The Fukushima reactor building that exploded March 12 is one of a series of identical General Electric reactors constructed in Japan and the US.  In this reactor design, the used nuclear fuel rods are stored in pools of water at the top of the reactor building.  These “spent” rods are still highly radioactive: the radioactivity is so great the rods must be stored in water so they do not combust.   The explosion at Fukushima Daiichi reactor unit 1 apparently destroyed at least one wall and the roof of the building: some reports stated the roof had collapsed into the building.

Two days later, the nearby building containing the plutonium-uranium (MOX) fueled Fuksuhima Daichii reactor unit 3 exploded.  So why bother about the rubble of reactor No 1?  The WaPo quotes a nuclear engineer who knows the answer:

Although Tokyo Electric said it also continued to deal with cooling system failures and high pressures at half a dozen of its 10 reactors in the two Fukushima complexes, fears mounted about the threat posed by the pools of water where years of spent fuel rods are stored.

At the 40-year-old Fukushima Daiichi unit 1, where an explosion Saturday destroyed a building housing the reactor, the spent fuel pool, in accordance with General Electric’s design, is placed above the reactor. Tokyo Electric said it was trying to figure out how to maintain water levels in the pools, indicating that the normal safety systems there had failed, too. Failure to keep adequate water levels in a pool would lead to a catastrophic fire, said nuclear experts, some of whom think that unit 1’s pool may now be outside.

“That would be like Chernobyl on steroids,” said Arnie Gundersen, a nuclear engineer at Fairewinds Associates and a member of the public oversight panel for the Vermont Yankee nuclear plant, which is identical to the Fukushima Daiichi unit 1.

People familiar with the plant said there are seven spent fuel pools at Fukushima Daiichi, many of them densely packed.

Gundersen said the unit 1 pool could have as much as 20 years of spent fuel rods, which are still radioactive.

We’d be lucky if we only had to worry about the spent fuel rods from a single holding pool.  We’re not that lucky.  The Fukushima Daiichi plant has seven pools for spent fuel rods.  Six of these are (or were) located at the top of six reactor buildings.  One “common pool” is at ground level in a separate building.  Each “reactor top” pool holds 3450 fuel rod assemblies.  The common pool holds 6291 fuel rod assemblies.  [The common pool has windows on one wall which were almost certainly destroyed by the tsunami.]  Each assembly holds sixty-three fuel rods.  This means the Fukushima Daiichi plant may contain over 600,000 spent fuel rods.

The fuel rods must be kept submerged in water.  Why?  Outside of the water bath, the radioactivity in the used rods can cause them to become so hot they begin to catch fire.  These fires can burn so hot the radioactive rod contents are carried into the atmosphere as vaporized material or as very small particles.  Reactor no 3 burns MOX fuel that contains a mix of plutonium and uranium.  Plutonium generates more heat than uranium, which means these rods have the greatest risk of burning.  That’s bad news, because plutonium scattered into the atmosphere is even more dangerous that the combustion products of rods without plutonium.

Chernobyl on steroids.  When the nuclear engineer from an identical plant states there’s any possibility of such a catastrophe, Washington, we have a problem.   Chernobyl’s contamination settled upon people and nations thousands of miles from that reactor’s location.  How far would “Chernobyl on steroids” travel?  And where are the up to 20 years of reactor no 1 spent fuel rods that could cause such a problem, and the spent fuel rods held – until the building exploded – in the spent fuel rod pool atop reactor no 3?

Along with the rest of the planet, Washington’s looking at the risk of a potential catastrophe.  At least when it comes to finding the fuel rods from reactor 1, Washington possesses some unique assets.  One asset – the secretive National Reconassiance Office – runs the spy satellites remote sensing devices that enable US national security to spy on planet Earth.   The NRO’s slightly less secretive cousin over at the the Pentagon is the Defense Intelligence Agency.  The DIA, in turn, controls MASINT “measures and signatures technologies”.

What is MASINT?  FDL’s recent guest Tim Shorrock answered that question a few years ago for CorpWatch:

MASINT is a highly classified form of intelligence that uses infrared sensors and other technologies to “sniff” the atmosphere for certain chemicals and electro-magnetic activity and “see” beneath bridges and forest canopies. Using its tools, analysts can detect signs that a nuclear power plant is producing plutonium, determine from truck exhaust what types of vehicles are in a convoy, and detect people and weapons hidden from the view of satellites or photoreconnaissance aircraft.

With assets like the NRO and the DIA’s MASINT capacity, even an Obama administration that couldn’t find out millions of of barrels of Corexit and crude oil would poison the Gulf should be able to help Japan’s Fukushima plant locate their missing fuel rods.  And do so before the missing rods – or any of the other pools of fuel rods in Japan’s stricken reactors – ignite Chernobyl on steroids.

Once Obama and his generals have found the fuel rods, let’s hope they’ll time out from Gridion dinners and collateral damage and let the Americans who pay for all the fancy spy technology know what’s happening.  Because now that Americans are hearing CNN’s Dr. Gupta talking about potassium iodide (KI) to prevent radiation toxicity, they’re going to be wondering if they need to take KI.  As long as we don’t see massive uncontrolled radiation releases from the stricken reactors, they probably won’t.  Should we see Chernobyl on steroids, Americans may need a whole lot more than KI.  And until the spent fuel rods are located, there won’t be enough information to let Americans plan how to protect their loved ones. Unless we all learn the fuel rods have caught fire.

[Note: revised at 3:15 PM Pacific on 3/14/11]

[Note # 2: The next to the last comment is a link to an article from MIT Tech titled:  "Opinion: What happened at the Fukushima reactor? Events in Japan confirm the robustness of modern nuclear technology — not a failure".  If Fukushima's a success, pray we never see a failure.

The idea that MIT of all places replaces empirical assessment with ideological cheerleading bordering on fanaticism is as instructive as it is alarming.]