel pins are then produced therefrom and these pins are inserted in a LWR in place of certain normal LWR fuel pins. The irradiation time of the fuel pins containing Pu is significantly longer than that of said normal pins. The irradiation is preferably repeated after about 200 years without any reprocessing of the spent fuel.

Abstract: The spacer grids consist of interlaced metal straps defining a regular lattice of cells. A spring for holding a fuel rod against bearing stops is fixed on at least one wall of each of the cells. In its part which constitutes the wall of the cell, the strap includes at least one stop produced by cutting and pushing the metal of the strap into the cell, so as to limit the displacement of a fuel rod housed in the cell. Stops for limiting the displacement of the fuel rod are placed preferably o the walls of the peripheral cells or corner cells of the spacer grid, opposite a peripheral belt of the spacer grid. The invention also relates to a fuel assembly which includes, in addition to structural spacer grids, end grids and additional mixing grids interposed between the structural spacer grids.

Abstract: A CEDM data acquisition system (40) receives analog coil-current signals from control element drive mechanism coils (18, 20); conditions the analog signals to remove noise induced therein by the electronic circuitry (44) associated with the control element drive mechanisms; digitizes the conditioned analog signals; displays the acquired test data; and records the data for future use. The inventive data acquisition system preferably has the ability to simultaneously measure, display and record coil-current data for all of the five coils associated with each CEDM rod-group with respect to time. Further, the inventive data acquisition system preferably allows the user to monitor, display and record data for up to eight CEDMs simultaneously. It also allows the measurement of rod-drop times during rod-drop testing of the CEDMs.

Abstract: A separator/injector having an outlet pressure higher than an inlet pressure thereof is introduced instead of the dynamic equipment for a reactor recirculation system that is necessary in the prior art, to achieve both liquid-vapor separation and forced circulation. A jet pump and a recirculation flow-rate control valve are provided in a lower portion of a downcomer portion of a reactor pressure vessel. A shroud head has a double-walled structure, a two-phase liquid-vapor flow that is flowing from a lower portion of the lower shroud head is accelerated by an accelerator nozzle of the separator/injector, and a liquid component of the thus-separated flow is increased in pressure and guided into a jet pump through a space formed between the double shroud heads.

Abstract: A suction strainer includes a hollow internal core tube and an external filtering surface built around the internal core tube. A plurality of openings are defined through the side wall of the internal core tube core. In some cases the openings through the side wall are constructed and arranged such that there is somewhat less open area near the downstream end than the upstream end of the internal core tube, and the amount of open area tapers between the upstream end and the downstream end. As a result, when liquid is drawn into the internal core tube through the plurality of openings, a substantially uniform inflow distribution may be defined along substantially the entire length of the internal core tube. The internal core tube functions as a rigid structural support for the external filtering surface, enabling the apparatus to withstand post-LOCA hydrodynamic forces.

Abstract: A method is provided for determining the fission heat flux of a prime specimen inserted into a specimen of a test reactor. A pair of thermocouple test specimens are positioned at the same level in the holder and a determination is made of various experimental data including the temperature of the thermocouple test specimens, the temperature of bulk water channels located in the test holder, the gamma scan count ratios for the thermocouple test specimens and the prime specimen, and the thicknesses of the outer clads, the fuel fillers, and the backclad of the thermocouple test specimen. Using this experimental data, the absolute value of the fission heat flux for the thermocouple test specimens and prime specimen can be calculated.

Abstract: Methods and apparatus for moving fuel bundles in a reactor pressure vessel (RPV) of a nuclear reactor are described. In one embodiment of the apparatus, a support tube facilitates the positioning of a multiple channeled magazine within the RPV, especially at locations adjacent fuel bundles. In the one embodiment, the support tube extends in the reactor pressure vessel into the area above the top guide. A magazine assembly is coupled to the support tube, and includes a magazine having a plurality of fuel bundle receiving channels. The magazine extends from the support tube so that it is adjacent the fuel bundles and the top guide. Grapples extend through the magazine channels, engage the fuel bundles, and retract the bundles into the magazine channels. The magazine and support tube, and thus the bundles, are then moved.

Abstract: A twist beam suspension includes a twist beam which is disposed so that the longitudinal direction thereof runs along with the transverse direction of a vehicle, and a pair of trailing arms being connected to a body of the vehicle and each of which is disposed at a respectively different longitudinal end of the twist beam and is disposed such that the longitudinal direction thereof runs along the longitudinal direction of the vehicle. The twist beam suspension further includes a restricting apparatus which restricts inward displacement of the pair of trailing arms relative to the body of the vehicle in the transverse direction of the vehicle prior to restricting outward displacement of the pair of trailing arms relative to the body of the vehicle in the transverse direction of the vehicle.

Abstract: A method and an apparatus detect the dropping of at least one control element in a reactor core of a power station by delaying signals output by detectors disposed along a fall path of the control element in such a way that they are approximately simultaneous. This improves a registration of the dropping of the control element by improving a ratio between a useful signal and a noise signal.

Abstract: A method and an apparatus are used for determining the neutron flux density of a neutron-emitting source, in particular a reactor core of a nuclear power facility. In the method, a first measurement signal and a second measurement signal, which differ from one another and are each monotonally dependent on the neutron flux density, are used to form a wide-range signal that depends uniquely on the neutron flux density. The wide-range signal is defined region-by-region, the wide-range signal is equated to the first measurement signal in a region where the values of the neutron flux density n are lower, n<n.sub.1, is equated to the second measurement signal in a region where the values of the neutron flux density are higher, n>n.sub.2, and is equated to a monotonal function of both measurement signals in an overlapping region located in between.