Japan's nuclear power plants

Two are at risk right now, according to CNN.

I understand that they need to keep the rods under water to keep them cool, and are apparently at risk because diesel generators are out, and they can’t pump water, so they are on battery backup and struggling to bring in new generators and/or batteries.

Why can’t the plants produce their own electricity?

Is it because they would produce more than they can handle?

they have diesel generators as backup power to run the plant. those are broken or inadequate to do the cooling.

I think they can produce their own electricity from the nuclear reactors. However, because of the quake it sounds like they took their reactors offline. Thing is they are still very hot so need to be cooled. The backup generators are supposed to provide the power for the pumps in this case.

Thanks, but I understand they took their reactors offline due to the quake/tsunami, and then needed their non-functional diesel generators to power the pumps.

But, now that the immediate danger is over, I’m asking why the powerplants can’t simply be brought back online to produce their own power for their own pumps.

My best guess is that because the grid is down, the power plant, if online, would produce too much electricity.

Is that correct? And if so, why can’t they make a big coil or something to dissipate mere heat into the air instead of radioactive steam?

Nuclear power plants are complex creatures. You cannot just turn reactors on and off with the flip of a switch. My (very) limited understanding is that the process to stop and start reactors is a lengthy process (as in days). If they started to shutdown the reactors then it’ll be awhile till they can start them again.

Again, my understanding of how these work is very, very limited. I’m not even sure that is what the issue is.

We need Una Persson in here for a solid answer.

the plants are still in danger of meltdown.

Thank you, now that does begin to make some sense. If it takes days to restart then the battery life immediately comes into question.

I guess the next question would be, if they understand this limitation, why aren’t battery backups sufficient? Yes, diesel generators, but with a nuke plant, inherent dangers, and the current political climate, I’m thinking full triple redundancy at a minimum.

I also have read Una Persson’s threads with mighty gusto over the years and would love a definitive answer.

sigh

Well, they have battery backups, diesel generators and power from the main grid from other plants.

I guess they assumed that was enough redundancy.

FWIW seems one of the reactors in Japan will melt down (or already has). Details are sketchy and while serious for the reactor they are saying there is little danger to people outside.

Sorry but I did not manage to read that article and draw the same conclusions. Apparently there are differing definitions of “Melt down”.

"Jiji news agency quoted nuclear authorities as saying that there was a high possibility that nuclear fuel rods at Tokyo Electric Power’s (Tepco’s) Daiichi No.1 reactor may be melting or have melted.

Experts said if that is the case, it means the reactor is heating up. If that is not halted, such as by venting steam which releases small amounts of radiation, there is a chance it would result in a rupture of the reactor pressure vessel.

But the risk of contamination can be minimized as long as the external container structure is intact, they said. The worry then becomes whether the quake has weakened the structure."

I guess I give CNN just a little more credit than “Jiji News Agency”

I hope I’m wrong.

From the article:

“Jiji news agency quoted nuclear authorities as saying that there was a high possibility that nuclear fuel rods at Tokyo Electric Power’s (Tepco’s) Daiichi No.1 reactor may be melting or have melted.”

“Melt down” means the fuel rods have melted (or at least some of them).

Don’t let Hollywood make you think “melt down” automatically mean the China Syndrome or an exploding reactor.

It is serious, make no mistake. So far though, if the officials reporting this can be believed and I see no reason not to in this case, the danger to the outside world is minimal. Radiation may be released but that is what the containment dome is there for. Their concern there is that the containment dome might have been damaged in the quake.

CNN just relayed a report from NHK that there was “an explosion outside” one plant, injuring some workers.

So right now, we’re waiting to see if it’s going to be either a Three Mile Island vs. another Cherynoble?
This is really Hollywood. I am just waiting for reports of Godzilla or Mothra next.

It took sheer grunt effort to cause Chernobyl to be Chernobyl.

True, an 8.9 quake can be said to have something in the realm of sheer grunt power, but even still I think that you could show Communism to be a more destructive force on the planet.

Pretty much.

From my admittedly layman’s opinion I am putting my money on Three Mile Island.

Chernobyl was a runaway reactor. So far it does not sound like that is the case here and I trust the Japanese to know their shit as well as construct a good power plant (the Soviets…cut corners).

That said officials are notoriously slow to admit the full extent of a disaster till it becomes unavoidably apparent something is wrong (e.g. your reactor just exploded). Here though no one is trying to cover up a mistake. They had a huge earthquake, it is the earthquake’s fault so there is less Cover Your Ass motivation here.

Chernobyl was as bad as it was because the idiots in charge deliberately did crazy shit without any thought to basic safety. Given that the Japanese weren’t running a complex and massively dangerous experiment on the plant when the earthquake struck, it will be Three Mile Island at worst.

This won’t stop the loons from howling. Nothing stops the loons from howling.

not to mention the RBMK reactor design was (in comparison) hilariously unsafe.

Just because you haven’t heard of something doesn’t make it unreliable. Jiji is the Japanese equivalent of the AP.

Right. In summary, Chernobyl happened because people were doing a dangerous experiment on a reactor design very few people use anymore, and failed to fix problems as they developed.

None of that is true of the Japanese reactor we’re talking about.