Patent Number: 
Section: claims

1. A method of an ultrasonic inspection in which an ultrasonic probe of an ultrasonic inspection apparatus transmits an ultrasonic wave to a reactor pressure vessel and receives the ultrasonic wave that is reflected on a penetration of the reactor pressure vessel, and an echo based on the reflected ultrasonic wave is displayed on a display unit of the ultrasonic inspection apparatus, the method comprising:a first step of calculating an inclination angle of the penetration relative to a wall surface of the reactor pressure vessel based on a result of the reception of the reflected ultrasonic wave; anda second step of calculating a circumferential direction position of the penetration having the inclination angle. 2. The method of an ultrasonic inspection according to claim 1,wherein the first step includes a step of subtracting an incident angle of the ultrasonic wave which provides the maximum intensity of the echo from 90 to obtain the inclination angle. 3. The method of an ultrasonic inspection according to claim 1,wherein the second step includes a step of solving an equation of the form, θcircumferential direction=cos−1(−cos θinclination/sin θMIN), to identify the circumferential direction position corresponding to the inclination angle, where θcircumferential direction is the circumferential direction position of the penetration, θinclination is the inclination angle that has been calculated in the first step, θMIN is a minimum value of an angle formed between the reactor pressure vessel and the penetration. 4. The method of an ultrasonic inspection according to claim 1,wherein the second step is to identify the circumferential direction position corresponding to the inclination angle, which has been calculated in the first step, based on the relationship between an inclination angle of the penetration and an circumferential direction position of the penetration, which have been calculated in advance. 5. The method of an ultrasonic inspection according to claim 1,wherein an image showing a cross section of the echo obtained from a result of an ultrasonic inspection performed on the penetration by the ultrasonic inspection apparatus and an image showing a cross section of the structure of the penetration to be inspected are combined and displayed on the display unit, the cross section of the structure of the penetration at the circumferential direction position that has been identified being present on the cross section of the echo. 6. The method of an ultrasonic inspection according to claim 5, the method further comprising the steps of:matching a scanning surface shown in the image showing the cross section of the echo with the position of a surface shown in the image showing the cross section of the structure of the penetration;calculating a distance between the center of the ultrasonic wave and the end of the inner diameter of the penetration to be inspected to obtain a position of transmission of an ultrasonic wave on the cross section of the structure; andmatching the position of a transmission point of the echo on the cross section of the structure with the position of the transmission of the ultrasonic wave on the cross section of the structure for image combining. 7. The method of an ultrasonic inspection according to claim 6, the method further comprising the steps of:calculating a distance between the center of the ultrasonic probe and the end of the inner diameter of a penetration adjacent to the penetration to be inspected;subtracting the calculated distance from a distance between the penetration to be inspected and the adjacent penetration to calculate a distance between the penetration to be inspected and the ultrasonic probe; andobtaining a position of transmission of an ultrasonic wave on the cross section of the structure. 8. The method of an ultrasonic inspection according to claim 6, the method further comprising the steps of:measuring a propagation distance of an echo transmitted from the penetration to be inspected or from the adjacent penetration;calculating a distance between the penetration to be inspected and the ultrasonic probe based on the propagation distance; andobtaining a position at which an ultrasonic wave is transmitted on the cross section of the structure. 9. An apparatus for an ultrasonic inspection of a reactor pressure vessel, the apparatus comprising:an ultrasonic inspection device;a scanning mechanism for causing an ultrasonic probe of the ultrasonic inspection apparatus to scan the outer surface of the reactor pressure vessel that is present between penetrations; andmeans for measuring an inclination angle of at least one of the penetrations relative to a wall surface of the reactor pressure vessel based on a result of transmission and reception of an ultrasonic wave by use of the ultrasonic probe. 10. The apparatus for an ultrasonic inspection of a reactor pressure vessel according to claim 9, further comprising:means for calculating a circumferential direction position of a penetration that is to be inspected by using an ultrasonic wave based on the inclination angle.