21st Century Energy

Reflections on fusion history, current events, and predictions for the 'fusion powered future.
TBenson
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Re: 21st Century Energy

Post by TBenson » Thu Oct 27, 2005 4:25 am

Interesting comments Anonymous guy, but regarding breeding plutonium...actually it's not at all difficult to breed more plutonium than the U235 that you are consuming. There have been many, many reactors already tested that burn up to 30% of the uranium, which includes essentially ALL of the .7% U235 plus another 30% of the U238. Additionally it's already been demonstrated that you can also breed Thorium in a 50/50 mix with the uranium.

What this all means...with properly designed reactors, current Uranium stocks are good for a minimum 200 years. Just the burnt leftover fuel currently being stored at reactor sites across the US could be burnt down in advanced reactors to provide 100 of those 200 years.

Plus, there are vast Uranium deposits we haven't even found yet, simply because nobody is looking.

Plus, we could use Thorium.

The bottom line is, nuclear fuels in advanced reactors could power the entire planet earth for a thousand years.

The claim that "the mining and extraction of Uranium requires burning more fossil fuels than the Uranium produces" is utterly untrue. In fact, the energy content of Uranium is so astronomical, it is by far the LEAST energy to mine and process of any energy source.

MARK-HARRISS
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Re: 21st Century Energy

Post by MARK-HARRISS » Thu Oct 27, 2005 7:07 am

I think there's three times as much thorium as any uranium, and all of that can used as a fuel once it's been irradiated.

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Richard Hull
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Re: 21st Century Energy

Post by Richard Hull » Thu Oct 27, 2005 1:44 pm

As I said before, to keep the US going with electricity pouring out of the outlets using only internal supplies, and not one imported BTU, it will be a situation of only coal or nuclear or both...........probably both. All the renewables will be relegated to the job of assist only.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
Retired now...Doing only what I want and not what I should...every day is a saturday.

Goldenspark
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Re: 21st Century Energy

Post by Goldenspark » Thu Oct 27, 2005 9:30 pm

"Wind has some merit, but it is dependant on batteries"
Not correct. There is now a massive push for offshore wind and wave that connects direct to the grid. Wind generators at 5MW each are possible now, with designs looking to go to 10MW. There is no doubt that these renewables must figure in the energy economy, if only because their time to generate is relatively short.

AnGuy
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Re: 21st Century Energy

Post by AnGuy » Thu Oct 27, 2005 11:20 pm

>...actually it's not at all difficult to breed more plutonium than the U235 that you are consuming. There have been many, many reactors already tested that burn up to 30% of the uranium, which includes essentially ALL of the .7% U235 plus another 30% of the U238. Additionally it's already been demonstrated that you can also breed Thorium in a 50/50 mix with the uranium.

No, That would mean nuclear energy is perpetual device. Creating more energy then consumed. All energy systems have entropy. When U235 splits, two neutrons are produced. At least one neutron must be used split another U235 atom so the reaction can continue. Plutonium is created when U-238 captures a thermal neutron . The U-239 decays into Pu-239. However very many neutrons are lost, becuase they are not captured and exit the bounds of the reactor, or are absorbed by other elements inside the reactor. The end result is the breeder reactors make better use of the U235 supply but the do not produce more fuel than consumed. Otherwise there would be no need to continue mining Uranium. Also remember the original purpose of breeder reactors was to create fissible material for bombs, not power generation.

>Plus, we could use Thorium.

Natural Thorium is non fissible becuas the fissible isotopes have short half-lives. India converts non-fissible Thorium into fissible material by using a small stock of Uranium. India has large quanities of Thorium but have very little Uranium and I believe they import all of their Uranium. Converting U238 into P-239 is more efficient anyway. India must use Thorium simply because they dont have any large natural uranium mines, and want to make the most of the fissible material they have on hand.

The only naturally occuring fissible materal available on Earth is U-235. Miniscule amounts of Th-233 or other fissible materials exist because of U-235 decay chain. This is because all fissible isotopes except U-235 have very short half-lives (on a Geological time scale). During the past 4.5 billion years, all Fissible materials have decayed into no-fissible materials. U-235 has a very large half-life, however even much of the planet's original stock of U-235 has already decayed. This is why only 0.7% of natural Uranium consists of U235.

longstreet
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Re: 21st Century Energy

Post by longstreet » Thu Oct 27, 2005 11:43 pm

I think you have a misunderstanding of what nuclear energy is. There is a huge amount of energy stored in the strong force. I hate making generalities, but really anything above iron has energy stored such that when atoms are broken apart the resulting matter has less energy in the strong force, giving off the difference as kinetics. The problem is getting a neutron to effectively split the atom.

Think of it as a giant brick sitting next to a ledge. U-235 can easily fall off the ledge and we extract the energy when it does, but U-238 is a little more stable so it doesn't fall off as much. When you breed plutonium it is much easier to push off, and you only sacrifice a tiny amount of energy to do it. The ledge is still huge and you can still get a lot of energy when it falls off, a lot more than what you used to make it a little less stable.

Even assuming you are cleaver enough to do all nuclear transitions there is a hard limit to the energy you can get. But this has nothing to do with entropy. If you want to talk about converting the nuclear heat into electricity, then that's where entropy comes in. But not in converting nuclear energy to kinetic/heat energy. That is more of a conservation of energy problem.

edit: I happen to think that I should say there is no problem with entropy because the potential energy of the system does not increase when you breed plutonium. Potential nuclear energy is always decreasing in all these reactions. It's just there is so much of it that we can waste some to make it easier on our reactors.

Here is a page that describes this better: http://hyperphysics.phy-astr.gsu.edu/hb ... ucbin.html

Carter

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Richard Hull
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Re: 21st Century Energy

Post by Richard Hull » Fri Oct 28, 2005 1:47 pm

All fission energy is just the reclamation of locked down fusion energy and that is the stored dynamic energy of gravitation that fused such atoms in the first place. All nuclear energy be it fusion or fission, as it occurs in nature, is 100% gravitational in origin.

There is no perpetual moion machine here, just a nearly undamped oscillator universally exchanging potential energies.

Fission is not much different from burning coal or oil except one utilizes chemical (electron orbital or coulombic exchanges) and the other uses gravitational exchanges long ago locked within the various nuclear forces.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
Retired now...Doing only what I want and not what I should...every day is a saturday.

AnGuy
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Re: 21st Century Energy

Post by AnGuy » Sat Oct 29, 2005 12:07 am

>Think of it as a giant brick sitting next to a ledge. U-235 can easily fall off the ledge and we extract the energy when it does, but U-238 is a little more stable so it doesn't fall off as much.

Only odd numbered isotopes are capable of sustaining fission reactions . Odd number isotopes such as Pu-239, U237, U235,U233,Th233, etc. release more than one neutron when they are split. Even number isotopes decay with alpha particles or release less than two neutrons when split and therefore cannot be used to sustain the reaction . Even numbered istopes such as U238 also required vast Neutron Energies to be split. I believe U238 requires Neutron energies > 1 MeV to split. These higher energy Neutrons tend to pass through heavy isotopes without any interactions. In breeder reactors, the neutrons produced by U235 are slowed down so they can be captured by U238 which later transmute from U239 to Np239 to Pu-239.


>Even assuming you are cleaver enough to do all nuclear transitions there is a hard limit to the energy you can get. But this has nothing to do with entropy.

Sure it does. The lower the entropy a system has, the more difficult it is to extract energy. Its seems very unlikely that we will be able to extract energy from the nuclear interactions you are suggesting. Fusion is probably by far much more practical, and after 50 years and 100 billions poured into Fusion reseach, we still can't get a positive energy gain.

>I hate making generalities, but really anything above iron has energy stored such that when atoms are broken apart the resulting matter has less energy in the strong force, giving off the difference as kinetics. The problem is getting a neutron to effectively split the atom.

There lies the true problem. Virtually every atoms doesn't want to give up free neutrons. In 99.9% of all instances of natural radioactive, atoms give up a alphas instead of free neutrons.

BTW: The original point I was making was on the practicality of using Fission as a fossil fuel replacement. The bottom line is that nuclear fission isn't going to save us from an energy crash, at best it could postpone the inevitable by a couple of decades (probably a lot less). Certainly once Peak Oil is global reconized those that have large Uranium reserves aren't likely going to want to share it with the have-nots, especially since its easily weaponized. Those with remaining Oil reserves are likely to act similarly. Thoses that have neither Oil or Uranium (or lack the capacity to use Nuclear Energy) are screwed. Peak Oil will result in Peak Energy since mining and refining Uranium is dependant on Oil.

Heres a couple of good articles to read:
http://www.dieoff.com/page125.htm (Energy's role in our civilization development)

http://www.lifeaftertheoilcrash.net/ (Peak Energy)

AnGuy
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Re: 21st Century Energy

Post by AnGuy » Sat Oct 29, 2005 12:27 am

>>"Wind has some merit, but it is dependant on batteries"

>Not correct. There is now a massive push for offshore wind and wave that connects direct to the grid. Wind generators at 5MW each are possible now, with designs looking to go to 10MW. There is no doubt that these renewables must figure in the energy economy, if only because their time to generate is relatively short.

I was referring to wind generation for individual homes. As far as commerical system there are limits too. Wind generation is dependant on a steady stream of wind. Not every place is suitable. and the amount of wind provided at any given time is unpredicable. For instance, One minute a 10 MW wind turbine might actually produce10 MW of power, but the next minute, the wind speed might fall and the turbine will only generate 3 MW. Unfortunately, electricity supply isn't elastic. If the load is 10 MW its needs a steady supply at 10MW, other wise pretty much all devices using electricity stop working. In many devices, noisy power will result in an early demise. Any national power grid based solely on Wind must include a fast storage system that can steady the output during wind power output fluxuations. It probably very unlikely that a system robust enough could be implemented without the use of base load fossil (or nuclear) power plants.

Q
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Re: 21st Century Energy

Post by Q » Sat Oct 29, 2005 1:32 am

i thought this was a good place to post this.

today's edition of the asheville citizen times had a small article on the front page about how duke power is wanting to build a new nuclear plant somewhere in the carolinas. the time table suggested is that the site should be choosen by the end of next year, and the reactors should be online by 2015 (assuming that the plan goes through).
not much else was said, though most of the article was the typical responces from the obviously "against anything nuclear" crowd. the only posative aspect mentioned in the article was that it would generate roughly 1000 full time jobs.
some how i doubt that nuclear power will be considered before it will be to late to build.

Q

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