25 Février 2016
February 25, 2016
By JIN NISHIKAWA/ Staff Writer
Nearly five years later, Tokyo Electric Power Co. said Feb. 24 that it has discovered a guideline in its operational manual that would have allowed it to announce meltdowns in the nuclear disaster in only days instead of the two months it actually took.
TEPCO apologized for failing to be aware for such a long time of the guideline on how to declare meltdowns at its Fukushima No. 1 nuclear power plant, triggered by the Great East Japan Earthquake and tsunami on March 11, 2011.
While the utility announced that reactor cores had been damaged at the No. 1 and No. 3 reactors by March 14 and at the No. 2 reactor by March 15, it did not admit that meltdowns had occurred in the three reactors until May 2011.
Based on its “nuclear disaster countermeasures manual,” which was revised 11 months before the disaster, the utility could have instead declared meltdowns at the three reactors by those dates, it said.
“We sincerely apologize for failing to confirm the presence of the guideline in the manual for five years,” a TEPCO spokesperson said Feb. 24.
The company will conduct an internal investigation to determine why it failed to promptly determine and announce meltdowns based on the manual.
In the few days after the Fukushima crisis unfurled, core meltdowns at the No. 1 to No. 3 reactors dispersed a large amount of radioactive materials into the environment.
Video footage of TEPCO’s in-house teleconferences around the time show that company executives recognized the possibility of meltdowns at the reactors from the early stages of the crisis.
But the company maintained that the reactors suffered "core damage," a condition in which nuclear fuel inside a reactor core is damaged, rather than a "meltdown" at news conferences and in its announcements. In May it officially acknowledged that meltdowns had occurred.
The utility has explained that the delay was caused by the lack of a basis to assess meltdowns in the wake of an accident.
Early on May 14, 2011, TEPCO confirmed that the No. 3 unit had suffered damage to 30 percent of its reactor core and 55 percent of the No. 1 reactor's core was damaged, based on rising radiation levels inside reactor containment vessels. It also determined that 35 percent of the No. 2 reactor’s core was damaged on the evening of May 15.
The newly discovered guideline in the disaster countermeasures manual, which was revised in April 2010, stipulates that the company should declare a meltdown when damage to a reactor core exceeds 5 percent, TEPCO officials said.
Company officials failed to announce the meltdowns because they were unaware of the guideline in the manual, according to TEPCO.
The existence of such a standard was confirmed earlier this month during an in-house investigation into how the utility responded to the Fukushima nuclear crisis.
The investigation is being conducted at the request of Niigata Prefecture where TEPCO's Kashiwazaki-Kariwa nuclear power plant, which the company aims to restart, is located.
In a statement on Feb. 24, Niigata Governor Hirohiko Izumida called on TEPCO to conduct a thorough internal investigation to uncover the “truth behind its concealment of meltdowns,” including determining who gave instructions.