Why is enrichment important for a fission chain reaction ?
- keeps neutrons from escaping the sample
-keeps neutrons from being absorbed by other isotopes
-allows neutrons to be absorbed by other fissionable nuclei
-provides enough fuel to make enough energy .
-allows neutrons to be absorbed by other fissionable nuclei
I disagree with the answer by anonymous. If a sample is enriched, say we're talking uranium, then it's the uranium that is enriched from say 3% or so to something larger like 50%. Therefore, a neutron has a larger chance of entering a U-235 atom than some other atom, thus the chances of a chain reaction with U-235 is enhanced many fold. I think the correct answer is -keeps neutrons from being absorbed by other isotopes BECAUSE the fissionable material is enhanced several fold which helps maintain a chain reaction AND by enriching the fissionable material it makes the other isotopes, fissionable or not, be there in much smaller amounts. In fact, by enriching the fissionable material it stand to reason that other materials there, even if they are fissionable (and most aren't) there won't be enough of them to sustain a chain reaction. The bottom line is that if there is a competition for the available neutrons between the U-235 (the fissionable material) and some other element, it stands to reason that by enriching the U-235 it increases the chances that U-235 gets the neutron rather than much much smaller amount of other elements capturing the neutron.
Enrichment is important for a fission chain reaction for several reasons.
Firstly, it helps to keep neutrons from escaping the sample. Neutrons play a crucial role in sustaining the chain reaction as they cause the fission of atomic nuclei, releasing additional neutrons. If the neutrons escape the sample, the chain reaction may slow down or stop altogether. Enriched fuel ensures that a sufficient number of neutrons are retained within the sample, allowing the reaction to continue.
Secondly, enrichment helps to keep neutrons from being absorbed by other isotopes present in the fuel. Some isotopes, such as various impurities or non-fissionable isotopes, have a tendency to absorb neutrons without undergoing fission. This reduces the number of neutrons available to sustain the chain reaction. By enriching the fuel, these neutron-absorbing isotopes can be minimized or eliminated, allowing more neutrons to be available for fission.
Thirdly, enrichment allows neutrons to be absorbed by other fissionable nuclei. Fission chain reactions occur when the nucleus of a fissionable atom undergoes a nuclear fission, splitting into two or more smaller nuclei. These smaller nuclei, in turn, release additional neutrons that can induce further fission events. By enriching the fuel, the concentration of fissionable nuclei is increased, increasing the likelihood of neutron absorption, and thus sustaining the chain reaction.
Lastly, enrichment provides enough fuel to make enough energy. Fission reactions release a significant amount of energy, and for practical applications such as nuclear power generation, it is important to have a sufficient fuel supply to sustain the chain reaction for an extended period of time. Through enrichment, the concentration of fissionable isotopes, such as uranium-235 or plutonium-239, can be increased, ensuring a sustainable supply of fuel to generate the desired amount of energy.
In summary, enrichment is important for a fission chain reaction because it helps to retain neutrons within the sample, prevents neutron absorption by non-fissionable isotopes, promotes neutron absorption by fissionable nuclei, and provides enough fuel to generate the desired amount of energy.