Fukushima No. 4 reactor saved by upgrade mishap

[bananas]

1. The reactor vessel also had a flaw

http://mobile.bloomberg.com/news/2011-03-23/fukushima-engineer-says-he-covered-up-flaw-at-shut-reactor.html

Fukushima Engineer Says He Helped Cover Up Flaw
at Dai-Ichi Reactor No. 4

By Jason Clenfield
March 22, 2011 8:54 PM EDT

One of the reactors in the
crippled Fukushima nuclear plant
may have been relying on flawed
steel to hold the radiation in its
core, according to an engineer
who helped build its containment
vessel four decades ago.

Mitsuhiko Tanaka says he helped
conceal a manufacturing defect
in the $250 million steel vessel
installed at the Fukushima Dai-Ichi No. 4 reactor while
working for a unit of Hitachi Ltd. (6501) in 1974. The
reactor, which Tanaka has called a “time bomb,” was
shut for maintenance when the March 11 earthquake
triggered a 7-meter (23-foot) tsunami that disabled
cooling systems at the plant, leading to explosions and
radiation leaks.

“Who knows what would have happened if that reactor
had been running?” Tanaka, who turned his back on the
nuclear industry after the Chernobyl disaster, said in an
interview last week. “I have no idea if it could withstand
an earthquake like this. It’s got a faulty reactor inside.”

Tanaka’s allegations, which he says he brought to the
attention of Japan’s Trade Ministry in 1988 and
chronicled in a book two years later called “Why
Nuclear Power is Dangerous,” have resurfaced after
Japan ’s worst nuclear accident on record. The No. 4
reactor was hit by explosions and a fire that spread
from adjacent units as the crisis deepened.

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