Japan's Rokkasho Reprocessing Plant Costs Rise to Record ¥15.98 Trillion
A fresh ¥360 billion cost increase at Japan's perpetually delayed nuclear fuel cycle plant underlines why the country's LNG dependency will not dissolve quickly.
The total bill for completing Japan Nuclear Fuel Limited's Rokkasho spent nuclear fuel reprocessing facility has climbed to ¥15.98 trillion, the highest figure on record and ¥360 billion more than the estimate issued just one year ago, according to data published in Japan NRG Weekly on Monday (2026-06-29).5
Construction costs alone rose ¥180 billion in the latest revision, reaching ¥3.92 trillion. The MOX fuel fabrication plant at the same Aomori prefecture site added ¥80 billion, bringing its total to ¥2.68 trillion. The two facilities are operationally bound together: MOX fuel cannot be produced without reprocessed plutonium from Rokkasho, and Rokkasho loses much of its rationale without a domestic MOX consumer.5
Rokkasho was originally scheduled to enter service in the late 1990s. It has been deferred more than two dozen times since. Each new revision to the schedule has arrived with a higher price tag, and this one carries greater weight than most because it covers the final-cost estimate — not a construction-phase projection. The plant is designed to extract the roughly 95-97% of uranium and plutonium remaining in spent fuel that can be reused, and to reduce the volume and danger of high-level radioactive waste awaiting disposal. Without it, storage pools at Japan's operating reactors accumulate spent fuel with no agreed exit route.5
The overrun arrives at a fraught moment for Japanese energy planning. Tokyo's latest national energy strategy foresees renewables accounting for between 40% and 50% of electricity generation by 2040, up from around 25% currently. Nuclear is expected to carry a meaningful share of the remainder, but the fuel cycle underpinning that strategy keeps getting more expensive to build. Researchers at Lawrence Berkeley National Laboratory have estimated Japan could reach 70% renewables reliably by 2035, but the government has not adopted that target, preferring a blended approach in which nuclear remains central.1
For LNG markets, the connection is structural. JKM spot stood at $15.52 per MMBtu as of Monday (2026-06-29), well below the $18.96 level recorded on May 18 (2026-05-18), when Iranian retaliation against US-Israeli strikes disrupted an estimated 17% of Qatar's LNG export capacity and shocked Asian buyers. The price retreat since then reflects supply returning and demand softening. But persistent delays at Rokkasho reinforce that Japan's baseload cannot pivot quickly away from imported fuel.2,4
Japan's April (2026-04) generation data showed how fast that dependency materialises under price stress. Coal-fired power supply rose 11.1%, the fastest pace in at least a year, while gas-fired output fell 12.9% to 16,447 gigawatt-hours, according to the Japanese Electricity Market and Policy Institute, as cited by Reuters. The shift toward coal was partly a response to elevated LNG costs during the Iran disruption.3
ICIS senior gas analyst Fei Xu calculated that Japan's increased coal burn in April (2026-04) displaced roughly four LNG cargoes — about half the annual reduction in imports the government had anticipated from a greater coal role. That gap between policy expectation and actual market behaviour matters for anyone modelling Japanese LNG demand over the next decade.4
Japan NRG Weekly also reported that the government's energy roadmap now targets the domestic capacity to build LNG carriers, a capability Japan has not exercised since 2019. Its inclusion signals how central long-term LNG supply security remains to official planning, even as Rokkasho's completion date and price tag continue to move in the wrong direction.5
Analysts at Trading Economics project JKM front-month at $17.47 per MMBtu by end of quarter, implying a partial recovery from current levels. Whether that materialises depends partly on how much nuclear generation Japan can actually bring online this summer and whether Iranian export disruption recurs. Rokkasho will not alter either variable this year, but its mounting cost will weigh on decisions about how long Japan's utilities commit to long-term LNG supply contracts before the domestic fuel cycle delivers anything close to what was promised.2