Tuesday marks three years since an earthquake and tsunami in Japan led to the world’s worst nuclear accident since Chernobyl. After a year in which leaks of contaminated water at the Fukushima Daiichi nuclear-power plant made headlines, here are some questions and answers on where the issue stands:
Q: Is the water problem fixed?
A: Not yet. A large amount of groundwater keeps flowing under reactors that suffered meltdowns, creating about 400 metric tons a day of highly contaminated water. The existing water cleaning system removes almost all radioactive cesium from it, but other radioactive materials remain. A new water cleaning system called ALPS has been proved in a laboratory to remove all radioactive materials except tritium, which is less harmful, but ALPS has not yet worked fully at the site. Getting it to do so is a top priority for Tepco.
Q: Isn’t it safer to encase the three reactors that suffered meltdowns with concrete walls and roofs like Chernobyl?
A: Opinions vary. Some experts say concrete casing would prevent new water from flowing into the most damaged parts of the plant, among other benefits. Mr. Koide said the idea would minimize workers’ exposure to radiation and could work so long as air-cooling of the reactors is possible. But Shunichi Tanaka, Japan’s top nuclear regulator, said even waiting 100 years wouldn’t significantly lower the risks posed by melted fuel. “Uranium and plutonium have a very, very long half-life. Playing for time would make little difference,” Mr. Tanaka said.
Q: Is there any other way to cut the water flow into the reactors?
A: The government is preparing to build underground ice walls around the first three reactors to block fresh water from flowing into them. The work will begin as early as this month and the ice walls encasing the reactors will be formed around spring in 2015, according to the government. Sumio Mabuchi, a lawmaker who has dealt with the contaminated water issue, proposes building another underground wall with a kind of concrete to prevent water from seeping in.
Separately, Tepco has been coating the seabed in the bay next to the plant with a kind of clay used in construction to prevent radioactive cesium trapped in the soil there from mixing with seawater. And an attempt to remove strontium from the soil in the site is under way.