Abstract: A method of decommissioning a nuclear facility including a plurality of sandboxes that cover a plurality of upper penetration holes, includes: exposing the plurality of pipes through the plurality of upper penetration holes by removing the plurality of sandboxes; and cutting the plurality of pipes through the plurality of upper penetration holes.

Abstract: A method of decommissioning a nuclear facility, including: exposing the plurality of upper penetration holes by removing the plurality of sandboxes; enlarging an upper space of the cavity by cutting an upper portion of the biological shield concrete that is disposed between the plurality of upper penetration holes and between the plurality of upper penetration holes and the cavity; and separating the nuclear reactor pressure vessel from the biological shield concrete.

Abstract: A tungsten sheet includes a tungsten layer. The tungsten layer includes a binder resin and a plurality of tungsten particles included in the binder resin. A tungsten composition amount of the tungsten layer is at least 70% by mass (wt %). An average particle diameter of the plurality of tungsten particles is more than 1 ?m and less than 15 ?m.

Abstract: A stainless steel is provided having good corrosion resistance and good low-temperature toughness. A stainless steel contains, in mass %, Cr: 15.5 to 18.0%. The stainless steel has a matrix structure having, by volume ratio, 40 to 80% tempered martensite, 10 to 50% ferrite and 1 to 15% austenite. When a microstructure image obtained by photographing the matrix structure at a magnification of 100 times is positioned in an x-y coordinate system and each of 1024×1024 pixels is represented by a gray scale level, ? defined by Equation (2) is not smaller than 1.55: 1.0?Mo+0.5W?3.5??(1). Here, Mo and W are the Mo and W contents in mass %.

Abstract: There is provided a holding device which can hold a molten corium for a predetermined period even when the molten corium is exposed to heat or undergoes any chemical reaction and which is applicable to practical use. There is provided a holding device provided below a nuclear reactor pressure vessel for holding a molten corium, wherein the holding device includes a base material in contact with a cooling medium, and a multilayer stack structure on the base material. The multilayer stack structure has a first layer having heat-resistant property, a second layer formed on the first layer and having heat-resistant property with lower heat conductivity than that of the first layer, and a third layer formed on the second layer and having corrosion-resistant property and impact-absorbing property.

Abstract: Nonconjugated conductive polymers absorb radioactive iodine, therefore are useful for protection against nuclear radiation. These polymers have at least one double bond per repeat unit. The ratio of the number of double bonds to the total number of bonds along the polymer chain is less than half. Examples of nonconjugated conductive polymers include: cis-1,4-polyisoprene (natural rubber), trans-1,4-polyisoprene (gutta percha), polybutadiene, polydimethyl butadiene, poly(b-pinene), styrene butadiene rubber (SBR), polyalloocimene, polynorbornene and many others. Through interaction with iodine atoms the double bonds in the nonconjugated polymers transform into radical cations leading to a dark color. The iodine atoms remain (immobile) bound to the polymer chain through the charge-transfer interaction, these polymers are very inexpensive and can be easily processed into any shape, structure and size. Therefore, these are useful for protection against nuclear radiation including radioactive iodine.

Abstract: A neutron absorbing insert for use in a fuel rack and method of manufacturing the same. In ones aspect, the invention is a neutron absorbing apparatus comprising: a plate structure having a first wall and a second wall that is non-coplanar to the first wall; the first and second walls being formed by a single panel of a metal matrix composite having neutron absorbing particulate reinforcement that is bent into the non-coplanar arrangement along a crease; and a plurality of spaced-apart holes formed into the single panel along the crease prior to bending.

Abstract: A neutron reactor includes a neutron shield which is disposed outside a nuclear reactor core and adapted to absorb neutrons leaking from the core. The neutron shield includes a plurality of containers each of which contains a powdered neutron absorbing material and which are stacked with one another in a vertical direction, and a cladding tube which houses the containers. The neutron absorbing material is composed of B4C powder.

Abstract: A multi-layered material composite is disclosed suitable for nuclear reactor applications to protect equipment from radiation damage. In one embodiment, the composite includes an internal neutron-absorbing layer and an external layer disposed on opposing sides of the internal layer. The external layers are made of metal or ceramic in various embodiments. The composite is disposed on or at least proximate to the an equipment component within the containment chamber of a nuclear reactor in some embodiments to protect the component from radiation damage.

Abstract: A nuclear fission reactor device including a core having an array of fissile material and which is capable of being transported to and from the place of operation using conventional transportation vehicles. In a first embodiment, the fissile material is a uranium hydride enriched 15%-to-20% with U-235. In a second embodiment, the fissile material is a uranium oxide enriched to 18% to 20% with U-235.

Abstract: A first-wall component of a fusion reactor has a heat shield and a heat sink. The heat shield is formed of a material from the group of graphite material, carbidic material, tungsten and tungsten alloy. The heat sink is formed of a spray-compacted copper alloy.

Abstract: A clamp assembly connects a diffuser adapter or lower ring to a diffuser tail pipe of a jet pump diffuser in a boiling water nuclear reactor. The clamp assembly includes at least two clamp segments shaped generally corresponding to an exterior circumference of the diffuser, a swivel link affixed at each end of each of the clamp segments, and at least two connecting bands pivotably secured to the swivel links between the ends of the clamp segments. The clamp segments each includes a locking assembly engageable with the diffuser adapter or lower ring and the diffuser tail pipe. The clamp assembly structurally replaces/repairs the weld joining the diffuser adapter or lower ring and the diffuser tail pipe.

Abstract: In a heat shield (1), in particular for combustion chambers and for thermal fluid flow machines, the heat shield consists of a feltlike material (3) composed of compressed and sintered intermetallic fibers. Advantageously, the intermetallic fibers consist of an iron based or nickel based intermetallic phase.

Abstract: A heat removal system for the under reactor pressure vessel area of a boiling water nuclear reactor system that provides both protection of the containment boundary from attack by molten core debris and cools the molten core debris to prevent a breach of the containment boundary in the unlikely event of a severe accident where the molten core penetrates the lower head of the reactor vessel is described. The heat removal system includes a glass matrix slab positioned adjacent the floor of the containment and a plurality of heat tubes at least partially embedded in the glass matrix slab and extending into the area under the nuclear reactor pressure vessel. The cooling system also includes a passive containment cooling system, and fused vent pipes connecting the suppression pool with the drywell.

Abstract: An absorption structure for absorbing neutrons and a method for producing the absorption structure include placing a neutron-absorbing material between a first sheet and a second sheet. The sheets are joined together and a plurality of voids is formed between them for receiving the neutron-absorbing material. At least one of the sheets has struts or bulges forming the plurality of voids and creating a material bond with the second sheet. The introduction of the neutron-absorbing material into the voids with a virtually arbitrary concentration also makes it possible to adjust the absorption capacity of the absorption structure within wide limits.

Abstract: A neutron shield is formed of a boron carbide-metal matrix composite having a density ranging from 2.5 to 2.8 g/cm.sup.3 and a composition ranging from approximately 10 to 60 weight % of boron carbide and 40 to 90 weight % of metal matrix. The metal matrix is aluminum, magnesium, titanium, or gadolinium or one of their alloys. The boron carbide includes one or more metal elements added to improve the chelating properties of the metal matrix material by forming intermetallic bonds with the metal matrix material. The metal additives are present in the composite in an amount less than approximately 6% by weight. The shield may be in container or plate form.

Abstract: A neutron absorbing apparatus which includes two adjacent neutron absorbing plates and a mounting assembly with latching means configured to be easily secured to fuel assemblies while the fuel assemblies remain under water in a fuel storage rack, thereby eliminating the need to remove the fuel assemblies or the fuel storage rack for installation. The two neutron absorbing plates are positioned orthogonally to form a chevron cross section which can be placed about the fuel assemblies by insertion in the existing space between the fuel assemblies and the cell walls of a fuel storage rack. A prescribed orientation of the chevron configured neutron absorbing plate in the cells of the fuel storage rack together with the selected use of a single neutron absorbing plate economically provides sufficient neutron absorption in all radial directions about the fuel assemblies to maintain safe storage condition sin closely packed fuel storage racks.

Abstract: In order to support a shroud against bending, shear, stress and torsion, straps which are preferably formed of the same material as the shroud, are placed in strategic positions with respect to cracks or the like type of weaknesses which have been detected, and fastened in place using a suitable fastening technique. In the preferred embodiments of the invention holes a formed using an EDM technique and bolt units which have an expanding portion are inserted into the holes, torqued and expanded in a manner which fastens the strap to the shroud. Welding and the like type of fastening techniques are not excluded and may used alternatively or in combination with the bolting technique as required.

Abstract: This invention provides austenitic steel having a superior resistance to neutron irradiation, a nuclear reactor and a nuclear fission reactor using such steel.In the present invention, austenitic steel containing at least one of Pd and Pt is used for a member which undergoes neutron irradiation in high-temperature water. More specifically, the steel consists essentially of not more than 0.02% C, not more than 1% Si, 0.5-15% Mn, 9-26% Cr, 8-20% Ni, 0.5-3% Mo, at least one kind of 0.1-16% selected from the group consisting of Pd and Pt, and not less than 50% Fe, and may further contain not more than 1.0% of at least one kind selected from the group consisting of Nb, Ti, Zr, Hf and V, and this is used for structural members in a core of a nuclear reactor and a nuclear fission reactor.

Abstract: A method of removing radioactivity from the interior of a building by transporting radioactive material within a slurry, precipitating out or otherwise filtering out the then contaminated material outside the building, thus removing it in a continuous fluid recirculation system, and storing the precipitated out material while providing shielding of radiation, thereby to provide radiation protection without requiring conventional large mass to block the radioactivity. A toxic waste storage facility includes a building having a portion located below ground level, walls for bounding an interior space in the building, and recirculating fluid for removing thermal energy from the building and for providing radioactive shielding and absorption at least at part of the roof of the building.

Abstract: The present invention provides an improved multilayered storage structure composite material. The composite contains a fibrous mat made from interwoven fibers, preferably metallic fibers, that is encased with a concrete-based mixture to form a mat layer. At least one concrete-based layer is also disposed within the composite, and this concrete-based layer preferably contains at least one shielding additive. The composite material is preferably formed into a containment vessel for the storage of hazardous, radioactive, and mixed waste materials.

Abstract: A superconductive apparatus having therein at least a superconductive member includes a lithium containing member so as to interrupt neutrons directed to the superconductive member.

Abstract: This invention relates to a method for protecting the integrity of the reactor container base in nuclear power plants, and a device for implementing the method.The proposed method and device are applicable to all reactor types (PWR or pressurized water reactor, BWR or boiling water reactor, HWR or heavy water reactor, etc.) and to all types of containing system (large dry type, steam suppression type, condensation on ice type, subatmospheric type etc.), although for simplicity the present text will describe only their application to a PWR with a steam suppression and large dry containing system.

Abstract: A method of forming a neutron-absorbing tube or a section of such tube, and the resulting tube. An elongate, generally rectangular metal ingot having a hollow interior is formed with at least one elongate metal divider in the interior forming chambers. The chambers are filled with a uniformly dispersed mixture of finely divided boron and particles of a finely divided metal, the ingot is then soaked to an elevated temperature and hot rolled to form a thin, rigid neutron-absorbing sheet having opposite metal edge portions and an elongated metal spacer portion at each metal divider. The sheet is then longitudinally bent at each spacer portion. A tube is formed by welding one or more bent sheet along the side edge portions.

Abstract: A radiation gradient is utilized to transform harmful radiant energy into safer, more useful forms, thus collecting, controlling and consuming the energies of radiant emissions and protecting the environment and living organisms from them. More specifically, there is disclosed a new process for shielding emitters of harmful radiation by establishing an electrical circuit, which process includes shielding the source of radiation while collecting the energy of relatively more radiation on an electrically conductive material and collecting the energy of relatively less radiation on other electrically conductive material, which may include a ground or external sink, thus establishing a difference in electrical potential, and transferring this potential difference, along with any potential difference from auxiliary devices, outside the shielded area, to resistors and/or variable other loads, which consume the voltage as it is created.

Abstract: A fuel handling system for nuclear reactor plants comprising an improved underwater grapple means for transferring fuel units while submerged within a water containing reactor vessel. Wherein a novel structure is provided which allows for direct viewing downward for operating the grapple hooks.

Abstract: A permanent pool seal and neutron shield 30 for providing an effective water barrier over the annular space 28 between a nuclear reactor vessel flange 24 and a surrounding annular ledge 22 includes annular deck sections 32 supported on spaced ribs 46.Flexible membranes 50,52 on the deck section peripheries accommodate relative movement. Openings 42, each with a removable plug structure which includes cover 44 and tapered can 60, provide vessel cavity 14 with ventilation and maintenance access. All cans 60 and similar containers 56 and 59 under the deck structure and flange 24 contain a shielding material 58 in the form of a boron-containing concrete. Supported below the cans is refractory insulating material 54.

Abstract: The absorption casing for the absorbing of radioactive radiation and fission products comprises four layers of different materials which retain the various kinds of radiation and the gaseous fission products. The first layer (36) consists of lead and absorbs the hard gamma radiation. The second layer (38) serves for the absorption of neutron radiation and consists of boron, hafnium, cadmium or beryllium. A third layer (42), consisting of aluminium, is provided for absorbing the alpha and beta radiation. Gaseous fission products are retained by a fourth layer (44) consisting of a zirconium alloy. The absorption casing provided with these layers is used for absorbing the radioactive radiation and for retaining the radioactive substances of the reactor of a nuclear power plant. In fast breeding reactors, a fifth layer (32), consisting of titanium, is used as an additional absorptive layer for absorbing the radioactive radiation issuing from the plutonium.

Abstract: A fuel handling system for nuclear reactor plants comprising a camera containing underwater grapple means for transferring fuel units while submerged within a water containing reactor vessel.

Abstract: A shield for a gas cooled nuclear reactor. The reactor vessel head is provided with two regions of material which act in synergism to reflect neutrons back to the core, attenuate gamma rays and neutrons, and allow heat recovery. The primary region attenuates gamma rays and provides significant neutron attenuation. The secondary region provides the residual neutron attenuation.

Abstract: A nuclear power plant installation comprises a nuclear reactor that is disposed in an underground reactor room and connected to power generating equipment on the ground surface by pipes which pass between the underground reactor room and the ground surface. A plurality of underground cavities are disposed above the underground reactor room, each of said cavities comprising steel bridgework that defines the sides and tops of the cavity and an unreinforced concrete floor which supports a mass of particulate shielding material within the cavity. An explosive charge embedded within each such mass may be detonated in the event of a malfunction of the reactor to fracture the floor structure in the cavity if the floor has not been fractured by the reactor malfunction, thereby to cause tons of mixed sand and boron powder to fall from said cavities into the reactor room and bury the malfunctioning reactor within a few seconds after the explosion.

Abstract: Shielding and exhaust covers are disclosed herein which are mountable on the primary manways of a nuclear steam generator for protecting maintenance personnel from potentially harmful radiation during maintenance operations. Each of these doors includes mounting flanges which are detachably mountable to the manway flange. These mounting flanges include brackets for mounting a jewel rail track assembly which in turn slidably mounts two opposing quarter circle panels which, when slid together, form a semicircular shielding cover. The shielding and exhaust covers of the invention may be easily mounted over their respective manways by a single person, and may be opened or closed by a single person standing to the side of the manway and hence out of the radiation shine eminating therefrom. Finally, the shielding material contained in each of the covers is hermetically sealed within stainless sheet metal, which renders it mechanically strong and easily decontaminated.

Abstract: A new design for nuclear reactor internals resulting in reduced fast neutron leakage to the reactor vessel. The first step of the two-stage process reflects high energy or fast neutrons back into the core, by placement of a reflector made of tungsten, stainless steel, or zirconium oxide in the baffle barrel region. The second stage involves reducing the energy of any fast neutrons that may pass through the reflector by the use of a neutron energy reducer, composed of an hydrogenous material such as titanium hydride, surrounding the core barrel in the areas of high neutron flux. In addition to protecting the reactor vessel wall and increasing the operating life of a nuclear reactor, the neutron economy in the core, and hence the operating efficiency of a nuclear power plant, are significantly increased.

Abstract: Nuclear residues with a Co60 specific activity of 1 to 100 Bq/g, such as concrete or metal parts of a nuclear reactor installation, are used as raw materials for the production of radiation shielding structures for such nuclear installation. The concrete reisdues can be broken up to form an aggregate for concrete which is cast to form such structures and metal objects can be added for the casting of transport and storage vessels for radioactive wastes.

Abstract: A thermal barrier for use in a nuclear reactor facility is disclosed herein. Generally, the thermal barrier comprises a flexible, heat-resistant web mounted over the annular space between the reactor vessel and the guard vessel in order to prevent convection currents generated in the nitrogen atmosphere in this space from entering the relatively cooler atmosphere of the reactor cavity which surrounds these vessels. Preferably, the flexible web includes a blanket of heat-insulating material formed from fibers of a refractory material, such as alumina and silica, sandwiched between a heat-resistant, metallic cloth made from stainless steel wire. In use, the web is mounted between the upper edges of the guard vessel and the flange of a sealing ring which surrounds the reactor vessel with a sufficient enough slack to avoid being pulled taut as a result of thermal differential expansion between the two vessels.

Abstract: Nuclear residues, such as concrete or metal parts of a nuclear reactor installation, are used as raw materials for the production of radiation shielding structures for such nuclear installation. The concrete residues can be broken up to form an aggregate for concrete which is cast to form such structures and metal objects can be added for the casting of transport and storage vessels for radioactive wastes.

Abstract: A neutron absorbing panel has improved resistance to loss of efficiency resulting from bending about an axis located at a designated side of the panel. The panel comprises a core of substantially uniform thickness formed of a sintered mixture of particles of neutron absorbing material such as boron carbide (B.sub.4 C) and metal such as aluminum. Metal cladding sheets are provided at both sides of the core, and aluminum is the preferred metal for both the metal core particles, and cladding. The sintered core lacks the ductility of the outer cladding sheets, and to improve bendability, the thickness of one cladding sheet is materially greater than the other. Bending of the improved panel about an axis spaced outwardly from the side thereof having the thinner cladding sheet leaves the outer surface of the panel at the bend smoother than when the cladding sheets are of uniform thickness, and substantially uniform neutron absorbing ability is retained.

Abstract: A shield panel for use in a nuclear reactor including a reactor vessel susceptible to embrittlement when bombarded with high energy neutrons and a nuclear reactor core mounted within the reactor vessel, the reactor vessel having a longitudinal axis and an inner surface surrounding the longitudinal axis, and the nuclear core emitting high energy neutrons which impinge on the inner surface of the reactor vessel. The shield panel includes a canister which contains a completely enclosed interior space and which is mountable between the inner surface of the reactor vessel and the nuclear core in a region wherein the reactor vessel is susceptible to a higher rate of embrittlement than the remaining portion of the vessel when bombarded with high energy neutrons emitted from the nuclear core, and a substance consisting essentially of a heavy metal and hydrogen filling the interior space of the canister.

Abstract: A modular radiation shielding system for use on the lower side of a nuclear steam generator tubesheet 14 to protect inspection and repair workers in the primary head 20 of the generator 10 from radiation of the tubesheet 14 and plurality of tubes 12 it secures. The modular assemblies each comprise a geometrically shaped lead panel 22 sheathed in a stainless steel box 30 with a transverse opening extending therethrough for alignment with a tube 12. A rapid installation tube gripper 40, which may have a lead nose for shielding, extends through the opening and into a tube 12 to hold the geometrically shaped modular assembly against the lower surface of the tubesheet 14.

Abstract: A shielding device is disclosed for use in shielding the under-vessel area from radiation emanating above the lower terminus of a control rod drive of a power generating nuclear reactor of the boiling water type. The device may be comprised of a plurality of individually mountable shell-like housings which are joined in mating contiguous relation to surround the lower terminus of a control rod drive. In the preferred embodiment, each such device is provided with an integrated access door which will allow access to and removal of any connectors and cables such as those of a position indicating probe.

Abstract: A neutron streaming shield comprising a plurality of wire mesh baskets, each basket located between two adjacent vessel nozzles, the total area of the nozzles and baskets being sufficient to intercept any streaming neutrons. The baskets are substantially filled with a multiplicity of randomly packed lumps of a neutron attenuating material, preferably a borated-hydrogenated-argillaceous media. Since the basket is somewhat flexible, it can be inserted in the annulus above the nozzles and then filled with the lumped material, forming a plurality of barriers to compliment the attenuating affect of the nozzles, such that any streaming neutrons will be stopped either by the nozzles or the lumped material in the baskets.

Abstract: A panel of neutron shielding material comprises outer sheathing layers of aluminum having therebetween alternate thin layers or plies of aluminum and metallurgically bonded uniform mixtures of aluminum particles and particles of a neutron absorbing material, preferably boron carbide (B.sub.4 C) in which the layers have their major dimensions extending substantially parallel to the outer aluminum layers. In a modified construction, the alternate layers or plies may extend perpendicular to the outer aluminum layers or plies. The assembly is hot rolled to a final thickness, usually about one quarter or one eighth inch, metallurgically bonding the aluminum sheets, strips, and/or particles and the aluminum and boron carbide particles into a continuous mass.

Abstract: A radiation shield superior to lead in absorbing/attenuating X-rays and the like made by molding with a resin binder a mixture of powders, namely lead oxide derived from scrap storage batteries, slag derived from electrorefining of aluminum, nickel or chromium as a by-product, and molybdenite. The molded shield may also contain zeolite for gas absorption and a reinforcing core of glass fabric.

Abstract: A nuclear reactor is provided with novel composite assemblies at selected locations at the periphery of the reactor core in order to reduce the rate of radiation exposure to a critical pressure vessel weld. The composite assemblies include a shield zone at a selected location close to the weld and a fuel zone incorporating fissile material. This approach reduces the rate of radiation exposure at at the weld while also contributing to production of power by the core.

Abstract: Radiation-shielding transparent material comprising an aqueous solution of thallium formate with or without thallium malonate, the solution having a density of 2.5 to 4.3 g/cm.sup.3, a radiation length of 3.8 to 1.9 cm, and a transmission of not less than 93% for light of 400 nm wavelength. The material is produced by deoxidizing thallium formate and dissolving the deoxidized thallium formate in deoxidized distilled water.

Abstract: A neutron protection thermal insulating material is obtained by adding a boron compound and, if necessary, a hydrous compound, to chrysotile asbestos fibers. To form the material, the asbestos is opened with the use of a surface active agent in the presence of water. The boron compound is added and air bubbles are incorporated into the mixture which is then dried, molded and compressed. The resulting product is characterized by a construction wherein the opened asbestos fibers are oriented in substantially parallel relation to each other and in the direction perpendicular to the compression direction and air pockets are flatly arranged between the fibers and substantially parallel thereto to reduce thermal conduction through the material in the direction parallel to the direction of compression.

Abstract: Radiation pellets having an outer shell, preferably, of Mo, W or depleted U nd an inner filling of lithium hydride wherein the outer shell material has a greater melting point than does the inner filling material.