CNN: Temperatures rising in reactor one at Fukushima Daiichi plant

Japanese officials are reporting rising temperatures at reactor one at the Fukushima Daiichi nuclear plant. Radiation levels are said to be registering at 100-thousand times the normal level, an amount workers could only be exposed to for fifteen minutes at a time.

Professor Cham Dallas is the Director of the Institute for Health Management and Mass Destruction Defense at the University of Georgia and has led 12 expeditions into the most contaminated areas of the Chernobyl nuclear disaster. Professor Dallas talks to American Morning's Kiran Chetry about the latest developments out of Japan.


----------------
Also Tepco is reporting that they cannot raise the water levels in reactor #1 (others as well). The melted portions of the fuel rods may fall and then heat the seals leading to leakage.

--
Note that Arnie Gundersen had an idea for why a BWR reactor would not hold water:
Unlike in newer reactor designs, the older boiling water reactors at Daiichi are pierced by dozens of holes in the bottom of their reactor vessels. Each hole allows one control rod — made of a neutron-absorbing material that quickly stops nuclear fission inside the reactor — to slide into the reactor from below, as happened when the earthquake shook the plant March 11. During normal operations, a graphite stopper covers each hole, sealing in highly radioactive primary cooling water, said Arnie Gundersen, a consultant at Fairewinds Associates with 40 years of experience overseeing boiling water reactors. But at temperatures above 350 degrees Fahrenheit, the graphite stoppers begin to melt. “Since it is likely that rubble from the broken fuel rods . . . is collecting at the bottom of the reactor, the seals are being damaged by high temperature or high radiation,” Gundersen said. As the graphite seals fail, water in the reactor will leak into a network of pipes in the containment buildings surrounding each reactor — the very buildings that have been heavily damaged by explosions. Gundersen said that this piping is probably compromised, leaving highly radioactive water to seep from the reactor vessels into broken pipes — and from there into the turbine buildings and beyond.

Who knew?

The one I think makes the most sense is that it's backing up through the feedwater pipes due to a broken valve. They're reportedly spraying water without knowing exactly what the levels in the reactor is - possibly filling it above the level of those pipes.

That only requires postulating one failure point (the issolation valve that is supposed to keep water flowing in only one direction). In the case cited above, there would have to be a leak in the pressure vessel AND an additional leak in the larger containment area.

sounds very plausible to me.

The water must also get through the next level of containment AND travel (somehow) to another building.

The other theory requires only a busted valve... Then the water is in a pipe that already leads to the other building. A leak in such a pipe after an earthquake isn't hard to believe.

containment, contrary to that report.

The "primary containment" is the heavy concrete shell (that looks like an inverted lightbulb). The steel reactor pressure vessel is inside that.

The control rods do pass through the bottom of the RPV, but are inside of the primary containment.

The more orifices you have in the containment, the less contained it will be. This is just unconscionable. And all that is to save on stainless steel, I presume. Fuck GE.

and Tepco lying on their safety reports also.

Which illustrates why that explanation is inaccurate or at best incomplete. Water leaking out of around the control rods would pool directly below the reactor inside primary containment. It doesn't explain how it would be found 200m away in the basement of the adjacent turbine building.

Not well shown on this diagram but I don't know of a clearer diagram.



The control rods would be inserted and removed from reactor from the bottom (silver directly below red RPV in center of diagram) and inside the torus. This is why the suppression pool is shaped like a torus to make room for the control rod assembly. think of a doughnut with the control rod assembly going through the middle.

Slighly different view of Oyster Creek reactor (same design GE BWR3 MK-1 containment)



The RPV, and control rod assembly are both inside primary containment. Still this is one reason why I prefer PWR. Control rods are inserted from the top.

outside the primary containment - that would be idiocy. I could not believe it, but I am somewhat relieved now. The control rods should be above the fuel - gravity working with you, not against you. These guys are really playing with nuclear fire. Don't we have any better engineers? I mean, people were not dumb in 1968, why did they do this. Oh, the money, of course. The invisible hand and all that. Well, now we have the invisible handout in the form of radiation. I am more enraged the more I think about this design.

In BWR (boiling water reactor) the water inside containment is boiling into steam and steam rises so the space above the reactor needs to be used for things like stream dryers and filters, etc. THere is no room for control rod assembly above the reactor.

In a PWR (pressurized water reactor) the water/coolant never boils. It is pressurized to 150x sea level pressure (150 atm) so although the water reaches >200 deg celsius it still below the boiling point. There is no need for any steam equipment above the reactor so the control rod assemblies are placed above the reactor and the bottom of reactor is one solid piece of aluminum.



The US has some BWR (about 30) but has mostly PWR. Japan has gone heavily towards BWR. Each type has its own advantages and disadvantages. For PWR the control rod placing is a big plus.