Questions remain over disaster at Fukushima

New evidence suggests the plant's reactors were always doomed to fail. David McNeill and Jake Adelstein report

International Atomic Energy Agency fact-finding team leader Mike Weightman inspects the damage to the Fukushima Daiichi nuclear power station in May, 11 weeks into the disaster (AP)

It is one of the mysteries of Japan's ongoing nuclear crisis: how much damage did the 11 March earthquake inflict on the Fukushima Daiichi reactors before the tsunami hit?

The stakes are high: if the earthquake compromised the plant and the safety of its nuclear fuel, every similar reactor in Japan may have to be shut down. With almost all of Japan's 54 reactors either offline (in the case of 35) or scheduled for shutdown by next April, the issue of structural safety looms over any discussion about restarting them.

Plant operator Tokyo Electric Power Co (Tepco) and Japan's government are hardly reliable adjudicators in this controversy. "There has been no meltdown," government spokesman Yukio Edano repeated in the days after 11 March. "It was an unforeseeable disaster," Tepco's then-president Masataka Shimizu famously and improbably said later. Five months since the disaster, we now know that meltdown was already occurring as Mr Edano spoke. And far from being unforeseeable, the disaster had been forewarned repeatedly by industry critics.

Throughout the months of lies and misinformation, one story has stuck: it was the earthquake that knocked out the plant's electric power, halting cooling to its six reactors. The tsunami then washed out the plant's back-up generators 40 minutes later, shutting down all cooling and starting the chain of events that would cause the world's first triple meltdown.

But what if recirculation pipes and cooling pipes burst after the earthquake – before the tidal wave reached the facilities? This would surprise few people familiar with the 40-year-old Reactor One, the grandfather of the nuclear reactors still operating in Japan.

Problems with the fractured, deteriorating, poorly repaired pipes and the cooling system had been pointed out for years. In September 2002, Tepco admitted covering up data about cracks in critical circulation pipes. On 2 March, nine days before the meltdown, the Nuclear Industrial Safety Agency (NISA) warned Tepco on its failure to inspect critical pieces of equipment at the plant, including recirculation pumps. Tepco was ordered to make the inspections, perform repairs if needed and report to NISA on 2 June. It does not appear, as of now, that the report has been filed.

Several workers at the plant recite the same story: serious damage, to piping and at least one of the reactors, occurred before the tsunami hit. All have requested anonymity because they are still working at or connected with the stricken plant. Worker A, a maintenance engineer who was at the Fukushima complex on the day of the disaster, recalls hissing, leaking pipes.

"There's no doubt that the earthquake did a lot of damage inside the plant... I also saw that part of the wall of the turbine building for reactor one had come away. That crack might have affected the reactor."

Worker B, a technician on site at the time of the earthquake, recalls: "It felt like the earthquake hit in two waves. The first impact was so intense you could see the building shaking, the pipes buckling, and within minutes I saw pipes bursting. Some fell off the wall...

"Someone yelled that we all needed to evacuate. But I was severely alarmed because as I was leaving I was told and I could see that several pipes had cracked open, including what I believe were cold water supply pipes. That would mean that coolant couldn't get to the reactor core. If you can't sufficiently get the coolant to the core, it melts down. You don't have to have to be a nuclear scientist to figure that out."

The suspicion that the earthquake caused severe damage to the reactors is strengthened by reports that radiation leaked from the plant minutes later. The Bloomberg news agency has reported that a radiation alarm went off about a mile from the plant at 3.29pm, before the tsunami hit. The reason for official reluctance to admit that the earthquake did direct damage to Reactor One is obvious. Katsunobu Onda, author of Tepco: The Dark Empire, explains it this way: A government or industry admission "raises suspicions about the safety of every reactor they run. They are using a number of antiquated reactors that have the same systematic problems, the same wear and tear on the piping". Earthquakes, of course, are commonplace in Japan.

Mitsuhiko Tanaka, a former nuclear plant designer, describes what occurred on 11 March as a loss-of-coolant accident. "The data that Tepco has made public shows a huge loss of coolant within the first few hours of the earthquake. It can't be accounted for by the loss of electrical power. There was already so much damage to the cooling system that a meltdown was inevitable long before the tsunami came," he said.

He says the released data shows that at 2.52pm, just after the quake, the emergency circulation equipment of both the A and B systems automatically started up. Between 3.04 and 3.11pm, the water sprayer inside the containment vessel was turned on. Mr Tanaka says that it is an emergency measure only done when other cooling systems have failed. By the time the tsunami arrived and knocked out all the electrical systems, at about 3.37pm, the plant was already on its way to melting down. Kei Sugaoka, who conducted on-site inspections at the plant and was the first to blow the whistle on Tepco's data tampering, says he was not surprised by what happened. In a letter to the Japanese government in 2000, he warned that Tepco continued to operate a severely damaged steam dryer in the plant 10 years after he pointed out the problem. The government sat on the warning for two years.

"I always thought it was just a matter of time," he says of the disaster. "This is one of those times in my life when I'm not happy I was right."

During his research, Mr Onda spoke with several engineers who worked at the Tepco plants. One told him that often piping would not match up to the blueprints. In that case, the only solution was to use heavy machinery to pull the pipes close enough together to weld them shut. Inspection of piping was often cursory and the backs of the pipes, which were hard to reach, were often ignored. Repair jobs were rushed; no one wanted to be exposed to nuclear radiation longer than necessary.

Before dawn on 12 March, the water levels at the reactor began to plummet and the radiation began rising. The Tepco press release published just past 4am that day states: "The pressure within the containment vessel is high but stable." There was one note buried in the release that many people missed: "The emergency water circulation system was cooling the steam within the core; it has ceased to function."

At 9.51pm, under the chief executive's orders, the inside of the reactor building was declared a no-entry zone. At around 11pm, radiation levels for the inside of the turbine building, which was next door to the reactor, reached levels of 0.5 to 1.2 mSv per hour. In other words, the meltdown was under way.

Sometime between 4 and 6am, on 12 March, Masao Yoshida, the plant manager decided it was time to pump seawater into the reactor core and notified Tepco. Seawater was not pumped in until hours after a hydrogen explosion occurred, at roughly 8pm. By then, it was probably already too late.

Later that month, Tepco went some way toward admitting at least some of these claims in a report called "Reactor Core Status of Fukushima Daiichi Nuclear Power Station Unit One". The report said there was pre-tsunami damage to key facilities, including pipes.

"This means that assurances from the industry in Japan and overseas that the reactors were robust is now blown apart," said Shaun Burnie, an independent nuclear waste consultant who works with Greenpeace. "It raises fundamental questions on all reactors in high seismic risk areas."