Читать книгу Meltdown - Yoichi Funabashi - Страница 11

4:46 P.M. Yoshida reported to the Nuclear and Industrial Safety Agency (NISA) and others that a specific event (inoperable emergency reactor core cooling equipment), as stipulated in Section 1, article 15 of the Act on Special Measures Concerning Nuclear Emergency Preparedness (NEPA), had taken place. At the time, he wrote: “We don’t know what is happening with the cooling operations due to an inability to monitor the water levels in Units 1 and 2.”

NINE MINUTES LATER, AT 4:55 P.M. This time, Yoshida contacted NISA to cancel his emergency report, because they had “recovered water level observation” in Unit 1. However, just before five p.m., the water level indicator once again could no longer be seen.

The Central Control Room was unable to confirm water levels in either Unit 1 or Unit 2. Nor could they confirm whether the isolation condenser (IC) in Unit 1 or the reactor core isolation cooling system (RCIC) in Unit 2 were working.

It was reported, “If the water level keeps dropping at this pace, the fuel rods in Unit 1 will start to be exposed by 6:15 p.m.” Yoshida merely answered, “Roger that.”

5:12 P.M. With just the aid of emergency lighting, the shift supervisor recorded the water level shown on the reactor water gauge (broadband = 1500 mm to –4000 mm). The water level was falling steadily. The time and measurement on the power panel next to the water indicator were recorded by hand, then reported to the station ERC. They were no longer able to use the Personal Handy-Phone System they had been using, so the power plant office at the Anti-Seismic Building and the shift supervisor at the control room were using a hotline. Yoshida once again filed a “state of emergency” to NISA.

Just when the Station Emergency Response Center received a report from onsite that “We are able to see the water level,” they received another call, saying, “Once again we have lost the ability to assess the water level.” Every time Yoshida received a figure, he checked with the reporting official, “Are those numbers really correct?” The answer he got was, “Umm, we aren’t sure.”²⁸

At the mercy of the figures on the water level gauge, the site was in a state of utter disarray. Maintenance Manager Takeyuki Inagaki recalls that “we were quite doubtful about the IC status, but we hoped that the isolation condenser was still partially working on Unit 1. Because it was the only information we got after getting SBO, we wanted to believe the signal, though we knew the water level must be going down.”²⁹ Ultimately, they were flying blind and wanted to believe any signal of hope.

QUITE SOME TIME AFTER SEVEN P.M. Staff from the control room reported that they could see, with a flashlight, billows of white steam on the far side of the glass of the double doors of the reactor building. It was also reported that radioactive material had been detected as far as outside of the control room and non-controlled areas.³⁰

“It looks like there’s a raw steam leak.”

On hearing people whispering these words, one of the subcontracted workers in the Anti-Seismic Building thought to himself, That’s the end of nuclear power. TEPCO is finished.³¹

In order to get the water indicator and other instruments back online, they needed to restore power via batteries or small generators, but Fukushima Daiichi NPS had nothing like this prepared at all.³²

The restoration team at Response Headquarters stripped batteries from several buses onsite, delivering a total of five to the control room. Lining them up two abreast, they hooked them up to the water gauge on the power panel.³³

9:19 P.M. The restoration team managed to reconnect the water gauge for Unit 1 after four hours without it. They reported to the Tokyo Head Office, “We have confirmation of the reactor water level. TAF +200 via battery hookup.”³⁴

This meant the water was twenty centimeters above the top of active fuel. The report of TAF +200 shocked everyone in the ERC.

“It’s awash.”

“This isn’t normal.”

Takeyuki Inagaki, the recovery team leader, felt his body tremble.³⁵

9:47 P.M. A report reconfirming the reactor water level was sent to the Tokyo Head Office. Around the same time, it was reported that the radiation dose in the Unit 1 Reactor Building had started to climb. The dosimeter of the TEPCO workers, who were entering the reactor building to check the water level, rose to 0.8 millisieverts in a short time.

9:51 P.M. The Unit 1 Reactor Building was put on “restricted access.”³⁶

It looked like the fuel had started to melt. Commensurately, a large volume of hydrogen was being generated and the pressure was mounting in the containment vessel. Radioactive material may have started to leak out of the containment vessel …

9:52 P.M. The power plant ERC reported to the authorities, concerned that the “water level is 450 mm from top of fuel,” that the reactor water level was above top of active fuel (TAF).³⁷

The water gauge continued to show the reactor water level was above TAF.

10:00 P.M. “TAF +550 mm.”

10:35 P.M. “TAF +590 mm.”³⁸

The operators had started to realize, however, that “something’s not right.” They recorded the rising water level figures on a whiteboard in the control room, then scrawled next to them, “the water gauge is unreliable.”³⁹

Izawa sent two operators to the scene to check whether the IC was working. Yoshida was also thinking, Something’s up. The first time he shook his head was when he received a report saying that the dose of Unit 1 reactor building had increased, before ten p.m.

The IC is moving, the water level is at a plus, why is the dosage going up? Something is wrong.

Is the water level wrong or is it a problem with something else?

At 11:50 p.m., the pressure of the dry well of Unit 1 was recorded to be at the high figure of 600 kPa. This exceeded the maximum working pressure of 427 kPa.

The cooling water must be missing.

Hasn’t the IC stopped yet? ⁴⁰

With the reactor pressure now high, depressurizing the reactors was no longer an option. Their only strategy left was to cool the reactors through restoring high-pressure water systems.⁴¹