Officials with Tokyo Electric Power Co. have outlined their plans  for ending the saga of the stricken reactors at the Fukushima Daichi power plant. In the first 3 to 6 months, according to the plan, crews will try to cool the reactors to a stable point, aiming for “cold shutdown” with temperatures within the reactors below 100°C. Then engineers will inject nitrogen into the pressure vessel surrounding each reactor. Using this inert gas should make it possible to minimize the use of water in the reactor vessel and reduce the risk of hydrogen explosions, which have already rocked three of the reactors. But crews will aim to use water to cool the outer containment vessel. The second step will focus on stopping the leakage of radionuclides into the air, essentially by fixing the outer walls of the damaged reactors or replacing them with freestanding, cubic containment barriers. There is no timetable for the government to ease restrictions on residents who live within the 20-kilometer-radius evacuation zone.
The Japanese effort “seems to be on track, but [there’s] a long way to go,” says Lake Barrett, who helped lead the cleanup effort for the U.S. Nuclear Regulatory Commission 3 decades ago at Three Mile Island in Pennsylvania.
He says a big challenge for the Japanese is to start recirculating water they’ve used to cool the reactors; they have already created 10 million gallons of radioactive water in a once-through process called “feed and bleed." "They need to get those cores on recirculation and off of feed and bleed. It is drowning them with radioactive water,” Barrett says. By the end of the shutdown effort at Three Mile Island, Lake says, U.S. engineers were left with far less radioactive water, about 600,000 gallons.