This is the fourth in a series on the Fukushima nuclear catastrophe based on the accounts of people who struggled to contain the crisis in its early stages. Job titles and ages are as of March 2011.

Ground Self-Defense Force member Yuichi Sato was on a firetruck heading for the Fukushima No. 1 nuclear plant the day after it had been decimated by the March 11, 2011, tsunami — without being notified what his mission was.

That morning, the truck was in the town of Okuma, Fukushima Prefecture, where the 22-year-old was born.

He was several kilometers from his destination, but the familiar sights were gone — the walls of houses had collapsed, road surfaces were buckled and the town looked deserted.

“It was like a ghost town,” said Sato, who was part of the GSDF’s artillery regiment based in the prefecture. “I thought everyone must have rushed to escape.”

The regiment’s firefighting unit had received orders the night before to go to the nuclear plant. His squad members thought their task was to prepare for the possibility of a fire, but Sato, even though he had been told since childhood that nuclear power is safe, felt something out of the ordinary was happening.

When they arrived at the plant gates at around 7 a.m. on March 12, he was greeted by an acquaintance who works for Tokyo Electric Power Co.

Sato wondered why the Tepco employee was wearing a mask. He didn’t know at the time that the radiation level at the site was rising because a meltdown was occurring in the No. 1 reactor due to the loss of its key cooling functions.

After entering the emergency response office building, the firefighting squad was finally told what to do.

At the time, Tepco was using a single fire engine to inject water into reactor 1, but every time the truck had to return to a storage tank to be refilled, it meant halting the flow of water being sprayed into the unit.

The SDF’s firetrucks were supposed to assist in the operation.

Inside the main control room for reactors 1 and 2, workers were demoralized and exhausted after an attempt to open valves to reduce the pressure in reactor 1 ended in failure because of high radiation levels inside the reactor building.

It was imperative to open the valves to prevent a rupture of the containment vessel.

“If we can’t do anything, what is the point of dozens of us staying here?” one worker demanded.

Rising from his seat, Ikuo Izawa, the 52-year-old head of reactor operators, called everyone to gather around.

“If the operators abandon the control room, it means giving up trying to control the reactors,” he told them. “Local people who are evacuating are counting on us.

“You must have a family too. Deserting the room means abandoning them. . . . We can’t just leave. I beg you. Please stay here.”

He then bowed deeply.

Izawa had not given up on venting the reactor. He decided to give it another try, even though the radiation level inside the building could have risen again since the first attempt.

But several minutes after two workers had departed to try to reach one of the venting valves, the emergency response office alerted Izawa that white smoke was coming from a 120-meter-high stack connected to the reactor’s containment vessel.

“White smoke,” Izawa murmured. Then he screamed. “Stop them!”

Izawa was sure that something unusual was occurring in the container where the two workers were headed. Two operators dashed out of the room and brought them back.

In fact, a different team from the emergency response headquarters was trying to open a release valve in a completely different way, using an air compressor to send air through a pipe connected to the valve.

The emergency response headquarters confirmed that the pressure in the containment vessel had dropped, determining that venting had occurred at 2:30 p.m.

But the result they were hoping for never materialized. At 3:36 p.m., the main control room was shaken by a blast. A hydrogen explosion had blown away the roof and walls of the No. 1 reactor building.

Mitsuhiro Matsumoto, a 47-year-old Tepco employee who was working to restore electricity to the troubled reactors, was just about to get out of a car parked near the emergency response office building when he heard a noise like a gigantic pop.

Then the air turned brownish with dust. Bolts and what looked like pieces of iron sheets rained down, accompanied by cottonlike yellow clumps. The clumps were heat-insulating material used in the walls of the building.

“You can’t see the No. 1 reactor from the office building, so we didn’t know what had happened. But the scene in front of us was really spooky,” Matsumoto recalled.

Nearby, other workers wearing full-face masks panicked. They looked for unlocked cars and squeezed themselves into them. They spent more than 10 minutes in terror until the dust was blown away and the sky reappeared.

The emergency first-aid room on the first floor of the emergency response office building was soon packed with workers, making it look like a field hospital. Some complained that their ears were ringing and others shook with fear.

At the main control room for reactors 1 and 2, Izawa instructed others to wear full-face masks, though no one knew yet what had happened at this point.

“I later found it was a hydrogen explosion at the building, but at the time, I thought the reactor containment vessel itself had exploded,” said Mitsuyuki Ono, 51, who was also in the room. “I thought it was all over.”

There were some 40 reactor operators in the room, but everyone was exhausted after trying to do all they could to prevent the worst.

Izawa decided to stay along with the more experienced workers, and let the others evacuate.

The roughly 10 workers who remained included Izawa, Ono and 48-year-old Kazuhiro Yoshida, whom Ono had once worked with in operating the No. 1 reactor.

Ono was wondering how he could communicate to his family what he thought might be his final moments. If he wrote anything down on paper, it would probably be incinerated if there was an explosion.

“Why don’t we take a photo at the end,” Yoshida proposed cheerfully, as if he had read Ono’s mind. Everyone seemed to liven up.

The room, which was dark due to the loss of power, was lit up with flashing cameras.

Ono, having a picture taken with Yoshida by his side, a junior operator whom he trusted and liked the most, thought: “If the radiation level rises or hot steam comes into the control room, I will probably die. But someone will find the camera some day. Then this picture will be the witness to my life.”

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