Merged 8.8 quake in Sendai, Japan

[One Skunk Todd]

Does spent fuel require active cooling? I'm trying to understand why there was a fire at reactor 4.

 

[Skwinty]

Does spent fuel require active cooling? I'm trying to understand why there was a fire at reactor 4.

Yes and if this active cooling is stopped, then within a matter of hours the water in the pool will start boiling.

 

[Skwinty]

I'm trying to understand why there was a fire at reactor 4.

According to the Japanese authorities, the fire was due to oil from various items of rotating equipment.

 

[MarkCorrigan]

I've tried to discuss issues and I'm certainly not fear mongering. I'm not paranoid about nuclear power, and my post a few pages back was attacked. It made me hesitant to say anything.

And you have to admit, DC has a point that not all countries have the ignorant USA news model.

I live in the UK. I take great pride in my BBC, and I consider it a fine source for accurate news a good 99% of the time.

The direction the BBC has taken over the coverage in Japan has sickened me greatly.

 

[The Central Scrutinizer]

And the dumbass mayor of Tokyo, whatever his name is

Mr. Miyagi.

 

[One Skunk Todd]

Yes and if this active cooling is stopped, then within a matter of hours the water in the pool will start boiling.

Cool thanks. So even with the control rods fully inserted some heat can be generated? So to completely stop heat generation you need to disassemble the pile/rods altogether?

 

[Belgian thought]

I live in the UK. I take great pride in my BBC, and I consider it a fine source for accurate news a good 99% of the time.

The direction the BBC has taken over the coverage in Japan has sickened me greatly.

Fully agree - have stopped watching. Too much toing and froing.

 

[Skwinty]

When the time comes to refuel, the reactor is cooled to a condition known as cold shut down. The rods are completely inserted into the core and the boric acid concentration in the coolant is substantially increased. The 3 primary pumps keep circulating the coolant through the core and steam from the steam generators is discharged to first the condensers and then the atmosphere.

I'm talking about PWR's here. Once cold shutdown is achieved, there is no more circulation of cooling water in the primary circuit, the reactor pit is flooded and the reactor head is removed.

The fuel elements are removed one at a time and the fuel elements are always submerged in a few metres of water. The fuel elements are transported to the fuel building via an underwater tunnel on a fuel transfer trolley.

Once the fuel element has been relocated in the spent fuel pool it will spend about 10 years cooling off, after which it can be transferred to dry storage. It is quite surreal to operate the fuel cranes in the reactor building and spent fuel building and see the eery Cerenkov radiation emanating from the fuel elements.

This effect lasts for a few years and that is why in photographs of spent fuel pools you always see the blue glow

 

[One Skunk Todd]

The hydrogen atoms in the coolant water are responsible for moderating or slowing the neutrons down.

In a PWR, hydrogen is not produced during normal operation, only when the fuel is uncooled and uncovered.

The temperature of the fuel can reach in excess of 2,200 deg Celsius.
Then, the water is disassociated into hydrogen and oxygen as well as the hydrogen contribution from melting Zirconium. (fuel cladding).

I would imagine the same is true for a BWR but I may be wrong.

At what temperature does disassociation stop? (And presumably hydrogen generation become less of a problem)

Also, the containment vessels are supposed to be pretty tough. As best I can tell from reading various sources the main fear right now is the hydrogen explosion at Daiichi 2 has damaged some of the cooling pipes and radioactivity is leaking out through the pipes/penetrations.

Some articles say the explosion damaged the vessel itself. Is that likely and/or possible? Are these explosions happening inside the vessel, outside, or both?

 

[One Skunk Todd]

When the time comes to refuel, the reactor is cooled to a condition known as cold shut down. The rods are completely inserted into the core and the boric acid concentration in the coolant is substantially increased. The 3 primary pumps keep circulating the coolant through the core and steam from the steam generators is discharged to first the condensers and then the atmosphere.

I'm talking about PWR's here. Once cold shutdown is achieved, there is no more circulation of cooling water in the primary circuit, the reactor pit is flooded and the reactor head is removed.

The fuel elements are removed one at a time and the fuel elements are always submerged in a few metres of water. The fuel elements are transported to the fuel building via an underwater tunnel on a fuel transfer trolley.

Once the fuel element has been relocated in the spent fuel pool it will spend about 10 years cooling off, after which it can be transferred to dry storage. It is quite surreal to operate the fuel cranes in the reactor building and spent fuel building and see the eery Cerenkov radiation emanating from the fuel elements.

This effect lasts for a few years and that is why in photographs of spent fuel pools you always see the blue glow

Cool! Thanks for the info. Nice to know perpetual active maintenance is not required.

 

[Kestrel]

Cool thanks. So even with the control rods fully inserted some heat can be generated? So to completely stop heat generation you need to disassemble the pile/rods altogether?

When the chain reaction is terminated, the short lived radionuclides created by the fission process keep generating heat. These decay rapidly over the course of a few days, but during this period a lot of cooling is required.

 

[Skwinty]

I will pick up again tomorrow evening as it is late now and I must go sleep.

I am due to be at the plutonium factory early in the morning as we are just starting a refueling outage and I have premodification testing to perform.

 

[Skwinty]

Perhaps the mods should move this discussion to the Science forum thread so we do not derail the quake thread.

Thanks

 

[dudalb]

I will pick up again tomorrow evening as it is late now and I must go sleep.

I am due to be at the plutonium factory early in the morning as we are just starting a refueling outage and I have premodification testing to perform.

I wonder what the main topic of discussion at work will be......

 

[Belgian thought]

When the chain reaction is terminated, the short lived radionuclides created by the fission process keep generating heat. These decay rapidly over the course of a few days, but during this period a lot of cooling is required.

I think there was talk of the rods melting. This may sound stupid, but do they melt at the top, or the bottom? i.e. how does the cooling affect this?

Also I read that there was only 5% damage to the container, what does that mean?

 

[mortimer]

Heard about that at lunch earlier. Those douchebags need to be slapped, along with Glenn Beck, Anderson Cooper, and Wolf Blitzer. And the dumbass mayor of Tokyo, whatever his name is

To be fair, Beck has actually done a pretty good job of dumbing down the actual truth about the nuke problem (to a level his typical audience would understand) and not screaming "Chernobyl".

 

[shuize]

Generally speaking, if all goes well, the post-shutdown cooling process should only take a few days. But, as we have seen, all has not gone according to plan; I would expect the reactor cores to be properly cooled down by week's end, however.

As someone who lives in Japan (although a fair distance away from Fukushima), my main questions are what sort of time line are we looking at now and what sort of progress (if any) have they made so far?

I think most people have been pretty calm up to now. But, in my case, it's the continuous negative trend of the nuclear crisis that has me concerned. Every morning we seem to wake up to even worse news than the day before with little idea of where this is headed or its capacity to spiral out of control. Any information on that score is appreciated.

I obviously don't know jack about the technical side of things. But I had heard that with proper water flow probably it'd take about a week to properly cool the cores. Is your one week estimate above also based on the same proper water flow assumption? Is that the only real solution? As a layman, I imagine scenarios of filling the buildings full of earth and concrete.

I'm sure the staff are doing everything they can. But part of me wonders why they haven't sent more assistance. Has the media over hyped the risks to Tokyo or are the problems they're facing just not the kind that can be solved with more people on the scene?

 

[jimbob]

It really isn't a coincidence you picked that flag, is it?

As showing support for Japan.

Why, what's wrong with it ?

Imperial Japan wasn't a very nice empire, even by the standards of empires.

 

[elgarak]

As someone who lives in Japan (although a fair distance away from Fukushima), my main questions are what sort of time line are we looking at now and what sort of progress (if any) have they made so far?

I think most people have been pretty calm up to now. But, in my case, it's the continuous negative trend in the reporting of the nuclear crisis that has me concerned. Every morning we seem to wake up to even worse news than the day before with little idea of where this is headed or its capacity to spiral out of control. Any information on that score is appreciated.

(Bold my addition)

I believe a great deal of your feeling is related to the sensationalist FUD style reporting. I am quite disappointed with the style of the big news outlets, even ones that I considered good. For this crisis, the best news I got from unrelated, independent sources -- bloggers, forum entries, Wiki-submitters.

I obviously don't know jack about the technical side of things. But I had heard that with proper water flow probably it'd take about a week to properly cool the cores. Is your one week estimate above also based on the same proper water flow assumption? Is that the only real solution? As a layman, I imagine scenarios of filling the buildings full of earth and concrete.

I'm sure the staff are doing everything they can. But part of me wonders why they haven't sent more assistance. Has the media over hyped the risks to Tokyo or are the problems they're facing just not the kind that can be solved with more people on the scene?

I'm a physicist, though not a nuclear one, and as far as I understand it, the best thing to do if you want to stop the reactor no matter what, is pumping water spiked with boron. Exactly what they are doing now. And once you have started doing that, there's not much else that you can do except waiting that the pile cools down (and maintaining water flow, which is limited by the outside connectors, so more equipment and more workers does not help you increasing that).

That, and of course taking care of the unpredictable side event, like a fire in the spend fuel pool of a reactor that you did not care about anymore.

 

[Kestrel]

I think there was talk of the rods melting. This may sound stupid, but do they melt at the top, or the bottom? i.e. how does the cooling affect this?

Also I read that there was only 5% damage to the container, what does that mean?

The rods melt when they are not cooled properly. If the reason they are not being cooled is a low water level, the rods would melt at the top.

As for what 5% damage means, I haven't a clue.