There have been new equipment and techniques developed for component inspection, maintenance, repair and replacement. These have been developed and tested in the laboratory and in full-scale experiments before being applied to plants (IAEA-TECDOC — 1175, 2000).

In Japan, techniques are being developed for the chemical decontamination of LWR reactor systems in preparation for the replacement of core internals. For the latter operations, full-scale mock-ups have been used. Techniques for the replacement of a PWR core barrel and bottom mounted instrumentation systems are being examined. Methods for the replacement of BWR core housing, core shroud, control rod housing and jet pump riser braces are also under consideration.

Holographic methods of inspection for the recognition and sizing of cracks are being developed. In Japan, intergranular stress corrosion cracking has affected reactor internals and core shroud and ways are being evaluated for mitigating this phenomenon. One solution is to replace components fabricated with SS type 304 with corresponding components made of SS type 316.

Manipulators are being developed for the purposes of in-pipe inspection, grinding and for repairing cracks in welds, e. g. between the vessel nozzles and pipes.

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