Abstract: In a method of decontaminating a primary loop of a pressurized water reactor, including a steam generator, reactor coolant pump and hot and cold legs in the loop, the primary loop is isolated from a nuclear reactor vessel by closing hot leg and cold leg loop stop valves. Decontamination process water is circulated from one side of the steam generator channel head to the other side of the channel head via a bypass pipe extending between the cold leg and the hot leg without bypassing the water through steam generator tubes extending between the sides of the channel head. The level of the decontamination water in the steam generator is maintained at two to three feet in the tubes.

Abstract: A nuclear reactor having a chemical decontamination clean-up system is provided in which every component of the chemical decontamination clean-up equipment which processes radioactive fluids is located within a shielded room of an existing on-site support building. Those components of the clean-up system not in direct contact with radioactive fluids are housed in portable trailers. The decontamination clean-up system is designed to provide for adequate shielding to minimize personnel exposure and also incorporates a modular design for component transportation and storage.

Abstract: A nuclear fuel assembly debris filter. Each fuel rod has a ring attached to the lower end cap. The rings are shaped and sized to define a space between the lower end cap and ring such that the space serves to trap, or filter, debris before it reaches the elevation of the fuel cladding. The rings may be circular, elliptical, or any suitable shape that provides the desired filtration effect.

Abstract: System and method for evaporating moisture from a gap defined between a heat transfer tube surrounding a repair sleeve in a nuclear steam generator. The nuclear steam generator has a heat transfer tube surrounding a repair sleeve that has been hydraulically expanded into engagement with the tube. The tube and the sleeve define a gap therebetween having moisture residing therein. The system includes an air compressor in communication with the gap for supplying air to the gap and a dryer in communication with the air compressor for drying the gas supplied to the gap. A heater in communication with the air compressor may also be provided for heating the air supplied to the gap, so that the moisture residing in the gap evaporates into the heated air. A vacuum pump in communication with the gap may be provided for decreasing the pressure of the heated air in the gap, so that substantially all the moisture evaporates from the gap and into the heated air.

Abstract: A method for enhancing the diffusion of gas bubbles or voids attached to impurity precipitates, and biasing their direction of migration out of the host metal (or metal alloy) by applying a temperature gradient across the host metal (or metal alloy). In the preferred embodiment of the present invention, the impurity metal is insoluble in the host metal and has a melting point lower than the melting point of the host material. Also, preferably the impurity metal is lead or indium and the host metal is aluminum or a metal alloy.

Abstract: A decontamination composition comprises 40 to 60 percent of a compound selected from the group consisting of oxalic acid, alkali metal and ammonium salts of oxalic acid and mixtures thereof; 5 to 20 percent of a compound selected from the group consisting of citric acid, alkali metal and ammonium salts of citric acid and mixtures thereof; 20 to 40 percent of a compound selected from the group consisting of polyaminocarboxylic acid, alkali metal and ammonium salts of polyaminocarboxylic acid and the combination of a polyaminocarboxylic acid and a neutralizing compound, and mixtures thereof; 0 to 2 percent of a nonionic surfactant; about 0 to 2 percent of a dispersant; and about 0 to 2 percent of a corrosion inhibitor. The present invention also relates to a method of decontaminating a surface whereby contaminants in the form of NORMs are removed therefrom.

Abstract: A unitary one-piece lower tie plate grid has a lower portion and an upper portion for supporting the fuel rods. The lower tie plate grid includes cylindrical boss portions extending upwardly from the lower grid portion and arranged in square matrices for receiving the lower end plugs of the fuel rods. Web portions extending upwardly from the lower tie plate portion interconnect the boss portions along the sides of the matrices. The lower grid portion includes a plurality of openings which open into the flow spaces defined by the convex portions of the bosses and the webs within each square matrix of the upper portion of the tie plate. Coolant flows through the openings into the flow spaces for further flow upwardly about the fuel rods. The openings are radiussed adjacent their lower ends and have divergent side walls downstream of a throat area to define a flow venturi.

Abstract: In a boiling water reactor fuel bundle, a three dimensional debris catching grid construction is placed within the flow volume defined by the lower tie plate assembly between the inlet nozzle and upper fuel rod supporting grid. A perforated plate is utilized having round holes as small consistent with the prevention of inadvertent closure due crudding and a hole pitch consistent with mechanical integrity requirements. The perforated plate is placed in a three dimensional construction such as a dome, cylinder, pyramid, inverted pyramid or corrugated construction spanning the flow volume of the lower tie plate assembly. As a consequence of this three dimensional grid construction, the total flow through area of the perforations in the metal plate does not introduce appreciable pressure drop in the lower tie plate assembly between the inlet nozzle and the rod supporting grid.

Abstract: A reactor coolant debris filter for insertion within a nuclear fuel assembly support.

Abstract: A unitary one-piece lower tie plate grid has a lower portion and an upper portion for supporting the fuel rods. The lower tie plate grid includes cylindrical boss portions extending upwardly from the lower grid portion and arranged in square matrices for receiving the lower end plugs of the fuel rods. Web portions extending upwardly from the lower tie plate portion interconnect the boss portions along the sides of the matrices. The lower grid portion includes a plurality of openings which open into the flow spaces defined by the convex portions of the bosses and the webs within each square matrix of the upper portion of the tie plate. Coolant flows through the openings into the flow spaces for further flow upwardly about the fuel rods. The openings are radiussed adjacent their lower ends and have tapered divergent walls opening into the flow spaces. In another form, the openings have a step intermediate the upper and lower surfaces of the lower grid portion to define a minimum cross-sectional flow area.

Abstract: The present invention relates to a process of decontaminating zirconium-based alloy claddings tubes used in nuclear reactor fuel rods. The process involved the use of a permanganate in a dilute acid solution. The process renders the alloy suitable for uncontrolled release into a non-radioactive environment.

Abstract: An arrangement of reactor coolant pump seals arranged in a generally annular stack with a plurality of stacking spacers in a test housing for emplacement in a chemical decontamination test loop enables a variety of flow characteristics to be simulated by varying the detailed arrangement of the RCP seals and supporting structure in the test housing. By adjusting parameters such as fluid chemistry, gross flow, pressure, and temperature in a controlled manner with systems incorporated into the test loop, additional information can be obtained regarding the feasibility of any specific decontamination process. The magnitude of process fluid flow across particular surfaces of one or more RCP seal components can be predetermined by selecting the placement, number and dimensions of penetrations in a flow distribution tube through which the process fluid enters the housing.

Abstract: A system for positioning a work point in three dimensional space has at least three reeving systems spaced apart from one another, with each reeving system having a adjustable support element connected to it. These support elements are also connected to the work point, with the length of the support elements between the work point and the reeving determining the work point's location. Associated with each reeving system is an actuator adapted for releasing and taking up the support element. A control system controls the actuators to release and take up each of the support elements to move the work point with respective to at least three spatial coordinate axes while controlling at least one motion parameter of the work point in a predetermined manner.

Abstract: A combined lower end fitting and debris filter for a nuclear fuel assembly is provided that does not require multiple parts, welding, brazing, mechanical fasteners, drilling or EDM operations to form the coolant flow holes. The lower end fitting and debris filter are cast as a single work piece that includes the coolant flow holes in the casting process. This is accomplished by casting the sections of the filtration surface having flow holes in a thickness that allows for the small coolant flow holes to be formed as part of the casting process.

Abstract: A process for the decontamination of solid surfaces contaminated with radioactive or heavy metal species using a solution based on one or more non-persistent complexing agents, or for the chemical cleaning of steam generator sludge using such a solution, or for removing radioactive or heavy metal species from a solution using a combination of a one or more non-persistent complexing agents and a solid support, followed in each case by thermal or thermal-chemical treatment to decompose said non-persistent complexing agent. The preferred non-persistent complexing agents are hydroxamic acids, and the most preferred is acetohydroxamic acid.

Abstract: A detection and inspection of cracks (135) on the internal surface of the adapter (2) is carried out, at least in a zone close to the weld for fastening the adapter (2), using remote inspection operations comprising at least one dye penetration inspection with remote borescope examination of the cracks (135) revealed by the dye penetration. At least one excavation cavity (136) is made by machining to a specified depth of the internal surface of the adapter (2) having a crack (135). As a function of the result of the dye penetration inspection, the zone is or is not built back up after excavation. The device comprises an assembly for moving a rod in translation and in rotation inside the adapter. Brushing, cleaning, or sprinkling means may be fastened to the end of the rod. The device also includes a second assembly for moving a borescope support inside the adapter and tooling for machining the internal surface of the adapter.

Abstract: In a method of treating a surface 12 of an object 10 contaminated with radionuclides 14, a laser source 16 is directed at the surface 12 to apply a local area 18 of intense heat to the surface 12. The laser source 16 is arranged to pass in a raster manner to cause local melting of the surface 12, surface 12 subsequently solidifying and fixing the radionuclides 14 therein. At least one layer of a coating material be applied before or after the application of the intense heat to fix and seal the radionuclides on or in the object.

Abstract: The apparatus is provided with a line (1) connected to the containment for feeding air to a water bath (5). The line (1) is connected to plurality of nozzles (4) disposed in the water bath (5) having at least one perforate baffle plate (27) disposed above said nozzles. A set (6) of static mixing elements (30, 31, 32) surrounded by a jacket (7) is disposed above said baffle plate (27). A dry separating stage is disposed above the water bath (5) and the set (6) and consists of an entry separator (8) and an agglomerator (9) which are in the form of annular discs. Air emerging from the set successfully flows through the entry separator (8) and the agglomerator (9) in opposite directions. The entry separator (8) and the agglomerator (9) consist of static mixing elements.

Abstract: A water quality control method for a nuclear power plant comprising the steps of maintaining the iron concentration in the feed water below 0.05 ppb by increasing iron removing rate at a condensed water purifying loop, shifting the pH of the reactor water below a pH of 6.8 determined at a room temperature by injecting carbon dioxide gas in the primary cooling system and further optionally reducing the dissolved oxygen concentration in the reactor water below 20 ppb by injecting hydrogen gas into the primary cooling system, whereby .sup.60 Co ion concentration in the primary cooling system is maintained low for a long interval.

Abstract: A device for trapping migrating bodies within the steam generator or secondary circuit of a nuclear installation is constituted by grids (6) placed between the upper part of the tube casing (8) and the pressure casing (7) of the steam generator. The meshes of the grids are so dimensioned as to prevent the passage of objects liable to jam between the tubes of the tube bundle of the primary circuit.

Abstract: In a boiling water nuclear reactor fuel bundle, a debris catching arrangement is disclosed for incorporation within the flow plenum up stream or below the rod supporting grid of the lower tie plate assembly. The device is preferably placed within the lower tie plate flow plenum between the fuel bundle inlet and the rod supporting grid structure supporting the fuel rods; alternate placement can include any inlet channel upstream of the fuel rods including the fuel support casting. The disclosed debris catching designs include strainer structures defining spatially separated straining or obstructing layers imparting to the fluid in the plenum a circuitous flow path. This circuitous flow path causes the two phase separation of the heavier debris from the lighter transporting water by flow direction change with the debris directed and detoured to a trapping structure.

Abstract: In a boiling water reactor fuel bundle, a three dimensional debris catching grid construction is placed within the flow volume defined by the lower tie plate assembly between the inlet nozzle and upper fuel rod supporting grid. A perforated plate is utilized having round holes as small consistent with the prevention of inadvertent closure due crudding and a hole pitch consistent with mechanical integrity requirements. The perforated plate is placed in a three dimensional construction such as a dome, cylinder, pyramid, inverted pyramid or corrugated construction spanning the flow volume of the lower tie plate assembly. As a consequence of this three dimensional grid construction, the total flow through area of the perforations in the metal plate does not introduce appreciable pressure drop in the lower tie plate assembly between the inlet nozzle and the rod supporting grid.

Abstract: The reactor coolant system (RCS) of a pressurized water reactor (PWR) is chemically decontaminated and cleaned utilizing apparatus which is comprised of components designed to operate at low pressures while still utilizing installed reactor coolant pumps and/or the residual heat removal pumps to generate the high flow rates required for the process. A high volume diverted flow of reactor coolant from the RCS is passed through letdown valves to reduce the high pressure produced by the installed pumps. Chemical decontamination and cleaning agents are mixed with the low pressure diverted flow and returned to the RCS by high head injection pumps. Contamination solubilized by the decontamination and cleaning agents is removed as the reactor coolant is recirculated through demineralizers. Filters remove particulates, and fines from the demineralizer resins.

Abstract: A method for preventing or reducing the formation of Co-60 contaminated material on the surfaces of a cooling water circuit of a nuclear reactor. The method is carried out during shutdown of the reactor. First, Co-60 contaminated material formed on the surfaces of the cooling water circuit is chemically removed. Then at least one iron compound is added to the cooling water in an amount sufficient to scavenge cobalt from the cooling water. Thereafter, oxygen is injected into the cooling water to provide a dissolved oxygen concentration sufficient to form an oxide film on the surfaces of the cooling water circuit. The oxide film so formed is substantially free of Co-60 isotope. This treatment reduces the radiation hazard to nuclear reactor personnel.

Abstract: A reactor water cleanup system includes a reactor pressure vessel containing a reactor core submerged in reactor water. First and second parallel cleanup trains are provided for extracting portions of the reactor water from the pressure vessel, cleaning the extracted water, and returning the cleaned water to the pressure vessel. Each of the cleanup trains includes a heat exchanger for cooling the reactor water, and a cleaner for cleaning the cooled reactor water. A return line is disposed between the cleaner and the pressure vessel for channeling the cleaned water thereto in a first mode of operation. A portion of the cooled water is bypassed around the cleaner during a second mode of operation and returned through the pressure vessel for shutdown cooling.

Abstract: A system of extracting fluid samples, either liquid or gas, from the interior of a nuclear reactor containment utilizes a jet pump. To extract the sample fluid, a nonradioactive motive fluid is forced through the inlet and discharge ports of a jet pump located outside the containment, creating a suction that draws the sample fluid from the containment through a sample conduit connected to the pump suction port. The mixture of motive fluid and sample fluid is discharged through a return conduit to the interior of the containment. The jet pump and means for removing a portion of the sample fluid from the sample conduit can be located in a shielded sample grab station located next to the containment. A non-nuclear grade active pump can be located outside the grab sampling station and the containment to pump the nonradioactive motive fluid through the jet pump.

Abstract: An anion exchange method conducted at a high temperature, which comprises using a crosslinked anion exchanger which comprises structural units having a quaternary ammonium group of the following formula (a) and structural units derived from an unsaturated hydrocarbon group-containing crosslinkable monomer, and of which at least 90% of anion exchange groups are present in the form of a group represented by ##STR1## as defined in the following formula (a): ##STR2## wherein R is a --(CH.sub.2).sub.n --group (n=an integer of from 3 to 18) which may include a cyclic hydrocarbon, each of R.sub.1, R.sub.2 and R.sub.3 which are independent from one another, is a C.sub.1 -C.sub.8 hydrocarbon group or a C.sub.1 -C.sub.8 alkanol group, the benzene ring of the formula (a) may be substituted by an alkyl group or a halogen atom, or may be condensed with other aromatic ring, and X is an anion.

Abstract: An apparatus decontaminates a radioactively contaminated surface region of a pipe, connector or vessel being open at one end, with a dry mechanical blasting medium. The apparatus includes a processing bell to be mounted on the open end of the pipe, connector or vessel. A flexible dustproof duct is connected to the processing bell. A retaining device protrudes into the duct and is movable from outside in the interior of the pipe, connector or vessel. A blasting head is disposed on the retaining device. A blasting system is connected to the blasting head and has a continuous circulation of the blasting medium.

Abstract: Stayrod arrangement for enhancing removal of sludge from nuclear heat exchangers. The stayrod arrangement includes a rod disposed adjacent a plurality of heat exchange tubes defining a tube lancing lane therebetween, the tube lane having sludge deposits therein. The rod has planer side portions oriented parallel to the direction of a fluid stream intended to flush the sludge deposits from the tube lane. An anti-rotation connector is connected to the rod for fixing the orientation of the rod with respect to the fluid stream.

Abstract: A system for containment of a supercritical water oxidation reactor in the event of a rupture of the reactor. The system includes a containment for housing the reaction vessel and a communicating chamber for holding a volume of coolant, such as water. The coolant is recirculated and sprayed to entrain and cool any reactants that might have escaped from the reaction vessel. Baffles at the entrance to the chamber prevent the sprayed coolant from contacting the reaction vessel. An impact-absorbing layer is positioned between the vessel and the containment to at least partially absorb momentum of any fragments propelled by the rupturing vessel. Remote, quick-disconnecting fittings exterior to the containment, in cooperation with shut-off valves, enable the vessel to be isolated and the system safely taken off-line. Normally-closed orifices throughout the containment and chamber enable decontamination of interior surfaces when necessary.

Abstract: A process for decontaminating radioactive material comprises the step of contacting the material with a dissolving composition to dissolve the contaminants in the material, said composition comprising a dilute solution of about 0.05 molar ethylene diamine tetraacetic acid, about 0.1 molar carbonate, about 10 grams per liter hydrogen peroxide and an effective amount of sodium hydroxide to adjust the pH of the composition to a pH from about 9 to about 11. Also included are the steps of separating the dissolving composition containing the dissolved contaminants from the contacted material and recovering dissolved contaminants from the dissolving composition that has been separated from the material. A composition for dissolving radioactive contaminants in a material, comprising a dilute solution having a basic pH and effective amounts of a chelating agent and a carbonate sufficient to dissolve radioactive contaminants is also provided.

Abstract: A device 20 for cleaning threaded studs 14 securing the dome-shaped head of a nuclear reactor pressure vessel to the vessel body 10 comprises a cylindrical brush holder 24 rotatably carried in a housing 22. An annular steel wire brush 28, disposed on the inner surface of the brush holder 24, is adapted to fit over and engage the threaded portion 14a of a stud 14. An electric motor 26 mounted on the housing 22 rotates the brush holder 24 as it is lowered onto an upstanding stud 14. A vacuum source connected to the housing 22 captures any particulate matter removed from the stud 14.

Abstract: High velocity reactor coolant water in a boiling water reactor or a pressurized water reactor transports radioactive ions and particles from a nuclear reactor vessel to the balance of the reactor coolant system where they deposit on chromium (III) oxide-containing surfaces. These radioactive deposits are removed in a dilute chemical decontamination process wherein permanganate ion-containing reactor coolant water is circulated throughout a reactor coolant system to oxidize chromium (III) oxide surfaces of the system to chromium (IV) oxide. Formic acid is added to the permanganate ion-containing reactor coolant water and then the formic acid-containing water is circulated throughout the reactor coolant system to reduce unreacted permanganate ions in the reactor coolant water to manganous ions.

Abstract: The adaptor plate (11) comprises ribs (12) which are substantially perpendicular to its faces, projecting from its lower face, delimiting between them cells and zones (15) into each of which emerges a plurality of through-openings (16) of substantially square cross-section which are arranged in a predetermined pattern.

Abstract: Where a concrete structure (12) has been contaminated with tritium (whether as gas or as water) the tritium atoms take the place of ordinary hydrogen atoms in water and in hydroxyl groups in the concrete, rendering it radioactive. The degree of contamination may be reduced by irradiating the surface with microwaves to vaporize water, while extracting water vapor from the surface region through a dust filter (28) and a water trap (30). This can considerably reduce the radioactivity, and hence the cost of disposal of the concrete.

Abstract: A lower tie plate for a nuclear fuel assembly is provided via an integral casting including a frame containing a first plurality of guide tube bosses in a central portion thereof, a second plurality of guide tube bosses concentric with the first plurality of guide tube bosses, and a plurality of teardrop shaped struts connecting the first and second guide tube bosses to one another and to the frame. The guide tube bosses serve to respectively directly receive individual guide tube cap screws of guide tubes of the nuclear fuel assembly. The interior top portion of the lower tie plate is configured to receive and support a debris screen.

Abstract: An alkaline-permanganate process for chemically decontaminating oxidized metal surfaces wetted by primary water circulating in cooling loops of nuclear reactors maintains permanganate-containing primary water at a temperature of about 90.degree. C. and at a pH of 9-12 to oxidize the wetted surfaces. Oxalic acid is then added to the water and the oxalic acid-containing primary water is maintained at a temperature of at least about 90.degree. C. and at a pH of about 5-7 while it is circulated to destroy the permanganate ions and manganese dioxide.

Abstract: A control rod driving hydraulic system of a control rod driving system of a nuclear power plant, in utilization of condensate as a control rod driving water comprises a water pressure control unit arranged for each control rod and a water pressure supply unit for commonly supplying water pressure to all control rods. The water pressure supply unit comprising a pump mechanism operatively connected to a condensate supply source for driving the control rod driving water, a filter mechanism operatively connected to the condensate supply source and the pump mechanism for filtering the condensate as the control rod driving water, a valve unit for regulating quantity of flow of the control rod driving water, and a valve unit for regulating pressure thereof. The filter mechanism including at least one hollow fiber filter unit for purifying the control rod driving water. The hollow fiber filter unit includes a backwash regeneration equipment.

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 device for monitoring the stack exit air in a reactor installation consists essentially of a pressure relief line (2) which connects the containment vessel (1) to the stack (5) and in which a filter unit (3) is located. Downstream of the filter, a sampling point (6) is provided in the pressure relief line, from where gas mixture is branched off via a sampling line (7). This gas is passed through a measurement section (14) and then returned into the pressure relief line (2). The concentration of the gas is reduced in a dilution unit (8) upstream of the measurement section (14). Cooling of the gas sample in the sampling line (7) before dilution is prevented by means of a heater (24).

Abstract: In addition to the metal-fiber filter and molecular sieve of a depressurization system for the containment vessel of a nuclear reactor, within an auxiliary equipment building adjacent the structure surrounding the containment vessel, at least one metal-fiber filter and at least one molecular sieve form filter elements of a system for evacuating the space between the structure and the containment.

Abstract: Apparatus for manipulating a vacuum hose in a reactor vessel comprises a housing with two opposing openings, an arm carried by the housing and deployable from a stowed position essentially completely within the housing to an extended position where the arm extends through the two openings in a generally horizontal position. The arm preferably has a two-fingered gripping device for gripping the vacuum hose but may carry a different end effector such as a grinding wheel. The fingers are opened and closed by one air cylinder. A second air cylinder extends the device. A third air cylinder within the housing pivotally pulls the opposing end of the arm into the housing via a pivoting member pivotally connected between the third air cylinder shaft and the arm.

Abstract: A steam generator chemical solvent mixing system and method is provided. The chemical solvent mixing system includes a pump, having a discharge port fluidly connected to a discharge line and a suction port fluidly connected to a suction line. An upper level injector, including an injector nozzle extends through one upper access opening in the outer casing of a steam generator and extends into the annulus of the generator between the tube bundle shroud and the outer casing, the upper level injector being fluidly connected to the discharge port of the pump. A lower access eductor is provided, including an eductor nozzle extending through one lower access opening of the outer casing and adapted to discharge solvent through one passageway in the tube bundle shroud and into the tube bundle of the generator, the lower access eductor being fluidly connected to the discharge port of the pump.

Abstract: Apparatus for working by laser, especially for the decontamination of a pipe of a nuclear reactor, comprising a laser source (18); an optical fiber (21) whose input is connected to the output of the laser source; a laser beam amplifier (20) whose input is connected to the output of the optical fiber; and a device (5) for transporting the laser beam emitted by the amplifier through the air to a working point.

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 invention provides a method of recovering and storing radioactive iodine by a freeze vacuum drying process, in which off-gas generated when spent fuel is subjected to shearing and dissolving treatments is scrubbed and, when necessary, is subjected to a precipitation treatment by addition of additives, after which waste liquid containing radioactive iodine is freeze-dried by a freeze vacuum drying process to recover radioactive iodine as iodine compounds. As a result, since the radioactive iodine does not vaporize, release of the radioactive iodine into the environment can be eliminated. In addition, consumption of a collecting agent such as silver zeolite for collecting vaporized radioactive iodine can be reduced. The iodine compounds containing the recovered radioactive iodine is given the same composition as a stable, naturally occurring mineral and is solidified and mineralized as by a high-pressure press. This makes it possible to store long half-life .sup.

Abstract: A method for chemically controlling cobalt decontaminating the water cooling system of a water cooled nuclear fission reactor to reduce the radiation hazard to personnel.

Abstract: A fuel assembly for a light-water nuclear reactor includes a plurality of vertical fuel rods (10, 42) which are arranged, in spaced relationship in a lateral direction, between a bottom tie plate (11, 44) and a top tie plate (12, 43), the bottom tie plate, defining through-going vertical channels (50) for conducting water through the bottom tie plate and into the spaces between the fuel rods. The bottom tie plate also defines horizontal channels (51, 52) which cross the vertical channels and which are preferably arranged, at edges (54) on the bottom tie plate, in open communication with the spaces between the fuel rods. Helical springs (61, 62) with horizontal symmetry axis are arranged in at least some of the horizontal channels where the horizontal channels cross the vertical channel so as to trap debris in the water passing upwardly through the through-going vertical channels.

Abstract: A filtered venting system located in association with a reactor containment vessel installed in a reactor building comprises a filter device disposed in the reactor building and including filter means, a first venting line disposed on an upstream side of the filter device and having one end connected to the reactor containment vessel and another end connected to the filter device, a stand-by gas treatment system including outlet fan means or pump means and connected to the first venting line at the downstream side of the fan or pump means, and a second venting line disposed at a downstream side of the filter device and another end connected to an outlet means/ The filter device being utilized for the stand-by gas treatment system for treating and removing a radioactive substance contained in an atmosphere delivered from the reactor containment vessel.

Abstract: The nozzle (8) comprises a transverse element consisting of a cross-braced structure (14) comprising wall elements (15) delimiting cells (16) of large dimensions. Ends of a plurality of mutually parallel leaves (18) are fixed to the inside walls of each of the cells (16) so that their faces are substantially parallel to the direction of circulation of the cooling water through the nozzle (8). The leaves (18) provide between them spaces of a width which is less than the size of the particles likely to be entrained in the cooling fluid and to lodge in the fuel assembly.