Discussion of Nuclear Power and Safety

[nathan]

"Japan suspended operations to prevent a stricken nuclear plant from melting down Wednesday after a surge in radiation made it too dangerous for workers to remain at the facility."

"The four reactors at Fukushima Daiichi have now been collectively hit by four explosions and two fires since a magnitude-9.0 earthquake on Friday shook the region 260 kilometres northeast of Tokyo."

"Japan’s nuclear safety agency said 70 per cent of the nuclear fuel rods may have been damaged at Fukushima Reactor No. 1, which suffered an explosion Saturday, triggering the crisis. The Kyodo news agency said 33 per cent of the fuel rods at Reactor No. 2, which was hit by an explosion on Tuesday, have also been damaged. The reactors’ cores are believed to have partly melted after the cooling mechanisms shut down."

source:
http://www.theglobeandmail.com/news/wor ... le1942915/

[mikenz66]

PS. this Wikipedia article has a useful level of detail.

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

Mike

[christopher:::]

Workers have returned to the plant!! Maybe they just needed a break, perhaps went out for some donuts and coffee? The green tea donuts are especially nice here in Japan, if you've never tried them.

[Kim O'Hara]

No matter what people say, alternative sources of power will not come anywhere close to meeting demand so getting off nuclear power in the short run would lead to global economic collapse. Eventually, gradually, yes, let's continuing moving in the right direction...

Hi, Phil,
This position seems extreme and, frankly, defeatist. Do you have any evidence for it, to set against evidence such as, e.g. the Global Status Report that Mawkish linked us to http://www.ren21.net/Portals/97/documents/GSR/REN21_GSR_2010_full_revised%20Sept2010.pdf? Or the IPCC summary on power generation (http://www.ipcc.ch/publications_and_data/ar4/syr/en/spms4.html)?

Kim

Edit: added link to IPCC report.

[Mawkish1983]

Emergency neutron absorbers (boron is common) should have been automatically deployed, shich would have stopped the reactor heating up by stopping the chain reaction. It seems this hasn't happened, because the core is heating up; the chain reaction may be happening still. It shouldn't be, but it looks like it is.

Hmmm. I believed nuclear was safe. I believed no country would take such huge risks without failsafes. I sat in countless hours of lectures as professor after professor explained how nuclear disaster was now impossible. I believed them. They were wrong, and so I am wrong.

Very disappointing to be lied to, but I was told the situation in Japan was impossible.

It's making take a long hard look at many technologies I support(ed), not just nuclear fission power.

[christopher:::]

I tend to mistrustful of anyone who holds something very dangerous in their hand, offers it to you and says "this is perfectly safe." More trustful when they say "this is very very dangerous, so we have to be very very very very careful."

Mawkish, have you ever seen the map of the radioactive fallout patterns from the US Nevada atomic bomb tests in the 1950s? I'd be curious to know if it was mentioned in any of your prof's classes.



And here's a scientific paper on radioactive fallout presented in 1958. They knew this was happening, knew that the radiation from their tests were coming back to the earth via rainfall and yet for some strange reason just kept on blowing the things up until the early 60s, when finally other scientists were able to show that strontium 90 was accumulating in the teeth of children all over the US...

http://www.nytimes.com/2011/01/10/science/10reiss.html

[chownah]

Since you are a phsicist and I'm a rice farmer I would appreciate your views on my assertion that there actually is a chain reaction going on in the reactors and this is why they need to be cooled

Hi Chownah,

It's a chain reaction if the activity (number of nuclei disintegrating) is increasing. That's what you need for an atomic explosion.

If I understand the reactor design correctly, without the water to slow down the neutrons (so that they can be absorbed by other nuclei, which subsequently disintegrate, producing more neutrons...) activity will decrease. (But there are other ways of doing this "moderation" of the neutrons, so what I say in this paragraph may not be technically correct.)

But though the activity is decreasing, the rods will still be heating up and will melt if they are not cooled, which is the problem...


Mike

Mike,
I believe you are incorrect on two things.

1. A chain reaction can occur without an increase in activity.....if the activity is increasing without control then it is called a runaway chain reaction....chain reactions can be moderated so that they are at one level or another...that's what the control rods on a reactor are used for.
2. Assuming that whatever is dissipating the heat does so at a constant rate or even a rate proportional to the temp of the surface of the rod then if activity is decreasing then the rod temperature will be decreasing...not heating up.....heating up is caused by an increase in thermal energy which in this case is caused by neutron impacts...heating up then is an indication of increased neutron impacts...at least this is all true if you begin at a steady state at the lower temperature (I have made an "initial steady state" to simplify the discussion as a full on discussion of dynamic state situations would probably lose most everyone at the outset).

but....being a rice farmer I'm always aware that my views in these matters may be wrong so I'm open to further discussion especially if it comes from a physicist.....

chownah

[nathan]

Very disappointing to be lied to, but I was told the situation in Japan was impossible.

It's making take a long hard look at many technologies I support(ed), not just nuclear fission power.

I don't know that you were deliberately lied to. What seems to happen is that expertise regarding what is known in various fields of predominantly objective knowledge like physics, something which many very intelligent people have acquired, and the deference that generally accompanies these accomplishments frequently becomes the hubris that one knows everything that can be known and/or that one is in control of these same physics, which is demonstrably not true. For better or for worse we have the dhamma inherently within the elements from which we and the world were formed, are formed and will re-form in the future and the dhamma will demonstrate the truth of our inability to exert complete control over these various forms regardless of what we have been told or by whom. Sometimes wisdom comes pleasantly and quickly sometimes slowly and painfully.

upekkha

[Kim O'Hara]

Hmmm. I believed nuclear was safe. I believed no country would take such huge risks without failsafes. I sat in countless hours of lectures as professor after professor explained how nuclear disaster was now impossible. I believed them. They were wrong, and so I am wrong.

Very disappointing to be lied to, but I was told the situation in Japan was impossible.

It's making take a long hard look at many technologies I support(ed), not just nuclear fission power.

It's good to find someone open-minded enough to reconsider their position on the issue, Mawkish.

There's a scientific maxim which you're probably familiar with: Extraordinary claims demand extraordinary proofs.
I'd like to propose a similar formulation for this situation: Extraordinary risks demand extraordinary safeguards.
In fact, to my mind, some risks are so great that no safeguards are adequate even if their probability is extremely low. We do have alternatives to nuclear power that don't have its inherent hazards, so they are automatically worth pursuing.


Kim

[Annapurna]

Hmmm. I believed nuclear was safe. I believed no country would take such huge risks without failsafes. I sat in countless hours of lectures as professor after professor explained how nuclear disaster was now impossible. I believed them. They were wrong, and so I am wrong.

Very disappointing to be lied to, but I was told the situation in Japan was impossible.

It's making take a long hard look at many technologies I support(ed), not just nuclear fission power.

Mawkish,

THANK YOU.

I am moved by your words.

Greenpeace and other environmental specialists always predicted this and got mocked.

If you haven't yet, I recommend 2 movies to you:

The China syndrome
But even more:

Silkwood.

It is a real case.

Don't believe everything you are told.

I'm not being condescending, I once was where you are now.

It's sobering.

[dhammapal]

The problem with solar and wind is that the sun goes behind a cloud and the wind doesn't blow. We need a baseload source of energy.

[chownah]

mikenz66,
from wikipedia (not always the best source)under the subject "nuclear chain reaction":
"....
Fission chain reaction

Fission chain reactions occur because of interactions between neutrons and fissile isotopes (such as 235U). The chain reaction requires both the release of neutrons from fissile isotopes undergoing nuclear fission and the subsequent absorption of some of these neutrons in fissile isotopes. When an atom undergoes nuclear fission, a few neutrons (the exact number depends on several factors) are ejected from the reaction. These free neutrons will then interact with the surrounding medium, and if more fissile fuel is present, some may be absorbed and cause more fissions. Thus, the cycle repeats to give a reaction that is self-sustaining.

Nuclear power plants operate by precisely controlling the rate at which nuclear reactions occur, and that control is maintained through the use of several redundant layers of safety measures. Moreover, the materials in a nuclear reactor core and the uranium enrichment level make a nuclear explosion impossible, even if all safety measures failed. On the other hand, nuclear weapons are specifically engineered to produce a reaction that is so fast and intense it cannot be controlled after it has started. When properly designed, this uncontrolled reaction can lead to an explosive energy release.
....."

This seems to indicate that a nuclear chain reaction only needs to be self sustaining at most and that it can be modulated by " precisely controlling the rate at which nuclear reactions occur,..."
Thus it seems that there is no requirement that there be an increase in activity.....and if this is so then there infact IS a chain reaction going on in the Japanese reactors....and this chain reaction is the cause of the heating which is causing the current problem.....am I reading this correctly?
chownah

[chownah]

The problem with solar and wind is that the sun goes behind a cloud and the wind doesn't blow. We need a baseload source of energy.

It is possible to use storage as the baseload source of energy.....in the near future many cars will have batteries and this collectively will provide a large storage capability to provide baseload supply.....there are of course other methods like pumping water into reservoirs above hydro dams during peak times to be passed through the generators at night for instance....also....if homes are equipped with fuel cells they could generate electricity and heat at night from hydrogen produced during peak times.....
chownah

[mikenz66]

Hi Chownah,

I gave you a summary of how I saw it,

This is the sort of way it is usually stated:
http://en.wikipedia.org/wiki/Chain_reaction

A chain reaction is a sequence of reactions where a reactive product or by-product causes additional reactions to take place. In a chain reaction, positive feedback leads to a self-amplifying chain of events.

So as far as I understand it is usual to say "chain reaction" is when there is an increase in activity. As you say, in a reactor there is a careful balance to prevent it running out of control, so in that case the situation is complicated and how you label it is, I guess, a matter of taste.

As for the current situation, my understanding is that if the water has evaporated then activity stops increasing. But it doesn't stop immediately (or completely), because there is still some neutron capture even without the water, so a lot of heat is still being produced, which will lead to melting of the rods.


Mike

[Kim O'Hara]

The problem with solar and wind is that the sun goes behind a cloud and the wind doesn't blow. We need a baseload source of energy.

It is possible to use storage as the baseload source of energy.....in the near future many cars will have batteries and this collectively will provide a large storage capability to provide baseload supply.....there are of course other methods like pumping water into reservoirs above hydro dams during peak times to be passed through the generators at night for instance....also....if homes are equipped with fuel cells they could generate electricity and heat at night from hydrogen produced during peak times.....
chownah

Well said, chownah
Can I add ...
(1) Base-load solar is on the way: http://blog.cleantechies.com/2011/03/15/baseload-247-solar-is-here/
(2) With larger power grids and multiple sources of renewable energy, fluctuations are to some extent evened out.
(3) With enough solar during the day and wind power whenever it is available, coal-fired (and nuclear) power stations can be run at lower loads and powered back up as needed, still avoiding those CO2 emissions.

The future, IMO, is going to be one of throwing every possible solution at our problems. None of them will be a complete fix, none of them can be an instant fix, but with all of them together we can avoid much human suffering.

Kim

[Justsit]

It's making take a long hard look at many technologies I support(ed), not just nuclear fission power.

Ah, Mawkish, you are actually in the enviable position of having some of your beliefs challenged. Now, after you've take that long hard look at the technology issue, you will perhaps be more likely to closely examine some other long held beliefs, in other areas of life. This is really a great opportunity to crack the containment vessel of ego - not a bad thing!

[Jhana4]

I've actually learned a lot of positive things about nuclear power as a result of engineering types standing up for nuclear power during this crisis. However, that was just the technical side of the issue. These people forgot the human failings side of it, which I believe is responsible for this crisis and why I am going to continue to be against nuclear power in my own country ( USA ).

I saw on CNN yesterday that the design for this plant was considered flawed back when it was built in 1972. Yet it was built and built in an earthquake zone nonetheless.

If people as conscientious and disciplined as the Japanese can do that, it makes very frightened with regards to nuclear power in the U.S.. Here, corporations being able to get away with selling people out is a much more normal occurrence ( example BP cutting corners on equipment and safety procedures).

[Mawkish1983]

Supply and demand. It seems that the solution is for everyone to make a joint-effort to reduce how much electricity we use. If we use less than we can generate via renewable means, there will be no need for fossil-fuel or nuclear powered plants.

In some ways I envy people who lived at the time of the Buddha.

[Mawkish1983]

If you haven't yet, I recommend 2 movies to you:

The China syndrome
But even more:

Silkwood.

I'm afraid I don't have very much free time at all, but I will add them to my 'todo' list (which is growing longer by the day).

Thank you Annapurna.

[poto]

Emergency neutron absorbers (boron is common) should have been automatically deployed, shich would have stopped the reactor heating up by stopping the chain reaction. It seems this hasn't happened, because the core is heating up; the chain reaction may be happening still. It shouldn't be, but it looks like it is.

Boron was injected. In fact, they injected boron almost right away, writing off the reactors as a total loss. There is no sustained reaction going on in the cores. What they are dealing with is the decay heat. Within a day or so of shutting down the reactor, the decay heat is reduced to about 1% of what it was when operating. Of course, that 1% is still millions of watts of thermal energy and needs to be dealt with.

Also, I heard the fire in reactor 4 was from leaked oil, not burning fuel rods as some in the media have claimed.

It is unfortunate that a small amount of fission products were released. However, there still has not been a large release and nothing really nasty so far. Every day that goes by without a complete meltdown is a good thing. More decay heat is dissipated with every passing hour. Either in a few days or a few weeks the reactors will cool enough to be below the boiling point of water. Then they won't have any more pressure or steam building up and things will be pretty much under control.

Had this been a hydro-electric dam or a natural gas plant that failed in the earthquake or subsequent tsunami, a lot more people would have been injured or killed. Generating gigawatts of power has inherent dangers. Nuclear power takes something like 100k times less the amount of fuel of other power sources. That means less deaths and injuries all the way from the mines to the power plants. Orders of magnitude more people have died mining coal than uranium. Wind turbines kill scores of birds every year, and there have been accidents resulting in deaths (people falling off) from wind turbines. Numerous people have died just from touching high voltage power lines. Any way you look at it, there are risks associated with building and maintaining a large high capacity grid. People are unfortunately going to be killed, no matter what technology we employ. The best we can do is attempt to build more safeguards into our systems and learn from past mistakes.

I'm keeping my fingers crossed that this tragedy will spur the development of the thorium fuel cycle. I'd love to see us drop our existing nuclear technology for thorium. Unfortunately, I think with the fear and panic in the general population, and politicians responding to that will squash a lot of future nuclear power development. This is most disappointing to me. I want to see our civilization reach out into space and we're going to need this type of technology to survive if we ever hope to colonize that last greatest frontier. Somehow I doubt that wind turbines and solar panels will be enough to power a space-faring civilization.