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It's still hard to tell what the exact situation is at Japan's Fukushima Daiichi nuclear power plant, 170 miles north of Tokyo. Concerns were first raised about damage Friday, after the earthquake and its aftershocks. Saturday, despite officials' decision to flood the first reactor at the plant, there was an explosion in the building housing it, though, The New York Times reports, "the steel containment of the reactor remained in place." That's the official line, at least. Now, Sunday, the battle is on to keep the same thing from happening in the third reactor. 

The Japanese government, while evacuating the area and declaring a state of emergency, has been maintaining that the public's health has not been jeopardized by the reported rise in radiation levels around the plant. But, as the BBC's Richard Black points out, "as with its counterparts in many other countries, Japan's nuclear industry has not exactly been renowned for openness and transparency." Tokyo Electric Power Company, or Tepco, which operates the plant, has some suspected coverups in its history, and might not be being entirely candid in its reports to the public and the government.

So: how to sort this out? Laying the more comprehensive reports side-by-side with some science analysis from the BBC, here's what we know--and what we know we don't know.

The Issue: Cooling  Water surrounds the nuclear reactors, cooling them, explains the BBC's Richard Black. "If the water stops flowing, there is a problem. The core overheats and more of the water turns to steam. The steam generates huge pressures ... and if the largely metal core gets too hot, it will just melt." Reactors like these are built with multiple measures to contain even a molten core, but the "big fear" among those skeptical of nuclear power has always been that these won't work.

Reactors 1 and 3 Are the Problem. Reactor 2 Is (Maybe) Stable  With an update, Black notes that Tepco first reported that water levels were "'lower than normal,' but stable" at Reactor 2. Then it emerged, however, that Tepco has been pumping "seawater and boric acid" to aid cooling not just into Reactor 3, as thought, but into Reactor 2 as well, so it's not entirely clear how "stable" Reactor 2's stability actually is. Reactor 1 was shut down after Saturday's explosion.

The Official Line About Saturday's Explosion Is Probably Right  Tepco and Japanese officials have maintained that the explosion near Reactor 1 didn't damage the actual reactor--just the building it was in. The New York Times gets a second opinion from David Lochbaum, "who worked at three reactors in the United States with designs similar to Daiichi." He seems to agree, saying "that judging by photographs of the stricken plant, the explosion appeared to have occurred in the turbine hall, not the reactor vessel or the containment that surrounds the vessel."

Radiation Levels Outside the Plant: Twice the Legal Limit  As part of the cooling efforts, "plant operators had to release radioactive vapor into the atmosphere," The New York Times reports.

That Said, This Is Nothing Like Chernobyl, Yet  "Russian authorities, with territory to the north and west within 1,000km of the plant, say they have detected nothing abnormal," reports Black at the BBC, and " levels of radioactivity - although above safe limits - are far lower than were detected during the Chernobyl accident in Ukraine, for example."

The Plant Is Probably Done-For  Experts reached by The New York Times say "the decision to flood the reactor core with corrosive seawater ... was an indication that Tokyo Electric Power and Japanese authorities had probably decided to scrap the plant." The BBC's Richard Black is more assertive: "the reactors will not operate again, even if there has not been a meltdown. Seawater is corrosive."

We Might Not Know Exactly What Happened for Months  On this much, everyone agrees, pointing to similar situations in the past.


Update: The New York Times reports Sunday night that "Pentagon officials" are saying "helicopters flying 60 miles from the plant picked up small amounts of radioactive particulates--still being analyzed, but presumed to include Cesium-137 and Iodine-121--suggesting widening environmental contamination." It is apparently looking like more cooling through seawater will be needed, with more radioactive steam released as a result. Reverting to normal cooling procedures would require the restoration of electricity to the plant.

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