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Mühleberg Nucear Power Plant
Optimising work and revision completed - plant once more up and running
Bern (ots) - Following completion of the annual revision and optimising work on the inlet structure of Mühleberg nuclear power plant (KKM), BKW FMB Energy Ltd. (BKW) restarted the facility at the weekend. Prior to the restart, the Federal Nuclear Safety Inspectorate (ENSI) approved the upgrades and authorised the facility's repowering. As part of the revision, BKW carried out various important renovation and maintenance work and performed the usual repeat tests on the plant's safety systems, including the core shroud. BKW is committed to the long-term operation of the KKM for as long as the plant's safety and profitability are assured.
The 2011 annual revision mainly involved extensive repeat tests as well as work on and in the reactor pressure tank. The welding on the pipes was checked using an accredited ultrasound test system, and a new state-of-the-art testing system was used to check the core shroud. The latter system had been accredited, in accordance with the applicable guidelines, by the Swiss Association for Technical Inspections: an independent centre for assessing and certifying test systems. The system provides much wider scope for testing and - unlike systems used to date - can also be used to determine not only the length but also the depth of any cracks identified.
Stability of core shroud confirmed
The measurements taken confirm that the welded joints of the core shroud exhibit no cracks which penetrate the wall, and that - in line with the trend identified in recent years - crack growth remains stable. The extensive checks and evaluation of the core shroud fracture mechanics once more confirm the stability and integrity of the core shroud.
Revision work completed on schedule
One of the two generators was also subjected to a comprehensive overhaul. Work begun in recent years to renovate the protective equipment for the plant's own electrical supplies was also continued, as a result of which the systems are now state-of-the-art. Finally, work on the main cooling water pipes was completed as part of a multi-year maintenance and checking cycle to ensure the facility's long-term operational life. The ordinary revision tasks culminated on schedule with the successful leakage test on the primary containment.
The comprehensive series of checks and inspections, particularly those performed on the safety systems, turbines, generators and transformers as well as the electrical protection and regulating systems, found no indications that the plant's safety was compromised. Extensive analyses confirmed that the components are reliable and able to guarantee the safe, long-term operation of the plant. Thirty-six of the 240 fuel rods for the operating cycle 39 were replaced. All fuel rods are in good condition.
Upgrade to protect against extreme flooding
Last week also saw completion of the work, begun in mid-August, to increase flooding protection even further and, in particular, to optimise the SUSAN inlet structure by installing three additional suction units and building an additional feed-in line for the SUSAN emergency cooling supply. The cost of these upgrades was below the CHF 10 million budgeted. The cost of production down time caused by the longer revision came to around CHF 28 million.
During the revision work, more than 1,000 experts were involved: 330 BKW employees and around 700 external specialists from Switzerland and abroad. The ongoing modernisation and preventive maintenance of the plant is performed in the interests of safety and with a view to its long-term operation. Continual upgrades optimise the plant's availability and sustainably increase production. Some 40% of current electricity requirements in BKW's supply region are met by the KKM.
Additional information on the revision and the core shroud will be provided at a media event
As part of the media event, Martin Saxer, deputy manager of the nuclear power plant, and Ulrich Imobersteg Head of Nuclear Engineering Technology, will be on hand to provide additional information to all interested members of the media. The discussion will be held today, 26 September 2011, at 14:00 at Mühleberg nuclear power plant. No guided tour is planned. A valid pass must be presented for entry to the nuclear power plant. To register, please e-mail firstname.lastname@example.org by 12:00. For background information on the core shroud, visit https://kernenergie.bkw-fmb.ch/kernmantel.html
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