This qualifies as real bad news from Japan, where the severity rating of the crisis at the Fukushima nuclear plant has been raised to the highest level: Japan nuclear crisis on same level as Chernobyl.

There’s no good news from Japan tonight: Japan Faces Potential Nuclear Disaster as Radiation Levels Rise.

TOKYO — Japan faced the likelihood of a catastrophic nuclear accident Tuesday morning, as an explosion at the most crippled of three reactors at the Fukushima Daiichi Nuclear Power Station damaged its crucial steel containment structure, emergency workers were withdrawn from the plant, and a fire at a fourth reactor spewed large amounts of radioactive material into the air, according to official statements and industry executives informed about the developments.

“No. 4 is currently burning and we assume radiation is being released. We are trying to put out the fire and cool down the reactor,” the chief government spokesman, Yukio Edano, told a televised press conference. “There were no fuel rods in the reactor, but spent fuel rods are inside.”

Government officials also said the containment structure of the No. 2 reactor had suffered damage during an explosion shortly after 6 a.m. on Tuesday.

They initially suggested that the damage was limited and that emergency operations aimed at cooling the nuclear fuel at three stricken reactors with seawater would continue. But industry executives said that in fact the situation had spiraled out of control and that all plant workers needed to leave the plant to avoid excessive exposure to radioactive leaks.

If all workers do in fact leave the plant, the nuclear fuel in all three reactors is likely to melt down, which would lead to wholesale releases of radioactive material — by far the largest accident of its kind since the Chernobyl disaster 25 years ago.

Another horrifying amateur video from Japan shows the giant waves striking the Japanese coastal town of Noda. At least 500 people died here.

Boing Boing has a great informative post if you need a refresher course in how nuclear power plants work: Nuclear energy 101: Inside the ‘black box’ of power plants.

According to experts, Japan’s nuclear nightmare may just be beginning.

WASHINGTON — As the scale of Japan’s nuclear crisis begins to come to light, experts in Japan and the United States say the country is now facing a cascade of accumulating problems that suggest that radioactive releases of steam from the crippled plants could go on for weeks or even months.

Here’s some new footage from BBC News, showing the first moments of the massive tsunami disaster.

The New York Times reports on the spreading nuclear crisis in Japan, where a state of emergency has now been declared at a fourth reactor.

The government confirmed that radiation had escaped from the worst-hit plant, and local officials said that 22 people outside the plant showed signs of radiation exposure and about 170 other people near the plant had likely been exposed, but it was unclear if they had received dangerous doses. Early Sunday, the government said three workers were suffering full-out radiation illness.

The developments prompted the evacuation of more than 200,000 people.

Uh oh.

[5:48 p.m. ET, 7:48 a.m. Tokyo] A meltdown may be under way at one of Fukushima Daiichi’s nuclear power reactors, an official with Japan’s nuclear and industrial safety agency told CNN Sunday.

A meltdown is a catastrophic failure of the reactor core, with a potential for widespread radiation release. However, Toshiro Bannai, director of the agency’s international affairs office, expressed confidence that efforts to control the crisis would prove successful.

The good news is that a major meltdown has apparently been averted at the Fukushima power plant in northern Japan, after the reactor was flooded with seawater. Also good news: the explosion that was seen yesterday was not inside the reactor itself.

TOKYO — Japanese officials took the extraordinary step on Saturday of flooding a nuclear reactor with seawater in a last-ditch effort to avoid a nuclear meltdown, after an explosion there escalated the emergency caused by the huge earthquake and tsunami that destroyed parts of the country’s northeastern coast on Friday.

Officials said late Saturday that leaks of radioactive material from the plant, in northern Japan, were receding and that a major meltdown was no longer imminent. But the government doubled its evacuation radius around the plant to 12 miles, and the worries about radiation and chaos from tens of thousands of people fleeing the area hampered efforts to search for survivors and forced Japan’s leadership to grapple with two major crises at once.

The NOAA Center for Tsunami Research in Seattle posted this computer model of the 2011 Honshu tsunami, as it propagated across the Pacific Ocean.