28 Mai 2014
May 27, 2014
Fukushima puzzle: Who ordered halt to pumping of seawater at stricken plant?
By HIDEAKI KIMURA/ Staff Writer
The identity of the individual in the prime minister's office who exacerbated the nuclear disaster seems destined to forever remain a mystery.
All that is known is that a call was made from the office in Tokyo to Masao Yoshida, the late manager of the crippled Fukushima No. 1 nuclear power plant, calling for reconsideration of his plan to pump seawater into the No. 3 reactor.
Giving up the plan to switch to seawater early on the morning of March 13, 2011, later led to a brief period when water was not being pumped into the No. 3 reactor. That led to overheating of the reactor, which dangerously added to the unfolding crisis triggered by the Great East Japan Earthquake and tsunami two days previously.
Plant operator Tokyo Electric Power Co. released video of teleconferences related to the Fukushima nuclear accident in 2012, but the footage left it unclear who had made the phone call to Yoshida asking that fresh water be used instead of seawater.
TEPCO officials cited concern that pumping in seawater would lead to irreparable damage.
Yoshida gave hours of testimony to the government's Investigation Committee on the Accident at the Fukushima Nuclear Power Stations between July and November 2011. The Asahi Shimbun recently obtained a copy. Yoshida died last July of esophageal cancer.
He was asked about the pumping in of water to the No. 3 reactor. Seawater had been pumped into the reactors of the Fukushima No. 1 plant in an attempt to cool the nuclear fuel.
Yoshida instructed his subordinates to continue pumping in seawater to the No. 1 reactor even after he received a phone call on the evening of March 12, 2011, from Ichiro Takekuro, the senior TEPCO expert who was based at the prime minister's office at the time of the accident. Takekuro gave the instruction to stop pumping seawater.
A similar debate about whether seawater or fresh water should be pumped in also took place for the No. 3 reactor early on March 13, 2011.
According to Yoshida's testimony to the government panel, nuclear fuel in the No. 3 reactor had become exposed because of a lack of water. At 5:42 a.m., Yoshida received a report that tanks holding fresh water were all empty. He decided to switch to seawater.
However, at 6:43 a.m. Yoshida received a phone call from a TEPCO employee based at the prime minister's office, saying there was an emergency.
Video of teleconferences have shown that at that time Yoshida was being asked to avoid using seawater as much as possible because of the damage it could do to the reactors.
When Yoshida received the 6:43 a.m. call, he immediately complied with the request to switch to fresh water.
In his testimony, Yoshida said that someone in the prime minister's office had picked up the phone used by the TEPCO employee.
Yoshida said, "I always felt that we would have to use seawater so I believe that I said from the very beginning that we had to go with seawater. However, I later received a phone call from the prime minister's office and told to do something, so I responded that we would try our best to find other sources (of fresh water)."
However, Yoshida became more fuzzy when the question turned to who made the call from the prime minister's office.
"I am sorry, but my memory of that moment is missing so I have no recollection of who it was that I spoke to," Yoshida told investigators. "I can only talk in terms of what may have been possible."
Yoshida gave as possibilities high-ranking TEPCO officials who were at the prime minister's office at the time as well as officials of the Nuclear and Industrial Safety Agency, the now-defunct body then responsible for regulating and supervising the nuclear power industry. However, he gave no definitive answer.
According to video of the teleconferences, at 9:13 a.m., Sakae Muto, the TEPCO executive vice president in charge of nuclear energy who was at the off-site center in Fukushima Prefecture, raised doubts about pumping in fresh water. He is heard saying, "We have to begin thinking about using seawater. Have you discussed this with the prime minister's office?"
Yoshida continued to scramble to find fresh water, but at 12:18 p.m. he gave the instructions to switch to seawater because all the fresh water had been used.
Yoshida felt it would take about 10 minutes to make the switch. However, it was not until 1:11 p.m. that the pumping of seawater began. That meant about a hour had passed with no water entering the No. 3 reactor.