At Crippled Japanese Nuclear Plant: 'Last-Ditch Effort' To Prevent Meltdown

posted 11:10 AM EST "...the plan to flood the core with seawater and boric acid may be unprecedented and will effectively destroy the power plant. If the plan fails and the core does meltdown...the only thing left to do will be to "seal it up with concrete." NPR

Also see Keith Olbermann's opinion piece from yesterday: Time to shut down this nation’s nuclear energy program. For good...President Obama should officially reinstate the unofficial moratorium, and pledge to begin the process by which we dismantle these sleeping monsters.

Evacuation zone extended, iodine distrubution planned

The evacuation boundary has been extended to 20 km (13 miles). Japanese officials told the U.N.'s atomic watchdog they were making preparations to distribute iodine, which can be used to protect people from radioactive exposure to thyroid. Reuters Other forms of radiation exposure, however, would still be a worry.

Fukushima Dai-ichi Unit 1 reactor schematic

The schematic diagram above shows the GE Mark I Boiling Water Reactor reactor building structure, the Fukushima Dai-ichi Unit 1.

The explosion at Fukushima has apparently disintegrated the upper third of  the reactor building. The video and pictures currently available indicate that the "blow out panels" of the  reactor building and roof cover were blown away by an energetic explosion likely due to a hydrogen gas detonation. The reactor core refuelling deck and the surface of the elevated irradiated nuclear fuel pool are now exposed to the atmosphere. Essentially, the photos show the remaining steel I-beam structure for the weather cover that was over the refueling deck and the top of the "spent fuel" pool. These panels are designed to "blow out" at overpressure.

The actual "pressure suppression system" structures credited for containment sit below this structure inside the concrete reactor building, namely the drywell and wetwell or "torus." The drywell is the large inverted lightbulb steel structure which is 100 feet tall and a nominal wall thickness of 1.5 inches.  The reactor vessel sits inside this structure. In the event of a coremelt accident involving high pressure and high temperature, the highly radioactive steam and pressure would be vented into the drywell and then routed through the large diameter pipes to the "wet well" or "torus" which is the large 18 foot diameter hollow doughnut-shaped structure that surrounds the drywell. The torus contains approximately 1 million gallons of water and designed to receive the pressurized radioactive steam where it is supposed to be quenched and contained.

The status of the reactor containment in the reactor building remains unclear, but apparently remains intact. Fuel damage has apparently occurred because elevated levels of radioactive iodine and cesium are being monitored outside of reactor containment.

What is additionally unclear is how much cooling water is left in the fuel storage pools and whether or not there has been damage to irradiated fuel stored in that pool.  There are reports of sea water being brought in to cool this facility.

Radiation levels are reported to have fallen following the explosion. David Lochbaum, Senior Reactor Safety Engineer for the Union Concerned Scientists, has reported that the explosion may acutally have occurred in the turbine hall building adjacent to the reactor building.

An anonymous Japanese government spokesperson has attributed the explosion to the buildup of a combination of hydrogen and oxygen that detonated inside the concrete reactor building but not the crdedited containment structure. Industry reports that the containment structure itself was not compromised or breached by the explosion.

List of US reactors with same weak containment design as Fukushima Daiichi nuclear power plant reactor units 1 and 3

General Electric Boiling Water Reactor MARK I Containments (24 units) in U.S.:

Browns Ferry 1, 2 and 3 Decatur, AL -- Brunswick 1 & 2 Southport, NC -- Cooper Brownville, NE -- Dresden 2 & 3 Morris, IL -- Duane Arnold Palo, IA --Edwin Hatch 1 & 2 Baxley, GA -- Fermi 2 Monroe, MI -- Hope Creek Artificial Island, NJ -- Fitzpatrick Scriba, NY -- Millstone 1 Waterford, CT -- Monticello Monticello, MN -- Nine Mile Point Unit 1 Scriba, NY -- Oyster Creek Lacey Township, NJ -- Peach Bottom 2 & 3 Delta, PA -- Pilgrim 1 Plymouth, MA -- Quad Cities 1 & 2 Cordova, IL -- Vermont Yankee Vernon, VT.

In 1986, Harold Denton, then the NRC's top safety official, told an industry trade group that the "Mark I containment, especially being smaller with lower design pressure, in spite of the suppression pool, if you look at the WASH 1400 safety study, you'll find something like a 90% probability of that containment failing." Denton has previously "served" as the NRC's point man sent into Three Mile Island Unit 2 reactor control room in the first hours and days of the 1979 meltdown accident.

Vermont Yankee, just two-three days ago, got a 20 year license extension from the US Nuclear Regulatory Commission, effectively overriding the deep and broad opposition to the license extension, from the Democratic Governor Peter Shumlin, to the State Senate which voted a year ago by 26 to 4 to shut down the reactor, all the way to grassroots environmental activists across the state. Obviously, the Vermont Yankee containment is questionable now -- it's been questionable for decades. While earthquakes may be considered rare in Vermont, they are not unheard of, or beyond the realm of possibility. But of course there are other pathways for accidents, or attacks, at Vermont Yankee, that could end in similar results as what is unfolding at Fukushima Daiichi nuclear power plant -- from age related degradation at the 40 year old Vermont Yankee atomic reactor causing systems, structures, or components to fail, to an intentional attack on the fragile, flimsy facility.

REACTOR EXPLOSION PHOTO