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North Anna unit back on line

North Anna Power Station’s Unit 1 was back in service on Sunday after shutting down automatically on Friday because of an electrical issue.

Unit 1 had completed a scheduled refueling and maintenance shutdown and returned to service on Thursday. Then it had an unplanned shutdown Friday afternoon after reaching 48 percent power, said Richard Zuercher, a spokesman for Dominion power nuclear operations.

The cause was an electrical relay associated with a service transformer. Service transformers move electricity from the grid to power electrical systems required for normal operations at the plant.

During refueling, one-third of the reactor fuel is replaced with new fuel, and other maintenance is done.

This time, station workers installed mechanical and electrical tie-in connections for hoses and external power supplies that could be used in an emergency to provide cooling water and electricity to the plant.

That work is related to post-Fukushima upgrades at the nation’s 100 commercial nuclear reactors.

A magnitude-9.0 earthquake and resulting tsunami seriously damaged the Fukushima Dai-ichi nuclear plant on Japan’s northern coast in March 2011. Nuclear fuel in three of the plant’s six reactors melted down, contaminating the plant site and the surrounding countryside.

The improvements at North Anna and at other commercial reactors are aimed at ensuring that emergency power and cooling water are available in the event of a disaster.

Inspections were also done on Unit 1’s three steam generators. They produce the steam needed to power a turbine generator, which produces electricity.

Rusty Dennen: 540/374-5431