A reactor on the Niigata coast idle for nearly 14 years reached commercial power in April and will displace 62 billion cubic feet of gas imports a year, but its first restart attempt lasted a single night

A long flat stretch of coast on the Sea of Japan, a low snow sky, a plant spread across more than a square mile of it.

Seven reactors stand here, which makes this the largest nuclear station ever built by installed capacity.

For nearly 14 years not one of them produced a watt of electricity for sale.

Keeping a machine at full output after 14 years idle is its own discipline too, because neutron embrittlement and calibration drift both sit unfinished for a decade.

On a February afternoon operators pulled control rods on the sixth unit and watched the flux climb.

Criticality came at twenty past three.

It was the second try.

What an alarm on one control rod does to a startup

Control rods in a boiling water reactor are steel chain assemblies driven in from below the core.

Withdrawing them is how a startup begins, and each rod is tracked by a monitoring system that watches its position and its rate of travel.

On the first attempt in January, an alarm sounded in that monitoring system for a single rod during withdrawal.

Procedure in that situation is not to investigate while climbing. Operators returned the rods and shut the reactor down within hours, well before midnight of the following day.

The lesson is inverted from what people expect. The event was not an alarm that failed to sound, it was an alarm doing exactly its job at the least convenient moment.

A startup halted by one instrument is the system working.

The coast this station sits on and why consent took so long

The station was not damaged by the earthquake and tsunami of March 2011, which struck a different coast entirely.

It had its own history though. A 2007 offshore earthquake shook the site hard enough to keep units out of service for years afterward.

This unit kept running after 2011 and went offline for scheduled inspection in the spring of 2012, which is the point the clock starts from.

Approval then required the consent of the prefecture, and that process ran longer than almost any other in the post accident era.

Local consent arrived in November 2025, and it was a political decision rather than a technical one. The regulator had signed off on the unit well before the prefecture did.

The regulator cleared the machine. The delay was the community.

What the record shows about the second attempt

On February 9 the reactor restarted at two in the afternoon local time, with criticality confirmed at twenty past three.

The unit is an advanced boiling water reactor rated at 1,356 megawatts gross, which international registers list nearer 1,315 net.

Generation resumed a week later, followed by a planned halt for abnormality checks and regulatory inspection.

The original target was mid March. The unit reached commercial power on the sixteenth of April, roughly a month behind that date and about 50 days behind the plan it held before the January halt.

Fully running, the unit is expected to produce about 9,500 gigawatt hours a year, enough for a sizable Japanese prefecture drawn from fuel already loaded.

A restart is a sequence, and sequences slip.

The gas that this one machine displaces

Here is the number that travels furthest from the site itself.

Running a year, this unit displaces roughly 1.4 million short tons of liquefied natural gas, or about 62 billion cubic feet of imports.

Gas supplied about 33 percent of all Japanese electricity in 2024, so a single large reactor shifts that share by the output of several gas fired units.

With this unit online the country counts 15 operating reactors totaling around 33 gigawatts, against a fleet that generated 9 percent of national electricity in 2024.

Demand certainty is what makes an expensive plant bankable, which is the same logic pulling small reactors toward data center customers.

The displacement figure, the annual output and the fleet totals come from the federal agency.

Cargoes are not canceled. They are never ordered.

What stays cold, and why the next one is harder

Six of the seven reactors here remain shut, and one of those six is the interesting case.

It is the twin of the unit now running, identical in design and rating, and its restart has been pushed to the end of the decade.

The obstacle is not the reactor. It is a set of anti terrorism protections regulators require before clearance.

Keeping a machine at full output after 14 years idle is its own discipline too, because neutron embrittlement and calibration drift both sit unfinished for a decade.

Squeezing more from an existing license is often the cheaper route, which is why operators study plant output through data validation.

The commercial operation date and the offline duration are recorded by a nuclear service.

One reactor is back, and the honest measure is whether it is still running in a year without another halt.