D Tibbets wrote:KitemanSA wrote:Dan,
Please read the first chapter of:
The Physics of Inertial Fusion.........
I think this will be my final argument on the nuclear binding energy, the mass defect, excess or deficit. Mostly because it is extremely complex the more you look at it and it is making my head hurt.
First- I argue that fusion of light elements releases energy (is exothermic), while fission of heavy elements releases energy. For both processes to work there has to be a balancing point between the competing processes ........................
My headache is better, so I will try again...
I cannot describe well the dead end for exothermic fusion reactions (Fe) , but if you are interested look at the information on page 4 of this presentation. The binding energy curve is displayed like I suggested earlier. The iron nucleus has the least energy per nucleon. LEAST ENERGY PER NUCLEON- think about that. If a nucleon (like a proton or neutron) has more energy outside the iron nucleus, compared to any other nucleus (lighter or heavier) then energy is released as the nucleus approaches the iron end point. Iron is the minimal energy state for any nucleus (again remember we are talking about +/_ energy associated with fusion or fission reaction, not matter- antimatter annihilation). This is obvious from the inverted Binding energy graphs- like the one in the referenced link. Any reaction that approaches this state can release excess energy, and any reaction going away from this minimum energy condition must absorb externally supplied energy. Any nucleon added to iron will contain more energy. Any nucleon removed from Fe will contain more energy. This is extreamly important, If this is not the case, then stars would be completely different.
If you are interested pursue stellar evolution
Just like in chemistry, once a certain threshold of energy is reached a reaction will tend to proceed to the least energetic product. In chemistry this is Gibbs free energy. In fusion it is the energy needed to overcome the Coulomb repulsion. It is not the product that has the most energy that is the end product, but the product that has the least energy (exothermic). The reverse can happen, but only if you add external energy (endothermic). Also, a product with more energy can the reactant(s) can be produced, provided that the final energy state of the product is less than the Gibbs free energy (keeping things simple and avoiding tunneling, etc). In some ways this has corollaries with nuclear reactions. Isomers, etc. can be considered as intermediaries. Note that catalysts, by definition does not change the reactant and product energy states. It does change the threshold that needs to be reached for the reaction to proceed. In chemistry this changing the Gibbs free energy. Also, by definition a catalyst is not consumed in a reaction, but only promotes the reaction. So, at least from a definition point of view- the nickel is not a pure catalyst, but a reactant. This is picky, but that nickel is apparently a reactant in the Rossi device, as I understand it, the situation is completely different from LENR claims where the nickel (or other metal) is a presumed catalyst, that permits light element fusion (like D-D) at remarkably low energy conditions (like lowering the Gibbs free energy- Coulomb repulsion). This does not challenge the Fe lowest energy position in the binding energy model. But, the Rossi claims do!
A nucleus with more energy (more mass deficit in this discussion- eg Cu63) yields Ni62 + proton +energy. This is fission
Nucleus with more energy - eg Fe 55 + neutron yields Fe56 + energy. This is fusion. These two reactions both produce exothermic energy. That would be impossible if there was not some less energetic product between these two isotopes. There CANNOT be a continuous process of excess energy release from fusion as nuclear mass (higher elements) are formed, unless you assume that fission is always endothermic, or fusion is always endothermic, etc. You cannot have both!
Despite looking I have not found any authoritative statements that are more clear than those I have already presented.
The Stellar evolution and nucleosynthesis is stars and supernova often are less obtuse than the physics discussions. Read some of this and ask yourself how can two opposing processes (fusion and fission) produce exothermic energy if your assumption is correct- that adding nucleons to a nucleus always releases energy. IE- that fusion always releases energy, irregardless of the final nuclear size. If that was the case several things are unavoidable. Stars would continue to burn well past iron (or even uranium) , and nuclear fission reactors could not work. There absolutely has to be this intermediate minimal energy point. And this is apparent in both physics and astronomy reasoning. The description of this may be obtuse but the experimental and theoretical consequences are not. If you anticipate this energy balance minimum point to occur at some more massive nucleus- like lead, that would be a work around for the Rossi claims, but it is completely contrary to the understanding of stars, if not other physics experiments and theory.
Again there has to be a low energy point between exothermic fusion and exothermic fission. Note that this low energy point is the change in the nuclear energy, not the total energy. Of course a Uranium atom has much more energy than a helium atom (E=MC^2), but that is not the issue. It is the nuclear binding energy, or packing density that determines the energy that can be implanted or removed from the nucleus as it grows or shrinks.
Again, the astronomy discussions are more obvious. It is not my confusion that impedes my arguments so much, as the vocabulary and my presentation skills that impedes my ability to communicate the absolutely necessary and accepted view on this topic.
Look at page 4:
http://www.ucolick.org/~rab/Ay2-Fall09/ ... /wk7_1.pdf