Life Extension of Critical Components Betterments and Modifications

Ageing plants reveal that some of the components within the primary circuit do not show the expected life time. Betterments have been enabled by repairing or replacing defective parts. ABB. has developed specific repair processes to meet these requirements. The goal is to be as flexible as possible in order to adjust methods, procedures, and equipment to the specific needs of each plant within the shortest time possible. Inspection methods and repair procedures are discussed to present betterments and modifications for some components within the primary circuit by explaining the ABB. approach for e. g. the Inspection of pressure vessel closure head penetrations: The manipulator is designed, constructed, controlled and monitored just like a manipulator developed for steam generator inspections and repair. The E CT-probes are qualified to resolve cracks ensuring a high sensitivity if there is no thermal sleeve or if the probe is inserted into the gap. Looking through the thermal sleeve by an E CT-probe reduces the sensitivity slightly. The inspection and repair of internals, e. g. fuel alignment pins and baffle former bolts: the UST-methods, the manipulator equipment, the tools and the procedures are provided to find defective pins resp. Bolts, and to replace them. Approximately 1000 fuel alignment pins have been replaced. Three inspection systems have been provided to inspect baffle former bolts. They were upgraded for an exchange of baffle former bolts. The bolt resp. pin betterment is achieved by an improved material and a ventilation preventing stagnant water. Advances in maintenance of steam generators: Focus is given to identify potentially defective steam generator tube areas within tube support plates or ABB reviation bars. The good experience gained with the Micro lock of ABB. removable plugs is transferred to the sleeves which have a Micro lock joint at the bottom. Chemically cleaning the secondary side of a steam generator utilizing the SIG process at intermediate temperatures was very efficient this spring in a full size cleaning. The amount of sludge and deposits removed was as predicted. The examples described above are typical illustrations of how ABB. meets the maintenance requirements of nuclear power plants. Our task is to recognize problems and provide fast and reliable solutions. Within a nuclear environment, a throw away mentality should and has to be suppressed, it can be only the very last choice for a problem, because it creates another problem: the waste disposal. Warranting and repairing components and parts in the nuclear island is complicated and expensive because of radiation, space limitations, remote under-water operations, and the required qualified procedures. Currently it is wishful thinking to provide a modular manipulator system which could cope with all situations. What can be done and is done successfully is to concentrate on a specific, proven and established repair technique. The manipulators employed have been most efficient if they are designed for inspection and repair work. Despite the atomization and computerization of remote control, it turns out that the most efficient feature in a repair job is the human being recognizing what is available from other job and what can be provided for this job. This is what makes the hard work of service personnel interesting and fascinating and will suit the plant and outage manager because they get solutions to their problems in due time