Abstract: A reactor coolant system of a pressurized water nuclear reactor with fuel assemblies in the core is simultaneously shutdown and decontaminated in less than 90 hours after the shutdown is initiated. A LOMI or Can-Derem decontamination reagent is added to reactor coolant to reduce iron and nickel in oxidized coatings before removing dissolved hydrogen and reducing the gamma emitting activity of the reactor coolant.

Abstract: An apparatus admits gas into the primary coolant of a pressurized water nuclear reactor having a coolant loop for a liquid coolant, in particular water, to which hydrogen is to be added. The coolant loop preferably includes a volume control tank for the coolant as well as at least one high-pressure pump which admits coolant that has been extracted from the coolant loop back into the coolant loop again. An admission point for the hydrogen is located in a suction line on the suction side of the high-pressure pump. A measurement line on the pressure side of the high-pressure pump communicates with the volume control tank or with a dewatering system. A device for measuring the hydrogen content in the coolant is incorporated into the measurement line. The measuring device is connected through a control device to a control valve, with which the delivery of hydrogen to the admission point can be controlled. The gas admission apparatus assures a definite, precisely maintained hydrogen content in the coolant.

Abstract: In a chemical decontamination apparatus, a catalyst decomposition column in an upstream side of an ion exchange resin column and a hydrogen peroxide injection apparatus in a further upstream side, reduce the amount of waste products caused by a chemical decontaminating agent where a mixed decontaminating agent for a composition trapped in a cation resin column and for a composition trapped in an anion exchange resin are used for the chemical decontaminating agent, selectively decompose the composition trapped in the cation resin column in an inlet side of a cleaning apparatus when radioactive nuclides in the decontaminating agent are cleansed using the cation resin column during decontamination, and decompose both compositions after completion of the decontamination. The chemical decontamination thus selectively decomposes the chemical decontaminating agent, which is a component of the load to the cation resin column.

Abstract: A radioactive substance decontamination method and apparatus which decontaminates a metal member contaminated by radioactive substance in a short period of time. This apparatus has (1) multiple reducing decontamination tanks having different radiation control values; (2) a carrier for immersing the metal member into the multiple reducing decontamination tanks and a washing tank; (3) a tube for transferring into the second reducing decontamination tank the reducing decontamination agent in the first reducing decontamination tank; (4) a reducing agent decomposer for decomposing a component contained in the reducing decontamination agent of the reducing decontamination tank where the radiation control value is the highest out of the reducing decontamination tanks connected by the tube; and (5) a washing tank for washing the reducing decontamination agent deposited on the decontaminated metal member.

Abstract: A foreign matter filter provided between a DFBN and a lower grid has two adjacent thin straps assembled into a lattice. The straps are equipped on the front and back sides with axially continuous protrusions.

Abstract: A fuel assembly lower tie-plate with better performance in capturing linearly elongated foreign substances. The lower tie-plate has a screening plate positioned below the network section in the lower tie-plate cavity. The screening plate is arranged substantially horizontally so that the lower tie-plate cavity is divided into upper and lower parts by the screening plate. Tubular filters are attached to the screening plate so that the tubular filters have openings below and above the screening plate. Top ends of the tubular filters are closed, and the openings above the screening plate are formed in side walls of the tubular filters. The lower tie-plate may be assembled by combining the screening plate, the network section and the nozzle section together, after the tubular filters have been attached to the screening plate.

Abstract: In a demineralization apparatus, a mixed bed of a gel type cation exchange resin having a moisture holding capacity of 41% or less or a degree of crosslinkage of 12% or greater is employed along with a porous type anion exchange resin. As a result, oxidation degradation of the cation exchange resin due to hydrogen peroxide can be inhibited and the performance of the ion exchange resins and of the condensate water demineralizer can be stabilized and maintained for a long period of time.

Abstract: A chemical etching solution in the form of jets (14) under pressure is put into contact with the radioactive substance fixed on the surface inside the hollow body (1), and the chemical etching solution that has come into contact with the radioactive substance is recovered and drained to outside the hollow body (1). The radioactive substance is in at least one of the following forms: a phase dissolved in the chemical etching solution; and particles detached from the metal surface by the jets (14) under pressure. The method and the apparatus of the invention serve to decontaminate the inside surface of the hollow body or a component placed inside the hollow body (1) which can be a cleaning vessel.

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: 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: Ozone gas having a high ozone concentration is generated by a solid electrolyte electrolytic process. An ozone solution is prepared by injecting the ozone gas into an acidic solution of pH 6 or below. The ozone solution heated at a temperature in the range of 50° to 90° C. is supplied to a contaminated object to oxidize and dissolve a chromium oxide film by an oxidizing dissolving process. The ozone solution used in the oxidizing dissolving process is irradiated with ultraviolet rays to decompose ozone contained in the ozone solution, the ozone solution is passed through an ion-exchange resin to remove ions contained in the ozone solution. An oxalic acid solution is supplied to the contaminated object to dissolve an iron oxide film by a reductive dissolving process.

Abstract: A water monitoring system for a nuclear reactor is provided. In an exemplary embodiment, the water monitoring system includes a fiber optic cable having a first end and a second end, with the first end configured to optically couple to the reactor cooling water distribution system, and at least one laser light source optically coupled to the second end of the fiber optic cable. The water monitoring system also includes a spectrophotometer optically coupled to the second end of the fiber optic cable.

Abstract: In a demineralization apparatus, a mixed bed of a gel type cation exchange resin having a moisture holding capacity of 41% or less or a degree of crosslinkage of 12% or greater is employed along with a porous type anion exchange resin. As a result, oxidation degradation of the cation exchange resin due to hydrogen peroxide can be inhibited and the performance of the ion exchange resins and of the condensate water demineralizer can be stabilized and maintained for a long period of time.

Abstract: A process for the treatment of radioactive graphite which includes the following steps: (i) reacting the radioactive graphite at a temperature in the range of from 250° C. to 900° C. with superheated steam or gases containing water vapor to form hydrogen and carbon monoxide; (ii) reacting the hydrogen and carbon monoxide from step (i) to form water and carbon dioxide; and (iii) reacting the carbon dioxide of step (ii) with metal oxides to for carbonate salts. The process enables radioactive graphite, such as graphite moderator, to be treated either in-situ or externally of a decommissioned nuclear reactor.

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: A fuel assembly lower tie-plate with better performance in capturing linearly elongated foreign substances. The lower tie-plate has a screening plate positioned below the network section in the lower tie-plate cavity. The screening plate is arranged substantially horizontally so that the lower tie-plate cavity is divided into upper and lower parts by the screening plate. Tubular filters are attached to the screening plate so that the tubular filters have openings below and above the screening plate. Top ends of the tubular filters are closed, and the openings above the screening plate are formed in side walls of the tubular filters. The lower tie-plate may be assembled by combining the screening plate, the network section and the nozzle section together, after the tubular filters have been attached to the screening plate.

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: The present invention provides a simple and inexpensive decontaminating method without producing any secondary waste due to decontamination. A method comprising steps of evaporating liquid ozone, feeding the gaseous ozone into a re-circulation line 2 in the upstream side of the re-circulation pump 3 to make ozone-rich water, circulating the ozone-rich water in the reactor-water re-circulation system, and remove radioactive materials from metallic surfaces.

Abstract: The present invention provides a simple and inexpensive decontaminating method without producing any secondary waste due to decontamination. A method comprising steps of evaporating liquid ozone, feeding the gaseous ozone into a re-circulation line 2 in the upstream side of the re-circulation pump 3 to make ozone-rich water, circulating the ozone-rich water in the reactor-water re-circulation system, and remove radioactive materials from metallic surfaces.

Abstract: A foreign matter filter provided between a DFBN and a lower grid has two adjacent thin straps assembled into a lattice. The straps are equipped on the front and backsides with axially continuous protrusions.

Abstract: A device and method for removing radioactive crud material deposited on surfaces of a nuclear fuel assembly in a nuclear plant is provided. The device comprises a container arranged to accommodate the nuclear fuel assembly, a first pumping means to pump a fluid, composed of water and ice, through the container in order to release the deposit from the nuclear fuel assembly by abrasion and to transport the released radioactive material out from the container. The first pump means also enables the feeding of a gas or steam or both to the fluid that is fed into and through the container in order to create a turbulence in the fluid. The device further comprises means, arranged in a &ggr;-radiation-dampening medium, disposed to receive the radioactive deposit transported out of the container by the fluid.

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: 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: The present invention is a control rod guide tube cleaning apparatus in a nuclear reactor which includes a rod member, one end side portion of which has a thickness such that the end side portion can pass through the inside of a connecting portion between a housing of a control rod drive mechanism and a control rod guide tube, a nozzle for sucking water, mounted on the rod member on the one end side so that the nozzle can go in and out of the rod member, a means for rotating the rod member in a horizontal direction, and a water passage for leading water sucked in the nozzle to an outside of the housing along the rod member. The rod member is inserted into the control rod guide tube through the inside of the housing. Then, the nozzle is rotated downward so that a suction port of the nozzle faces the bottom inside portion of the control rod guide tube for the suction of dust and debris. The nozzle is rotated in the horizontal direction by rotating the rod member in the horizontal direction.

Abstract: A CRUD collection system for removing deposits from a nuclear reactor fuel rod submerged in pool water. The system includes a sealable collection head for containing a portion of the fuel rod. The collection head includes at least one seal positioned to receive the fuel rod. Also provided is a liquid inlet communicating with an interior portion of the collection head, the inlet is configured to inject a liquid into the interior to displace the pool water therefrom. At least one blade is provided that is positionable in scraping engagement with the fuel rod. Also included is a liquid outlet for eliminating a CRUD sample and the liquid to a filter.

Abstract: A boiling water reactor having a reactor pressure vessel with two recirculation loops hydraulically connected thereto is decontaminated by installing plugs in the outlets of jet pump ram's head manifolds located within the reactor pressure vessel to isolate the recirculation loops from the reactor pressure vessel. A monitoring gas is bubbled into some of the ram's head manifolds through the plugs to monitor the process pressure within the manifolds and riser pipes connected with the manifolds. The level of the decontamination solution in the riser pipes can be determined by determining the differential pressure due to the vertical height of the decontamination solution in the loops.

Abstract: A method and an apparatus for deionizing water are disclosed. A condensate in the secondary cooling water system in a PWR nuclear power plant is passed through a mixture of an anion exchange resin and a cation exchange resin having a crosslinking degree of about 12 to 16%. The cation exchange resin has an improved, ion exchange capacity. thereby decreasing the frequency of changing the condensate.

Abstract: A CRUD collection system for removing deposits from a nuclear reactor fuel rod submerged in pool water. The system includes a sealable collection head for containing a portion of the fuel rod. The collection head includes at least one seal positioned to receive the fuel rod. Also provided is a liquid inlet communicating with an interior portion of the collection head, the inlet is configured to inject a liquid into the interior to displace the pool water therefrom. At least one blade is provided that is positionable in scraping engagement with the fuel rod. Also included is a liquid outlet for eliminating a CRUD sample and the liquid to a filter.

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: An inlet mixer from a diffuser installed inside a nuclear reactor pressure vessel is removed, crud from a inner wall surface of the tubular portion of said removed inlet mixer or said installed diffuser is scraped off remotely in water, and said scraped crud is retrieved and monitored.

Abstract: A method of performing maintenance on a structural member inside a reactor pressure vessel includes lowering an annular guide rail having a second lug until the guide rail rests on an upper flange of a core shroud provided inside the reactor pressure vessel, detachably mounting the second lug of the guide rail to a first lug mounted on the core shroud, positioning a discharging nozzle at a position at which compressive remaining stress is added to a surface of the core shroud by moving the discharging nozzle in a radial direction and an axial direction of the core shroud by a discharging nozzle moving apparatus mounted on a turnable revolving on the guide rail and discharging water to add compressive remaining stress to a surface of the core shroud from the discharging nozzle.

Abstract: A preventive maintenance apparatus for structural members inside a nuclear reactor pressure vessel includes a ring-shaped guide rail having a plurality of lugs which is placed on an upper flange of a core shroud provided inside a reactor pressure vessel. At least some of lugs separately engage with a plurality of guide rods provided on an inner surface of the reactor pressure vessel. A turntable is rotated on the guide rail. A first discharging nozzle moving apparatus placed on the turntable moves a first discharging nozzle for adding compressive remaining stress to an outer surface of the core shroud in a radial direction of the core shroud and in an axial direction of the core shroud. A second discharging nozzle moving apparatus placed on the turntable moves a second discharging nozzle for adding compressive remaining stress to an inner surface of the core shroud in a radial direction of the core shroud and in an axial direction of the core shroud.

Abstract: The proposed installation comprises an abrasive liquid jet cutting module using a mobile nozzle (25) rotatable in all directions and which also supports a sensor (37) so that it can previously recognize the position or shape of the structure to be cut, a dosimeter (49) to measure its irradiation and a decontamination device (51) to eliminate all excess contamination from it. Cutting residue may be collected by suction. The installation is more universal than previously known installations.

Abstract: Apparatus for rectifying the tendency of a fuel assembly (1) to incline from the perpendicular has a top nozzle support (19) and a base assembly (18) for supporting, respectively, a top nozzle (7) and a bottom nozzle (2) of the fuel assembly. Incorporated in the base assembly is an elevating device (78, 79) which is operable to raise the fuel assembly. When raised, a grinding assembly (62) in the base assembly is able to remove material from the lower surfaces of the bottom nozzle so that they lie in a horizontal plane. The elevating device comprises a gimbal mounting arrangement which includes a gimbal (94) movably supported on a gimbal mount (88) by means of cooperating male and female spherically-shaped bearing surfaces. The grinding assembly includes a grinding wheel (66) which is mounted on a rotor (43) arranged for rotation about an axis along which the elevating device raises the fuel assembly so that material can be removed from each of the lower surfaces during one revolution of the rotor.

Abstract: Metal ions are added to a circuit (20, 30) for the reactor water or feed water of a nuclear plant. This is accomplished by dissolving a soluble metal compound the counter-ion of which is possible to decompose to gaseous products and water in water in a reaction vessel (41) in an equipment arrangement (40). The solution is subsequently conducted to a series of vessels (42) for the decomposition of the counter-ion. The solution is then possibly transformed to a mixture or a slurry which is conducted to a vessel (43) for degassing the gaseous products before the addition to the circuit (20, 30) for the reactor water or feed water.

Abstract: The method is to developed a two-phase flow in the circulation circuit. This method is defined by the fact, that a two-phase flow is developed by means of hydrogen introduction into the coolant. Hydrogen can be introduced in mixture with an inert gas or water steams.

Abstract: Methods are provided to at least slow the dissolution of silica in an aqueous environment. In the subject methods, the silica surface is contacted with a multivalent metal cation capable of complexing with oxygen atoms present on the silica surface, where contacting is preferably accomplished by introducing a source of the multivalent metal cation into the aqueous environment. The subject methods find particular use in the inhibition of the dissolution of silica comprising neutron poisoning materials employed in the storage of spent nuclear fuel.

Abstract: A process for the decontamination of radioactive materials which process comprises the steps of: i) contacting the material to be decontaminated with a dilute carbonate containing solution in the presence of ion exchange particles which either contains or have a chelating function bond to them; and ii) separating the ion exchange particles from the dilute carbonate containing solution. The radioactive materials which are treated may be natural materials, such as soil, or man-made materials such as concrete or steel, which have been subjected to contamination.

Abstract: In order to treat an aqueous acid effluent resulting from the decontamination of a component of a nuclear power station, the effluent containing an organic load comprising an organic reducing agent and nitrate ions and at least one oxidizing compound is introduced into the effluent. The effluent is then subjected to ultraviolet radiation and the totality of the organic load is thus converted into water and carbon dioxide, as well as possibly into at least one oxide of a chemical element present in the organic load, while neutralizing the effluent.

Abstract: A method for operating the LOMI decontamination process in a regenerative manner. The method incorporates an initial injection of a dilute LOMI solution (vanadous formate, picolinic acid and sodium hydroxide) into a decontamination circuit followed by operation of a small cluster of cation exchange columns during the decontamination process. The cation exchange resin is used to remove metals in the same manner as in prior decontamination processes but operation of the cation exchange resin is continued to allow picolinic acid initially bound to the cation exchange resin to be released and recycled to the LOMI solution. Operation of the cation exchange columns ceases after the picolinic acid has been released but before the metals (e.g. sodium, iron and vanadium) are released back to the LOMI solution. The cluster of cation exchange columns are operated according to a sequence wherein one column is releasing picolinic acid while another is binding picolinic acid.

Abstract: The invention relates to a process for removing dust from at least one nuclear fuel pellet (7) having undergone a grinding operation, which has left on the pellet surface dust of the material from which said pellet is formed. The process comprises subjecting said surface to the impact of a laser beam (3) having characteristics suitable for bringing about the disincrustation of the dust from said surface, and eliminating from said surface the products resulting from the dust disincrustation.The invention also relates to an apparatus for performing this process.Application to the dust removal from MOX pellets.

Abstract: An underwater laser processing method is carried out by irradiating, through a laser beam irradiation apparatus, a laser beam having a high output, a short pulse and a visible wavelength to a surface of a structure immersed in a water to improve residual stress of a material of the surface of the structure and remove a crack or a CRUD thereof. The laser beam irradiation apparatus comprises a pulse laser device suspended into a water in which a metal material is accommodated from an upper side thereof for irradiating a laser beam having a visible wavelength to a processing position, a beam strength adjusting device for adjusting an output per 1 pulse of a laser beam generated by the pulse laser device and a mechanism for adjusting a spot diameter and a multiplexing ratio of an irradiated beam.

Abstract: An improved method for removing scale, sludge, corrosion and other debris and deposits from the interior of a heat exchanger vessel such as a nuclear steam generator, includes generating pressure pulses in a non-corrosive, strongly basic, amine-containing chemical cleaning agent in aqueous solution after the agent has been introduced into the interior of the vessel to create shock waves in the liquid for dislodging, dissolving and fluidizing sludge and corrosion products. The chemical cleaning agent is an aqueous solution containing at least one of the group of lower alkyl amines, e.g., dimethylamine, ethylamine, 1,2-diaminoethane, or diaminopropane, lower alkanol amines, e.g., ethanolamine, 2-methyl-2-amino-1-propanol, and 5-aminopentanol, lower alkoxy alkyl amines, e.g., 3-methoxypropylamine, and cyclic diimines, e.g., 1,10-phenanthroline, 2,9-dimethyl-1,10-phenanthroline, 4,7-dimethyl-1,10-phenanthroline, 2,2'-bipyridine, and 4,4'-bipyridine, and terpyridine, or combinations thereof.

Abstract: The present invention provides a process for decontaminating a surface of nuclear or fissile materials or both. The process includes impacting ortho-boric acid crystals onto the surface. The present invention also provides an abrasive media comprising ortho-boric acid crystals having a boron-10 content of at least 19 percent by weight.

Abstract: A pre-oxidation treatment for decreasing the amount of chromium deposited on out-of-core surfaces such as the internal surfaces of recirculation piping. Hydrogen peroxide is injected into the reactor coolant through the recirculation line during reactor shutdown after H.sub.2 addition has been terminated. A dilute acid solution (e.g., nitric acid) is also injected into the loop to serve as a catalyst to accelerate the oxidation reactions. An appropriate water pH (e.g., in the range of 5-6) is maintained by acid injection. The coolant temperature during shutdown is maintained at approximately 150.degree. C. or lower. The peroxide concentration in the recirculation piping is maintained at approximately 1 ppm or higher as needed. The oxidation process should be allowed to take effect in the proposed temperature range with the recirculation pump in operation for at least a few hours to 24 hours, depending on the temperature and the oxide film thickness.

Abstract: In a nuclear reactor water cleanup pump, a purge fluid is continuously delivered during at least the operation of the pump into the cavities containing the bearings and the electrical motor at a desired flow rate. The desired flow rate being based on the heat loss from said pump and a differential temperature defined as being the difference between the predetermined temperature of the purge fluid delivered into the pump and the desired temperature for the purge fluid exiting the pump.

Abstract: The invention relates to an arrangement for carrying out leak detection of a fuel assembly for a pressurized-water nuclear reactor. A substantially vertical hollow mast means open in both ends houses the fuel assembly to be examined. The fuel assembly is drawn to the inside of the mast means from its lower side. The part of the mast means housing the fuel assembly is lifted to a position in which the fuel assembly is provided near but below the water surface of water inside the nuclear reactor. Water is sucked from a position inside the mast means above the fuel assembly. A gas separating means separates gases present in water sucked from the inside of the mast means. The separated gas is analyzed in a gas analyzing means regarding its amount of gaseous fission products.

Abstract: A fuel bundle and lower tie plate assembly for a nuclear reactor includes a plurality of fuel rods supported between an upper tie plate and a lower tie plate assembly. The lower tie plate assembly includes an upper grid portion and a lower body portion, the upper grid portion having a plurality of fuel rod supporting bosses interconnected by a plurality of webs thus forming flow openings between the bosses. The body portion includes an inlet nozzle and a peripheral wall extending between the bottom nozzle and the upper grid portion to define a flow volume therein. A debris catcher is located within the flow volume and includes a pair of superposed plates, the plates each having a plurality of holes of substantially the same size, shape and pitch, but wherein the holes of one of the pair of plates are offset from the holes of the other of the pair of plates by one half the hole pitch.

Abstract: The lower tie plate grid includes cylindrical bosses and webs interconnecting the bosses for supporting nuclear fuel rods and defining flow openings through the grid. Coolant flows through the flow openings for flow upwardly about the fuel rods. The grid includes upper and lower portions and a screen is disposed between the upper and lower grid portions upon assembly with the bosses and webs of the respective upper and lower grid portions in registry with one another. The grid portions are welded to one another whereby the apertured screen serves to separate debris from the coolant flowing through the flow openings. The screen has openings in registry with the openings defined by the bosses for receiving the end plugs of the fuel rods.