Merged nuclear power safe?

[Alferd_Packer]

I wouldn't say that. How many plants were built after that?

I don't think that it is entirely fair to blame the stoppage of nuclear power plant construction in the U.S. on TMI.

I think economics was the biggest reason.

The last plants built wound up costing over 200% more than originally estimated.

 

[BenBurch]

You know that old phrase when somebody asks if something is safe; "Safe as houses."

I think we could make the argument that in this calamity, the nuclear plants were SAFER than houses.

 

[bobdroege7]

I'm still pro nuclear, but the events here have me concerned about what has happened.

I'm not familiar with the BWR-3 designs involved in Japan, but have experience and knowledge of the safety systems designed to prevent this kind of accident in a BWR-6 which is a more modern design but still some 30 years old.

I have seen brief descriptions of modern BWR designs that said to be 1000 times less likely to suffer these kinds of accidents due to such features as coolant pumps internal to the reactor vessel as well as natural circulation capabilities that would prevent loss of cooling type accidents under loss of off-site power with no operator action for hours.

In the case of the Fukushima plants that have experienced explosions, following the loss of cooling leads be to believe that the cores of the plants involved are piles of slag.

In my experience the safety systems that should be in place, should also be behind thick walls of concrete, if they are built that way in the great corn/bean desert of Illinois where there is no threat of a tsunami, why did all the safety systems fail?

Did they have hydrogen recombiners to deal with the hydrogen produced when the core becomes uncovered?

Why did the diesel generators fail? In my opinion, there should have been a dozen locomotive sized diesel generators on site, did they all fail and why?

If the nuclear plant I worked at were at the Fukushima site and there was a Tsunami coming, the safest place to be would be in the control room which is almost 100 ft above the water level of the lake used as ultimate heat sink. The diesel generators were inside 3 foot concrete walls and so are the rest of the safety systems, as well as the control room.

I also wonder what kind of regulatory environment exists in Japan. In the US at least at the last time I was working at a nuclear plant there were both the Nuclear Regulatory Commission and the Institute of Nuclear Plant Operators. The NRC being a government agency paid for by licensing fees and INPO being staffed by the operators of various plants in a self regulating style.

And in closing there is too much disinformation going on as well as misunderstanding of the historical events.

Cherenobyl was a prompt criticality event, as was PL-1 in Idaho, where the power level went up to hundreds or thousand times rated power causing an explosion.

At Three Mile Island, several failures resulted in the water level in the core dropping below a safe level resulting in overheating of the fuel rods. The fuel rods being made of a Zirconium alloy which burns in the presence of water at a lower temperature than the melting point, which is where the hydrogen comes from. Once this burning starts, there really is no stopping it, which is why there are no partial meltdowns.

This was probably TLR but there you go.

 

[bobdroege7]

I don't think that it is entirely fair to blame the stoppage of nuclear power plant construction in the U.S. on TMI.

I think economics was the biggest reason.

The last plants built wound up costing over 200% more than originally estimated.

I don't either, and I think cheap natural gas had a lot more to do with it.

Cheap fuel, cheap construction, cheap financing, short build time, cheap regulatory hurdles etc.

 

[Java Man]

And as it turns out (assuming no further events at the plant) any money spent on upgrading those plants would not have saved any lives whereas spending however many millions on other areas may have.

Obviously everyone is happy no more life was lost to radiation. But those reactors will have to be replaced. In the meantime there is a power shortage. Had that money been spent on upgrading them ten years ago with newer technology then those cores could be powered up again. Providing the needed energy. The money now needed to repair things would not need to be subdivided into cleaning and repairing melted cores.

My "crisis" isn't a nuclear blowout. Which would be the most dire, extreme and undesired event. Nevertheless the current situation is quite a nightmare that could have been prevented if the cores were replaced with newer models. The Japanese are looking at quite an expense down the road and that's without a blowout.

How safe exactly do you want the plants to be and how often should we upgrade them to make them even safer?

Well it would be good to decommission designs that can cause a meltdown in case of a cooling failure. Given we already have designs that work that way.

And by safe I don't only mean a huge radioactive cloud. But safe in the knowledge that it's working ok, that it shutdown ok, that you can now reactivate it to power the grid in this crisis, etc etc etc. It retrospect it begins to look a lot cheaper and better to have gone through the expense of upgrading it.

And why specifically nuclear plants and not dams and oil refineries and chemical plants?

We can sure talk about that in another thread if you want to.

 

[Corsair 115]

Human endeavour shouldn't be limited to things that are safe, if we want to get anywhere.

That reminds me of the science fiction novella With Folded Hands by Jack Williamson. It involves the invention of mechanicals (robots) which are programmed to serve humans and protect them from harm. Only the mechanicals execute their programming far too well, and soon begin to see virtually every human activity as being potentially harmful and thus must protect humans from these activities. (The story doesn't end well for humanity.)

 

[Belz...]

Yes, but until Chernobyl that was also true for all the nuclear power plants, wasn't it? And until last week the Japanese plants were quake safe, too ...

That's weird logic.

 

[Aepervius]

@bobdroege7 you are speaking of rapidly zirconium cladding oxidation. That is a problem yes, but if the containment reactor stay integral, it would be a hassle, not the big danger the media are making it be.

Otherwise the same good question you asked, we all have, but no answer have been forthcoming on how exactly the backup generator failed, and why were they insufficiently protected agaisnt a tsunami. But then again that earthquake was special.

 

[Belz...]

Yup, I'm willing to bet a fair amount of cash that these chemical plants and related infrastructure damage will have a far greater environmental effect than anything happening with the nuclear plants.

That's a tragedy in itself. The perceived evil of nuclear radiation allows greater evils to continue to exist (coal plants, solar and wind, etc.)

 

[BenBurch]

Bob,

As I understand it, the generators were not destroyed, but flooded.

As for hydrogen re-combiners; passive catalytic re-combiners have a problem when the amount of hydrogen is very large. The catalyst heats up and can become so hot that it ignites the hydrogen.

This may in fact be what happened here; I do not know if these plants had a passive catalytic system.

 

[Skwinty]

Skwinty... sounds as if the reactor cores are being directly flooded with seawater.

That seems to be the case. The entire containment is being flooded with sea water to remove residual heat.

Reactor cores are not generally flooded with coolant I assume..

When the reactor is operating, water must flow over the fuel elements in the core to remove the heat. This water is flashed to steam to drive the turbine.

Is this seawater being circulated somehow do you know? Thanks.

I think the only circulation taking place is natural circulation. ie from hot to cold areas.

The objective is to keep the reactor submerged with water to cool things down.

If you read the 03.pdf I linked to, you should get a better idea of the different types of cooling modes for normal operations.

http://www.nrc.gov/reading-rm/basic-ref/teachers/03.pdf

 

[Frank Newgent]

Skwinty... sounds as if the reactor cores are being directly flooded with seawater.

That seems to be the case. The entire containment is being flooded with sea water to remove residual heat.

Reactor cores are not generally flooded with coolant I assume..

When the reactor is operating, water must flow over the fuel elements in the core to remove the heat. This water is flashed to steam to drive the turbine.

Is this seawater being circulated somehow do you know? Thanks.

I think the only circulation taking place is natural circulation. ie from hot to cold areas.

The objective is to keep the reactor submerged with water to cool things down.

If you read the 03.pdf I linked to, you should get a better idea of the different types of cooling modes for normal operations.

http://www.nrc.gov/reading-rm/basic-ref/teachers/03.pdf

yeah, thanks... some reactor set-ups use the heated water to push the turbines and some have cooling systems removed from this process.

What I am asking is the seawater being used to cool the core just sitting there on the core? Is it being circulated to cool it down and then pumped back in? Is it being pumped out of the building and new seawater pumped in?

I am merely curious. Thought somebody might know around here.

 

[Thunder]

is this seawater used to cool the rods..now radioactive?

 

[Corsair 115]

is this seawater used to cool the rods..now radioactive?

From post #7:

The seawater used as cooling water will be activated to some degree. Because the control rods are fully inserted, the Uranium chain reaction is not happening. That means the “main” nuclear reaction is not happening, thus not contributing to the activation. The intermediate radioactive materials (Cesium and Iodine) are also almost gone at this stage, because the Uranium decay was stopped a long time ago. This further reduces the activation. The bottom line is that there will be some low level of activation of the seawater, which will also be removed by the treatment facilities.

 

[Skwinty]

Frank, it is not possible to state exactly what is being done other than flooding the entire containment.

I suspect that they are not using pumps to recirculate the water through heat exchangers, just pumping the water in and ensuring a constant level as the water boils off.

This of course is only an opinion and could be wrong. There is not enough specific detail available.

 

[bobdroege7]

If they are trying to flood with seawater, obviously they are not able to flood with fresh water, which means all emergency cooling systems are not functional.

Which means molten piles of slag giving off hydrogen which is exploding, which is bad.

I would go with a 5 rating, unless they find all the missing workers alive and well.

Skwinty, I wish you would specify which containment you are calling first, second and third.

In my understanding the containments are in order the fuel pellets, the zircaloy cladding, the reactor coolant, the pressure vessel, the drywell, the containment dome and the vapor shield.

Latest news is saying the core is completely uncovered in at least one of the plants and some are saying the core is burning. So the information coming out is a little better.

 

[technoextreme]

Heh. I finally figured out the fallacy that has been really annoying the hell out of me. Its the nirvana fallacy which is a subset of the false dilemma category.

We can sure talk about that in another thread if you want to.

Nope. Lets talk about it here because its the fundamental problem with your twisted warped logic. What makes nuclear power plants so special in their safety record that you single them out in terms of their safety as opposed to pretty much anything else. Dams can burst and break killing people. The electrical grid itself is woefully inadequate. Roads and bridges are can be quite dangerous.

 

[Alferd_Packer]

The probable result is a mess inside of the containment that will cost millions Billions to clean up.

Fixed that

 

[Skwinty]

Skwinty, I wish you would specify which containment you are calling first, second and third.

Containment 1 is the Zircalloy cladding and you cannot flood inside that.

Containment 2 is the pressure vessel which you can flood.

Containment 3 is the concrete containment structure which can be directly flooded.

Look at the cutaway drawing in the pdf file page 16.

As far as I understand, fire trucks are pumping the sea water into containment and not recirculating this water.

 

[MarkCorrigan]

i hope so.

There's no "hope so" about it.

The reactor and power station it was contained in is about 40-50 years old, and it still has more than adequate safety measures. Unless someone totally screwed up the building of the plant (ludicrously unlikely) the containment area will lock down and no one will be hurt by the nuclear fuel.