Not fishing for trouble
A number of fish species caught off the coast of the Fukushima Prefecture in 2011 and 2012 had levels of cesium contamination greater than Japan's regulatory limit for seafood (100 becquerels per kilogram), but both U.S. and Japanese scientists have also reported a significant drop in overall cesium contamination of ocean life since the fall of 2011. The biggest contamination risks came from bottom-dwelling fish near the Fukushima site. [In Photos: Fukushima Butterflies Plagued With Defects]
The radioactive groundwater leaks could still become worse in the future if TEPCO does not contain the problem, U.S. scientists say. But they cautioned against drawing firm conclusions about the latest impacts on ocean life until new peer-reviewed studies come out.
"For fish that are harvested 100 miles [160 kilometers] out to sea, I doubt it’d be a problem," said Nicholas Fisher, a marine biologist at Stony Brook University in Stony Brook, N.Y. "But in the region, yes, it's possible there could be sufficient contamination of local seafood so it'd be unwise to eat that seafood."
The overall contamination of ocean life by the Fukushima meltdown still remains very low compared with the effects of naturally occurring radioactivity and leftover contamination from U.S. and Soviet nuclear weapons testing in the 1960s. Fisher said he’d be "shocked" if the ongoing leaks of contaminated water had a significant impact on the ocean ecosystems.
Source of radioactive water
TEPCO is facing two huge issues in stopping the radioactive water leaks. First, groundwater from nearby mountains is becoming contaminated as it flows through the flooded basements of the Fukushima plant's reactor buildings. The water empties into the nuclear plant's man-made harbor at a rate of about 400 tons per day — and TEPCO has struggled to keep the water from leaking beyond existing barriers into the ocean.
"This water issue is going to be their biggest challenge for a long time," said Dale Klein, former head of the U.S. Nuclear Regulatory Commission. "It was a challenge for the U.S. during Three Mile Island [a partial nuclear meltdown in Pennsylvania on March 28, 1979], and this one is much more challenging."
Second, TEPCO must also deal with contaminated water from underground tunnels and pits that hold cables and pipes for the Fukushima nuclear plant’s emergency systems. The underground areas became flooded with highly radioactive water during the initial meltdown of the Fukushima plant’s reactors, and have since leaked water into the ocean despite TEPCO’s efforts to seal off the tunnels and pits.
TEPCO has also been racing to deal with the problem of storing hundreds of thousands of tons of radioactive water from the Fukushima plant, said Hiroaki Koide, a nuclear engineer at Kyoto University in Japan. The Japanese utility is testing a water decontamination system called ALPS that can remove almost all radioactive substances except for tritium, but has put much of the contaminated water in storage tanks in the meantime.
"The tanks are an emergency solution that is not suitable for long-time storage," Koide said. "Water will leak from any tank, and if that happens, it will merge with the groundwater."
What must be done
So what solutions exist beyond building more storage tanks? Klein reviewed a number of possible solutions with TEPCO when he was picked to head an independent advisory committee investigating the Fukushima nuclear accident.