Abstract: Chirp waves generated in a transmitting/receiving unit is supplied to ultrasonic sensors. Signals output from the ultrasonic sensors are supplied to the transmitting/receiving unit and summed in a signal processing/recording unit. The signal processing/recording unit performs mutual correlation processing between the summed signals and the chirp waves and calculates a peak generation time difference. Necessity of exchanging a pipe is determined by calculating and recording the thickness of a pipe from the calculated time difference and calculating a difference between thicknesses measured in the past and the present.

Abstract: Chirp waves generated in a transmitting/receiving unit is supplied to ultrasonic sensors. Signals output from the ultrasonic sensors are supplied to the transmitting/receiving unit and summed in a signal processing/recording unit. The signal processing/recording unit performs mutual correlation processing between the summed signals and the chirp waves and calculates a peak generation time difference. Necessity of exchanging a pipe is determined by calculating and recording the thickness of a pipe from the calculated time difference and calculating a difference between thicknesses measured in the past and the present.

Abstract: A method for improving a residual stress in a pipe includes improving the residual stress in the inner surface to the compressive direction by rapid cooling of the inner surface after heating of the pipe. The heating is to heat a vicinity of a welded part of the pipe from the outer surface to raise the temperature to a construction temperature. The rapid cooling is to rapidly cool the inner surface in the vicinity of the welded part by supplying cooling water into the pipe. The heating and the rapid cooling are repeated twice or more. A method for construction management includes determining whether construction has been executed properly based on a maximum value of a lowering rate of an outer surface temperature of the pipe when the cooling water is supplied for the rapid cooling of the inner surface and a thickness of the pipe in a measuring position of the outer surface temperature.

Abstract: Even a site having a complicated curved surface shape, such as a welded spot on a bottom of a nuclear reactor core, is simply and electrolytically etched without discharging an etching liquid in a large amount, whereby grain boundary on the surface of the nuclear reactor core internals can be confirmed visually. When the surface of nuclear reactor core internals is electrolytically etched, a sponge provided with holes having a communicating structure is integrated with an etching liquid, and the etching liquid is gelled, while the integrated combination is disposed in front of an electrode, followed by the application of voltage to turn on electricity at a state in which said electrode is electrically connected to the cathode of a direct-current power supply, and brought into contact with or approximated to the surface of the core internals electrically connected to the anode of the direct-current power supply.

Abstract: A method for improving a residual stress in a pipe includes improving the residual stress in the inner surface to the compressive direction by rapid cooling of the inner surface after heating of the pipe. The heating is to heat a vicinity of a welded part of the pipe from the outer surface to raise the temperature to a construction temperature. The rapid cooling is to rapidly cool the inner surface in the vicinity of the welded part by supplying cooling water into the pipe. The heating and the rapid cooling are repeated twice or more. A method for construction management includes determining whether construction has been executed properly based on a maximum value of a lowering rate of an outer surface temperature of the pipe when the cooling water is supplied for the rapid cooling of the inner surface and a thickness of the pipe in a measuring position of the outer surface temperature.

Abstract: Even a site having a complicated curved surface shape, such as a welded spot on a bottom of a nuclear reactor core, is simply and electrolytically etched without discharging an etching liquid in a large amount, whereby grain boundary on the surface of the nuclear reactor core internals can be confirmed visually. When the surface of nuclear reactor core internals is electrolytically etched, a sponge provided with holes having a communicating structure is integrated with an etching liquid, and the etching liquid is gelled, while the integrated combination is disposed in front of an electrode, followed by the application of voltage to turn on electricity at a state in which said electrode is electrically connected to the cathode of a direct-current power supply, and brought into contact with or approximated to the surface of the core internals electrically connected to the anode of the direct-current power supply.

Abstract: In order to provide a boiling water type nuclear reactor use control rod with a guide use roller which improves corrosive environment at a clearance in the guide use roller and suppresses a generation of stress corrosion cracking while maintaining sliding function of the control rod by the guide use roller, at least one of a handle 5, a lower portion supporting plate 2a and a dropping speed limiter 2 is provided with the guide use roller, and a space which causes water flow in a clearance between a pin 9 and a pin hole 12 in the guide use roller is provided adjacent the clearance.

Abstract: In order to provide a boiling water type nuclear reactor use control rod with a guide use roller which improves corrosive environment at a clearance in the guide use roller and suppresses a generation of stress corrosion cracking while maintaining sliding function of the control rod by the guide use roller, at least one of a handle 5, a lower portion supporting plate 2a and a dropping speed limiter 2 is provided with the guide use roller, and a space which causes water flow in a clearance between a pin 9 and a pin hole 12 in the guide use roller is provided adjacent the clearance.