Fukushima engineers knew of critical design flaw years in advance

Officials at the Tokyo Electric Power Company (TEPCO) and engineers at the Fukushima nuclear power plant knew for years about a critical design flaw in the plant's older reactors, but declined to do anything about it, according to a report in The Wall Street Journal.

An electric switching station the size of a kitchen table was the major component to fail when the facility was swamped by seawater in the tsunami following the March 11 earthquake. In older reactors, the switching station is housed in a vulnerable outbuilding rather than in the building that houses the reactor.

When the switching stations went offline, operation of the reactors' cooling systems became impossible, leading to the meltdowns in the unstable fuel cores. The reactors based on the newer design successfully shut down when the plant was inundated.

Dozens of former officials and workers told the Journal that Tepco failed to avail itself of opportunities to retrofit the reactors in the decades since their construction. They blame a combination of "complacency, cost-cutting measures and lax regulation".

All of the Fukushima reactors were designed by GE and the design is shared by 23 of the plants older than 30 years in the United States.