Dave, since you're in the industry can you help us understand exactly what are the risks are here? I feel like the media is over-hyping, yet sometimes you don't know if the Gov't is simply saying little to prevent panic. They say it can never be as bad as Chernobyl... or can it?
I just have no concept of the magnitude of this thing, it's embarrassing.
It's pretty frustrating watching and reading the media stories on this. Either the media sensationalizes this kind of stuff, or they completely screw up the information they're told when presenting it to us.
At first, it was obvious TEPCO was downplaying this, which I thought was "OK" since the poor Japanese have enough to worry about. Friday night I was on TEPCO's website reading their public disclosure documents directly. Saturday it became obvious they were screwed.
You only need two things for nuclear power plants to keep them safe: water, and a way to inject it where needed. They just had no way to inject water without power. That's why they had to depressurize their primary system down from ~1000psi to ~100psi so they could use portable fire pumps to inject water. Of course, depressurizing meant they vented steam and radioactive gases (and hydrogen of course) to their secondary containment building which caused an explosion. Power plants in the US have proceduralized steps to ensure venting doesn't approach the design limit for hydrogen combustability inside containment (4%). Japan probably does too, but they had to keep venting to reach the lower pressure necessary for the weak fire pumps to begin injecting water. They had no choice.
The reactor was the immediate concern to keep cool since it has the most energy from decay heat. The older, more dead fuel in their spent fuel pools just took longer to heat up the existing water in the pool and begin to boil off. They probably just lost sight of this in their battle with four reactors. With no power to alarm monitors, they didn't have blaring alarms telling them spent fuel pool temperatures were rising until they started boiling and slowly dropping level until the level reached the top of the fuel assemblies. Once that happens, you're screwed again until you can dump water in the pool and recover the fuel assemblies.
Now they say they have offsite power they're getting ready to rig up that might let them use the plant equipment. Problem is, will the plant equipment work after an earthquake that exceeded their design basis limit? Have they pumped the water out that submerged their switchgear? Will the temporary offiste power hold up to the high electrical demands that four units require?
They're certainly not out of this unfortunately.
Chernobyl was a graphite-moderated reactor, designed to produce plutonium. The fact that they could get electricity from it was a bonus. It wasn't regulated, wasn't maintained, wasn't operated properly, and wasn't designed properly (from a safety standpoint). The Japanese BWR's will not "explode" like Chernobyl, but there may be periodic venting of radioactive gas and possibly hydrogen explosions, and at worse case, bulk release of fission product gases from the fuel rods if they cannot be cooled. Effectively, that's like a "dirty bomb," but with significantly more radioactive material from all the fuel in the cores and spent fuel pools. It could be VERY bad. In that case, they would have to try and bury all the reactors and spent fuel pools with sand and concrete like Chernobyl. The Asian countries would be praying for windy conditions that blows the radioactive gases out to the Pacific. That could be bad too.
Look at this website. It's the most factual stuff you can read, and has good explanations of what's going on:
http://www.nei.org/newsandevents/information-on-the-japanese-earthquake-and-reactors-in-that-region/
:frown:
Dave
! It boils down to sacrifice. At what level would you put yourself in danger to help others? I think that's a question every man should come to terms with - IMO. These workers know the sacrifice they're making and chose to make it. I salute them and hope that I'd be able to be as honorable and courageous. I hope I'm never put to such a test! I'm afraid I'd fail miserably. May their actions be a model we all look up to.
