Method of checking installed state of jet pump beam
View Patent ↗A jet pump beam (hereinafter, referred to as a beam) is fitted into a pair of projecting portions installed to a transition piece, and after the beam is arched, a beam bolt engaged with the beam is tightened. An end of the beam bolt comes in contact with a top surface of an insert member fitted into an elbow disposed between the pair of projecting portions. An ultrasonic sensor head is fixed to the beam bolt, and ultrasonic waves are sent to the beam bolt from the ultrasonic sensor in the ultrasonic sensor head. An ultrasonic measuring apparatus obtains echo intensity of each of reflected waves generated at the end of the beam bolt and a bottom surface of the insert member, and based on the echo intensities, an echo intensity ratio R is calculated. The installed state of the beam is checked using the echo intensity ratio R.
1. A method of checking an installed state of a jet pump beam, comprising:
inserting end portions of a jet pump beam disposed above an inlet mixer
into grooves formed in a pair of projecting portions of a transition piece provided to a riser pipe disposed in a reactor pressure vessel
while a portion of the inlet mixer is disposed between the projecting portions,
while one end portion of the inlet mixer is inserted to a diffuser provided in the reactor pressure vessel, and
while another end portion of the inlet mixer is communicated with the riser pipe disposed in the reactor pressure vessel;
arching the jet pump beam by moving a center portion of the jet pump beam upward;
pushing a first curved surface
formed at a lower end portion of a screw member engaged with the arched jet pump beam,
against a second curved surface
formed at a top surface of an insert member fitting into the portion of the inlet mixer,
by tightening and elastically deforming the screw member,
the second curved surface having a second radius of curvature larger than a first radius of curvature of the first curved surface;
sending ultrasonic waves to the screw member
from an ultrasonic sensor in contact with an upper end of the screw member,
toward a lower end of the screw member,
while the first curved surface of the screw member is pushed against the second curved surface of the insert member;
obtaining both
a first echo intensity of first reflected ultrasonic waves reflected at the first curved surface, and
a second echo intensity of second reflected ultrasonic waves reflected at a bottom surface of the insert member opposite from the second curved surface; and
checking installation of the jet pump beam using the first echo intensity and the second echo intensity,
based on a change in contacting area
between
the first curved surface of the screw member, and
the second curved surface of the insert member,
occurring upon tightening and elastically deforming the screw member.
2. The method of checking an installed state of a jet pump beam according to claim 1 , wherein the checking installation of the jet pump beam is performed based on an echo intensity ratio obtained using the first echo intensity and the second echo intensity.
3. The method of checking an installed state of a jet pump beam according to claim 1 , further comprising
putting an ultrasonic sensor head
provided with the ultrasonic sensor and a housing forming a hole having an open end for holding the ultrasonic sensor,
in contact with the screw member.
4. The method of checking an installed state of a jet pump beam according to claim 2 , further comprising
putting an ultrasonic sensor head
provided with the ultrasonic sensor and a housing forming a hole having an open end for holding the ultrasonic sensor,
in contact with the screw member.
5. The method of checking an installed state of a jet pump beam according to claim 1 , further comprising
providing contact between the ultrasonic sensor and the screw member
by covering the screw member with a housing of an ultrasonic sensor head
that includes the ultrasonic sensor disposed in a hole formed in the housing and opened toward outside at one end of the housing.
6. The method of checking an installed state of a jet pump beam according to claim 5 , wherein a pushing load of the ultrasonic sensor against the upper end of the screw member is at least partially applied by a pushing spring disposed in the hole.
7. The method of checking an installed state of a jet beam according to claim 1 , wherein a pushing load of the ultrasonic sensor against the upper end of the screw member is adjusted by a weight installed on a housing of an ultrasonic sensor head that includes the ultrasonic sensor.