The UK’s 1198MWe Sizewell B pressurised water reactor was powered down to 600MWe and the partial outage will continue until 19 June.
EDF Energy, which operates the plant, was asked by National Grid to cut capacity at Sizewell to help it manage the grid amid weak demand.
National Grid ESO on 7 May confirmed it will pay EDF to reduce output from the Sizewell B over the summer to help keep the power system stable.
ESO said it had agreed a one off, fixed term contract with EDF to reduce output from Sizewell B nuclear power station, as opposed to daily payments to reduce output via the balancing market. It said the agreement is a more cost efficient and secure outcome for consumers, and that it gives additional options to the ESO’s control room engineers.
ESO has also launched a new voluntary service for small scale renewable generators to receive payments from the ESO, if it asks them to turn down or turn off their generation of electricity.
In the four weeks from 23 March, UK generation fell 17.2%, compared with the same period last year. EDF has said it would "explore ways it can respond flexibly" to help the grid. Sizewell B, which opened in 1995, has more flexibility to alter its output than the UK's advanced gas-cooled reactors.
Photo: Sizewell B turned 25 this year