For those still interested in the possibility of energy release (heat) from the 62Ni + P reaction that Rossi claims-
Sorry for the delay, but I needed to try to look up more resources and cogitate for a while before trying again to explain why Ni62 is the tipping point for fusion / fission exothermic reactions. The arguements have become circular and positions are entrenched, but I'll try again.
If you claim that fusion past 62Ni still releases energy- increases KE of the system, as would seem to be the case if you only consider the total binding energy graph, while ignoring the two opposing force contributions. Then the Universe could not exist as we know it. There is an exucuse that might allow this though. That the energy balance issues are muted because of the statistical likelyhood of various fusion reactions past nickel. Neutron nucleosynthesis would seem to be a problem, but concidering that free nucleons are aviable in large numbers only in special situations, and many of these light element neutron producing reactions are endothermic themselves.
The problem with this excuss, is that it does not explain the exothermic fission reactions. If continous nucleon additions to a nucleus results in a lower potential energy state for the nucleus (equivalent to a more stable state) and a resultant increased kinetic energy state for the system, how can the reverse occur spontaniously, and how can the kinetic energy of the system be increased by fission. It violates basic thermodynamics in this model. Both can only occur if there is a turn around point/ minimal potential energy condition somewhere between exothermic fusion and exothermic fission. This has been measured as occuring at 62Ni.
Despite some sloppy efforts on my part, the fact remains that many resources on the NET and nuclear texts clearly stipulate that fusion does not produce energy (exothermic) past 62Ni. Despite chrisMB's efforts for graphing total binding energy per nucleus- element- isotope, this is a graph that is not seen in references. Why? It is because it is not good for calculating the energy direction. It is convient for calculating delta energy, as it eliminates a needed step when using the binding energy per nucleon tables/ graph, but it is missleading because the total binding energy does not determine the energy direction, but the binding energy per nucleon does. This is stated many times in various resources.
The best mechanistic explaination is that the exothermic- endothermic determination is not the binding energy of the nucleus, but the potential energy of the nucleus. This is why I think the inverse of the binding energy per nucleon graph is useful It more directly represents this minimal bound potential energy state.
http://www.schoolphysics.co.uk/age16-19 ... bfca51b99a
The stability of the nucleus determines the energy direction. As in any reaction, the product with the least potential energy is the most stable and reactions that go towards this state release kinetic energy in the process. The nuclear binding energy per nucleon represents the potential energy of the nucleus. The binding energy per nucleon is a binding energy/ an attractive energy and this is generally represented as a negative number in physics. Repulsive energies are represented as positive numbers. The binding energy per nucleon is the sum of these two numbers. Both are energy and contributes to the total binding energy quantity/ mass deficite, but it is the sum of these negative and positive numbers that determines the potential energy/ packing fraction/ nuclear density/ stability. And it is this that determines the potential energy of the nucleus- ie: the binding energy per nucleon. The convention of representing the binding energy as a positive value, a peak, can contributes to the confusion.
The link below gives the best explaination I have seen. It says that the strong force tries to compact the nucleons more and more, but due to the short range of the force and the finite size of the nucleons,it saturates/ approaches a slope of zero. If the strong force was the only consideration the packing would increase indefinately though in eventually nearly infinately small incriments. The potential energy would continually become smaller, so adding nucleons would always be exothermic.
But, there is a second force involved. The Coulomb force is repulsive. While it is weaker, it has a longer range. As the nucleons are added together the finite sized nucleons pile up into a larger and larger volume. This is why the strong force attraction saturates. Because of the greater range of the coulomb force (electromagnetic force) the protons are pushed apart. This adds to the potential energy of the nucleus up to the point where one or more nucleons are actually pushed out of the nucleus. At this point the electromagnetic stored energy (potential energy) is released as kinetic energy. Note that this is the reverse of what is generally considered the energy balance for tearing the nucleus apart entirely (the total binding energy) This is nonsence, unless you accept that the total binding energy is the sum of these two seperate and competing processes without accounting for the positive or negative sign of the numbers. And this is thus not representative of the net effect of these numbers. The total effect is represented by the difference between them (which by the way maximizes at 62Ni) Past 62 Ni the electromagnetic force mediated energy is increasing more rapidly than the strong force mediated energy, thus the net attractive energy is now decreasing. The nucleus diameter/ volume increases, and thus the packing becomes less. This is the addition of positive potential energy. And as potential energy of a portion of a system increases, the energy (kinetic energy) from another part of the system must decrease. This is an endothermic process for the portion of the system outside the nucleus, ie:the system cools- the KE of the system goes down while the potential energy of the nucleus goes up.
These two competing forces - one negative, the other positive from a potential energy perspective results in a crossover point where the dominance is reversed (actually this is not quite true. The electromagnetic force dominates at the point where the nucleus quickly falls apart ~ Uranium, but past 62Ni the electromagnetic effect is increasing more rapidly than the Strong force effect, the packing of the nucleus has reached it's maximum and starts relaxing- the potential energy begins to increase). This occurs at 62Ni (or some references use 56Fe- it depends on the definitions and the mechanisms by which the isotopes are constructed). In short, fusion up to 62Ni generally harvests excess strong force energy, while fission down to 62Ni harvests excess electromagnetic energy. 62Ni is the baseline.
"The stability of a nucleus depends on the average binding energy per nucleon not the total binding energy. In other words it depends on the energy needed to remove a single nucleon rather than all the nucleons"
http://www.furryelephant.com/content/ra ... ss-defect/
Pushing protons together increases potential energy [edit- in an unbound system]
Imagine pusing two protons closer and closer to each other. They repel each other because they are both positively charged so you have to do more and more work as they get closer. Energy and work are equivalent ideas.
If you let the protons go then they fly apart again, so you get the energy back. Because you can get the energy back we say that you store potential energy as you push protons together.
The maximum potential energy is when they are quite close together and it's zero when they're a long way apart. Low energy means more stable. If the protons don’t touch then the stable, low-energy state is for them to be a long way apart.
Like falling into a well
When two protons are close enough the strong force binds them tightly together. It’s as if they’ve fallen down a deep well and the potential energy has suddenly become very negative.
In other words once nucleons are bound in a nucleus then the stable, low energy state is for them to stay bound.
Negative potential energy is energy you didn't have to put in
Potential energy is normally defined to be negative for attractive forces and positive for repulsive ones. Only attractive forces, like gravity and the strong force, bind systems together. All bound systems have negative potential energy.
When the protons aren’t bound in the nucleus you store potential energy by pushing the protons together. When the protons are bound in a nucleus you store potential energy by pulling the protons apart, provided they don't unbind.
You have to do more work pulling the nucleus apart than you had to put in squeezing the protons together to make it. Energy is released when the protons bind together because the total potential energy of the system is reduced.
The energy seems to come from nowhere because the strong force suddenly attracts the protons when they are very close.
The stability of a nucleus depends on the average binding energy per nucleon not the total binding energy. In other words it depends on the energy needed to remove a single nucleon rather than all the nucleons.
The average binding energy per nucleon goes up and then goes down as you make bigger and bigger nuclei. More binding energy per nucleon means more stability for the whole nucleus.
So as you make bigger and bigger nuclei the stability starts low, rises rapidly, then drops off slowly.
But if the total binding energy always increases how can the average binding energy per nucleon rise then fall?
Here is an analogy. Imagine a group of people playing a game. The objective is for each person to acquire as many of their own points as possible. More points means more stability. The total number of points that the whole group has is irrelevant.
When a new member joins he or she bring points with them. All the points are pooled and the total shared equally. At the moment there are five members. They each have 100 points. What happens when a sixth member joins?
Regardless of whether they bring 90, 100 or 110 points, the total points for the group always increases. This is like adding nucleons to a nucleus. The total binding energy always increases.
But what happens to the points of each member when the total points are shared out equally? If the new member brings only 90 points the total still increases. But each player ends up with fewer points. Each is less ‘stable’.
Using mass defect to see whether a nuclear reaction can happen spontaneously
We can use the idea of mass defect to work out whether a nuclear reaction can happen.
Nuclear reactions can only happen spontaneously if the products are more stable than the reactants. More stable means lower energy. Lower energy means lower mass.
So if the mass goes down then a nuclear reaction can happen spontaneously. If it goes up then it can’t.
For example you can tell that oxygen-16 can't emit an alpha particle to form carbon-12 because the mass of the alpha plus carbon-12 nucleus is bigger than the original oxygen-16 nucleus.
The net binding energy of a nucleus is that of the nuclear attraction, minus the disruptive energy of the electric force. As nuclei get heavier than helium, their net binding energy per nucleon (deduced from the difference in mass between the nucleus and the sum of masses of component nucleons) grows more and more slowly, reaching its peak at iron. As nucleons are added, the total nuclear binding energy always increases—but the total disruptive energy of electric forces (positive protons repelling other protons) also increases, and past iron, the second increase outweighs the first. One may say 56Fe is the most efficiently bound nucleus.
And, if you place more confidence in a physics text that in internet snippets, then look again at this Text Book
http://www.scribd.com/doc/46231603/Plas ... ion-Energy
To error is human... and I'm very human.