2 Japanese nuclear reactors may be in meltdown

[mental4astro (Alexander)]

I didn't make myself clear with what I ment by "money, money, money".

It is ment in the context of "quick and cheap" electrical power. Cheap for the short term which is so short sighted of the real cost.

The real cost comes in two ways: Storing the waste safely ( and there is a huge amount of it) for hunderds of thousands of years, and the massive complications that can occur when the poo hits the fan when things go wrong. How cheap is it now???

I also understand the reasons for Japan for using nuclear power, but even when the decision was first made, there were safer alternatives that never got a look in, like geothermal. The irony is that Japan propably has one of the easiest to access geothermal sources on the planet. Developing this may have taken longer, but the long term cost is really zero compared to nuclear.

I'm sorry, but for me it still is money, money, money.

It was never ment to question the bravery of those men and women who are risking their lives. If there is a God, these people are going to be looked after in the next life. I can't say the same thing about some others.

I also understand the 'political' aspect you mention Andew, but this isn't politics. Its ethics.

[casstony]

Originally Posted by Kal

How dangerous is it to have uncooled spent fuel rods? How hot can they get? What is a worse case scenario?

Uncovered spent fuel rods burn and emit large amounts of radiation into the air.
http://www.nytimes.com/2011/03/16/wo...ia/16fuel.html

Allowable radiation doses for the workers have been increased so they can return to try to prevent this from happening.

[avandonk]

Originally Posted by sjastro

Bert,

A nice story but it seems to defy the laws of nuclear physics....

I've never heard of a uranium hexafluoride solvent that can also serve as a nuclear moderator to produce thermal neutrons that can initiate the reaction.

Regards

Steven

There is a fuller report in Nature and New Scientist. Once you get a couple of kg of U235 in the one place you have a problem!

bert

[gary]

Originally Posted by Kal

How dangerous is it to have uncooled spent fuel rods? How hot can they get? What is a worse case scenario?

Hi Kal,

The cited article from the yesterday's New York Times sums up the potential danger of
the spent fuel rod pools.

Whereas each reactor is within its own primary containment vessel, the spent fuel
rod pools sit outside of that primary vessel and on top of it, within the secondary containment building.

When you consider that the hydrogen explosions have blown the tops of
the secondary containment buildings of units 1 and 3, the spent fuel rods pools
essentially now have nothing between them and the outside world.
Unit 4 also has some holes in its roof and there has been concern as to
whether Unit 2 may blow its roof as well.

In fact if the roofs were completely blown off, it might have been somewhat easier
for the Chinook helicopter they considered using to drop water directly into the pool.
Unfortunately, judging from the photos of the very damaged buildings, at best
there appear to be various apertures in what was the roof but whether any of them
are above the pools has not been made clear in any report I have read today.

Add into the mix the risk of another hydrogen explosion occurring in any of the
units at the same time whilst the helicopter is hovering, the extent of the existing
damage which might hinder any ground crew brave enough to physically make
their way through the debris and get a hose up there, plus the risk of radiation
exposure for the crews and it really is a dire situation.

With the Washington Post reporting that the attempt yesterday to have a Chinook
drop sea water being aborted because radiation levels were too high, that in itself
is a major set back and one can only hope that the levels drop to a sufficiently
low level later today to make a second attempt possible.

But one way or the other they are going to have to get more water into those pools.

Without cooling, the spent rods get extremely hot and the fuel can melt through
the zirconium alloy tubes they are encased in. A zirconium fire can then occur,
which in the instance of these reactors, will now release radiation directly into
the atmosphere.

The Washington Post quotes Robert Alverez, from the Institute of Policy Studies,
as saying, "If the fuel pools are exposed to the air, the radiation doses coming from
them could be life-threatening up to 50 yards".

See http://www.washingtonpost.com/nation...mha_story.html

Obviously if this situation were to occur, a viscous circle could come about
whereby the radiation hazard from just one pool might then further hamper
efforts to stabilize the situation at the other units.

[DJDD]

Originally Posted by toc

I remember reading that the Germans came up with a reactor design that involved carbon spheres to isolate the fuel, and made it impossible for a meltdown to occur. Might have dreamed it though.

EDIT: Found it on Wikipedia:

http://en.wikipedia.org/wiki/Pebble_bed_reactor

Looks like it has problems as well...

thanks for the link, which highlights the "pros" and cons of this type of reactor.

I notice that most of the pros and cons are theoretical as there have only been pilot-scale versions, although there was already an accident in one of those in Germany, caused by a jammed pebble. So what this means, I think, is that unless we build a few hundred of these reactors we won't find out about what we did not plan for.

also, the pebble bed reactor is, i think, the type that those wishing for nuclear power to be generated in Australia are pushing to build. I remember when the nuclear debate in australia was just beginning (during the Howard years-not political comment just a timeframe) and seem to recall that the proponents of this type of reactor said that a meltdown could not occur. As I said, all based upon a couple of pilots and theory. And even if a meltdown is very unlikely to occur we have already seen that other parts of the process can lead to dire consequences. Whilst some would say these are just engineering issues that can be resolved I wonder if it is worth it and it seems we just are not good at predicting enough potential problems.

[DJDD]

I am just rereading the blog posts, etc. from some of the links that people have shared and thinking about all of the "expert" commentators (nuclear scientists, ex-nuclear scientists, ex-nuclear scientists who are pro-nuclear power in Australia) I have heard speak on the radio.

So many seem to have gotten it wrong, saying the risk of serious contamination is low or that, whilst extremely serious, the situation may have hit the peak yesterday (prior to the current discussion about the spent fuel rod pools). of course, they always seem to then end with something about not having the entire picture so there may be further complications...

Here is one I just re-read, about spent fuel rod pools and the low risk of serious accident occuring:

It is important to note that each of these occurrences (cooling system failure, pool water boiling, fuel rod overheating in air, zirconium oxidation reaction) would each have to last sufficiently long in order to cause an accident, making the total likelihood of a serious situation very low.

and, yes, I recognise the irony that I am not an expert in the field even though I am commenting upon pebble-bed reactors in a previous post...

[sjastro]

Originally Posted by avandonk

There is a fuller report in Nature and New Scientist. Once you get a couple of kg of U235 in the one place you have a problem!

bert

Bert,

Do you have the New Scientist reference?

I have a couple of questions.

(1) Where does the initial neutron (pre fission) source come from?

U235 emits alpha particles. The alpha particles cannot overcome the columbic barrier of U235 nuclei nor any of nuclei of the uranium hexafluoride solvents to produce pre fission neutrons.

(2) How does neutron energy moderation occur?

None of the uranium hexafluoride solvents are recognized neutron moderators. So even if it was possible to generate neutrons, if the neutrons are not thermal, radiative capture may occur where gamma radiation is emitted from the U235 nucleus instead of nuclear fission.

It seems likely the workers would have succumbed to alpha radiation rather than any nuclear reaction.

Regards

Steven

[avandonk]

See here

http://www.wise-uranium.org/eftokc.html

quote from article

"The amount of uranium contained in this tank must be strictly controlled to avoid criticality. These controls however failed, and 16 kg instead of the permitted 2.4 kg were poured into the tank. About 6 kg were already sufficient to initiate a criticality under these circumstances."

This is what happens when you have untrained people doing a highly technical job and decide to take 'obvious' shortcuts.




Bert

[CraigS]

Bert;

I see no evidence of anything other than an accident.

The officials admitted negligence and received sentences.

JCO shut the facility down and is compensating the victims.

What else could the authorities or companies do ?

Cheers

[mental4astro (Alexander)]

This is a truely facinating thread. I'm learning so much. Ta.

[CraigS]

Bring on fusion ..

[avandonk]

Their negligence was hiring homeless men to do the dirty work without safeguards or supervision. How else do you explain 16kg in the tank when 2.4kg was the absolute maximum to avoid criticality.

The whole sorry saga was written up in Nature and New Scientist with all the details of mismanagement.

I doubt if you would even sit next to 16kg of 18% U235 even when it had not undergone criticality. The natural decay rate of U235 is quite high and can be calculated for 18% x 16kg which is nealy 3kg of pure U235!

This is a dry technical report of negligence bordering on stupidity not an accident.

Bert

[RickS (Rick)]

I don't think it has been mentioned here already... there is an interesting ongoing commentary at the MIT NSE Nuclear Information Hub: http://mitnse.com

[DJDD]

Originally Posted by RickS

I don't think it has been mentioned here already... there is an interesting ongoing commentary at the MIT NSE Nuclear Information Hub: http://mitnse.com

that is where I took my quote about the low risk of the spent fuel rod pools becoming a danger...

the discussion is interesting but anything beyond pure information, e.g. what are spent fuel rods, and into risks and outcomes seems to be speculation.

[avandonk]

As a final note if a homeless alcoholic man was seen vomiting and bleeding from all his orifices the immediate conclusion would be that it was self inflicted not due to massive doses of radiation.

This is called a sound management policy.

I am sure far more sound management decisions to save money have been made to produce the current situation. This is what happens when bean counters attempt to make what should be technical decisions.

Bert

[FredSnerd (Claude)]

The dinosaurs had big bodies and little brains and walked the earth for 160 million years. Humans have comparatively little bodies and huge brains and have walked the earth for what; maybe 1.5 million years. Does anyone really think we’ll make it to 2 million years? Not likely is it? But of course when we go we want to make sure that every other living organism on earth goes with us. At the moment there’s almost 500 nuclear reactors on earth and every one of them is like having a wolf by the throat. You can’t leave them unattended because if you do they’ll all meltdown and spray radioactive poison in the atmosphere that will linger for thousands of years. If and when a more encompassing crisis hits will people continue to maintain all those reactors. This is time bomb stuff.


It’s interesting to see that a few have posted the link to the article from BraveNewClimate (the voices of reason amongst us). But of course BraveNewClimate is a site specifically dedicated to the promotion of nuclear power around the world (which doesn’t seem to have mattered to the voices of reason). And what’s really interesting is how some of the more emphatic statements in that article have been removed or toned down since it was first posted a few days ago. Because of course many of the things they said a few days ago couldn’t possibly happen are happening today, including their claim that this could never develop into a Chernobyl. Well, so much for that. And of course if a crisis like Chernobyl is averted, its no thanks to the nuclear power industry but to the 50 workers who will probably lose their lives to save the thousands in Japan and beyond who might otherwise be effected.



500 nuclear reactors on earth and counting, which means the probability of this happening again is ever increasing. And of course the more regularly this happens the more we become acclimatised and accept it. Which reminds me of something else that seems to have been removed from the BraveNewClimate article. The suggestion in the earlier versions that although a meltdown should be avoided, if it happens it’s not really that disastrous.

[gary]

Originally Posted by Sydney Morning Herald 12:10 am Thu 17th March

A Japanese military helicopter has dumped water from a huge bucket onto the stricken Fukushima nuclear power plant, television images show.

A total of three twin-rotor CH-47 Chinooks of the Self-Defence Forces each emptied more than seven tonnes of water onto reactors No.3 and No.4, public broadcaster NHK said.

Story here -
http://www.smh.com.au/environment/he...317-1bxm8.html

NHK report operations will be limited to 40 minutes per helicopter per day because of
the radiation hazard.

NHK report attempts will be made this afternoon to restore the power supply to the reactors facility.
Since the original pumps have been damaged, a spokesman reports they will attempt to install a temporary cooling
system.

[sjastro]

(1) Where does the initial neutron (pre fission) source come from?

U235 emits alpha particles. The alpha particles cannot overcome the columbic barrier of U235 nuclei nor any of nuclei of the uranium hexafluoride solvents to produce pre fission neutrons.

Thanks for the info Bert.

With regards to where the initial neutrons came from, I should have realized that heavy elements such as U235 can undergoe spontaneous or natural fission which provides the neutrons to initiate the chain reaction.

Ironically and tragically the water cooling jacket used at the Tokai plant acted as a neutron moderator resulting in thermal neutrons which initiated an accidental nuclear fission.

Regards

Steven

[DavidU (Dave)]

The spent fuel rods are exposed and they are dumping water on the building via helicopters. These pilots should get medals !

[DJDD]

Originally Posted by FredSnerd

And of course if a crisis like Chernobyl is averted, its no thanks to the nuclear power industry but to the 50 workers who will probably lose their lives to save the thousands in Japan and beyond who might otherwise be effected.

hear hear!

Which reminds me of something else that seems to have been removed from the BraveNewClimate article. The suggestion in the earlier versions that although a meltdown should be avoided, if it happens it’s not really that disastrous.

I am sure there will lots of backfilling on this topic.
but no-one will remember or care except a committed few...