Workers raced to place sandbags around the leaking tank to stem the spread of the water, contaminated by levels of radioactive cesium and strontium many hundreds of times as high as legal safety limits, according to the operator, Tokyo Electric Power, or Tepco. The task was made more urgent by a forecast of heavy rain for the region.
But a Tepco spokesman, Masayuki Ono, acknowledged that much of the contaminated water had seeped into the soil, which would have to be dug up and removed. And he said the tainted water could eventually reach the ocean, adding to the tons of radioactive fluids that have already leaked into the sea from the plant.
The new leak raises disturbing questions about the durability of the nearly 1,000 huge tanks Tepco has installed about 500 yards from the site’s shoreline. The tanks are meant to store the vast amounts of contaminated liquid created as workers cool the complex’s three damaged reactors by pumping water into their cores, along with groundwater recovered after it poured into the reactors’ breached basements.
Hints of the latest leak began to emerge on Monday, when workers discovered puddles of radioactive water near a tank. Further checks revealed that the 1,000-ton vessel, thought to be nearly full, contained only 700 tons, with the remainder having almost certainly leaked out.
Mr. Ono said that Tepco had assumed the tanks would last at least five years. But the tank that leaked could have been in place no more than two, and workers previously found smaller leaks from similar tanks at least four times. And Hiroshi Miyano, an expert in nuclear system design at Hosei University in Tokyo, said that the tanks would be vulnerable to earthquake or tsunami, with the potential for a huge spill.
A powerful earthquake and tsunami knocked out the Fukushima complex’s cooling systems in March 2011, causing meltdowns at three reactors. The accompanying radiological release was rated at Level 7, the highest on the scale and on par with the 1986 accident at Chernobyl. Japanese regulators said Wednesday that they were preparing to raise the rating for the latest leak to Level 3, indicating a “serious incident,” from an initial reading of Level 1.
Each increase on the scale is meant to represent a 10-fold increase in the severity of the leak, according to the International Atomic Energy Agency, which introduced the scale in 1990. Ratings are made by local regulators or sometimes even the plant operators themselves, and not by the I.A.E.A., however.
Tepco has stumbled repeatedly in its handling of the disaster and its efforts to clean up the plant. After its recent admission that contaminated water had reached the open ocean after breaching an underground barrier built to contain it, Japan’s popular prime minister, Shinzo Abe, ordered his government to intervene.
Tepco hopes to clean the water using an elaborate filtering system and start releasing water contaminated at low levels into the ocean. Those plans have been delayed by technical problems and protests from fishermen.
Desperate for options to stem the leaks, Japan’s Nuclear Regulation Authority has suggested surrounding the plant with a huge underground ice wall. That plan has its own drawbacks, however, and would require huge amounts of electricity.
“We are extremely concerned,” Hideka Morimoto, a spokesman for the authority, was quoted by The Associated Press as saying.
At some point, Tepco will have no choice but to start releasing some of the water, said Dr. Miyano, the expert in nuclear system design. The continued problems have heightened public scrutiny of Tepco and have made it harder to build public consensus around any release of water, he said.
“That just makes the problem worse, with no viable solution,” he said.
Makiko Inoue contributed reporting.
Article source: http://www.nytimes.com/2013/08/21/world/asia/300-tons-of-contaminated-water-leak-from-japanese-nuclear-plant.html?partner=rss&emc=rss