The owner of one of the UK’s six nuclear power plants has said it will not extend its life beyond a planned shutdown in summer, despite officials raising concerns over the danger of blackouts in the months that follow. The French-owned EDF Energy sent a memo to staff on Monday in which it said it would not postpone the closure of the two reactors at Hinkley Point B in Somerset, which are scheduled to be shut down on 8 July and 1 August. The closure of the plant will remove nearly a gigawatt of power generation capacity from the UK’s system – enough to supply 1.5m homes – before a winter in which the war in Ukraine is expected to weigh heavily on electricity supplies. The government has played down fears of power cuts later this year, after it emerged that officials had modelled a “reasonable worst-case scenario” that could include millions of households being forced to limit their electricity consumption at peak times. That modelling, which was first reported by the Times, included an option to extend Hinkley Point B, something mooted by experts and politicians for months. But it is understood the government had not made any formal request for EDF to keep the reactors open. The government is scrambling to secure enough electricity to maintain buffers during the winter as households struggle with a cost of living crisis driven by energy prices that are expected to increase further in the autumn. Last week the business secretary, Kwasi Kwarteng, wrote to the National Grid’s electricity system operator, asking it to work with the owners of coal-fired power plants that were due to closed down in September to extend their operating lives. This was despite the government’s commitment to rapidly phase out the heavily polluting fuel. Chris Philp, a culture minister who does not have oversight of the energy industry, told Times Radio on Monday morning that Kwarteng was considering whether Hinkley Point B might continue beyond its “planned end of life”. But later in the day EDF wrote to staff: “Although it is technically feasible to extend operations [at the nuclear plant] for up to six months, the time required to do this and to be confident we would be ready for winter operating has now run out.” The memo, which was revealed by the Financial Times, added that an extension would involve compiling a detailed safety case that would have to be approved by the UK’s nuclear regulator. A government source said any decision to apply for an extension would be a matter for EDF and the regulator, and added that the government had secured enough power capacity even without extending the operation of the coal or nuclear plants. However, industry sources with knowledge of the matter said it was very likely that EDF would require a written request from a minister before deciding to go through the laborious process of submitting a new safety case to the regulator, which is run at arm’s length from the Department for Business, Energy and Industrial Strategy (BEIS). “On Hinkley B, there is no technical reason it can’t continue to operate, if they can satisfy the regulators. For EDF, it will be fundamentally an economic decision,” said Malcolm Grimston, an honorary senior research fellow at Imperial College London’s centre for energy policy and technology. Insiders in the sector expressed concern over the lack of time the government had left to take any action, with one saying: “They’ve left it right to the very end, and we’re not sure if it’s possible.” Sue Ferns, the senior deputy general secretary of the Prospect union, which represents engineers including those who work in the nuclear industry, said: “All options to prevent energy blackouts this winter must be explored. “The government must ask nuclear power plant operators to urgently explore safely extending the life of reactors due to be decommissioned in the coming months, including Hinkley Point B, which is otherwise due to come offline this summer.” A spokesperson for Boris Johnson said: “Neither the government or National Grid expect power cuts this winter.” Sources at BEIS also suggested the prospect of rolling blackouts was “very unlikely”. EDF declined to comment. A government spokesperson said: “Any extensions to operational dates for the UK’s nuclear power stations are a matter for the operator of the stations, EDF and the regulator the Office of Nuclear Regulation, which are based on safety considerations. “The government has no direct involvement in this process and has not made any requests of this kind.”