TOKYO — For months now, it has been hard to escape the continuing deluge of bad news from the devastated Fukushima nuclear power plant.
Even after the company that operates the plant admitted this summer that tons of contaminated groundwater was leaking into the Pacific Ocean every day, new accidents have added to the uncontrolled releases of radioactive materials. This week, newly tainted rainwater overflowed dikes. Two weeks before that, workers mistakenly disconnected a pipe, dumping 10 more tons of contaminated water onto the ground and dousing themselves in the process.
Those accidents have raised questions about whether the continuing leaks are putting the environment, and by extension the Japanese people, in new danger more than two and a half years after the original disaster — and long after many had hoped natural radioactive decay would have allowed healing to begin.
Interviews with scientists in recent weeks suggest that they are struggling to determine which effects — including newly discovered hot spots on a wide swath of the ocean floor near Fukushima — are from recent leaks and which are leftovers from the original disaster. But evidence collected by them and the plant’s operator, the Tokyo Electric Power Company, or Tepco, shows worrisome trends.
The latest releases appear to be carrying much more contaminated water than before into the Pacific. And that flow may not slow until at least 2015, when an ice wall around the damaged reactors is supposed to be completed. Beyond that, although many Japanese believed that the plant had stopped spewing radioactive materials long ago, they have continued to seep into the air.
“This has become a slowly unfolding environmental misery,” said Atsunao Marui, a geochemist at the Geological Survey of Japan who has studied contaminated groundwater flowing from the plant. “If we don’t put a stop to the releases, we risk creating a new man-made disaster.”
Even the most alarmed of the scientists who were interviewed did not extend their worries about the new releases to human health. With more than 80,000 residents near the plant evacuated almost immediately after the disaster, and fishing in nearby waters still severely restricted, they say there is little or no direct danger to humans from the latest releases. But, they say, that does not rule out other impacts on the environment.
And while the air and water releases are a small fraction of what they were in the early days of the disaster, they are still significantly larger than what would normally be permitted of a functioning plant.
Both Tepco and the government say the largest continuing problem, the water releases, is not a cause for concern, because the radiation is diluted in the vast Pacific, limiting any potentially dangerous effects to the plant’s artificial harbor. But while scientists agree that dilution has made radiation levels outside the harbor, and even some places inside, low enough to pass drinking water standards, they say there are worrisome problems that may be the result of new leaks.
Besides the discovery of widespread radioactive hot spots, the government’s fisheries agency said that more than 1 in 10 of some species of bottom-feeding fish caught off Fukushima are still contaminated by amounts of radioactive cesium above the government’s safety level.
The latest concerns began in June, when Tepco announced a sharp rise in the amount of radioactive contaminants, including strontium 90, found in groundwater near two of the ruined reactors. The company says the source of the increased contamination appears to be highly radioactive water that had been trapped since the accident in conduits around the reactor buildings and had slowly found its way out.
The planned ice wall is meant to contain this water, as well as to sever the flow of groundwater that pours daily into the damaged reactor buildings while following its natural course from mountains behind the plant down toward the sea. (That water, which becomes sullied by radioactive materials from the melted nuclear fuel, is captured and stored in a cityscape of tanks.)
The magnitude of the recent spike in radiation, and the amounts of groundwater involved, have led Michio Aoyama, an oceanographer at a government research institute who is considered an authority on radiation in the sea, to conclude that radioactive cesium 137 may now be leaking into the Pacific at a rate of about 30 billion becquerels per year, or about three times as high as last year. He estimates that strontium 90 may be entering the Pacific at a similar rate.
Dr. Aoyama notes that those amounts would be much smaller than the amount of cesium 137 alone released into the Pacific during the accident itself, which he estimates at up to 18 quadrillion becquerels. Still, other scientists suspect that the new releases are having measurable effects beyond the harbor.
Blair Thornton, an associate professor at the University of Tokyo’s Underwater Technology Research Center, helped find the hot spots, spread across at least 150 square miles of the ocean bottom offshore from the plant. He said they appeared to be formed when radioactive particles like cesium and strontium, which are heavier than water, collect in low points like trenches.
Radiation levels there should naturally weaken over time, Dr. Thornton said, as sea currents deposit new sediments on top of toxic particles. The fact that radiation levels are still up to hundreds of times as high as they are in other areas of the sea floor raises the possibility that the spots are being blanketed in new contamination from the plant, he said. The other possibility, Dr. Thornton said, is that radioactive particles released by the original accident bonded to mud on the sea bottom and are not disappearing as quickly as expected.
In either case, researchers say, the hot spots are a concern because shrimp and small fish tend to gather in depressions on the ocean floor for protection. If the radioactive materials are entering their bodies, those particles could work their way into the food chain, requiring that fishing be suspended for longer than local fishermen had hoped.
The hot spots could explain why cesium-contaminated fish are still being caught off Fukushima, some scientists say. While the number of such fish has been steadily falling, it has not dropped as quickly as expected.
“Obviously, there is some continuing source of cesium 137,” said Jota Kanda, an oceanographer at the Tokyo University of Marine Science and Technology. “We are not sure exactly what is happening, but we are seeing a bigger than expected effect on the environment.”
Less attention has been paid to the continued airborne releases of cesium from the site’s crippled reactors, whose layers of protection were damaged or destroyed. The plant still emits 10 million becquerels per hour into the atmosphere, according to Tepco. While the amounts of airborne emissions dropped sharply after the accident, which spewed radioactive materials across a wide swath of northeastern Japan, they have held steady since February 2012, Tepco said.
Tepco has tried to stop these continuing releases by taking steps like erecting a cover over one damaged reactor, but it acknowledges that radioactive materials still escape through tiny gaps in the cover, or through damaged ventilation systems and cracks in the reactor buildings. So long as such air and water releases continue, experts warn, there will be no end to Fukushima’s slowly unfolding environmental damage.
“These aren’t levels that are going to directly affect human health,” Masashi Kusakabe, a researcher at an institute that has monitored cesium in the ocean for the government, said, referring to releases into the Pacific.
“But that doesn’t mean that therefore these releases are good or acceptable,” he said. “There is no precedent for what is happening, so we are on untrodden ground.