What are the sources of neutrons in starting up a nuclear reactor?

In summary, the conversation discusses the sources of neutrons in a nuclear reactor, including spontaneous fission, cosmic rays, and alpha particles from elements like Cf-252 and Pu-Be. It is noted that after one cycle, the fuel itself provides enough neutrons and a new source is not needed.
  • #1
tiepngh
5
0
Thank for all if you understand my ideal.
My problem is i don't know what's neutron which cause of fission in critical accident?
seem it must be have the first neutrons, and then reaction fission occurred ?
eg The critical model in some nuclear accident, what is neutron source?
The nuclear bomb? ...
thanks...
 
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  • #2
There are always some neutrons just floating around. Spontaneous fission and cosmic rays are examples.

Also what kind of accident are you concerned about. Reactors are going all the time, so there are plenty of neutrons. Accident means it got out of control somehow.
 
  • #3
The fuel itself is decaying naturally, releasing neutrons. In a reactor the fuel is arranged in such a way that the neutrons cause MORE decays, but even a small amount by itself is releasing neutrons at a fairly steady rate.
 
  • #4
forward:Sorry i Can't include a link
There are several sources of neutrons for starting up a reactor:

a) Cf-252 spontaneously fissions and thereby releases neutrons.
Small wires of Cf-252 are inserted into selected fuel assemblies
(the spontaneous fission rate is so high that only gram amounts
of Cf-252 are needed).

b) Antimony-berylium or Pu-Be sources are also used. In these sources,
the Antimony or the Plutonium emits a high-energy alpha which
is absorbed by the Berylium which then emits a neutron, among
other things.
c) As the fuel is irradiated, Pu-240 builds up. It also spontaneously
fissions, giving rise to neutrons. There are some spontaneous
fissions in U-238 as well. I seem to recall that there may be some
(alpha, n) reactions directly in the fuel, although I am uncertain
as to the magnitude of this contribution.
It is likely that after a core has been irradiated it has enough background
neutrons that the Cf-252 and berylium sources are no longer needed. So
far as I know, however, no one has put this theory to the test in a power
reactor.
 
  • #5
googlefans said:
forward:Sorry i Can't include a link
There are several sources of neutrons for starting up a reactor:

a) Cf-252 spontaneously fissions and thereby releases neutrons.
Small wires of Cf-252 are inserted into selected fuel assemblies
(the spontaneous fission rate is so high that only gram amounts
of Cf-252 are needed).

b) Antimony-berylium or Pu-Be sources are also used. In these sources,
the Antimony or the Plutonium emits a high-energy alpha which
is absorbed by the Berylium which then emits a neutron, among
other things.
c) As the fuel is irradiated, Pu-240 builds up. It also spontaneously
fissions, giving rise to neutrons. There are some spontaneous
fissions in U-238 as well. I seem to recall that there may be some
(alpha, n) reactions directly in the fuel, although I am uncertain
as to the magnitude of this contribution.
It is likely that after a core has been irradiated it has enough background
neutrons that the Cf-252 and berylium sources are no longer needed. So
far as I know, however, no one has put this theory to the test in a power
reactor.

Cores do not need a new neutron source after being through one cycle unless they are starting with completely fresh fuel. The once and second burned fuel provides enough neutrons to not require a new neutron source. This isn't a theory, this is actual practice.
 

1. Where is the Neutron source located?

The location of the Neutron source varies depending on the type of source. Natural Neutron sources, such as the Sun and Earth's atmosphere, are located in space. Artificial Neutron sources, such as nuclear reactors, are typically located in power plants or research facilities.

2. How is the Neutron source created?

Neutron sources can be created through natural processes, such as nuclear fusion in stars, or artificially through nuclear reactions in nuclear reactors. In nuclear reactors, uranium or plutonium atoms are bombarded with neutrons to create a chain reaction that releases large numbers of neutrons.

3. What materials are used to create Neutron sources?

The most commonly used materials for artificial Neutron sources are uranium, plutonium, and other radioactive isotopes. These materials are chosen because they are able to undergo nuclear reactions and release neutrons.

4. Can Neutron sources be controlled?

Yes, artificial Neutron sources can be controlled through various methods such as controlling the amount of nuclear material present, using control rods to absorb neutrons, and regulating the rate of nuclear reactions. This allows for the safe and controlled release of neutrons for various purposes.

5. What are the applications of Neutron sources?

Neutron sources have a wide range of applications in science, medicine, and industry. They are used for research in nuclear physics, materials science, and biology. They are also used in medical treatments, such as cancer therapy, and in industrial processes, such as detecting defects in materials and analyzing the composition of objects.

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