Читать книгу Meltdown - Yoichi Funabashi - Страница 38

The explosion at Unit 3 dislodged and closed the circuit to the vent valve that had been opened in Unit 2. Water couldn’t be injected into the reactor, because the reactor pressure was higher than the discharge pressure of the firefighting pumps.⁴³

Yoshida felt that some change was underway in Unit 2.

2:54 A.M., MARCH 14. Videoconference.

Yoshida: “Muto-san, what has us worried is why the RCIC is holding out so long.”

Muto: “Yes, that’s worrying.”

Komori: “I think it’s more than the normal run of things.”

Yoshida: “So, it wouldn’t be strange for it to give up the ghost at any moment. It seems to be hanging in there.”

Muto: “You’re quite right, which means, which means, which means …”

Yoshida questioned the fact that the reactor core isolation cooling system (RCIC) in Unit 2 was continuing to cool. Komori was also puzzled. The usual lifespan of a RCIC was eight to ten hours. For some reason or another, it was still working after nearly sixty hours.⁴⁴

2:58 A.M., MARCH 14. Videoconference.

A report that preparations for venting Unit 2 were complete came in from the field at Fukushima Daiichi to the Head Office.

Vice President Sakae Muto at the offsite center asked, “Am I right in understanding that you’re ready to vent if the pressure in the containment vessel rises?”

The recovery team replied, “We can if the drywell pressure goes as high as the level of bursting the rupture.”

When the SR valve is open, steam is blown into the suppression chamber. This acts to raise both the temperature and the pressure in the suppression chamber, necessitating venting. Muto was trying to confirm that.

This was followed by a conversation between Yoshida and Muto.

“Then there’ll only be water.”

“Just water. It’s a feat of strength.”

“Everyone seems a little relieved thinking the supply of seawater is endless, but isn’t there some way now of pumping directly from the sea without having to do the extra job of transferring it to the pit?”

“No, no. Of course, that’s the natural course of actions to take and we’re trying it. We’ve been trying since last night, but it’s not working out as planned.”

The stumbling block was the ten-meter difference in height between sea level and the plant. Since they couldn’t get hold of a pump that was capable of sucking up water despite the height difference, they couldn’t use the inexhaustible expanse of sea before their eyes.⁴⁵

Before one p.m. on March 14, Yoshida took a call from TEPCO Head Office.

“We’re thinking of opening a hole in the blowout panels using a water jet as a way to prevent a hydrogen explosion at Unit 2.”

Yoshida listened.

“Urgently consider ways to make holes from the outside, including the use of a helicopter, since operations from the inside of the building would be difficult, due to the scaffold problem, and so on.”

Yoshida was trying to make the point that it was already impossible at the site to put up scaffolding either inside or outside with the rising exposure dosage.

Head Office’s response: “We’re in the midst of planning a method of making holes by attaching a water-jet to a ladder truck, but transportation of the necessary heavy equipment is being held up because of tsunami warnings.”⁴⁶

A little later, Takahashi at the Head Office contacted Yoshida.

“We’ve had a call from the Kantei urging us to move quickly, not to worry about exposure, to keep working even up to 500 millisieverts.”⁴⁷

It sounded like “encouragement” to the effect that Head Office was doing its best to deal with the government by working with the Kantei—in truth, with Takekuro, TEPCO’s liaison—so they wanted the onsite team to do its best despite the high radiation levels, and could they not “get a hole open” if at all possible?

In relation to this, an hour or so later, it was conveyed from Head Office: “It’s been decided to raise the exposure limit for workers involved in emergency restoration from 100 millisieverts to 250 millisieverts.”

It is true that it had been discussed at 1:20 p.m. on March 14 in a meeting at the Kantei whether the exposure level for TEPCO workers could be raised from 50 to 250 millisieverts. This was the result of Takekuro lobbying NISA and the NSC, but it was Madarame who stated “It’s possible” during the meeting, and that was how the decision to raise the permissible level to 250 millisieverts came to be made.⁴⁸

If they could get water in by 3:30 p.m., the water level wouldn’t drop below the top of active fuel (TAF). But it didn’t look like that was going to be possible.

At 3:57 p.m., the technical team at Fukushima Daiichi reported to Yoshida.

“It’s about the time TAF will be reached, we said 4:30 p.m., but if we can correct the pressure, we reckon 5:30 p.m.”

4:00 P.M. Yoshida heard the latest simulation results for Unit 2. They projected that the water level would reach TAF around 5:30 p.m.⁴⁹

4:13 P.M. Yoshida spoke at the videoconference.

“Everyone, listen up! Everyone at Head Office, please listen, too. I’ve just had a call from Chairman Madarame at the NSC, and he says shouldn’t we be giving priority to pumping in water [to lower reactor pressure] over venting the containment vessel.”

On the ground, they were proceeding with preparations for the vent. Conveying this, with Madarame still on the line, Yoshida also asked one of the technical staff, “What does Safety reckon? About this assessment?”

Madarame advised from the phone, “Don’t you think it’s better to open the SR valve and pump in water to lower the pressure rather than trying to keep the PVC [primary containment vessel] alive? If you drop the pressure, the water will flow in. I think you should be pumping water in quickly.”

The analysis official from the technical team that was called “Safety” answered.

“Water temperature in the suppression chamber has exceeded 130 degrees Celsius.”

Yoshida spoke again with Madarame.

“Mr. Chairman, when I asked Safety, they said the water temperature in the suppression chamber is over 100 degrees Celsius. They’re saying there’s a high chance that it won’t go in. I’ll get Safety to speak.”

The present status was that because of the high temperature in the pressure control room (S/C), there was a possibility that the steam would not condense enough to lower the pressure even if they opened the SR valve. If that happened, the pressure in the reactor wouldn’t drop, and they’d be unable to inject water. That was the assessment of those in the field, and the technical officials supported it.

A technical official explained to Madarame, “We’d like to go ahead with venting as per provision policy.”

The technical official explained to Madarame what that was. After hanging up, he reported, “He’s satisfied.”

A few minutes later, however, they received a call from the field.

“We’ve turned on the power, but the necessary valves for venting aren’t moving. We need to check it out.”

The report came back that “it’s no good, even though the compressors are working.”

They tried to open the vent valve with air pressure from a portable compressor in the same way as for Unit 1, but although the compressor was working, the vent valve wouldn’t open.

4:21 P.M. Yoshida received a report from the restoration team working on the venting that they could not vent. Shimizu, who had been following this exchange on videoconference, suddenly butted in.

“Yoshida-san, Yoshida-san … Shimizu here. Please use Chairman Madarame’s method.”

Yoshida: “Yes, I understand.”

Shimizu: “Please do so.”

Shimizu spoke as if to warn Yoshida. Yoshida still wanted to get Muto’s opinion and looked for him, but could not get hold of him, because Muto was in mid-flight on a helicopter heading back to Head Office.

Shimizu pressed the point.

“You’re all right with that, yes?”

In the end, Yoshida decided to lower pressure by releasing the SR valve and at the same time preparing to vent.

4:34 P.M. The Central Control Room (Units 1 and 2) went to work on opening the SR valve in Unit 2. Ten 12v batteries had been brought in from cars onsite in the morning of the previous day, March 13. They tried the trick that had worked for opening the Unit 3 SR valve in Unit 2, but the SR valve refused to open. They could not vent. The SR valve would not open. There was nothing they could do.⁵⁰

4:51 P.M. Videoconference.

Shimizu: “Assuming that the SR valve doesn’t open and water can’t be injected, what will take place over how much time after that? But you’re trying to release the pressure in the pressure vessels, right?”

Head Office recovery team: “Yes, we’re trying to release the pressure.”

Shimizu: “Via the SR valve?”

Head Office recovery team: “That’s right.”

Shimizu: “Up until now, it hasn’t been done?”

Head Office recovery team: “No, it hasn’t been done yet.”

5:08 P.M.

Fukushima Daiichi power generation team: “We thought we would first open the SR valve A at, ah, 16:43, but it didn’t work. At that point, the water level in the reactor was –300 mm … We tried opening a different SR valve at 16:57. However, the water level in the reactor at that point was –500 mm …”

TEPCO Fellow Akio Takahashi: “That’s not good at all, eh?”⁵¹

When it was reported via videoconference that opening the SR valve “hasn’t been done yet,” the more than two hundred people packed into the ERC fell quiet. Takeyuki Inagaki, head of the recovery team, was also there. Inagaki felt at that time “like lead had been poured into my stomach.” And it was not just Inagaki. He recalls, “Everyone felt that it was all over if it didn’t open.”⁵²

Yoshida went down to the corridor on the first floor of the Anti-Seismic Building from the second floor ERC. It was necessary to tell associate company workers about this state of affairs. Everybody looked exhausted.

These people shouldn’t be caught up in this.

Yoshida turned to them and said, “We have tried our all, yet things are in a truly terrible state. Everyone, please go home. I would like you to go home.”

Yoshida did not use the word “evacuate.” The words “please go home” came out of his mouth instead. Izawa recalled that it was difficult to discern exactly what Yoshida meant by this, but either way, panicked staff began to leave as quickly as possible.⁵³ After that, Yoshida went to the first-floor smoking room without returning to the ERC and took out a cigarette. He was struck by a feeling of futility to the point of being unable to speak. He was in a daze.

Whether water will go in or not, it’s just waiting from now. It’s exactly like gambling. ⁵⁴

After a smoke, he did not return to the ERC but went into the site superintendent’s office on the second floor. There, he curled up his tall frame and closed his eyes. His face was pallid with fatigue.

Perhaps it was for about ten minutes. Opening his eyes, Yoshida unfurled his heavy, tired body.⁵⁵

5:56 P.M. Videoconference. There was a report at TEPCO Head Office.

“We’re repeatedly trying to open the main steam escape valve. We’ve failed three times because there isn’t enough power due to the low voltage.”⁵⁶