The nuclear comeback has a very specific sound to it right now, and most of it is press releases. Microsoft signed a deal that is bringing a Three Mile Island reactor back online. Amazon and Google are funding small modular reactors that do not commercially exist yet. Utilities are dusting off plans for full-size plants because the data centers feeding the AI boom need round-the-clock power that wind and solar cannot promise on their own. Read from a distance, it looks like a supply problem you solve with money and permits.<\/p>\n
Then you get to the steel. Every one of those big reactors, and a lot of the small ones, needs a pressure vessel, the giant forged can that holds the reactor core and the water around it. The best versions are forged in one piece, with no weld seams to fail.<\/p>\n
And the plant that has dominated that work for decades sits in a small port on the northern Japanese island of Hokkaido, running a press you cannot buy your way around. Not the regulators, not the reactor designers. A forging line, in a single town, is one of the tightest chokepoints in the entire build-out.<\/p>\n
Strip a large reactor down to its single most important part and you get the reactor pressure vessel: a thick steel cylinder, often around 40 feet tall, that has to contain the fuel, the coolant and the nuclear reaction itself for the 60-year life of the plant. It has to hold pressure, shrug off decades of radiation, and never crack. That last requirement is where the forging gets interesting.<\/p>\n
You can build a vessel out of several forged rings welded together, and plenty are. But every weld is a spot you have to inspect for the entire life of the reactor, and every weld is a potential weak point. The World Nuclear Association<\/a> puts it plainly: reactor vendors prefer the big forgings made as single integral pieces, and the fewer welds in the vessel, the better. Forge the ring in one seamless piece and you delete a failure mode before the plant ever switches on.<\/p>\n The catch is that forging a single piece that big is brutally hard. For the largest Generation III reactors, you need a press in the range of 14,000 to 15,000 tons squeezing a steel ingot of 500 to 600 tons, and those presses are not common. A single one tends to turn out only about four pressure vessels a year, slotted in around everything else it makes.<\/p>\n The plant that has owned the high end of this work is the Japan Steel Works site at Muroran, on Hokkaido. The complex runs two of the 14,000-ton hydraulic forging presses this job requires, and according to the World Nuclear Association it can take steel ingots up to 670 tons, the largest commercially available. JSW describes the Muroran plant<\/a> as running melting, forging, heat treatment and machining in one bayside complex, which is part of how it holds tolerances almost nobody else can hit.<\/p>\n JSW has been at this for a while, and its back catalog is a little unsettling. The company was founded in Muroran in 1907, and during the war the same plant forged the 18-inch gun barrels for the battleship Yamato, then the largest warship in the world. The ship was sunk. The plant survived the bombing and turned to civilian steel.<\/p>\n It has been forging nuclear components to US Nuclear Regulatory Commission standards since 1974, and the World Nuclear Association counts around 130 JSW reactor pressure vessels in service around the world today. When the first two EPR reactors were built in Finland and France, the pressure vessels were forged at Muroran.<\/p>\n Put the pieces together and you get a bottleneck with very little give. JSW claims roughly 80 percent of the world market for large forged nuclear components, a figure the World Nuclear Association still cites and that independent analyses put at the same level heading into 2026. The forging cycle for one of these large pieces runs well over 18 months before it is even machined and assembled into a finished vessel, and a single press only makes a handful a year.<\/p>\n So utilities do the only thing they can, which is get in line early. Buyers have a long habit of reserving forging slots years ahead of breaking ground, sometimes putting down deposits to hold their place, for components that will not be poured until designs clear regulators that have not approved them yet. When the customer is paying upfront to wait, you already know who holds the leverage in that relationship, and it is not the customer.<\/p>\n None of this means Muroran is the only forge on Earth. A handful of plants can now make very large nuclear forgings, among them Doosan in South Korea, China First Heavy Industries and Shanghai Electric in China, Russia’s Atommash, and Framatome’s Creusot Forge in France. The very largest single-piece work was, for years, something only JSW could do.<\/p>\n The nozzle shell ring for the EPR needed a 500-ton ingot, and the World Nuclear Association notes that for a long time JSW was the only forge that could produce it.<\/p>\n That is no longer strictly true, and you can see the shift out in the field. The 500-ton pressure vessel that Britain just lowered into Hinkley Point C with the world’s largest crane<\/a> was forged by Framatome in France, not Japan. France is also now forging its own giant steam generators<\/a> for its next round of reactors, running the plant like a car factory. The build-out is global, from Britain to the reactor Turkey just lowered through an open roof at Akkuyu<\/a>, and every one of those vessels traces back to one of only a handful of forges worldwide.<\/p>\n Still, on the biggest seamless vessels and across the broad market, JSW’s lead is the kind that takes a rival the better part of a decade and a press costing well over $100 million to seriously challenge.<\/p>\n What has changed in 2026 is the scale of demand pointed at that short list, and the reason is the same one driving most energy stories right now: computing. The International Atomic Energy Agency reckons the world’s data centers could burn through more than 1,000 terawatt-hours of electricity<\/a> this year, roughly what the entire country of Japan uses.<\/p>\n AI clusters want enormous, constant, carbon-free baseload, which is a fairly exact description of a nuclear plant, and the hyperscalers have started buying it directly. Layer in the broader restart of large reactors across the US, Europe and Asia, plus a wave of small modular designs, and the World Nuclear Association already counts more than 70 reactors under construction worldwide.<\/p>\n JSW has noticed. In early 2026 the company folded its steel arm back into the parent and built a new Materials and Engineering division around the Muroran plant, explicitly to chase rising demand for the metal that goes into nuclear and high-efficiency power generation as AI use expands. Its steel-and-energy order book already stretches years out. The town that forged the Yamato’s guns is, once again, the place a global build-out has to wait on.<\/p>\n It is a strange shape for a chokepoint. The AI story usually points at chip fabs in Taiwan and GPUs from Nvidia, and those are real constraints. But a chunk of the same buildout also runs through a forging press on a bay in northern Japan, turning a 600-ton glob of steel into a seamless can that has to hold a nuclear reaction for six decades. You can design a reactor in a few years and approve it in a few more.<\/p>\n You cannot rush a single press into making more than it makes, and you cannot weld your way out of the problem without adding the exact weak points the whole approach exists to avoid. The nuclear revival keeps a standing reservation in Muroran, and the line only moves as fast as the press.<\/p>\n","protected":false},"excerpt":{"rendered":" The nuclear comeback has a very specific sound to it right now, and most of it is press releases. Microsoft … <\/p>\nOne press, one town, and the guns of the Yamato<\/h2>\n
This is why utilities order years in advance<\/h2>\n
JSW is not quite alone anymore<\/h2>\n
The data-center boom lands on a Japanese loading dock<\/h2>\n