# Neutrons, fertile, fissile and fissioning

• B
• Flexwheeler
In summary: Can you please explain easier.What is unclear?Could you please explain in simple terms what you meant. I am unfamiliar with what you explained.
Flexwheeler
TL;DR Summary
How do you turn fertile material to fissile without fissioning when they are afterwards are hit with neutrons again?
How do you turn fertile material to fissile without fissioning when they are afterwards are hit with neutrons again?

Remove it fast enough. That's how plutonium for weapons is extracted, for example. Or choose a neutron energy spectrum that breeds fissile material but doesn't lead to much fission.

I don't understand what you meant with "choose a neutron energy spectrum that breeds fissile material but doesn't lead to much fission". Please explain.

The probability that material A is converted to B by a neutron depends on the energy of the neutron. The probability that B is converted to C also depends on the energy - but in a different way. There can be an energy range where the transition of A to B is likely but B to C is unlikely. That's where you want your neutrons.

But realistically, removing the material often enough is easier. Let's say you convert 1% of A to B in a week and 1% of B to C. Start with 100% A. After a week you'll have ~99% A, ~0.995% B and ~0.005% C - you lost less than 1% of your B to further conversion as B was in for less than a week on average. After two weeks you'll have ~98% A, ~1.98% B and ~0.02% C. Losses now reached 1%. After 10 weeks you'll have ~90% A, ~9.5% B and 0.5% C. Loss is now 5%. That's probably still fine. Separate A, B and C, put A back into the machine, use C elsewhere if possible or store it as waste.

Sorry I do not understand. Can you please explain easier.

What is unclear?

Could you please explain in simple terms what you meant. I am unfamiliar with what you explained. How do you control or choose energy spectrum? Can you tell me how it is done with the 3 fissile material (U-233, U-235 and Pu-239) choosing a neutron energy spectrum that breeds fissile material but doesn't lead to much fission.

Last edited:
Flexwheeler said:
How do you control or choose energy spectrum?
With moderators and the choice of the fission material.

I don't have a specific example with real isotopes, but here is a toy example: X can only fission with fast neutrons, but it can capture both fast and thermal neutrons. After capturing a neutron and maybe beta decays it becomes material Y. If material Y also needs fast neutrons to fission then you can collect it in an environment where you have mainly thermal neutrons: They can convert X to Y, but they can't fission Y.

I am sorry I do not understand.

## 1. What are neutrons?

Neutrons are subatomic particles that have no electric charge and are found in the nucleus of an atom.

## 2. What does it mean for an element to be "fertile"?

In the context of nuclear science, a fertile element is one that can absorb neutrons and potentially undergo nuclear reactions, but is not capable of sustaining a chain reaction on its own.

## 3. What is the difference between a fissile and a fertile element?

A fissile element is one that is capable of sustaining a chain reaction on its own, while a fertile element can only undergo nuclear reactions when bombarded by neutrons from a fissile element.

## 4. What is fissioning?

Fissioning is the process of splitting an atomic nucleus into smaller fragments, releasing a large amount of energy in the form of heat and radiation.

## 5. How is fissioning used in nuclear power plants?

Nuclear power plants use controlled fission reactions to generate heat, which is then used to produce steam and drive turbines to generate electricity.

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