EDF and its Chinese partner will put aside an additional £3 billion in case of emergencies during the building and running of Hinkley Point C.

An EDF spokesperson said the money was needed “if something extreme happens” but didn’t elaborate on what that might be.

Initally the French energy giant said it would provide £12 billion while its Chinese partner China General Nuclear (CGN) would invest £6 billion in the nuclear power plant in Somerset.

However in a statement published ahead of its annual shareholders’ meeting, EDF stated: “The partners’ equity commitment includes a contingency margin and could reach a total of £13.8 billion for the EDF Group and £6.9 billion to CGN.

“CGN would pay to EDF for the acquisition of its shares in the project a premium on top of its share of the development costs already expensed.”

The company added it anticipates a 115-month – or nine and a half year – construction period after the final investment decision until commissioning of the first reactor.

The final investment decision for Hinkley Point C has been delayed several times. UK MPs on the Energy and Climate Change Committee have called back EDF chiefs for questioning following the delay.

The UK Government has pledged an initial investment of £2 billion for the project, which is expected to provide around 7% of the UK’s electricity needs.

Last year EDF said first operation of the nuclear power plant was scheduled for 2025.