- #1
jschmidt
- 22
- 0
Hello,
I'm wondering if the brains here can help me point to some good sources for some particular information I'm looking for, and perhaps help me figure out the correct math for some problems I'm interested in solving.
I've seen a statement that, in general, ball-park figures, nuclear fission releases about a million times more energy than combustion. I believe that is at a discrete 'event' level, by which I mean, for nuclear fission, one event is the fissioning of a single nucleus (or a decay event, which is slightly different than fission, but also yields energy), while for combustion, I think a single event would be the binding of one atom of hydrogen or carbon, with one or two atoms of oxygen?
I know that the unit of energy usually used for discussing how much energy such atomic events release is the electronvolt, which according to Google, has the following equivalence relationship:
1 electron volt = 1.60217646 × 10^-19 joules
A Watt is one joule per second, so to produce 1 watt of power continuously, you need to release 1.60217646 × 10^19 electron volts in reactions, yes? I think I saw someone once say something along the lines of a combustion event releasing something like 3 electron volts, and nuclear fission releasing 1.something million eV? Can anyone provide me a good source, for citation, for the amounts of energy released by different combustion and nuclear reactions (e.g. a hydrogen combustion releases a slightly different amount of energy than a carbon combustion, which is slightly different than a nitrogen combustion, all of which will be happening in coal combustion, I believe, but all in the same order of magnitude, while a U-233 fission might release a bit more or less energy than a U-235 fission, which is different than a Pu-239 or Pu-240 fission, but they will all release about the same order of magnitude of energy, yes)?
Once I have the figures to work with, I want to do some math to figure out, in approximate values, how many combustion reactions happen per second to produce each watt of thermal power, vs how many fission and decay reactions happen per second in nuclear to produce each watt of power.
Can anyone provide any source for how much energy is released by various decay events which are common in nuclear fuel? I know that decay contributes a minority, but not negligible, amount of the power in a nuclear reactor. Obviously, there was enough decay heat to cause serious problems at the Fukushima-1 nuclear plant. . .
Bringing this back to Nuclear vs Coal, and the statement that nuclear fission releases about a million times more energy than combustion, in discussing nuclear power with people, and why it takes much less nuclear fuel than combustion fuel to produce a certain rate of energy, my understanding is that, ultimately, what it comes down to is this:
We want to get some amount of power out of an electric plant. Thermodynamic efficiencies of steam turbines give us basically, about 30-40% efficiency, resulting in needing to 'burn' (I use the term loosely here, to also include nuclear fuel in a critical reaction state) fuel at some rate, X. The rate of 'burn' for coal is about a million times faster than the burn rate for nuclear fuel, to produce the same rate of thermal heating, yes? This in turn means that, over time, you need about a million times more coal than nuclear fuel
Is that about right?
Now, it's also my understanding that current reactor technology in use in the U.S. (I think the Canadian CANDU reactor is slightly more efficient, but not greatly so) is very inefficient with its fuel, extracting only about .5% of the energy from Natural Uranium (partly because we enrich the natural uranium up to Low Enriched Uranium (LEU), during which process, we create about 5 units of 'depleted uranium' for each unit of LEU which ends up in a reactor)? Is that figure correct? I've seen that figure (or something close to it) multiple places, but never with a citation. Can anyone provide me with a strong citation to use for reference for the correct figure?
Because of that inefficient use of nuclear fuel, the current nuclear to coal ratio (by mass) is more on the order of 1:5,000 than 1:1,000,000?
But, with next generation reactors, such as Thorium or Fast Breeder Reactors, we could get much, much closer to that 1:1,000,000 (due to technology limits, I wouldn't be surprised if we couldn't get exactly to 1:1,000,000, but I could live with 1:900,000 *grin*), correct?
I'm wondering if the brains here can help me point to some good sources for some particular information I'm looking for, and perhaps help me figure out the correct math for some problems I'm interested in solving.
I've seen a statement that, in general, ball-park figures, nuclear fission releases about a million times more energy than combustion. I believe that is at a discrete 'event' level, by which I mean, for nuclear fission, one event is the fissioning of a single nucleus (or a decay event, which is slightly different than fission, but also yields energy), while for combustion, I think a single event would be the binding of one atom of hydrogen or carbon, with one or two atoms of oxygen?
I know that the unit of energy usually used for discussing how much energy such atomic events release is the electronvolt, which according to Google, has the following equivalence relationship:
1 electron volt = 1.60217646 × 10^-19 joules
A Watt is one joule per second, so to produce 1 watt of power continuously, you need to release 1.60217646 × 10^19 electron volts in reactions, yes? I think I saw someone once say something along the lines of a combustion event releasing something like 3 electron volts, and nuclear fission releasing 1.something million eV? Can anyone provide me a good source, for citation, for the amounts of energy released by different combustion and nuclear reactions (e.g. a hydrogen combustion releases a slightly different amount of energy than a carbon combustion, which is slightly different than a nitrogen combustion, all of which will be happening in coal combustion, I believe, but all in the same order of magnitude, while a U-233 fission might release a bit more or less energy than a U-235 fission, which is different than a Pu-239 or Pu-240 fission, but they will all release about the same order of magnitude of energy, yes)?
Once I have the figures to work with, I want to do some math to figure out, in approximate values, how many combustion reactions happen per second to produce each watt of thermal power, vs how many fission and decay reactions happen per second in nuclear to produce each watt of power.
Can anyone provide any source for how much energy is released by various decay events which are common in nuclear fuel? I know that decay contributes a minority, but not negligible, amount of the power in a nuclear reactor. Obviously, there was enough decay heat to cause serious problems at the Fukushima-1 nuclear plant. . .
Bringing this back to Nuclear vs Coal, and the statement that nuclear fission releases about a million times more energy than combustion, in discussing nuclear power with people, and why it takes much less nuclear fuel than combustion fuel to produce a certain rate of energy, my understanding is that, ultimately, what it comes down to is this:
We want to get some amount of power out of an electric plant. Thermodynamic efficiencies of steam turbines give us basically, about 30-40% efficiency, resulting in needing to 'burn' (I use the term loosely here, to also include nuclear fuel in a critical reaction state) fuel at some rate, X. The rate of 'burn' for coal is about a million times faster than the burn rate for nuclear fuel, to produce the same rate of thermal heating, yes? This in turn means that, over time, you need about a million times more coal than nuclear fuel
Is that about right?
Now, it's also my understanding that current reactor technology in use in the U.S. (I think the Canadian CANDU reactor is slightly more efficient, but not greatly so) is very inefficient with its fuel, extracting only about .5% of the energy from Natural Uranium (partly because we enrich the natural uranium up to Low Enriched Uranium (LEU), during which process, we create about 5 units of 'depleted uranium' for each unit of LEU which ends up in a reactor)? Is that figure correct? I've seen that figure (or something close to it) multiple places, but never with a citation. Can anyone provide me with a strong citation to use for reference for the correct figure?
Because of that inefficient use of nuclear fuel, the current nuclear to coal ratio (by mass) is more on the order of 1:5,000 than 1:1,000,000?
But, with next generation reactors, such as Thorium or Fast Breeder Reactors, we could get much, much closer to that 1:1,000,000 (due to technology limits, I wouldn't be surprised if we couldn't get exactly to 1:1,000,000, but I could live with 1:900,000 *grin*), correct?