A radioactive leak was detected at a nuclear power station in Somerset last week, it has emerged.
The leak did not affect the running of Hinkley's two reactors
The incident happened at Hinckley Point B power station near Bridgwater on 21 July, British Energy has confirmed.
Monitoring equipment detected radioactivity in carbon dioxide (CO2) gas in the reactor basement area, a company spokesman said.
He added that the CO2 leak was quickly stopped and none of the gas was discharged into the environment.
"We estimate that a very small amount of CO2 gas, less than half a tonne, was released into the reactor basement area," he said.
"The incident had no impact on operation of the stations' two reactors and they continue to run normally.
"Our highly-trained staff dealt with the incident safely and professionally."
Although no radioactivity leaked out of the power station, the Environment Agency has been informed and will carry out independent monitoring of the incident.
In July 2003 part of Hinkley Point B was closed for several hours after radioactive dust leaked into the atmosphere.