A plan to connect six reactors at the crippled Fukushima No. 1 nuclear power plant, which could have reduced the damage from the Great East Japan Earthquake and tsunami, never left the drawing board, according to sources.
Tokyo Electric Power Co. sources said while consideration had been given in 2006 to connecting all sources of electricity at all six reactors, no decision was made because of technical problems.
However, nuclear engineering experts said the work could have been implemented and added that overconfidence about the low possibility of all reactors losing all their electrical sources was likely behind the failure to proceed with the reconstruction work.
"TEPCO officials likely concluded that there was no need to spend time and money because of an overconfidence that a loss of electricity sources would never occur," said Tadahiro Katsuta, associate professor of nuclear engineering at Meiji University. "If the work had been carried out, there was the possibility that damage could have been reduced."
After the March 11 tsunami hit the Fukushima No. 1 plant, the No. 1 to No. 4 reactors lost their electrical sources. The inability to properly cool the reactors led to a core meltdown and hydrogen explosions that severely damaged the reactors and spewed large amounts of radioactive materials into the atmosphere.
The No. 5 and No. 6 reactors were connected in terms of electricity sources and the emergency diesel generator at the No. 6 reactor, which was the only one that continued to work, enabled cooling to continue at those two reactors.
As an emergency measure, TEPCO officials laid electrical cables between all six reactors by April 25.
Because TEPCO proceeded with such work after the quake and tsunami, experts said if reconstruction work had been conducted in 2006, there was the possibility that a major accident could have even been prevented.
According to former TEPCO executives, a plan was considered in 2006 to strengthen the electricity facilities at the Fukushima No. 1 plant to avoid a critical accident that might occur should all electrical sources be lost due to a natural disaster.
The No. 1 to No. 4 reactors on the south side of the plant were connected by electrical cables and those four reactors could share electricity if the need arose.
The No. 5 and No. 6 reactors on the north side of the plant also shared electrical sources with each other, but those two reactors were not connected to the four to the south.
The plan for reconstruction work considered installing steel towers to link the electrical cables or digging tunnels through which cable could connect all six reactors.
The former TEPCO executive said, "An estimate of the construction needed for the reconstruction work, including related civil engineering work, totaled several billions of yen and there was a plan to go ahead with the work."
However, according to an explanation by other TEPCO officials, there were many structures and buried objects that would have been a hindrance to laying cables in the plant and there were also concerns that if the electrical cables became too long a drop in voltage might have occurred. Those reasons led TEPCO officials to abandon any further consideration for more specific plans.
Katsuta, the Meiji University nuclear engineering professor, said the buried objects could have been moved and any voltage drop could have been overcome by using transformers.
Shiori Ishino, a professor emeritus of nuclear engineering at the University of Tokyo, added, "Since they hurriedly implemented measures after the accident, why could they not have done similar work beforehand? A serious analysis of what was involved in the decision should be made."
In response, a TEPCO spokesperson said while it is true that consideration was given for the reconstruction work at one time, there are no documents showing that a decision was ever made on it.
"Connecting cables between the six reactors after the accident was nothing more than an immediate measure taken during an emergency," the spokesperson said.
(This article was written by Hiroo Sunaoshi and Kentaro Uechi)
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