Abstract: In a submersible ultrasonic cleaning system for use in highly radioactive environments (e.g., cleaning radiated nuclear fuel assemblies), a bond between energy producing transducers and an radiating wall is strengthened with a polyurethane adhesive such as Permabond PT326, or 3M DP-190 adhesive. In various diagnostic tests, one or more of the transducers are operated in an energy-transmitting mode while one or more other transducers are operated in an energy-detecting mode to detect a weakened transducer/wall bond and/or acoustic conditions of the working fluid.

Abstract: A high-temperature containment-isolation system for transferring heat from a nuclear reactor containment to a high-pressure heat exchanger is presented. The system uses a high-temperature, low-volatility liquid coolant such as a molten salt or a liquid metal, where the coolant flow path provides liquid free surfaces a short distance from the containment penetrations for the reactor hot-leg and the cold-leg, where these liquid free surfaces have a cover gas maintained at a nearly constant pressure and thus prevent high-pressures from being transmitted into the reactor containment, and where the reactor vessel is suspended within a reactor cavity with a plurality of refractory insulator blocks disposed between an actively cooled inner cavity liner and the reactor vessel.

Abstract: A filter including a plurality of flow ducts extending in a longitudinal direction and each delimited between one pair of walls is provided. The filter includes deflectors protruding into each duct alternately from the pair of walls with overlapping in the longitudinal direction to define a zigzag shaped flow channel and provided with at least one set of holes aligned in the longitudinal direction to define through the overlapping deflectors a passage for accommodating a lower end pin of a fuel rod.

Abstract: A radiation exposure reduction method includes the steps of: injecting iron into a coolant which flows from the reactor cooling system to the reactor core in a nuclear power plant; and ferritizing and fixing radionuclides or parent nuclides thereof, which are contained in the coolant, on the surface of a reactor core structure, wherein an iron citrate which is soluble organic iron, or iron oxalate or iron fumarate which has a particle diameter of 3 ?m or less, is used as the iron to be injected into the coolant.

Abstract: The geometric dimensions and shape of a device for removing solid particles from the cooling medium that is circulated in the primary circuit of a nuclear reactor, in particular a boiling water nuclear reactor, are such that the device can be inserted in lieu of a fuel element or fuel assembly into an empty fuel element or assembly position of the reactor core of the nuclear reactor.

Abstract: Example embodiments are directed to upper tie plates for debris mitigation and fuel bundles that use the upper tie plates. Example embodiment tie plates may include a plurality of debris capture elements that overlap each other so as to create debris traps for particulate debris that would fall onto the fuel bundle. Example embodiment fuel bundles may use the upper tie plates for debris mitigation.

Abstract: Disclosed is an apparatus for performing an automated cleaning of nuclear fuel cladding-tubes. The apparatus comprises a pre-cleaning holding section disposed at a first side of the apparatus, a primary cleaning-material supplying section and a primary cleaning section disposed at a second side of the apparatus, a secondary cleaning section and a secondary cleaning material supplying section disposed at the second side of the apparatus and beside the primary cleaning section, an inspection section disposed at a third side of the apparatus that is opposite to the second side, and a post-cleaning holding section disposed at the fourth side of the transferring section. The pre-cleaning holding section and the post-cleaning holding section includes a cladding-tube guide where the cladding-tube is loaded before and after cleaning. Primary and secondary cleaning material supply sections are disposed at a lateral side of the primary and secondary cleaning sections respectively.

Abstract: In a head-end process for the reprocessing of reactor core material with embedded fuel particles, reactor core material is arranged in a reactor containing a fluid. The reactor comprises a voltage discharge installation in the fluid. Voltage discharges are applied through the fluid for fragmenting the fuel particles into fragmentation products and the fragmentation products are segregated.

Abstract: Crystal habit modifiers (CHM) are provided to ameliorate deposit-related concerns in nuclear plant systems. The principal targets for utilization of crystal habit modifiers are Pressure Water Reactor (PWR) primary-side fuel rod crud and secondary-side steam generator deposits and Boiling Water Reactor (BWR) coolant system deposits.

Abstract: A method for cleaning an irradiated nuclear fuel assembly includes chemically enhancing a technique utilizing an apparatus including a housing adapted to engage a nuclear fuel assembly. A set of ultrasonic transducers is positioned on the housing to supply radially emanating omnidirectional ultrasonic energy to remove deposits from the nuclear fuel assembly. Any corrosion products remaining after ultrasonic fuel cleaning will have exposed surfaces that are susceptible to chemical dissolution.

Abstract: The present invention relates to the field of energy generation. More particularly, the present invention relates to devices, systems, and methods for use in generating energy with graphite-moderated nuclear reactors. Embodiments of the invention include devices, systems, and methods for use in generating power that use graphite having a neutron diffusion coefficient higher than that of Acheson graphite. Specifically included embodiments comprise providing artificial graphite manufactured under high pressure during the graphitization process to cause a larger neutron diffusion coefficient than graphite not produced under pressure (Acheson graphite). Suitable graphite according to the invention includes graphite prepared under high pressure during the graphitization phase of the manufacturing process, which produces graphite with an increased diffusion coefficient by reducing the microcrystal diffraction scattering and increasing the non-diffractive (inelastic) scattering of the graphite.

Abstract: A method for cleaning an irradiated nuclear fuel assembly includes chemically enhancing a technique utilizing an apparatus including a housing adapted to engage a nuclear fuel assembly. A set of ultrasonic transducers is positioned on the housing to supply radially emanating omnidirectional ultrasonic energy to remove deposits from the nuclear fuel assembly. Any corrosion products remaining after ultrasonic fuel cleaning will have exposed surfaces that are susceptible to chemical dissolution.

Abstract: An apparatus for cleaning an irradiated nuclear fuel assembly includes a housing adapted to engage a nuclear fuel assembly. A set of ultrasonic transducers is positioned on the housing to supply radially emanating omnidirectional ultrasonic energy to remove deposits from the nuclear fuel assembly.

Abstract: In a head-end process for the reprocessing of reactor core material with embedded fuel particles, reactor core material is arranged in a reactor containing a fluid. The reactor comprises a voltage discharge installation in the fluid. Voltage discharges are applied through the fluid for fragmenting the fuel particles into fragmentation products and the fragmentation products are segregated.

Abstract: The invention refers to a filter (1) for separating particle from cooling water in a nuclear plant, and a fuel assembly with such a filter. The filter has an inlet end (2) and an outlet end (3) and permits through-flow of the cooling water in a main flow direction (x). The filter includes a number of sheets (4) extending in the flow direction from the inlet end to the outlet end. The sheets are arranged beside each other and form passages for the cooling water. The sheets include a first portion (4?) extending from the inlet end (2), a second portion (4?) extending from the outlet end (3), and a third portion (4??) extending between the first portion (4?) and the second portion (4?). The sheets (4) have along the first portion continuous wave-shape extending in a direction (y) transversally to the flow direction (x) and along the third portion a continuous wave-shape extending in the flow direction (x).

Abstract: The invention provides a method of separating uranium from at least fission products in irradiated nuclear fuel, said method comprising reacting said irradiated nuclear fuel with a solution of ammonium fluoride in hydrogen fluoride fluorinating said reacted irradiated nuclear fuel to form a volatile uranium fluoride compound and separating said volatile uranium fluoride compound from involatile fission products. The invention thus provides a reprocessing scheme for irradiated nuclear fuel. The method is also capable of reacting, and breaking down Zircaloy cladding and stainless steel assembly components. Thus, whole fuel elements may be dissolved as one thereby simplifying procedures over conventional Purex processes.

Abstract: A modular submersible repairing system is capable of dealing with various tasks somewhat inefficiently, though, and of being inserted and installed in a reactor instantly, and highly maneuverable. A repairing method is carried out by the modular submersible repairing system.

Abstract: The present invention concerns a process for dissolving ruthenium deposits that are present on a surface and a process for decontaminating the internal circuits of nuclear fuel reprocessing plants using the said dissolution process. The process according to the invention comprises bringing the said surface into contact with an aqueous solution of perruthenate, with the said aqueous solution having a pH equal to or greater than 12, so that the ruthenium is oxidised.

Abstract: An object of the present invention is to provide a method of operating a nuclear reactor, which is capable of effectively suppressing the initiation and growth of SCC of reactor structural members of a BWR without increasing the dose rate of a main steam system and thereby reducing radioactivity of reactor water, by carrying out, at a suitable period, a control for injecting hydrogen in the reactor water while adjusting the pH of the reactor water on the alkali side.

Abstract: Disclosed a method for radioactive decontamination of a steel surface, which is performed by bringing the surface to be decontaminated into contact with a pickling solution comprising a first iron oxidation agent, wherein bringing into contact being achieved by means of the direct continuous introduction into the pickling solution of a gas comprising a second oxidation agent, and a device for implementing the said method.

Abstract: A method for removing a wide variety of radioactive contaminants from a contaminated surface sufficient for the surface to be classified as a low-level waste or as free release. Contaminated surfaces may be classified as Class C, Class B, Class A, or high-level radioactive wastes prior to treatment. An aqueous solution having a wetting agent and a complex substituted keto-amine is provided. The aqueous solution is left on the surface for a time sufficient to remove the radioactive contaminants into the aqueous solution which is then removed. Depending on the type and condition of the surface, an acid may be added to the aqueous solution to aid in the contaminant removal process. However, typical metals surfaces may often be treated effectively without the use of concentrated acids or with dilute concentrations of such acids. The method of the present invention has the effect of removing substantially all of the radioactive contaminants from a variety of previously contaminated surfaces.

Abstract: A method for removing radioactive contaminants from a given surface. An aqueous solution having a wetting agent and a complex substituted keto-amine is provided. The solution is left on the surface for a time sufficient to remove the radioactive contaminants into the aqueous solution which is then removed. Depending on the type and condition of the surface, a concentrated acid may be added to the aqueous solution to aid in the contaminant removal process. In such a case, a pH of less than 3.0, and preferably less than 1.5 is maintained. If a concentrated acid is used, the acidic solution containing radioactive contaminants is preferably neutralized by an alkaline material to a pH of between 5.5 and 9.0. Removal of thorium contamination from railcars is one useful application of the invention. The method of the present invention has the effect of removing substantially all of the radioactive contaminants from a previously contaminated surface.

Abstract: An old core shroud (11) and an old jet pump (16) received in a reactor pressure vessel (1) are cut and carried out. A module of core internals having a new core shroud (N11), a new jet pump (N16) and a new baffle plate (N29) integrated is carried into the reactor pressure vessel (1) in which an old baffle plate (28) and an old shroud support cylinder (13) welded and fixedly secured to the reactor pressure vessel (1), and an old shroud support leg (12) fixedly secured to said old baffle plate (28) and said old shroud support cylinder (13) are left. Then, the new baffle plate (29) is fixedly secured to the old baffle plate (28), and the new core shroud (11) is fixedly secured to the old shroud support leg (12).

Abstract: To suppress a decrease of thickness due to corrosion of structural members and to achieve a removal of radionuclides with good efficiency in a nuclear power plant, oxidation decontamination is first conducted. An aqueous potassium permanganate solution is supplied from a circulation line to a reactor pressure vessel, which is a stainless steel structural member, and a reactor water cleanup system piping and a drain piping, which are carbon steel structural members. These structural members are oxidation-decontaminated by the action of potassium permanganate. Then the above-mentioned structural members are reduction-decontaminated by using an aqueous oxalic acid solution. The aqueous oxalic acid solution contains hydrazine.

Abstract: A method for removing radioactive contaminants from a given surface. An acidic solution having a pH of less than 3.0, and preferably less than 1.5, of a complex substituted keto-amine, and a mixture of a saturated and unsaturated lower alcohol (e.g. isopropyl alcohol and propargyl alcohol), and concentrated acid is applied to a contaminated surface. The solution is left on said surface for a time sufficient to remove the radioactive contaminants into the acidic solution and then removed. The acidic solution containing the radioactive contaminants is preferably neuralized by an alkaline material to a pH of between 5.5 and 9.0. Removal of thorium contamination from railcars is one useful application of the invention. The method of the present invention has the effect of removing substantially all of the radioactive contaminants from a previously contaminated surface.

Abstract: An apparatus for cleaning an irradiated nuclear fuel assembly includes a housing adapted to engage a nuclear fuel assembly. A set of ultrasonic transducers is positioned on the housing to supply radially emanating omnidirectional ultrasonic energy to remove deposits from the nuclear fuel assembly.

Abstract: The present invention concerns a process for dissolving ruthenium deposits that are present on a surface and a process for decontaminating the internal circuits of nuclear fuel reprocessing plants using the said dissolution process.

Abstract: A new approach to scabbling of surfaces of structural materials is disclosed. A layer of mildly energetic explosive composition is applied to the surface to be scabbled. The explosive composition is then detonated, rubbleizing the surface. Explosive compositions used must sustain a detonation front along the surface to which it is applied and conform closely to the surface being scabbled. Suitable explosive compositions exist which are stable under handling, easy to apply, easy to transport, have limited toxicity, and can be reliably detonated using conventional techniques.

Abstract: A novel support material for radionuclides has a higher capacity for radioactive substances than previously known support materials. Miniaturized radioactive radiation sources made from the support material display an enhanced dose capacity. The support material is made by the mixing of a suitable solid support with a polysaccharide followed by malleabilization.

Abstract: An apparatus for cleaning an irradiated nuclear fuel assembly includes a housing adapted to engage a nuclear fuel assembly. A set of ultrasonic transducers is positioned on the housing to supply radially emanating omnidirectional ultrasonic energy to remove deposits from the nuclear fuel assembly.

Abstract: A preventive maintenance method and apparatus for a structural member in a reactor pressure vessel according to the present invention reduce a tensile residual stress on a surface of the structural member by impinging a water jet from a nozzle onto a plane surface of a deflector to thereby change direction of flow of the water jet, and impinging the water jet after being deflected onto the surface of the structural member. This method and apparatus are applicable to a narrow space portion, and can improve a residual stress on the surface of the structural member and can also prevent damage such as stress corrosion cracking.

Abstract: A maintenance of a suppression pool or spent fuel storage pool in a reactor primary containment vessel of a nuclear power plant includes a cleaning step of a water in the suppression pool and a decontamination step of an interior of the suppression pool, and in the maintenance, the coated film applied on an inner surface of a wall portion of the suppression pool is inspected. These cleaning, decontaminating and inspecting steps are performed by divers while maintaining a water level in the suppression pool.

Abstract: A process for generating an inerting gas for rendering an atmosphere inert, such as within a containment shell of a nuclear power plant. Inert gas is kept in liquid or solid phase in a first reservoir. A sufficient amount of heat to vaporize the liquefied or solidified inert gas is made available in a heat transfer medium in a second reservoir. When inerting gas is needed, the heat transfer medium and the liquefied or solidified inert gas are brought into thermal contact with one another. An apparatus for generating the inerting gas is provided as well. The process and the apparatus are particularly suitable for generating a large amount of inerting gas, as a result of which it can be ensured that the containment shell of a nuclear power plant is rendered inert within a short time.

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: A process for obtaining a sample from an atmosphere in a closed gastight vessel, preferably from a reactor safety vessel of a nuclear power station, includes passing a sample through a venturi nozzle immediately upon entry of the sample into a sample-taking container in a vessel. The sample is mixed in the venturi nozzle with a transport fluid serving as a washing liquid. Gaseous constituents of the sample being soluble and/or condensable in the washing liquid are subsequently discharged together with the washing liquid from the sample-taking container and from the vessel by triggering a pressure reduction. A device for obtaining samples from an atmosphere in a closed gastight vessel, preferably from a reactor safety vessel of a nuclear power station, includes a sample-taking container having a bottom and a given volume. A washing liquid is disposed in the sample-taking container and has a volume being at most approximately equal to half of the given volume.

Abstract: A chemical decontamination clean-up system for use on-line in a nuclear reactor primary system includes a pump arrangement within the nuclear reactor primary system for pumping primary system fluids to a cleaning system located directly downstream from the pump assembly. The cleaning system includes a plurality of first demineralizer banks arranged in a predetermined flow pattern for receiving the primary system fluids. Each of the first demineralizer banks comprises at least two individual, resin-filled demineralizers arranged in parallel wherein primary system fluids are demineralized. Each of the demineralizer banks includes valving for selectively directing the primary system fluids from the pump arrangement to selected demineralizer banks in the plurality of the first demineralizer banks. A second demineralizer bank receives the primary system fluids from the plurality of first demineralizer banks.

Abstract: In a device for monitoring the atmosphere within the containment shell (1) of a reactor plant, a sample removal means (41) is provided in the containment shell, from which a gas mixture is led via a measuring line (42) through a measuring zone (14) and subsequently discarded. The concentration of the gas is reduced upstream of the measuring zone (14) in a dilution plant (40).

Abstract: A system for monitoring the radioactivity of a liquid waste stream includes a pair of tanks into which the liquid waste stream is directed during alternating fill cycles. At the conclusion of each fill cycle, the liquid waste is recirculated through the chamber of a radioactivity monitor. A pair of opposed radiation detectors, external to the chamber, generate activity measurements to a controller indicative of the radionuclide concentration levels in the liquid waste. The tanks are then emptied either to the environment or back to a decontamination facility for further processing depending on the indicated radionuclide concentration level. System operation, including periodic servicing of the monitor, is automatically coordinated by the controller to avoid interruption of the liquid waste stream filling the tanks.

Abstract: The present invention presents a novel apparatus and a method of demolishing a biological shield wall of a nuclear reactor using a concrete cutter device working on a wire saw, said apparatus comprising a concrete cutter device consisting of a driving part for a wire saw and a concrete cutting part attached on the engaging receiver of the driving part, a core boring machine to be attached interchangeably on the receiver in the place of the cutting part and a carrier truck to carry the wire saw driving part of said cutter device, further the concrete cutting part having a pair of vertical rods supported on a table movable vertically and adjustable in a distance of the rods and, at the bottom end of the rods, supporting pulleys and guide rollers for disposing the wire saw are provided.

Abstract: A unique and optimum nuclear steam supply system operating configuration for integration of a chemical decontamination system is disclosed. The chemical decontamination system is connected to, and returns to, the residual heat removal system downstream of a residual heat removal heat exchanger, thereby utilizing the residual heat removal system to control the temperature of process fluids entering the decontamination system. A reactor coolant pump or pumps generates heat for the chemical processes as needed and a nitrogen blanket within the primary system pressurizer is utilized for system pressure control.

Abstract: Apparatus and method for decontaminating radioactive materials by stimulating the atomic system of radioactive materials. The stimulus is kept applied to the radioactive materials for a predetermined time. In this way, the rate of decay of the radioactivity of the materials is greatly accelerated and the materials are thereby decontaminated at a rate much faster than normal. The stimulus can be applied to the radioactive materials placing them within the sphere or terminal of a Van de Graaff generator and allowing them to be subjected to the electrical potential of the generator, such as in the range of 50 kilovolts to 500 kilovolts, for at least a period of 30 minutes or more.

Abstract: An auxiliary flexible vacuum seal for preparing a reactor coolant pump for vacuum degasification of the reactor coolant system employs a flexible boot member having a pair of longitudinally-displaced opposite open end portions and a pair of side-by-side longitudinally-extending side portions in the form of flanges defining a split in the boot member along a side thereof and extending between the open end portions for allowing flexing of the boot member between open and closed side configurations to permit its installation and removal on and from the pump. The seal also employs clamping brackets and fasteners for releasably and sealably clamping together the flanges of the boot member at the split to retain the boot member in its closed configuration.

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: In an apparatus for separating radionuclides from non-radionuclides in a mixture of nuclear waste, a vessel is provided wherein the mixture is heated to a temperature greater than the temperature of vaporization for the non-radionuclides but less than the temperature of vaporization for the radionuclides. Consequently the non-radionuclides are vaporized while the non-radionuclides remain the solid or liquid state. The non-radionuclide vapors are withdrawn from the vessel and condensed to produce a flow of condensate. When this flow decreases the heat is reduced to prevent temperature spikes which might otherwise vaporize the radionuclides. The vessel is removed and capped with the radioactive components of the apparatus and multiple batches of the radionuclide residue disposed therein. Thus the vessel ultimately provides a burial vehicle for all of the radioactive components of the process.

Abstract: An auxiliary seal for preparing a reactor coolant pump for vacuum degasification of the reactor coolant system includes at least a pair of sealing segments. The sealing segments are composed of metal and have semicircular shaped bodies with attaching ears and an anchoring flange fixed thereon. The attaching ears extend radially outward from opposite ends of the sealing segment bodies. The ears on one segment body when aligned with and attached by fasteners to the ears on the other segment body draw the sealing segments together in releasably attached relation to one another and in sealing and clamping engagement about a shaft of the pump. The segment bodies also have interior and exterior circumferential recesses with O-rings therein which seal respectively with a portion of the pump shaft and a portion of a housing of the pump. The annular flange extends radially outward from the sealing segment bodies and is attachable to the housing portion for anchoring the seal segments thereto.

Abstract: A continuous dissolution apparatus for spent nuclear fuel in which a container (2) for holding a dissolution processing solution (1) is continuously supplied with nitric acid from a feed port (3), while the processing solution is continuously drawn out from an outlet (4). Baskets (71-74) in the container are packed with spent-fuel chops (6), which are continuously dissolved by the processing solution. The container is provided with a solution reserving section (4) for lowering the concentration of radioiodine contained in the dissolution processing solution, and a partition wall (10) is formed between the solution reserving section and a container body. The dissolution processing solution having overflowed from the upper edge of the partition wall flows into the solution reserving portion (14) through a perforated plate column (11).

Abstract: A process for precluding or reducing the danger to a system or its surroundings by mixtures comprising reactive substances which react chemically and/or physically and the release of pollutants during an accident, in particular by the combustion of hydrogen in the containment of a nuclear power plant and/or by the release of fission products therefrom, wherein at least one portion of said reactive substances and/or pollutants are kept separately during system malfunction or are at least partially separated into two areas and kept separately there, or wherein a potentially dangerous reaction is stopped in a first, especially hazardous area by transferring at least one portion of at least one of said reactive substances into a second area.

Abstract: A process for the controlled discharge from a reactor containment structure of a gas cooled nuclear power plant and the installation for achieving this process include parallel discharge circuits from a reactor containment structure to a discharge stack. The flow of discharge from the reactor containment structure normally flows in a primary discharge circuit and may be directed wholly or partially to the parallel secondary discharge circuit. The secondary discharge circuit contains means for reduction of the temperature of the discharge, means for deposition of particulate fission products and they also contain means for recombination of combustible gases and means for filtration of the discharge. Nuclear power plant installations and processes for controlling the discharge from a reactor containment structure in this fashion permit safe discharge of naturally occurring leakage for gas cooled nuclear reactors, as well as leakage occurring in the event of reactor failure.

Abstract: A procedure for vacuum degassing of a reactor coolant system which basically utilizes existing equipment to degas and refill the coolant system. The level of radiogas and non-radiogas concentration is reduced to low residual levels in less than two hours to expedite shutdown operations. The procedure enhances residual heat removal by using the steam generators as reflux condensers. During draindown of the reactor coolant to the midplane of the reactor vessel outlet nozzles, a two-phase pump is used and a vacuum is established in the vapor space created in the reactor pressure vessel, and the steam generators.

Abstract: A process and an installation for the securing against excessive pressure in a prestressed concrete pressure vessel of a gas cooled high temperature reactor and for the prevention of activity release into the environment. The process comprises three steps and in each step pressure reducing installations become effective upon the rise of pressure in the prestressed concrete pressure vessel over a predetermined value. In the first step the pressure vessel is relieved by means of the operational gas purification apparatus and a conveying blower into the storage vessels for the cooling gas. In case of a further rise in pressure, in a second step a discharge path equipped with a safety valve and a check valve is opened, which also relieves into the storage vessels while by-passing the gas purification installation.