Power, Patience, and the Point We're Missing: All Nine UK Nuclear Reactors Online and the Broader Implications

Somewhere on the East Lothian coast this weekend, Torness Reactor 2 began warming up. It had been offline since late February for its 13th statutory inspection and refuelling outage – a meticulous, safety-mandated process that involves the Office for Nuclear Regulation granting explicit consent before a single watt is returned to the grid. That consent has been granted. The reactor is rising. And as it synchronises with the network, something will be true of the United Kingdom's nuclear fleet that I have not seen in over fifteen months of tracking it daily, and – to the best of my knowledge – has not been true for considerably longer than that.

Every single one of Britain's nine nuclear reactors will be generating electricity at the same time.

It won't last long. Torness Reactor 1 has already lowered power output ahead of its own offload refuelling outage next week. The window of completeness is days, not weeks. But it is real, and it is worth pausing on — because it sits at a remarkable confluence of history, engineering, and policy that deserves more attention than it will likely get.

The Fleet That Refused to Die

Let's start with the fact that these reactors were never supposed to still be here.

The UK's Advanced Gas-Cooled Reactors — seven of the nine currently operating units — were designed with service lives of 25 to 30 years. The youngest of them, Torness and Heysham 2, came online in 1988. They are 38 years old. They have been inspected, extended, inspected again, and extended again. Graphite cores have been monitored for cracking. Gas circulators have been replaced. EDF has invested heavily in plant upgrades that most observers, a decade ago, assumed would never be sanctioned.

The result is a fleet that has confounded expectations not through luck, but through disciplined engineering and meticulous safety oversight. And the reliability of these machines is, to put it plainly, remarkable.

Consider: between 2014 and 2016, and already in its twilight years, Heysham 2's Unit 8 ran without interruption for 940 consecutive days — setting a world record for the continuous operation of any commercial nuclear reactor. Two and a half years. No shutdowns, no forced outages, no drama, no dependence on the Strait of Hormuz. Just quiet, reliable generation. For context on how extraordinary that is, the previous record had been held since 1994 by Canada's Pickering Unit 7, at 894 days. Heysham beat it by nearly seven weeks. The record has since passed to India's Kaiga Unit 1 (962 days, 2018) and then to Canada's Darlington Unit 1 (963 days, 2020) — but the fact that a British AGR built before the Intel 486 held the world record for four years tells you something important about what these machines are capable of.

This is not how wind and solar work – and that is not a criticism of wind and solar, which are vital and cheap and increasingly abundant. But an offshore wind farm generates at capacity perhaps 40–45% of the time. It cannot be scheduled. It cannot be dispatched. It responds to the weather, not to the grid operator. Nuclear, by contrast, runs continuously. It can be planned around. It provides the firm, always-on baseload that holds the system together while intermittent renewables do their work. The two are not competitors; they are complements. A clean grid needs both. Today, for a brief moment, Britain has all of the former.

The Last Reactor in Scotland

There is a particular poignancy to Torness's role in all of this.

Scotland generates extraordinary quantities of renewable electricity. In recent years, wind power alone has frequently exceeded Scottish demand, with surplus exported South. By most measures, Scotland has one of the cleanest electricity mixes in Europe. But behind that impressive headline sits a structural vulnerability: Scotland has no firm low-carbon generation other than nuclear. Peterhead gas station is the only other always-on source, and it is emphatically not low-carbon.

Image Credit: John (https://en.wikipedia.org/wiki/File:Torness_Power_Station_from_the_east.jpg)

Torness is not merely one of Scotland's power stations. It is the only remaining nuclear power station Scotland has, and it is the single largest contributor to Scotland's electricity generation – responsible for around 17% of the nation's electricity in 2024, more than any other individual generating asset. This is a far cry from the innovation of Dounreay in the North of Scotland, the site of the world’s first Fast Reactor to supply energy commercially (Fast Reactors are making a comeback, globally because they can process waste from other nuclear reactors), and Hunterston which, at the time of commissioning, was the largest generating nuclear plant in the world. In its nearly four decades of operation, Torness has generated enough clean electricity to power every home in Scotland for approximately 29 years.

When it closes – currently scheduled for March 2030 – Scotland will have no firm, dispatchable, low-carbon electricity generation at scale. That is not a problem that wind turbines solve. It is a gap that demands a serious answer, and the Scottish Government's current hostility to new nuclear means that answer is not yet forthcoming. The Nuclear Industry Association's call for a "Torness B" deserves to be taken seriously. For now, though, Torness stands – both reactors spinning – and that matters enormously.

The Wylfa Symmetry

If Torness's story is one of quiet persistence, the wider nuclear story this week has acquired a dimension that feels almost scripted.

Four days ago, on 13 April, the UK Government and Rolls-Royce SMR signed a formal contract for the delivery of three Small Modular Reactors at Wylfa, on the Anglesey coast in North Wales. The contract, backed by up to £599 million from the National Wealth Fund, triggers immediate site-specific design work and allows long-lead equipment orders to be placed. It is the formal starting gun for Britain's first SMR programme.

Wylfa. The name should ring a bell. It was home to the last of Britain's original Magnox reactors – the first generation of the UK's civil nuclear fleet, built in the 1960s. Wylfa's final reactor closed in December 2015, ending 44 years of operation. It was the last Magnox station and the end of the first chapter.

Now, in the same week that the complete second-generation AGR fleet comes online together for what may be the final time, construction begins – conceptually, if not yet in concrete – on the third. The site that closed the Magnox age is reopening to build the SMR age. It is a beautiful historical arc, entirely unplanned, and genuinely worth appreciating.

The three Rolls-Royce units at Wylfa will generate approximately 1.4GW between them, with a target of grid connection in the mid-2030s. Combined with Hinkley Point C – still under construction, now targeted for first power around 2030 – and the recently confirmed Sizewell C, the UK's long-term nuclear trajectory is, at last, pointing upward after decades pointing down.

The Valley Ahead

It would be dishonest to write about this moment without acknowledging what comes next.

The nine reactors generating today represent roughly 5.8GW of low-carbon firm capacity. By the end of 2030, the entire AGR fleet – eight reactors, multiple gigawatts – will be retired. Sizewell B, the UK's sole pressurised water reactor (PWR), will remain. Hinkley C's first unit may, if schedules hold, be approaching commissioning. But the arithmetic is stark: the UK will enter the early 2030s with perhaps just 2–3GW of nuclear capacity before new builds begin to restore the fleet. That is a nuclear valley, and it is real.

The Wylfa SMR contract and the Sizewell C final investment decision are genuinely good news. But design approval for the Rolls-Royce reactor isn't expected until late 2026, and a final investment decision at Wylfa won't come until the turn of the decade. The mid-2030s target is credible – but it is a target, not a guarantee. Anyone who has followed UK nuclear's recent history (Wylfa Newydd, Moorside, Oldbury, and the sorry saga of Hinkley itself) will apply appropriate levels of scepticism.

Today's moment doesn't resolve that tension. It simply makes it more visible, and more precious.

A Brief, Complete Thing

I've been watching our fleet of ‘nukes since January 2025, using the excellent https://www.energydashboard.co.uk/, and cross-referencing with Elexon's REMIT, and in that time I have never seen all nine reactors generating simultaneously. Based on the rotation of outages across the fleet, it is likely that this has been the case for considerably longer. The overlap today exists because of careful scheduling, successful inspections, extended lifetimes, and a degree of good fortune – and it will be gone within days when Torness Reactor 1 steps down for its own outage.

There is something faintly elegiac about it. All but one of these marvellous machines are between 38 and 43years old. They were built in an era when nuclear was Britain's future; they survived an era when it became Britain's embarrassment; and they are now generating in an era when it is, cautiously, Britain's priority again. The complete fleet, briefly online together, is a small but genuine symbol of that continuity.

The reactors that were supposed to close in 2013 are still running in 2026. The site that shut the last Magnox reactor in 2015 is building the first SMR. And for a few days, all nine of Britain's nuclear generators are turning at once.

It's worth noting. I'm glad I was watching.

The author has been tracking daily UK nuclear generation output since January 2025. Current fleet status and outage schedules are published by EDF Energy at edfenergy.com/energy/power-station/daily-statuses, and Elexon’s REMIT at https://bmrs.elexon.co.uk/.