# Nuclear reactions

1. Jul 8, 2008

### solars

Fusion reaction is not possible at room temperature because:
1) nuclei only moves at high temperatures
2) nuclei move too slowly at room temp

Another question that I am also wondering is that when comparing the fission of a uranius nuclear to fusion of deuterius. Which one releases more envery. or is the amount of energy dependent on how much reactants are involved?

2. Jul 8, 2008

### Hootenanny

Staff Emeritus
The latter is indeed correct.
The amount of energy released depends on a number of factors including the isotope used, the amount of fissionable material and the total decay time. However, when comparing the energy released by the fission/fusion of different radioactive isotopes a quantity known as the Decay Energy or Q value is used to compare the energy released by a specific decay to other decays.

The Decay Energy is defined as the difference is mass between the parent and daughter nuclei multiplied by c2:

$$Q = \left[\left(\text{Mass of Parents}\right) - \left(\text{Mass of Daughters}\right)\right]c^2$$

3. Jul 8, 2008

### Staff: Mentor

Fusion reaction is possible at room temperature

See for example S.E. Jones, "Muon-Catalysed Fusion Revisited," Nature 321: 127-133 (1986)

4. Jul 8, 2008

### Hootenanny

Staff Emeritus
I could have swore the OP said fission, I guess I need my eyes testing .

5. Jul 8, 2008

### solars

Are you referring to cold fusion?

6. Jul 8, 2008

### solars

thanks for clearing things up!

7. Jul 8, 2008

### Staff: Mentor

Yes. But this is not cold fusion that you may have heard about, with heavy water electrolysis. This is completely different process, in which you have (so far) to put more energy into system that you will get from it. First, you generate muons. They have identical charge as electron, so if they are combined with D or T nuclei they produce molecules similar to H2+. But muons are much heavier then electrons, so nuclei in such molecule are so close that they can fuse. And it happens at room temperature.

8. Jul 8, 2008

### Andrew Mason

This is not possible at room temperatures. The coulomb repulsion between two nuclei is huge I don't see how the nuclei will never get close enough at 273K. Mind you, temperature is a statistical distribution, so individual molecules can have greater energy than that mean. However, you need temperatures of about 120,000,000 K to fuse two hydrogen nuclei.

Although muon molecules (which would last a very short time - microseconds) might be smaller (assuming both atoms had their electrons replaced by muons at the same time) getting the nuclei to fuse requires overcoming the coulomb repulsion between protons. This requires energy (about .01 Mev). Where does the energy come from?

AM

9. Jul 8, 2008

### Staff: Mentor

Wikipedia article at http://en.wikipedia.org/wiki/Muon-catalyzed_fusion lists several papers on the subject published in peer reviewed journals. Basic idea is that the molecule is 207 times smaller than 'normal' H2+ molecule, which means separation between nuclei is small enough for tunneling. I suppose numbers given in the wikipedia article are taken from the papers listed.

To be honest - I will be not able to answer your questions. I know about the muon catalyzed cold fusion from a friend of mine, he is radiochemist working at Warsaw University, for some reasons he was investigating the idea last year and told me about over a beer.