The operator of the crippled Fukushima No. 1 nuclear power plant sat on its hands for more than two years despite having pledged to seal a leaking hole in a turbine building, The Asahi Shimbun has learned.
Tokyo Electric Power Co. said in April 2011, just one month after the Great East Japan Earthquake and tsunami triggered the Fukushima nuclear disaster, that it would block the connection between a turbine building and an underground pit to prevent radioactive water from leaking into the sea. However, the utility only began preparing for shielding tests this summer, after contaminated water was found to be leaking into the sea.
TEPCO's inaction is likely responsible for the spread of radiation.
During the early phases of the nuclear meltdowns, water, used to cool the overheating reactors, filled the reactor and turbine buildings as well as adjacent underground pits.
On March 27, 2011, TEPCO workers found that radioactive water, measuring more than 1,000 millisieverts per hour, lay in an underground pit adjacent to the turbine building for No. 2 reactor. The following day, at a news conference to announce the findings, TEPCO officials explained that the tsunami had likely broken open a barrier between the underground pit and the basement level of the turbine building, thereby creating a water channel.
One TEPCO official, answering a question from an Asahi Shimbun reporter on that occasion, acknowledged the possibility that radioactive water could seep from pit joints out into the ground and eventually reach the sea.
Radioactive water was found leaking into the sea near a water intake for the No. 2 reactor on April 2, 2011. The leak was plugged four days later.
On April 17, 2011, TEPCO released a road map toward bringing the nuclear crisis under control. To illustrate the measures it had "considered" or "taken" to prevent a recurrence of the leak from the No. 2 reactor, the utility released a public announcement that explicitly mentioned "shielding the connection between the pit and the turbine building," alongside two other measures it had already taken.
TEPCO, in fact, had yet to seal that connection, and left it unattended afterward. Officials of the utility apparently believed that stopgap measures, which consisted of using concrete and crushed stone to seal the seaward end of the pit, were sufficient.
TEPCO said in June this year it had detected high levels of radioactive substances in groundwater sampled from a well on the ocean side of the turbine buildings. The utility, which acknowledged July 22 that radioactive water was leaking into the sea, came under fire when it was uncovered that its officials had reached that conclusion on July 19.
Experts believe some of the radioactive water lying in pits likely seeped out into the ground and eventually reached the ocean.
TEPCO officials have said the turbine building remains connected with the pit, which means highly radioactive water may still be leaking.
In response to questions from The Asahi Shimbun, TEPCO officials insisted that the act of sealing the seaward end of the pit constituted "shielding the connection between the pit and the turbine building" as stated in the announcement material.
The utility did consider plugging up the leak hole in the turbine building after it put together a set of "reliability enhancement measures" in May 2012 at the behest of the government, but the sealing work "has not been done to this day because of the (technical) difficulties involved," the officials added.
(This article was written by Senior Staff Writer Toshihiro Okuyama and Toshio Tada.)
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