Abstract: When a power source is lost after an operation stop of a nuclear power plant, a first open/close valve is opened via a first battery at an early stage and steam in a reactor pressure vessel (RPV) is condensed in a suppression pool. The heat of the water in the suppression pool is transmitted to a cooling water pool located below inner space between first and second reactor containment vessels surrounding the RPV. A second open/close valve is opened via a second battery at the early stage and cooling water in a tank is injected into the RPV. After the early stage, a third open/close valve is opened via a third battery, and a cooling medium becomes steam by an evaporator in the RPV, the steam being condensed by a condenser disposed in the inner space to become a liquid of the cooling medium and is returned to the evaporator.

Abstract: A bath containing nickel ions and formic acid is injected into a film-forming aqueous solution flowing in a circulation pipe connected to a feed water pipe made of carbon steel in a BWR plant. This solution is supplied into the pipe through the circulation pipe, and a nickel metal film is formed on an inner surface of the pipe. After the film is formed, a film-forming aqueous solution containing iron (II) ions, formic acid, nickel ions, hydrogen peroxide, and hydrazine is supplied to the pipe. A nickel ferrite film is formed on the surface of the nickel metal film in the pipe. The nickel ferrite film comes into contact with water containing dissolved oxygen at or above 150° C. to transform the nickel metal film into a nickel ferrite film. A thick nickel ferrite film is formed on the inner surface of the feed water pipe.

Abstract: Disclosed is a water jet peening method that includes the steps of: preparing a water jet peening apparatus having a supporting member, a first divider plate, a nozzle support body, and a second divider plate; inserting the water jet peening apparatus into a piping in which a structure or electronic device is mounted that is susceptible to damage by a jet of water discharged from a jet nozzle or by shock waves; disposing either the first divider plate or the second divider plate between the jet nozzle and the structure or electronic device; filling water into an internal area formed in the piping between the first divider plate and the second divider plate; and subjecting the inner surface of the piping to water jet peening by allowing the jet nozzle to discharge a jet of water into the water in the internal area.

Abstract: A shroud support of a BWR includes a shroud support cylinder, shroud support legs welded to a bottom of a reactor pressure vessel (RPV) and a shroud support cylinder, and an annular shroud support plate disposed between the RPV and the shroud support cylinder and welded to the RPV and the shroud support cylinder. A support apparatus is set a CRD housings installed to the bottom of the RPV. A rail guide member horizontally set to the support apparatus reaches directly below the shroud support plate through an opening between the shroud support legs. A bent rail is set on the rail guide member. The bent rail setting a repair device is pushed out along the rail guide member toward the RPV through the opening portion by the rail push-out apparatus set on the support apparatus. The bent rail is spread at directly below the shroud support plate.

Abstract: An eddy current flaw detection system includes an eddy current flaw detection probe having a substrate facing an inspection surface, and at least one exciting coil and at least two detecting coils provided on the substrate, a scanning device which scans the probe on the inspection surface, a scan control device which drives and controls the scanning device, an eddy current flaw detection device which acquires results of detection of a plurality of detection points corresponding to combinations of the exciting and detecting coils for each scan position of the probe, and a data processing/display device which processes data from the scan control device and the eddy current flaw detection device and thereby displays a result of flaw detection. The data processing/display device acquires three-dimensional coordinates of the detection points for each scan position of the probe and thereby creates three-dimensional flaw detection data.

Abstract: An ultrasonic sensor has a piezo-electric element attached at an end surface outside a reactor pressure vessel (RPV) of a sensor leading edge portion. The sensor leading edge portion passes through a bottom head of the RPV and is installed on the bottom head. Ultrasonic waves generated by the piezo-electric element are propagated to the sensor leading edge portion and are propagated to reactor water in the RPV from the sensor leading edge portion. When water surface of the reactor water in the RPV exists below a core support plate, the ultrasonic waves propagated inside the reactor water are reflected on the water surface. Ultrasonic waves reflected on the water surface are propagated into the reactor water, enter the sensor leading edge portion, and are received by the piezo-electric element. Using the ultrasonic waves received by the piezo-electric element, the water level in the RPV is obtained.

Abstract: A reactor water-level/temperature measurement apparatus is disclosed that includes an in-core instrumentation tube inserted into an in-core instrumentation housing and an in-core instrumentation guide tube, a plurality of water-level/temperature detection sensors provided in the tube, a temperature measurement device measuring the temperature of a thermocouple included in each of the sensors, a heater control device for controlling a current flowing to a heater wire included in each of the sensors, a storage device used for storing a threshold-value table, and a water atmosphere and a sensor failure and a water-level/temperature/failure determination device.

Abstract: A top head of a reactor pressure vessel is provided with a plurality of control rod drive mechanism (CRDM) penetration pipes arranged in a square grid-like pattern. The CRDM penetration pipes are joined by a tube support member disposed among them. The top head is placed on a tank and water is filled in an inner region of the tank and the top head. A travel apparatus moves a nozzle lifting/lowering apparatus to a predetermined location and a lifting/lowering mechanism is operated to lift a jet nozzle above the tube support member in the neighboring four CRDM penetration pipes. An ejection outlet of the jet nozzle is directed to a weld between one of the CRDM penetration pipes and the top head, and a water jet is ejected to start WJP. A nozzle turning mechanism turns the jet nozzle, and WJP is executed sequentially to the four CRDM penetration pipes.

Abstract: An ultrasonic reactor water level measuring device and an evaluation method are provided and prevent a reduction in the measurement accuracy of a water level that is in a wide measurement range. The ultrasonic reactor water level measuring device includes an upper tube extending from a gas phase portion in a reactor, a lower tube extending from a liquid phase portion in the reactor, measurement tubes connected to each other and arranged at multiple stages between the upper tube and the lower tube, and units for generating and receiving ultrasonic waves, the units being arranged at bottom portions of the measurement tubes. The ultrasonic reactor water level measuring device measures levels of water within the measurement tubes and calculates a water level within the reactor from the sum of the measured water levels, the sum excluding an overlapped part of the measurement tubes.

Abstract: In a sliding bearing, load carrying capacity and bearing rigidity is increased without increasing a size of the bearing and the pressure of the fluid. The sliding bearing comprises a cylindrical-shaped sleeve supporting a rotatable shaft via fluid, and hydrostatic pressure pockets provided in the inner periphery of the sleeve. The hydrostatic pressure pockets constitute a plurality of rows of circumferentially disposed hydrostatic pressure pockets via orifices. At least one of the hydrostatic pressure pocket rows is arranged adjacently to each of both end portions of the inner periphery of the sleeve. And a circular cylindrical inner peripheral surface region without the hydrostatic pressure pockets is provided at a center portion of the sleeve. A width of the circular cylindrical inner peripheral surface region provided in the axial direction of the shaft is made wider than a sum of widths of the hydrostatic pressure pocket rows.

Abstract: A preventive maintenance apparatus has a movable body and a water jet peening apparatus (WJP apparatus). The movable body installs a jet nozzle for driving and floating bodies on a base body. The movable body suspended in cooling water in a reactor pressure vessel jets high-pressure water from a high-pressure pump from the jet nozzle, advances in the cooling water, and is inserted into a pipe with the cooling water filled which is connected to the reactor pressure vessel. The posture of the movable body in the pipe is controlled by buoyancy adjustment of the floating bodies and the movable body can easily pass through a curve pipe portion. The high-pressure water from a high-pressure pump is jetted from jet nozzles of the WJP apparatus and for the inner surface of a vertical pipe portion, the WJP is executed.

Abstract: Vibration of a jet pump installed in a reactor pressure vessel of a boiling water reactor is monitored. Ultrasonic waves are transmitted from an ultrasonic sensor installed on an outer surface of the reactor pressure vessel toward a throat and a diffuser of the jet pump. When the ultrasonic waves reach respective outer surfaces of the throat and diffuser, reflected waves are generated at the respective outer surfaces. The ultrasonic sensor receives those reflected waves. The ultrasonic signal process section obtains a distance in the horizontal direction between the throat and the diffuser based on a time difference of the reflected waves reflected from respective reflection surfaces of the throat and diffuser and a sound speed in reactor water in the neighborhood of the throat and diffuser. A relative vibration is obtained based on the change with time of the distance.