The Yomiuri Shimbun
Prime Minister Naoto Kan's blood must have run cold around 10 p.m. on March 11, the day of the Great East Japan Earthquake, when he received the first report on the terrible situation at the Fukushima No. 1 nuclear power plant.
The report from the Nuclear and Industry Safety Agency of the Economy, Trade and Industry Ministry predicted reactor cores at the nuclear power plant--where power and all functions to cool the reactors were lost in the quake and tsunami--would be exposed to air, and that extreme heat generated by fuel rods would damage their encasing tubes later that night.
Fuel rods would melt down, and the following morning the pressure inside the reactors' containment vessels would reach the maximum allowed for by the facilities' designers, the report predicted.
Kan and everyone at the Prime Minister's Office understood the seriousness of the situation described by the report.
There were only two options that might prevent a meltdown of the reactors--either restore the plant's power supply and cooling functions immediately, or pour water directly into the reactors. If neither course of action could be taken, the pressure inside the reactors would become so great that they would be destroyed.
The report concluded that valves in the containment vessels would have to be opened, to release radioactive steam and reduce the pressure inside.
However, opening the valves was considered a last resort. Although it could prevent the reactors from breaking apart, it would release steam with high levels of radioactive materials into the atmosphere.
Such a step had never been taken at a nuclear power plant in Japan.
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Countdown to power loss
The Prime Minister's Office, the nuclear safety agency and even Tokyo Electric Power Co., the operator of the Fukushima plant, were filled with relief immediately after the earthquake. They had been told backup diesel generators would provide sufficient support to stabilize the Nos. 1 to 3 reactors, which were in operation when the quake hit.
However, subsequent tsunami destroyed 12 of the 13 emergency generators.
"Round up all the power-supply cars and send them to the plant right now!" shouted a TEPCO supervisor at the utility's head office in Tokyo.
Nuclear reactors have emergency cooling systems that channel water into the reactor, using a turbine that can be powered by residual heat. However, the systems rely on emergency batteries to power the water intake valves.
The emergency batteries at the Fukushima plant were expected to run out of power around midnight.
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Options exhausted
TEPCO dispatched power-supply vehicles from various power stations around the country to the crippled nuclear plant. However, the vehicles had to travel very slowly because of damage to roads in northeastern Japan. The first power-supply car did not reach the plant until 9 p.m. on March 11.
Once at the site, the lack of preparation became apparent. Cables needed to connect the vehicles' high-voltage electricity to plant facilities were not long enough. TEPCO immediately ordered additional cables, but precious time had been wasted. Power would not be restored at the plant by midnight.
The pressure inside the containment vessels rose above the maximum allowed for by the facilities' design, and radiation levels at the plant increased sharply. No option was left but to open the valves.
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Anger rose as TEPCO dithered
TEPCO began preparations for opening the valves around 7 p.m. on March 11. Pressure inside the No. 1 reactor was particularly high.
"Soon, the reactor won't be able to withstand the pressure," said an official of the accident headquarters at the plant, which was keeping in touch with TEPCO's head office via video phone. "We have to vent the pressure immediately."
"Pressure inside the containment vessel of the No. 1 reactor has gone up dramatically," the agency told Banri Kaieda, economy, trade and industry minister, at 12:45 a.m. on March 12. In fact, it had reached 1.5 times the designed maximum, meaning the condition of the reactor was critical.
"To get things under control, we have to pour water into the reactors and then vent the steam that is generated," Haruki Madarame, chairman of the Cabinet Office's Nuclear Safety Commission, told Kaieda.
At 1:30 a.m. on March 12, Kan, Kaieda and Madarame gathered at the crisis management center in the basement of the Prime Minister's Office.
The three urged TEPCO officials to vent the steam as soon as possible. But TEPCO officials said there was no way of opening the valves because there was no power supply.
Exasperated, Kaieda called the utility's head office in Tokyo and the accident headquarters at the plant every hour, pressuring them to open the valves immediately.
TEPCO workers tried to open the valves by manually overriding the automatic system, but struggled to make progress because they had to work in darkness.
At dawn, pressure inside the No. 1 reactor was more than twice the designed maximum.
Eventually, at 6:50 a.m., the government ordered the utility to open the valves under the Nuclear Reactor Regulation Law.
When Kan visited the accident site shortly after 7 a.m. and found TEPCO had not opened the valves yet, he reprimanded company officials. The officials replied they would like to have another hour to make a decision on what to do.
Kan blew his stack.
"Now's not the time to make such lackadaisical comments!" the prime minister told the TEPCO officials.
Yet even still, the utility spent three more hours discussing the matter before finally opening the valves at 10:17 a.m.
Five hours after that, a hydrogen explosion occurred at the No. 1 reactor, blowing apart its outer building.
(Apr. 12, 2011)
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