Yes, Fukushima Daiichi is still releasing radioactive material into the environment, but the situation in 2025 looks very different from the crisis in 2011. There are two distinct things happening: small, uncontrolled leaks of contaminated water that continue to seep from the damaged site, and a large, deliberate discharge of treated water into the Pacific Ocean that began in August 2023. Understanding the difference between these two processes is key to making sense of the current situation.
Uncontrolled Leaks Still Occur
The three reactor buildings that melted down in 2011 still contain roughly 70,000 cubic meters of highly radioactive cooling water in their basements. Groundwater flowing beneath the site seeps into these basements at a rate of about 200 cubic meters per day, mixing with contaminated water before it can be pumped out. That number is actually an improvement. In 2015, inflow rates were closer to 400 cubic meters per day before pumping systems and drainage wells brought it down.
A frozen soil wall, essentially a perimeter of underground pipes chilled to freeze the earth around the reactor buildings, was installed to slow groundwater infiltration. It helped, but it didn’t stop the problem entirely. Rainwater also plays a role. A 2025 study published in Water Research traced cesium-137 still reaching the ocean through a drainage channel at the plant. The researchers found that rainfall washing over the reactor building rooftops accounted for 53% of the cesium-137 flowing through that channel. Scientists have observed unexplained seasonal spikes in cesium-137 concentrations in nearby marine waters since 2016, and this rooftop drainage appears to be a major contributor.
So the short answer is that the site has never fully stopped leaking. The volumes and radioactivity levels are far lower than during the initial disaster, but contaminated groundwater and rainwater runoff continue to reach the ocean through pathways that aren’t completely controlled.
The Deliberate Treated Water Discharge
Separate from those uncontrolled leaks, Japan began intentionally releasing treated water from the site into the Pacific in August 2023. Over the years, TEPCO accumulated more than 1.3 million tons of contaminated water in over a thousand storage tanks on the plant grounds. That water is run through a filtration system called ALPS, which removes most radioactive isotopes but cannot remove tritium, a weakly radioactive form of hydrogen that bonds with water molecules.
Before release, the treated water is diluted with seawater to bring tritium concentrations well below Japan’s regulatory limits. The International Atomic Energy Agency reviewed the first 17 batches of discharged water and confirmed that tritium levels remained “far below Japan’s operational limits.” In a December 2024 review, the IAEA task force found no inconsistencies with international safety standards and reaffirmed its earlier conclusion that the discharge would have “a negligible radiological impact on people and the environment.”
This discharge will continue for decades. The full process is expected to take roughly 30 years as TEPCO works through the massive volume of stored water while also managing the new contaminated water generated daily.
What Monitoring Shows in the Ocean
Fukushima Prefecture conducts regular seawater sampling at nine monitoring points near the plant. Between August 2023 and March 2026, tritium concentrations in those samples ranged from undetectable to 5.5 becquerels per liter. To put that in perspective, the World Health Organization’s guideline for tritium in drinking water is 10,000 becquerels per liter. The measured levels are roughly 2,000 times lower than what’s considered safe to drink.
Cesium-137, a longer-lived and more biologically significant isotope, has been measured at 0.16 becquerels per liter or less in the sea area near the plant. Fukushima’s monitoring agency reports that concentrations of all radioactive isotopes in seawater have consistently remained well below both national discharge standards and WHO drinking water standards.
Is Local Seafood Safe?
Japan tests fish and seafood from Fukushima waters extensively. The national safety limit for radioactive cesium in food is 100 becquerels per kilogram, one of the strictest standards in the world (the US limit is 1,200 Bq/kg, and the EU uses 600 Bq/kg for most foods). Monitoring data from recent years shows that the vast majority of Fukushima seafood samples fall far below even Japan’s strict threshold. Several countries, including China, imposed import bans on Japanese seafood after the treated water discharge began in 2023, though those restrictions reflect political concerns more than detection of unsafe contamination levels in the food supply.
Strontium-90, another isotope of concern because it accumulates in bones, has been measured in seafood near nuclear facilities at levels well below national safety limits and consistent with normal background radiation. Studies covering 2021 through 2023 found strontium-90 levels in fish, shrimp, shellfish, and other marine species that matched background readings from areas with no nuclear activity.
What’s Still Happening at the Site
The bigger picture at Fukushima Daiichi is a decommissioning project that will stretch into the 2050s at the earliest. Three reactor cores melted through their containment vessels in 2011, and removing that molten fuel debris remains one of the most technically challenging nuclear engineering tasks ever attempted. TEPCO has made limited progress retrieving small samples of the debris using remotely operated tools, but full removal is still years away.
In the meantime, the site requires constant management: cooling water must be circulated through the damaged reactors, groundwater must be pumped and treated, contaminated soil and debris must be stored, and the tank farm of treated water must be gradually emptied. Each of these processes carries some risk of accidental release, though monitoring systems are far more robust than they were in the early years after the disaster.
The practical reality is that Fukushima Daiichi will continue releasing radioactivity into the environment for decades, both through the planned treated water discharge and through smaller uncontrolled pathways like groundwater seepage and rainwater runoff. Current monitoring consistently shows that these releases result in radiation levels in the surrounding ocean that are a tiny fraction of international safety limits. The site is not “fixed,” but it is managed, monitored, and slowly shrinking as a radiological hazard.