Questions and Answers on Nuclear Fission

I try to keep questions submitted by groups as the are. Unclear or trivial questions are not replied. Reply has not been proof read.

Q
Fission reactors
Because of the enormous cost involved in the development of the first nuclear fission reactor and the almost conscripted, yet necessary, participation of so many highly regarded scientists (several past and future nobel prize winners), do you think that a controlled nuclear fission chain reaction would ever have been achievable except under the shadow of a world war?
A
No doubt, WW II accelerated the development of fission and fusion bombs as well as fission nuclear reactors. Without the strong support by the US and other governements, their development will be delayed. I think they will still be developed.

Q
Natural fission reactors
Can we utilize Natural fission reactors in our energy production?
A
Yes, we can, but natural fission reactors are things of the past. Besides, they are not frindly to people or anything close by either!!!

Q
Neutron cross section
What are the major differences between thermal neutron cross sections and thermal neutron cross section for fission?
A
Sometimes we mean the same thing. However, thermal neutron cross sections may include absorption of these neutrons not leading to fission.

Q
Particle accelerators
What are the differences by using Linear particle accelerators and Cyclotrons to accelerate particles?
A
Linear particle accelerators take a lot of space to achieve the same energy as the cyclotrons. The accelerated particles may be the same except their energy.

Q
Nuclear waste
Where and how is the radioactive waste from current operating nuclear reactors in Canada stored?

How does the government process the nuclear waste produced by the CANDU reactor since it produces more waste than other types of reactors? Is it more efficient in terms of producing electrical power than other reactors (say the Breeder Reactors)?

Since the products of nuclear reactors are still radioactive, why can't they be still used?
A
Currently, there is a project to store the waste under ground in the Canadian Shield. Under these hard rocks, they probably will not get anywhere, thought the scientists and engineers.

The Atomic Energy of Canada Ltd is the agency responsible for the nuclear industry, and its leaders decided that the Canadian Shield is the best solution for the time being.

The CANDU reactors have some advantages, but efficiency is not one of them. Efficiency probably will have to be measured in economic terms, and I have no data to give a good answer in this regard.

Fresh nuclear waste releases a lot of energy, but after a while, the amount of energy is not worth much anymore, even though the wast is radioactive.

Q
Chernobyl accident
How far reaching were the effects of the Chernobyl accident? Why was most of the blame put on the operators, and not those who designed the system, who could have done so in such a manner than the opportunity human error would be minimized? Why has research for Nuclear Fission been much more successful than Nuclear Fusion?
A
There are many documentaries made about this accident, and it affects the life of many people in Russia and in Europe.

From the scientific point of view, we want to know why and how it happened. In this regard, we point out the human error, which sounds like a blame. Had the designers knew that they would test it the way they did, they probably would design it to prevent such a test.

Q
Breeder reactors
How do Breeder reactors really work? can they keep making fuel forever? Since it just makes a different "fuel" for a different kind of reactor, can this be done till the fuel become Fe (iron)? Can an infinite amount of fuel be created?
A
Breeder reactors have their functions. One has to replenish the material to be converted to the fuel. One also have to replace the fuel. The fuel will not turn into iron! The energy is still from the fission of 235U or 239Pu.

Q
Control rod
How does the control rod release neutrons in a fission reactor?
A
Control rods absorb neutrons to stop fission reaction in a reactor.

Q

Why is the distribution of fission products the way it is (why are the peaks at certain points and what restricts the product nuclides formed)?
A
Humans cannot answer the question WHY for natural phenomenon, but the two peaks are due to assymmetric splitting of the nuclei. When plotted in one diagram, they appear as two peaks with a valley in the middle.

Q
b for barn
On page 238, what does b mean in the table?
A
In the table, we use / b to indicate the quantities are divided by the unit barn (b). Thus, we do not need to put b associated with every number.

Q
Cosmic rays
Where do the particles in cosmic rays come from? Why don't they form larger particles? Do they permeate space everywhere?
A
Cosmic rays comes from stars and space materials. They fill the universe. As indicated in the module, they are mostly protons. Sun flares may be are some of the sources. There are trillions of stars out there.

Q
CanDu reactor
The Canadian Deuterium Uranium Reactor design is self regulating based on the requirement for it's heavy water moderator to be present to support fission. It would seem that the loss of coolant (the moderator) would result in a shutdown of the reaction, as the neutrons kinetic energy distribution would shift above that required to maintain the necessary neutron flux. Had CANDU been used in Chernobyl or 3 Mile Island, it seems like the accidents couldn't have happened. It would seem that there isn't any substantive reason to rely on other technologies for power generation. So, why do other reactors continue to be used?
A
The reactors in Three Mile Island and in Chernobyl are not the CANDU type. The one in TMI is a pressurized light water reactor, and the one in Chernobyl is a graphite moderated reactor.

Even CANDU reactors cannot absolutely prevent accidents. By your argument, the TMI reactor should not have had the accident. The reality is that the radioactive fission products still releases a lot of energy and the energy caused the meltdown of the core.

Energy from the fission products also caused the accident in Chernobyl.