Single rod leak detection and repair of leaking or damaged fuel assemblies

In some circumstances, it is necessary to perform rework operations on some fuel assemblies in order to make them reusable in reactors, movable, transportable or consistent with fuel reprocessor specifications, depending on the plant utility policy. These rework operations are of two types: - Those which consist in restoring the leak tightness of the fuel assemblies. They are made after a series of tests allowing the localization of the failed fuel rods: at first, overall leak detection is provided by monitoring primary coolant activity during reactor operation; then, during refuelling, leaking assemblies are identified by subjecting each of the assemblies scheduled for reloading to a sipping test; finally individual leaking fuel rods are singled out before the defective assemblies can be repaired, i.e. failed rods can be replaced. - Those which involve replacement of part of or the whole assembly structure (combined or not with replacement of failed fuel rods). In order to meet these two needs for rework operations, FRAGEMA has developed a full range of test and tooling systems for detecting single leaking rods in irradiated fuel assemblies and for restoring fuel assemblies to be used in PWR nuclear power plants. As an illustration of the means available, two of these systems are described