UPDATE 1-UK Dungeness B21 nuclear unit off for maintenance

(Recasts with British Energy comment, pvs FRANKFURT)

LONDON, July 10 (Reuters) - The Dungeness B21 nuclear reactor in southeast Britain was taken out of service for planned maintenance that takes place every three years, a spokesman from operator British Energy (EDF.PA) said on Friday.

The spokesman said the 555 megawatt (MW) unit had been out of service since 1800 local time (1700 GMT) on Thursday. He declined to comment on when it was scheduled to restart.

British Energy is owned by France's EDF.

(Reporting by Vera Eckert, additional reporting by Nao Nakanishi in London, Editing by Peter Blackburn)