Reactor Containment & Fuel Storage from UCS; (h/t commenter lobster)

It’s Wednesday, 10:30 a.m. EDT; Wednesday night, 11:30 p.m. in Japan

Japanese officials and media are now acknowledging they’re in a very long term nightmare at Fukushima Daiichi Nuclear Station. They’re out of quick solutions — like getting power to the units to restore normal cooling — that provided an earlier hope. And they’re even running out of acceptable long-run answers.

All of their choices are between bad and godawful. They face years of battling an unstable set of partially damaged reactors and spent fuel storage pools, some of which can become critical, even literally so.

The day to day problem focuses on water — how to keep enough covering the fuel rods inside the reactors, but also what to do with it once it becomes contaminated and leaks out, and what to do when they can’t keep enough of the right kind of water at the right place at the right time. And it’s become a logistics problem. Where do you put the huge and growing quantities of contaminated water?

They’ve got hundreds of tons of contaminated water preventing workers from getting close enough to pumps, valves, monitors needed to stabilize conditions. So they have to pump this water out and put it somewhere, but where? There are tanks at/near some units that can hold some of it, but not all, and external temporary storage may allow exposure to the atmosphere. Meanwhile, they must keep pumping more fresh water into the reactors and spent fuel storage pools, while more leaks out.

There are large pools of dangerously contaminated water in the turbine buildings adjacent to each reactor buidling, with more leaking in from somewhere, and few places to put it. Just outside the turbine buildings, there are long, deep trenches nearer the ocean and likely filled with water from the tsunami. But they’re now contaminated with radiation and water leaks from the turbine building.

Where can they put all this water? And given varying degrees of contamination, which water should they put where? For example, should they just pump out the least radioactive water in the trenches/pools and dump it in the ocean? That would be awful, but there’s no other safe tank, pool or storage basin large enough or available quickly enough, and they need to move it quickly. That’s this week’s dilemma, and next week, or tomorrow, there will be another.

While they worry about where to put all the contaiminated water, some of it keeps geting more contamination. Government and TEPCO (utility) officials now generally acknowledge that the fuel rods within Units 1, 2, and 3 suffered what they’re calling “melting,” meaning some portion of the fuel cladding distintegrated and the fuel inside broke down, releasing further radiation. There’s general agreement the fuel rods at Units 1-3 were early on partially or fully uncovered for at least several (10-20?) hours, leading to the explosions at each Unit early on.

Yesterday, there was a [still unconfirmed] claim by a former GE expert in the reactor design at Fukushima Daiiche that at least some of the fuel in Unit 2 had not only melted but had burned through the reactor vessel and onto the concreat reactor floor. That’s always a very bad sign, because it puts the irradiating fuel outside containment; but it’s just one nightmare scenario they face. [See comment thread from previous update for discussion of its plausibiity] If that claim were true, from there, the molten fuel on the floor could undergo further melting, be exposed to more water/steam (possible uncontained steam exlosion?) and/or continue melting through the floor on its way to . . . down and out.

But it’s not just the continuing need to keep injecting more water into the reactors. There’s also the spent fuel storage pools, especially Unit 4′s pool, which has a full inventory of relatively “unspent” fuel that was removed from Unit 4′s core before the earthquake. The storage pools are also outside containment, so it’s important to keep them cooled and avoid even the smallest likelihood of going critical.

Unit 4′s pool may have a serious leak, and the fuel rods there (and other units) likely were uncovered for some unknown period. They have to keep this fuel covered to prevent further damage and radiation releases, but the water is leaking out and/or boiling off when the rods overheat. They have to deal with this every day, from now on, until that fuel is removed . . . how? and placed somewhere safe . . . where?

In the great Dr. Who series, Tom Baker had a solution. His Tardis could not only travel through time, but once you got inside the British call box, there was infinite space inside. You could just pump all the contaminated water into one of the infinite number of rooms and levels and never worry about it again. But that’s science fiction. Without a Tardis, the Japanese have to think about pumping lots of this water directly into the ocean, or into a large super tanker that just sits along the coast for . . . years? . . . until . . . what?

So they’re stuck; they have to keep inventing ad hoc temporary fixes for months, possibly years. Wet blankets to cover the Units? Tanker ships filled with radioactive water sitting off the coast? And so far, I haven’t heard or seen a single expert, pro-industry, anti-industry, or just smart people trying to help, tell us there’s a simple answer.

But not to worry. Yesterday, a US NRC official assured a Senate Hearing that of course we’d make our nukes improve their safety features if that was warranted, but there’s no reason to hold up current licensing efforts. And today, Barack Obama will reportedly embrace President McCain’s energy policy: let’s move ahead with every dangerous energy source that has suffered catastrophic failure in the last two years.

Helpful Sources:

NYT: Japan’s Confidence Slips in Nuclear Crisis

NHK World

NHK English tv feed

Union of Concerned Scientists

Kyodo News: Japan Nuclear Crisis

Nuclear Power Plant Primer — good expert video

Unit by Unit status updates (pdf) at the IAEA site

NYT Radiation chart
Washington Post simple graphics

TEPCO press releases

fleep.com/earthquake
NHK press releases
The Breakthrough Institute (including the Twitter feeds)