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

Abstract: A water jet peening apparatus which can carry out an efficient peening work on a large-diameter cylindrical structure by injecting a jet stream which contains air bubbles caused by cavitation at a low angle of incidence is provided. The apparatus is comprised of a nozzle which introduces a high pressure water and injects a water jet stream containing air bubbles caused by cavitation at the cylindrical structure disposed in water, wherein the angle of injection of the jet stream is smaller than 45 degrees relative to a tangent of the cylindrical structure.

Abstract: A water jet peening apparatus which can carry out an efficient peening work on a large-diameter cylindrical structure by injecting a jet stream which contains air bubbles caused by cavitation at a low angle of incidence is provided. The apparatus is comprised of a nozzle which introduces a high pressure water and injects a water jet stream containing air bubbles caused by cavitation at the cylindrical structure disposed in water, wherein the angle of injection of the jet stream is smaller than 45 degrees relative to a tangent of the cylindrical structure.

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

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

Abstract: A 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: An underwater laser processing system has a laser torch; a laser torch driving mechanism for changing a laser emission position of the laser torch; and a chamber with one end opened to an external environment, which contains the laser torch; wherein a partitioning wall for preventing permeation of water is provided between a free end of the chamber and the laser torch. The system is used for detecting a sensitized portion and repairing it at one time using a sensitization detecting arrangement. Moreover, it is used for forming an alloying layer by melting a sprayed coating film, and for forming a new surface layer by emitting a laser beam through a solution containing a metal component.

Abstract: A fluid jet nozzle has a water chamber accommodating therein pressurized fluid, an orifice communicating with the water chamber and contracting the fluid from the water chamber, a throat communicating with the orifice and through which the fluid from the orifice passes, a multiplication chamber communicating with the throat and receiving the fluid from the throat for multiplying cavitation, and a diffusion chamber receiving the fluid from the multiplication chamber for diffusing the fluid.

Abstract: An apparatus preventive maintenance having a driving mechanism capable of driving a jet nozzle 24 to cause it to travel upward-and-downward, to rotate and to swing is settled on the top of a housing in the bottom portion of a reactor pressure vessel and on a hole for a fuel support piece, water pumped by a high pressure pump is spouted from a jet nozzle, and cavitation bubbles generated during the spouting are supplied to the positions to be treated for preventive maintenance, such as housings in the bottom portion of the reactor pressure vessel. Therewith, the residual tensile stress in the position to be treated is improved in a releasing direction by the energy generated by the collapsing of the cavitation bubbles.

Abstract: Low temperature water in a low temperature water tank 12 installed outside a reactor pressure vessel 9 is pumped by a high pressure pump 15 and supplied through a conductor 17 under pressure. The supplied water is ejected, as a stream of cold water jet 8, from a nozzle 14 connected to the conductor 17 and introduced into the reactor pressure vessel 9 by a driving mechanism. The stream of cold water jet 8 ejected from the nozzle 14 is directed to impinge against a predetermined position of a core shroud 13 in reactor water 11 filled in the reactor pressure vessel 9 and being at temperature higher than the low temperature water. Then, while continuing to eject the cold water jet 8 from the nozzle 14, the nozzle 14 is moved away from the predetermined position, or the ejection of the cold water jet 8 from the nozzle 14 is stopped, allowing the predetermined position to be heated again with the temperature of the reactor water 11.

Abstract: The invention is a fastening device for fastening a plurality of structures using a bolt and a nut. At least two bolts are provided each having a screw portion at one end. At least one nut is provided for each of the bolts. The nut has a flange having a diameter greater than a distance between axes of the bolts with relative rotation of the nuts being restricted by fixing mutually overlapping portions of the flanges of the nuts threaded on the bolts to each other.

Abstract: The layer thickness of an object including a substrate and a layer formed thereon is measured by the following steps. First, with regard to a reference system consisting of a reference substrate and a reference layer formed thereon, which are formed of the same materials as those of the object, and an ultrasonic wave propagation medium, the incident angle .theta. at which an ultrasonic wave is applied through the propagation medium to the reference layer and the product H of the frequency of the ultrasonic wave and the thickness of the reference layer are calculated, the incident angle .theta. and product H having such values as minimize the intensity of the ultrasonic wave reflected from the reference layer. The layer of the object is put in contact with the ultrasonic wave propagation medium, and an ultrasonic wave is applied to the layer through the propagation medium at the incident angle .theta..

Abstract: Novel derivatives of 1-phenyl-1H-pyrazolo[3,4-d]pyrimidine substituted at the 4-position of the pyrimidine ring are provided. A typical example is 1-phenyl-1H-pyrazolo[3,4-d]pyrimidine-4-carbonitrile. The compounds exhibit excellent anti-carcinogenic activities as evidenced by the animal test with mice.

Abstract: An improved lith-type silver halide photosensitive material of a wide latitude for infectious developing is disclosed which comprises, in an amount of 5 mg to 5 g per mole of silver halide, a compound represented by the following general formula: ##STR1## wherein R.sub.1 is a substituted or unsubstituted alkyl, aryl, aralkyl, arythio or aryloxy group, and R.sub.2 is hydrogen, halogen, alkyl, alkoxy or nitro.