Fission is started in nuclear power plants by withdrawing the control rods. The rods are pulled in groups beginning around the perimeter of the reactor. These are extracted and pulled all the way out. The reactor design permits this to happen without starting the reactor up. Then the middle rods are pulled. These actually permit the reactor to start up. The rods being pulled last are the "control group" because they are going to set up the operating conditions. Rods pulled to control the reactor, those in the middle, permit a more uniform burn of the fuel. If it was done differently, the fuel in the middle would burn more quickly. And the fuel around the perimeter would not be used as efficiently. Here's the scoop. The control rods are a neutron absorbing material. They have to be because they must be able to absorb neutrons to control or shut down the reactor. Boron works really well because 1) boron has a fairly high neutron absorption cross section (it is a good or "big" target for a neutron), and 2) as boron is transmuted by neutron absorption, it (usually) becomes another boron isotope, and boron's isotopes all have good neutron absorption cross sections so they all continue to be pretty good neutron absorbers. The rods are pulled to a point where there is not enough of them in the reactor to absorb the neutrons that are spontaneously being generated by the fuel. (It always generates a few neutrons. Always. And that's the hinge for critical mass.) So the rods are pulled and the effective critical mass is reached and the chain begins. Monitoring instruments pick up the increase in neutron flux. Operators know the chain has begun and is building. Then by gradually heating things up and incrementally pulling the rods a bit more, the plant is brought to operating temperature and is able to provide heat to generate steam in a secondary system. The secondary system is gradually heated by bleeding steam when things in the primary are heated up. That way the secondary system can be brought on line efficiently and power production can begin. There are more subtle aspects to reactor operations, but this is a good start on a path to understand the workings of the reactor.
To sustain a fission chain reaction, each fission reaction must result in one more fission reaction. And that one should result in one more, and so on.
In actuality, a spontaneous fission event begins a nuclear chain reaction. It kick starts a nuclear chain reaction. And a neutron from that fission will initiate another fission to continue and rev up that nuclear chain reaction.
Neutrons released during a fission reaction trigger other fission reactions.
In a nuclear fission reaction, a freely moving neutron undergoes neutron capture and initiates the nuclear fission of a fuel atom.
No, a chain reaction is not possible in a substance that emits no neutrons when it undergoes fission. Neutrons are required to sustain a chain reaction by triggering the fission of other atoms in the substance. Without neutron production, the fission process cannot continue to release energy and sustain the chain reaction.
To sustain a fission chain reaction, each fission reaction must result in one more fission reaction. And that one should result in one more, and so on.
A stable nuclear fission reaction will be sustained if every fission produces one additional fission reaction.
The first time a fission chain reaction was produced was in 1942
fission..sup
In a chain reaction, each fission reaction must produce at least one additional fission reaction to sustain the reaction. This is necessary to achieve a self-sustaining nuclear reaction where each fission event leads to more fission events, releasing energy in the process. Without this multiplication of fission reactions, the chain reaction would not be able to continue and sustain itself.
For a chain reaction to occur, each fission must produce at least one more fission reaction. This leads to a self-sustaining reaction where each fission event triggers more fission events, resulting in a continuous release of energy.
another name for nuclear fission is: E=MC squared
In a nuclear fission reaction, the energy comes from the splitting of atomic nuclei.
Atomic fission bomb.
In actuality, a spontaneous fission event begins a nuclear chain reaction. It kick starts a nuclear chain reaction. And a neutron from that fission will initiate another fission to continue and rev up that nuclear chain reaction.
Neutrons released during a fission reaction trigger other fission reactions.
Nuclear explosions happen for many reasons: An uncontrolled chain reaction (fission reaction) occurs with uranium 238, A fission reaction is where 1 large nucleus (centre of an atom) splits up into 2 or more smaller nuclei giving off neutrons. These neutrons then hit another nucleus changing it into smaller nuclei and so on. e.g. (chain reaction) feel free to add some more info...