Four days before the Great East Japan Earthquake, nuclear regulators were stunned by an estimate that a massive tsunami 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 the industry ministry’s Nuclear and Industrial Safety Agency — the predecessor to the Nuclear Regulation Authority — that a tsunami as high as 15.7 meters could reach the nuclear plant, according to the worker’s testimony at the Tokyo District Court.
Surprised by the estimate, the regulators said that the watchdog could instruct Tepco to take countermeasures, said the Tepco official, who was involved in crafting safeguards against tsunami at the plant.
On March 11, the nuclear plant was hit by a massive tsunami following a 9.0-magnitude earthquake. The natural disaster triggered an unprecedented triple meltdown at the facility.
The power company had compiled the 15.7-meter tsunami estimate in 2008 based on a long-term assessment by a government organization.
The Tepco official appeared at the court on Wednesday as a witness in a criminal trial of three former Tepco executives over the nuclear accident.
After the 2011 meeting with the regulators, the company decided to hold in-house talks to be attended by Tepco leaders on measures against tsunami. But the quake and tsunami occurred before Tepco held any such meeting, according to the testimony.
The 2011 tsunami that hit the Fukushima plant was larger than had been estimated, the Tepco worker recalled.
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 should have been able to predict the risk that a tsunami could hit the power plant.
The defense maintain that the nuclear accident was impossible to have predicted because the tsunami estimate was just a trial calculation.