Abstract: A nuclear fuel spacer grid, fabricated by intersecting a plurality of grid strips and used for placing and supporting a plurality of elongated fuel rods within a nuclear fuel assembly, is disclosed. The spacer grid of this invention has a plurality of dimple vanes on its grid strips. The dimple vanes are designed to guide the coolant from one cell to neighboring cells of the spacer grid, thus accomplishing a desired coolant mixing effect and increasing the thermal allowance of the fuel rods and accomplishing a high performance fuel assembly. The spacer grid also has a multi-spring structure, consist in of one arc-shaped main spring and two bow-shaped sub-springs. The main spring directly supports the fuel rod within the spacer grid, while the sub-springs have the same radius of curvature as that of the external surface of the fuel rod and effectively support the fuel rod when the main spring fails to support the fuel rod.

Abstract: The present invention relates to the heat treatment processes for manufacturing high toughness SA 508 Gr.3 steels including the intercritical heat treatment step in addition to the conventional heat treatment process, wherein the intercritical heat treatment(IHT) is added between the quenching step and the tempering step and is performed at 680° C. to 750° C., which is the ferrite/austenite two phase region, for 1 hour to 8 hours. When compared with the conventional heat treatment process the room temperature impact energy and the upper shelf energy of the steels manufactured by the invention increase significantly and the ductile-to-brittle transition temperature decreases. Also the present invention relates to the modified tempering processes for manufacturing high toughness SA 508 Gr.3 steels, wherein the tempering after the intercritical heat treatment is performed at the temperature lower than 635° C.

Abstract: The invention presented herein relates to a niobium-containing zirconium alloy for use in nuclear fuel cladding. The Zr alloy of this invention with superior corrosion resistance is characterized as comprising an alloy composition as follows: 1) niobium (Nb), in a range of 0.8 to 1.2 wt. %; one or more elements selected from the group consisting of iron (Fe), molybdenum (Mo), copper (Cu) and manganese (Mn), in a range of 0.1 to 0.3 wt. %, respectively; oxygen (O), in a range of 600 to 1400 ppm; silicon (Si), in a range of 80 to 120 ppm; and the balance being of Zr, 2) Nb, in a range of 1.3 to 1.8 wt. %; tin (Sn), in a range of 0.2 to 0.5 wt. %; one element selected from the group consisting of Fe, Mo, Cu and Mn, in a range of 0.1 to 0.3 wt. %; O, in a range of 600 to 1400 ppm; Si, in a range of 80 to 120 ppm; and the balance being of Zr, 3) Nb, in a range of 1.3 to 1.8 wt. %; Sn, in a range of 0.2 to 0.5 wt. %; Fe, in a range of 0.1 to 0.3 wt.

Abstract: A method of manufacturing new UO2-based fuel pellets by recycling irradiated UO2-based fuel pellets. Irradiated UO2-based fuel pellets are oxidized so as to make U3O8-based powder, and then the U3O8 -based powder is mixed with an additive which contains at least one oxide of an element selected from the group consisting of niobium, titanium, vanadium, aluminum, magnesium, chromium, silicon and lithium. Green pellets are formed from the mixed powder, and then sintered, preferably at 1500° C. or higher, in a reducing gas atmosphere to produce UO2-based fuel pellets with high densities.

Abstract: Disclosed is a method of manufacturing large-grained uranium dioxide pellets through the use of U3O8 single crystals. The method consists of two main steps; producing U3O8 single crystals and manufacturing large-grained UO2 pellets. The U3O8 single crystals are produced by annealing U3O8 powder to make U3O8 polycrystalline aggregates having a large crystal size, and by dividing the U3O8 polycrystalline aggregate into its constituent U3O8 single crystals. Large-grained UO2 pellets are produced by forming a mixture comprising UO2 powder and the U3O8 single crystals, making granules of the mixture, pressing the granules into green pellets, and sintering the green pellets above 1600° C. for more than one hour in a reducing gas. The U3O8 powder is produced preferably by heating defective UO2 pellets in air to oxidize UO2 to U3O8. The invention provides a method of manufacturing a large-grained UO2 pellet with defective pellets reused.

Abstract: Disclosed is an alloy steel of high corrosion resistance to hot molten salts containing chlorides and/or alkali oxides. The alloy steel is manufactured from a composition comprising 20-40 weight % of Ni, 0-8 weight % of Cr, 0.05 weight % or less of C, 0.5 weight % or less of Si, 1.0 weight % or less of Mn, 0.05 weight % or less of S, and the balance of Fe to total weight. With a low Cr content, the alloy steel is superb in the corrosion resistance to chloride and/or alkali oxide-containing molten salts, including LiCl—Li2O. Also, the alloy steel shows stable corrosion resistance to molten salts even at high temperature as well as low temperature in addition to being superior to workability. Thus, the alloy steel can be processed into plates, bars or pipes which are used for structural materials and structural components for treating molten salts.

Abstract: A method and an apparatus for electrokinetically decontaminating the soil contained in a radioactive waste drum are disclosed. The radioactively contaminated soil is put into drums, and the drums are carried to a temporary storage or to a disposal site. If the extremely low level radioactive soil is decontaminated rather than carrying the soil to the temporary storage or to a disposal site, and if the decontaminated soil is returned to the nature, then the limited storage capacity can be saved. Further, if a high level radioactive soil is treated to a low level one, and if thus a low level radioactive soil is stored in a storage, then the safety is improved. In the present invention, electrodes are buried into the contaminated soil contained in a radioactive waste drum, and a dc current is supplied, so that the radioactive nuclide and impurities can be removed by the electroosmosis and the electromigration.

Abstract: The present invention relates to a coating method for the preparation of a coated nuclear fuel. Particularly, the present invention relates to the coating method of nuclear fuel surface with more than two coated layers of carbides, borides or nitrides and their compounds comprising deposition or permeation steps of i) elements or mixture that can form carbides, borides or nitrides and ii) a layer of pyrolytic carbon or boron prepared by chemical vapor deposition(CVD) or sputtering in sequence or in reverse sequence, or nitrogen prepared by gas permeation in sequence, on the nuclear fuel surface. The coated layers are formed with carbides, borides, nitrides or their mixture at high temperature and pressure by a combustion synthesis.

Abstract: A spacer grid with H-springs for use in a nuclear reactor fuel assembly is disclosed. In the spacer grid, two sets of intersectional grid strips are arranged in sets at an angle to each other prior to being encircled by a plurality of perimeter strips, thus forming a plurality of four-walled cells individually placing and supporting an elongated fuel rod therein. A plurality of regularly spaced openings are formed on each of the grid strips and perimeter strips at portions corresponding to the cells. An H-shaped spring is set in each of the openings and has a specifically curved rib capable of being brought into conformal surface contact with a fuel rod placed in each of the cells. The H-shaped spring thus elastically supports the fuel rod. Two positioning dimples are provided on each of the strips at positions above and below each of the openings.

Abstract: A method for manufacturing a gas mask canister using a HEPA filter media having plastic separating plates inserted into between HEPA filter media at certain intervals. The HEPA filter, impregnated activated carbon, and a pre-filter are accommodated within a cylinder. The cylinder is inserted into a canister having an upper portion and a lower portion detachably coupled together. The impregnated activated carbon, the plastic separating plates and the casing of the canister can be reused, and the rest of elements are burned. A vinyl coating sheet is peeled off from the canister after each use. An indexing tab for recording the number of times of peeling is attached on each of vinyl coated sheets, so that the number of uses can be known.

Abstract: The present invention is related to the method for surface-alloying comprising the steps of: (a) plating alloying ingredients on the surface of metal or alloy substrate to form plated layer, and (b) melting this surface using a laser beam to form an alloyed layer of which composition is different from that of base material. And, the method of this invention may further include surface-reforming method of metal or alloy substrate. And the method of this invention may further include surface-repairing method of damaged metal or alloy substrate. Using the method of this invention, an alloyed layer, which has improved resistance to grain boundary related material degradation phenomena, e.g. stress corrosion cracking, abrasion, fatigue, erosion, and so on, can be formed.

Abstract: A grid with coolant deflecting channels for used in nuclear fuel assemblies is disclosed. In the grid, two sets of intersecting grid strips are arranged in sets at right angles to each other prior to being encircled by four perimeter strips, thus forming a plurality of four-walled cells individually placing and supporting an elongated fuel rod therein. Each of the grid strips is made up of two narrow sheets which are deformed at a plurality of regularly spaced portions to provide nozzle-type coolant deflecting channels. The channels individually have an upright Y-shaped or reversed Y-shaped configuration capable of so deflecting coolant as to mix low temperature coolant with high temperature coolant. The channels thus form a uniform temperature distribution within a fuel assembly. The channels are so inclined with respect to the axes of the fuel rods as to form wide and linear positioning springs at middle portions thereof.

Abstract: The present invention relates to an apparatus for measuring surface relief profile of an object by projecting a line-shaped laser sheet beam in triangulation method and anisotropic magnification optics for improving the measurement resolution. The purpose of the present invention is to provide a system or an apparatus capable of measuring relief profiles with anisotropic magnification optics composed with one or more positive and one or more negative cylindrical lenses, which allows it to obtain magnified images along the direction vertical to the length-wise direction of the image of a line-shaped laser sheet beam for higher resolution in the relief profile measurements along the direction parallel to the length-wise direction of a line-shaped laser sheet beam image to measure the same range of area as the range without anisotropic magnification optics.

Abstract: Novel calix[4]arene dibenzo crown ethers useful to selectively extract cesium are represented by the formula: wherein R is a C.sub.1 -C.sub.10 normal alkyl, a phenyl or a methoxyphenyl, R' is hydrogen, p-tert-butyl or a C.sub.1 -C.sub.10 normal alkyl, R" is a C.sub.1 -C.sub.10 normal alkyl, and n is an integer of 0-2. The novel compound is prepared at high yields by introduction of benzene rings into the crown ether ring of calix[4]arene crown-6-ether. The calix[4]arene dibenzo crown ethers are superior in selective absorptivity for cesium ions by virtue of their 1,3-alternate conformational structure and thus, can be used as selective extractants able to separate cesium ions at a high efficiency.

Abstract: An strain measuring apparatus for analyzing the stability of a steel structure and a method thereof employs a controller for receiving a variation difference amount from the strain gauge input unit measured using a strain gauge between a strain degree obtained by applying a weight to a steel structure and a strain degree obtained by applying a weight to a steel structure having a hole formed at a predetermined portion and measuring a strain existing in the steel structure based on the variation amount using particular equations. A control command input unit inputs an initialization command for initialing the existing strain measuring apparatus, a radius of the hole formed in the steel structure, a distance between the center of the hole and the center of the strain gauge attached to the steel structurc and an external operating signal including a proceeding command which represents a testing procedure into the controller.

Abstract: The present invention is directed to an advanced zirconium alloy having superior corrosion resistance and high strength suitable for fuel rod cladding, spacer grids and other structural components in a reactor core of nuclear power plants.

Abstract: The invention presented herein relates to a zirconium alloy with superior corrosion resistance and high strength for use in fuel rod claddings, spacer grids and structural components as used in reactor core of light water and heavy water nuclear power plant. The zirconium alloy of this invention with superior corrosion resistance and high strength comprises an alloy composition as follows:niobium(Nb), in a range of 0.05 to 0.3 wt. %;tin(Sn), in a range of 0.8 to 1.6 wt. %;iron(Fe), in a range of 0.2 to 0.4 wt. %;a selected one from the group consisted of vanadium(V), tellurium(Te), antimony(Sb), molybdenum(Mo), tantalum(Ta), and copper(Cu), in a range of 0.05 to 0.20 wt. %;oxygen(O), in a range of 600 to 1400 ppm; andthe balance being zirconium(Zr).

Abstract: A boost and buck chopper type potential source excitation system for a synchronous type electric power generator which is capable of having an operational characteristic which is better than that of a conventional voltage source excitation system with respect to a rated input voltage and forcing an excitation field by boosting an excitation input voltage using a boost chopper when an excitation input voltage is decreased due to a failure in a cable. The system includes a boost chopper for receiving an output voltage from the buck transformer, converting the thusly received voltage into a direct current voltage, adjusting a level of the same, outputting the same to the thyristor as an excitation voltage, boosting the direct current voltage when the output voltage from the electric power generator is decreased, and outputting the thusly boosted voltage to the thyristor.

Abstract: A seismic isolation bearing device is disclosed in which a laminated elastic rubber-steel bearing adapted to isolate horizontal seismic loading cooperates with a vertical isolation device employing a compression spring, or equivalent device, effective for isolating vertical seismic loadings whereby a three dimensional seismic isolation device is effective to isolate both vertical and horizontal seismic loadings to insure the structural integrity of a superstructure against damage induced by seismic events. The isolation device formed of an isolation cylinder fixed to the structure, with an upper fixing plate vertically movable within the cylinder. A plurality of steel balls being disposed within a space formed between the perimeter of the upper fixing plate and the interior wall of the isolation cylinder. The balls facilitating the guided relative vertical movement between the upper fixing plate and the isolation cylinder.

Abstract: A method is disclosed in which fuel scrap of UO.sub.2 alone or UO.sub.2 containing an oxide of plutonium, gadolinium or erbium is recycled into the manufacture of nuclear fuel pellets. The fuel scrap consisting of defective fuel pellets is comminuted through oxidation to fuel particles of U.sub.3 O.sub.8 alone or U.sub.3 O.sub.8 containing an oxide of plutonium, gadolinium or erbium, and a sintering aid containing an element selected from the group consisting of aluminum, magnesium, niobium, titanium, vanadium, chromium, lithium, silicon, tin and mixtures thereof is added in a quantity of about 0.02% to about 2% by weight to the sintering powder which consists of said recycled fuel particles and fresh fuel powder having a composition of UO.sub.2 alone or UO.sub.2 in a mixture of PuO.sub.2, Gd.sub.2 O.sub.3 or Er.sub.2 O.sub.3. The sintering powder is then mixed uniformly, in which the amount of the recycled fuel particles is in the range of about 10% to about 100% by weight.