TEPCO’s huge tsunami estimate stunned regulators just before 2011 disaster

April 12, 2018

Tokyo- Four days before the March 2011 disaster, nuclear regulators were stunned by an estimate of huge tsunami that could hit Tokyo Electric Power Company Holdings Inc.'s Fukushima No. 1 power plant, a TEPCO employee testified Wednesday.

At a meeting on March 7, 2011, the TEPCO worker told officials of the industry ministry's Nuclear and Industrial Safety Agency, a predecessor of the Nuclear Regulation Authority, that tsunami as high as 15.7 meters could reach the nuclear plant, according to the testimony before Tokyo District Court.

Surprised at the estimate, the regulators said in a stern tone that the watchdog could instruct TEPCO to take countermeasures, said the TEPCO official, who was involved in crafting measures against tsunami at the plant.

On March 11, 2011, the northeastern Japan plant was hit by massive tsunami following a 9.0-magnitude earthquake. The natural disaster triggered an unprecedented triple meltdown at the power plant.

The power company compiled the tsunami estimate in 2008 based on a long-term assessment by a government organization.

The TEPCO official appeared at the court as a witness in a criminal trial of three former TEPCO executives over the nuclear accident.

After the meeting with the regulators, the company decided to hold in-house talks on measures against tsunami that would be attended by TEPCO leaders. But the quake and tsunami occurred before TEPCO had any such meeting, according to the testimony.

The Fukushima plant was hit by tsunami that was larger than estimated, the TEPCO worker recalled.

The former executives, including former Chairman Tsunehisa Katsumata, 78, were indicted in February 2016 for allegedly neglecting to take measures against massive tsunami, in line with a decision by a prosecution inquest panel composed of ordinary citizens.

Lawyers appointed to act as prosecutors claim that the former executives were able to predict the arrival of huge tsunami at the power plant.

Meanwhile, the defense side said the nuclear accident was unpredictable because the tsunami estimate was a trial calculation. Jiji Press