Device for measuring and correcting a parallelism error in a nuclear fuel rod

1. A device for measuring and correcting a parallelism error of the upper plug end of a nuclear fuel rod placed on a rack, said device comprising:

a location with longitudinal axis for receiving said fuel rod,

device for measuring a parallelism error and corrector for correcting said error, said corrector being arranged opposite the measuring device relative to the longitudinal axis of the location of the fuel rod, in order to allow a measurement of the parallelism error during correction of said error,

positioner for positioning said device relative to the fuel rod, said positioner being intended to cooperate with the fuel rod and the rack, the rack comprising two parallel supports, spaced apart from each other and each supporting a longitudinal end of said fuel rod, said positioner comprising two horseshoe-shaped pieces whereof the inner ends are intended to rest on the fuel rod, the two pieces being spaced apart by a given distance, so as to allow the overlap of the support of the rack on which the upper plug end of the fuel rod rests when the device is put into place, said support having a thickness substantially equal to the distance separating the two horseshoe-shaped pieces,

holder for holding the fuel rod while making it possible to rotate said fuel rod around its longitudinal axis, said holder being positioned between the positioned and the measurement device and corrector, said holder comprising a lower claw and an upper claw intended to grip the fuel rod, the lower claw forming a reference to measure the parallelism error.

2. The device for measuring and correcting a parallelism error according to claim 1 , wherein the measuring device comprises a probe intended to come into contact with the periphery of the upper plug end of the fuel rod, said probe being able to move along an axis transverse to the axis of the location of the fuel rod.

3. The device for measuring and correcting a parallelism error according to claim 1 , wherein the corrector comprises a push-piece intended to come into contact with the periphery of the upper plug end of the fuel rod, said push-piece being able to move along an axis transverse to the axis of the location of the fuel rod, the axis of movement of the push-piece and the axis of movement of the probe being contained in a plain containing the axis of movement of the fuel rod.

4. The device for measuring and correcting a parallelism error according to claim 1 , wherein the claws are made from a friction-reducing material.

5. The device for measuring and correcting a parallelism error according to claim 1 , wherein the upper claw is mounted hinged around an axis parallel to the axis of the location of the fuel rod, and means for locking the lower and upper jaws in the holding position being provided.

6. The device for measuring and correcting a parallelism error according to claim 5 , wherein a stop is fixed on the rod to which the push-piece is fixed so as to limit the movement of the push-piece towards the probe.

7. The device for measuring and correcting a parallelism error according to claim 1 , wherein the corrector comprises a push-piece intended to come into contact with the periphery of the upper plug end of the fuel rod, said push-piece being able to move along an axis transverse to the axis of the location of the fuel rod, the axis of movement of the push-piece and the axis of movement of the probe being contained in a plain containing the axis of movement of the fuel rod, and wherein the push-piece is mounted on one end of a threaded rod mounted in a tapped hole made at the end of an arm, said rod comprising a handle at the end opposite that on which the push-piece is fixed, making it possible to manually move the push-piece.

8. The device for measuring and correcting a parallelism error according to claim 1 , comprising a ring between the holder and the corrector, with an axis parallel to the axis of the location of the fuel rod, said ring being intended to be passed through by the fuel rod and intended to react the deformation stresses applied to the fuel rod.

9. The device for measuring and correcting a parallelism error according to claim 1 , comprising an axial stop for the fuel rod, said stop being arranged transversely relative to the axis of the location of the fuel rod, downstream of the measuring device in the direction of insertion of the fuel rod into the device.

10. The device for measuring and correcting a parallelism error according to claim 1 , wherein the measuring device and the corrector are supported by a platform connected to the positioned by two parallel beams intended to border the fuel rod.

11. The device for measuring and correcting a parallelism error according to claim 1 , wherein the upper claw is mounted hinged around an axis parallel to the axis of the location of the fuel rod, and means for locking the lower and upper jaws in the holding position being provided, and wherein the locking means comprises a threaded rod hingedly mounted around an axis parallel to the axis of the location of the fuel rod, on a side opposite that on which the upper claw is hinged, and a button screwed on the threaded rod, the upper claw comprising a notch to receive the threaded rod, the button being arranged opposite the lower claw relative to the upper claw to ensure the locking of the lower and upper claws, when the rod is in the notch.

12. A method for measuring and correcting a parallelism error of an upper plug end of a nuclear fuel rod placed on a rack, comprising:

a) placing a measuring device on the fuel rod at the upper plug end, the measuring device including a locator with a longitudinal axis for receiving the fuel rod, a parallelism error measurer for measuring a parallelism error, a parallelism error corrector for correcting parallelism error, a positioner for positioning the device relative to the fuel rod, and a holder for holding the fuel rod while permitting rotation of the fuel rod around its longitudinal axis,

b) moving the fuel rod along its axis to position it between the parallelism error measurer and parallelism error corrector,

c) locking the holder,

d) rotating the fuel rod and detecting the parallelism error,

e) determining the correction to be made,

f) orienting said error towards the parallelism error corrector,

g) correcting said error by applying a deformation stress applied by the parallelism error corrector, and simultaneous checking with the information provided by the parallelism error measurer,

h) verifying the parallelism error by checking that it is below a given threshold value,

i) repeating steps d) to g) if the value of the parallelism error is above the given threshold value.