Japan Atomic Energy Research Institute

Noriya Ebine

Katsuyuki Ara

Nobuya Nakajima

In a method of and an apparatus for checking the degradation of the pressure vessel of a nuclear reactor with the pressure vessel of the nuclear reactor being directly measured in a non-destructive manner, a magnetic yoke having an exciting coil and a magnetic flux measuring coil is closely placed in contact with the inner wall of the pressure vessel of the nuclear reactor. The hysteresis magnetization characteristics of the closed magnetic path formed by the magnetic yoke and the pressure vessel of the nuclear reactor are measured. The coercive forces are obtained by the hysteresis characteristics. The hardness of the material comprising the pressure vessel of the nuclear reactor at the part of the magnetic path formed in the pressure vessel of the nuclear reactor is obtained from the coercive forces and the degradation of the material comprising the pressure vessel is checked from the hardness.

Method of and apparatus for checking the degradation of a pressure

A method of and an apparatus for measuring the thickness of the overlay clad of the pressure vessel of a nuclear reactor with good accuracy are disclosed. A magnetic yoke having an appropriate length and cross-sectional area of the magnetic path is placed closely in contact with the surface of the overlay clad of the pressure vessel of the nuclear reactor to form a magnetic path by the magnetic yoke and the pressure vessel of the nuclear reactor, the magnetic yoke is magnetized, the distribution of the magnetic field on or near the surface of the overlay clad in contact with which the magnetic yoke is closely placed is measured and the thickness of the overlay clad of the pressure vessel of the nuclear reactor is identified from the medium value or the half value width of the distribution of the magnetic field thus measured.

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Ibaraki-ken, Japan

Noriya Ebine