Patent ID: 6876195

Claim:
A process for measuring a thickness of a layer of oxide on a rod cladding in a fuel assembly having a bundle of rods distributed in an axial direction of the bundle, such that the rods are disposed in parallel rows with passing spaces provided between them and each disposed between two rows of rods comprising: moving an eddy current probe under water and remotely in a bath in at least one space between two rows of rods, such that one of an active portion and a measuring head of the probe comes into contact with a generatrix of each rod in one of one and an other of the rows situated on either side of the passing space; collecting and processing a signal of the probe corresponding to at least one of components of a voltage signal of the probe supplied with alternating current in an impedance plane to obtain values of the thickness of oxide on the rods with which the probe comes into contact, based on a calibration curve that is updated each time the probe passes in a space between two rows of rods further comprising: moving the probe along a whole length of the space between two rows or rods and in an extension thereof such that the active portion of the probe comes into contact with either side of the passing space and standard tubes in an outward direction and in a return direction, opposite to the outward direction; collecting and transmitting the probe signal in digital form to an arithmetic unit having software for processing the signal and determining the thickness of the oxide layer; determining troughs of the probe signal as the signal travels in the passing space between the rows of rods; adjusting the calibration curve based on values of the trough signal corresponding to a contact between the probe and the standard tubes of known oxide thickness, the trough values on contact with the standard tubes checked for consistency as the probe travels in an outward and in a return direction; determining values of the thickness of the oxide layer corresponding to the signal troughs as the probe travels in the passing space between the rows of rods from the calibration curve; checking a consistency of the thickness values obtained for each rod within a row of rods; and recording and displaying consistent values of the thickness of the oxide layer for each rod.