Japan Earthquake/Tsunami

2227: Radiation levels at Fukushima 1 nuclear plant have again topped legal limits, Kyodo News network says.

It's actually alot easier to shut them down then start them up usually. Even a full shutdown procedure is much faster. And if something bad is happening you can just drop all the rods and be fully shut down in a second or so. This will pretty much always work unless the path ways are blocked which pretty much means you already had core dmg and things have already melted/buckled/deformed etc. And well even if everyone was braindead or just plain dead automatic protective electronics should force a scram anyways. Even in the event of something like that or recriticality from stuff melting back together and such we can always pump in boron to chemically shutdown the reactor. The problem with that is before you can start it back up you got to pretty much flush every last bit of boron out which is a hassle and a half. Plus you just made alot of nuclear waste you got to dispose of.

Depends on what you mean by shutdown. Yes there will always and forever be nuclear reactions going on. And fission products will continue to decay for a very long time as will activated material such as Co or Mn. Though most of them are done within a couple months. Well most is done within a day but yeah. Heck immediately after shut down you are producing about 7% of whatever thermal output you had before shutdown from just radioactive decay. But that drops off to half a percent after a day. A month or 2 ambient heat losses are enough to the point you actually have to heat the water up to keep it from getting too cool. But then again even before initial startup there were some spontaneous fissions that could go on to cause more. Without these "source" neutrons you couldn't start the reactor up regardless of the control rods without like shooting it with some.

But w/o those active cooling generators, its kinda hard to keep the cold water going, thus cooling down the rods inside the reactor. I don't know if back up generators are enough, though. Wonder how much does the amount of running water being provided to keep a outside turbine running, to keep cold water flowing into a reactor??? Can a generator or (s) do the same type?? I'm safely assuming so, b.c the Japanese are doing this already..

Not really sure what you are trying to say here. Cooling is acheived by pumping water thru the core. As it travels thru the water heats up which in turn cools down the reactor. In this type of reactor it actually boils and alot of heat is transfered. The steam goes to a turbine which spins using up alot of the energy. Then it goes to a condensor which is just a heat exchanger to cool the rest of the way back down and condense it to completely liquid form and help increase pressure a little so it can be pumpped back into the core.

The problem comes from to run most steam turbine for useful power you have minium pressure requirements which you wont be able to achieve for long shutdown. And since they lost external power and back up disiel generators were down they couldn't pump any water back into the reactor. So it just kinda sits there and gets hotter. Pressure builds up... which they can vent but they don't like to. This is part of the reason navy uses PWR instead of BWR. We could just bleed steam real easy to cool ***down

In case of leak or something you can just pump water in and discharge/vent it out and not even care about going thru the whole cycle. Heat production is very low right now. Even without actual water flow there will be heat transferred to the water assuming there is some in the core and that will transfer to the piping to the outside air which at this point might be enough as long as the piping doesn't have lagging on it which idk about there plants but that's one of the things we can do for emergency cooling or just to buy time to get something better in the works.

well couple thimngs they said was some the rods were partially exposed and may have partially melted. they tryed external genertors but that failed and they had replace cooling valves and they locked up once already. Presure build up from hydrogen becoming real prob and so far attepts to releive it have failed.

Jaerik.. idk was chernobyl a Gen 2 reactor? just wondering.. ( NVM I could google it and find out msyelf)

I don't know if this has been posted yet, but I just saw the news talking about a volcano that erupted in the southern area of Japan.

Not surprising, given all the seismic activity still going on there.

jeez i think only think left to happen is a damn meteor to come crashing down..

You better not *** jinx it!

2327: Pumping seawater into damaged nuclear reactors in Japan should keep them from a catastrophic full-scale meltdown, but conditions are still so volatile that it is far too early to declare the emergency over, nuclear experts have told Reuters. It is probably the first time in the industry's 57-year history that seawater has been used in this way, a sign of how close Japan is to facing a major nuclear disaster, according to the scientists.

2330: The experts interviewed by Reuters warn it is still far too early to definitively say the day has been saved, especially as the information from the power company and the authorities is incomplete. But they say that with every hour that goes by, the chances of a major catastrophe are diminished - as long as water from the sea or elsewhere keeps reactor cores from overheating. Japanese authorities "appear to be having enough success to have forestalled a definite core melt accident that's difficult to control", said Mark Hibbs of the Carnegie Endowment for International Peace. "After three days that is very good news." But still, he added, it is "a touch-and-go situation".

You better not *** jinx it!

Lastly, people need to keep from buzzwording "meltdown". Unfortunately the last 50 years haven't been gentle to that word and I feel it's been somewhat subconsciously lost in translation.

That's weird since situations like Chernobyl technically aren't physically possible in PWRs or BWRs. People can't help but keep referencing it in the news because that's all they know.

That's weird since situations like Chernobyl technically aren't physically possible in PWRs or BWRs. People can't help but keep referencing it in the news because that's all they know.

0024: US search and rescue teams are "on the ground" in Misawa, northern Japan, the White House says. They number 144 people and 12 dogs trained to detect survivors trapped under rubble, and have 45 metric tonnes of rescue equipment with them, AFP reports.

I don't know, I figure RBMK differences in design and conditions are significant enough to be distanced enough from the term BWR so I differentiate.

Oh jesus. That poor Steam Generator. That's *** scary. D1G at prototype had a sodium line in it :D