Maintenance Work on Russian Nuclear Power Plant Prolonged

May 18 - BBC Monitoring Former Soviet Union

Re-starting the operation of the 5th power unit of the Novovoronezhskaya nuclear power plant has been postponed for three months because of the large amount of maintenance needed, the unit's chief, Viktor Boldyrev, told ITAR- TASS today.

The unit which has the capacity of 1m kW was due to be back on grid on 30 May, but "the end of September 2005 would be a more realistic deadline", Boldyrev said.

The 5th power unit was closed down in September 2004 after several cracks had been detected in the pipes of the generating set lid intended to localize radioactive emissions. According to specialists, the defects were caused by metal fatigue due to the effects of adverse conditions during almost 25 years of exploitation.

Boldyrev noted that the plant's 5th power unit was the first nuclear reactor of VVER-1000 type in the history of the Russian atomic industry. Later, the technology for the production of pipes was changed, which ruled out the possibility of similar defects on other power units.

The specialists of the Novovoronezhskaya nuclear power plant decided to replace all 109 pipes on site. Nobody in the world has ever done this. If the whole generating set lid had to be transported to the manufacturing plant, the power unit would have been out of commission for two years. Moreover, the lid itself is radioactive, so its transportation to the plant would create additional problems.

In the next three months the welding of the pipes will be completed and all new connections, as well as safety systems, will be checked.

Two generating sets with a total capacity of 800,000 kW are now operating at the Novovoronezhskaya nuclear power plant. Radiation levels in and around the station are within the norm.