Plant owner British Energy did not release any more details on the problem but it was not thought to be significant.
The last shutdown at Torness happened on April 12 when a reactor was closed for a planned repair to the turbine generator water system. The reactor was back in service on April 28. There have now been nine stoppages at Torness in 12 months.
The Scottish Government has recently pledged to extend the life of Hunterston B to at least 2016, and keep the younger Torness plant running "until the end of its operational life".
This will take it until 2023 but there are no plans to replace the reactors beyond this time.
(Source: News Scotsman)