Nozzle inner radius inspection system

The lip of the inner radius of a nozzle mounted through the wall of a nuclear reactor vessel is sandwiched between a transmitter and receiver of ultrasonic sound. The transmitter scans the internal surface of the nozzle lip while maintained a constant average distance from a receiver scanning the nozzle surface on the reactor vessel side of the lip. The two surfaces intersecting to form the inner radius vary in angle as the surfaces are scanned by the transmitter and receiver. Linkage is shown between the transmitter/receiver and the boom with which they are caused to sweep the lip to simultaneously accommodate the saddle shape of the inner radius and the varying angle between the lip surfaces.

We claim:

1. A nondestructive inspection apparatus for the inner radius lip of a nuclear reactor vessel nozzle which apparatus includes a boom hub whose axis coincides with the centerline of the nozzle and is adapted to rotate about and horizontally translate along the nozzle axis, including,

a first elongated arm pivoted by its first end from the forward end of the boom hub,

a roller connected to the second end of the elongated arm which is pivoted from the hub to engage the roller with the cylindrical internal surface of the nozzle as the boom hub is rotated in a sweep about the centerline and translated along the centerline,

an elongated base link pivoted by its first end relative to the second end of the arm,

a transmitter of ultrasonic sound connected to the second end of the base link adapted to move over and direct ultrasonic sound through the inner radius nozzle lip toward the interior of the reactor vessel,

a receiver of the sound from the transmitter connected to the base link and positioned to move over the nozzle surface which forms the inner radius with the internal nozzle surface,

and a means connected between the base link and the elongated arm arranged to generate a force on the base link to rotate the second end of the base link and the attached transmitter and receiver toward the lip surfaces,

whereby pivoting of the base link and translation of the boom hub combine to accommodate the saddle shape configuration of the inner radius in maintaining the transmitter and receiver a constant average distance from each other as the boom hub rotates the arm in sweeping the circumference of the nozzle lip.

2. The inspection apparatus of claim 1, wherein,

the base link is connected by its second end to the transmitter and receiver through a seesaw linkage pivoted between its ends,

and the transmitter and receiver are each connected to an end of the seesaw link by pivots which provide for accommodation to the angle formed between the surfaces defining the inner radius.

3. The inspection apparatus of claim 2, wherein,

dual receivers are pivoted from one end of the seesaw link and oriented so that one of the receivers is aligned to receive the strongest signal from the transmitter at the 6 and 12 o'clock positions of the sweep while the other receiver is aligned to receive the strongest signal from the transmitter at the 9 and 3 o'clock positions of the sweep,

whereby the two receptions of the dual receivers are combined into a single signal over the complete sweep.

4. An inspection apparatus for the lip of the inner radius of a nozzle penetrating the wall of a nuclear reactor vessel, including,

a transmitter sled positioned on the internal surface of the nozzle as one lip surface and in a plane including the nozzle centerline,

a receiver sled positioned on the other lip surface and in the plane including the centerline,

a seesaw link connected to each sled through pivots which maintain the sleds a constant average distance from each other as the sleds are moved along the lip surfaces on each side of the inner radius,

an elongated arm pivoted by its first end from a boom hub carried at the centerline of the nozzle and mounting a roller at its second end engaging the inner surface of the nozzle,

a base link pivoted from its first end to the second end of the elongated arm and connected to the middle of the seesaw link through a pivot at its second end,

and means generating a resilient force connected to the base link to pivot the base link about its first end and thereby urge the sleds toward their lip surfaces,

whereby the boom hub is rotated and translated at and around the centerline of the nozzle while the base link is resiliently urged to pivot from its first end to maintain the sleds of their lip surfaces as the angle varies during the sweep of the inner radius.

5. The inspection apparatus of claim 4, wherein,

the means for resiliently pivoting the base link from its first end is a spring connecting at a point intermediate its ends and a point on the elongated first arm.

6. The inspection apparatus of claim 4, including,

a transmitter of ultrasonic sound mounted on the transmitter sled and oriented to direct its sound at an angle to the plane including the nozzle centerline and the sleds,

a first receiver mounted on the receiver sled and oriented to receive transmitted sound reflected from a defect in the lip at maximum strength when the sweep is at its 6 and 12 o'clock positions,

a second receiver mounted on the receiver sled and oriented to receive transmitted sound reflected from a defect in the lip at maximum strength when the sweep is at its 9 and 3 o'clock positions,

and manifesting means connected to both receivers to combine the signals of reflected sound continuously during the sweep.