A planned maintenance shutdown at the Point Lepreau nuclear generating station will likely take longer than expected after a problem with an electrical transformer was recently discovered, NB Power has confirmed.

Lepreau was powered down six weeks ago for its first extensive check up and repair following recommissioning in late 2012.

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It costs NB Power several hundred thousand dollars every day the Point Lepreau nuclear generating station is offline.

The maintenance outage was scheduled to take 45 days and the plant was due to come back online next Wednesday.

However, NB Power spokesperson Deborah Nobes says the electrical transformer problem is likely to extend the outage by an extra week.

It costs the utility several hundred thousand dollars every day Point Lepreau is offline.

The nuclear plant performed well through last winter, operating at 100 per cent power for 19 consecutive weeks from November to April.

Despite that stretch, however, the plant has not yet met overall production targets since returning to service in November 2012, following a $2.4-billion, 4.5-year refurbishment.  

Various problems with boiler water chemistry, refuelling procedures and steam lines drove production levels down significantly during its first 12 months.

Longest scheduled outage for 20 years

In April, the plant went offline for a few days due to a problem with one of the turbine system pumps on the non-nuclear side.

The current maintenance outage is the longest one scheduled for the next 20 years and is meant to prepare the plant to run straight out for the next 98 weeks at an average output in excess of 95 per cent.

NB Power has acknowledged that not enough maintenance was done on the nuclear reactor in the 1980s after it was initially commissioned, allowing it to wear out prematurely.

Following the plant's refurbishment, the utility pre-scheduled a minimum of a month-long maintenance outage every other year to try and catch problems early and extend its operating life.

NB Power is also making several modifications to the station during the shutdown to comply with the latest Canadian Standards Association fire standards and emergency preparedness issues identified by the nuclear industry following the accident at Fukushima.

Point Lepreau is Atlantic Canada's only nuclear reactor. The 660-megawatt plant produces enough electricity to power more than 333,000 homes per year, officials have said.