– Japanese scientist: Fukushima meltdown occurred within hours of quake (Washington Post, May 26, 2011):
At a second meeting Thursday related to the Fukushima Daiichi crisis, a U.S. Energy Department official warned that the nuclear facility still faces grave danger.
John E. Kelly, deputy assistant secretary for nuclear reactor technologies, said that protective components at the facility could crack because of high salt levels. There “is still a concern about more massive failure” of steel in the “lower head,” an important part of the containment system, Kelly told an NRC advisory committee. About 100 to 200 tons of salt left by the emergency pumping of salt water to cool the reactors are probably corroding the containment components.
Kelly also stressed that Tepco would have to continue pumping water into the damaged reactor units and venting radioactive steam for a year or more.
Tepco has built a low-level waste storage facility on the site but has no plans to move the waste elsewhere, he added. “It could be almost 30 years before they could use the site, so it’s almost permanent.”
Kelly made his comments during a hearing of the NRC’s advisory committee on reactor safety, which is drawing lessons from the disaster for the U.S. nuclear industry.
Kelly said an enormous number of unknowns, including the cause of an explosion at the unit 4 reactor, the safety of pools of used nuclear fuel and the condition of key protective components, remain.
More damaging revelations emerged earlier Thursday in Tokyo, where Tepco told reporters that a new leak in a storage container had dumped an additional 60 tons of radioactive water into the environment.
A high-level team of investigators from the International Atomic Energy Agency arrived in Japan this week to begin a 10-day investigation of the crisis.
In the United States, the NRC is in the midst of a wide-ranging 90-day review of U.S. nuclear power plant safety regulations in light of Japan’s crisis, the worst nuclear accident since the 1986 explosion at the Chernobyl power plant in Ukraine.