Which of the following options are correct regarding controlling the rate of nuclear reaction?
Which of the following options are correct regarding controlling the rate of nuclear reaction?
The correct option is D The constituents of the nuclear fuel determine the rate of the chain reaction
So as we discussed in the hint, all the emitted neutrons triggering a fission reaction is the main reason of an uncontrolled chain nuclear reaction. So according to the options given we have been asked that whether the Size, Energy of neutron and constituent of the fuel can control the reaction or not?
Let's talk about each factor one by one.
1. Size
If the fission event takes place near the surface of the bulk Uranium material taken, there is a good chance that the neutrons produced will escape from the material without coming in contact with another U-235. The fraction of neutrons lost in this way will be larger if small pieces of Uranium fuel are used as smaller the size more the surface area hence more uranium nuclei's neutrons have a probability of being lost. Controlling the size will thus control the rate of fission.
2. Energy of neutrons
The neutrons produced in the fission have kinetic energy ≈ 2Mev. They are called fast neutrons. The U-235 has a good probability of absorbing a neutron of energy ≈ 0.04 ev which are called slow neutrons. The neutron hence may not get absorbed by a U -235 even if they collide. If the material is large enough the neutron will suffer multiple collisions in the bulk and lose its kinetic energy to become a slow neutron. It may then absorbed by a U -235.
3. Constituent of Uranium fuel
U-238 can absorb neutrons of energy 1-100 eV. If the fuel is enriched with this isotope a neutron before being absorbed by U-235 has a good chance to be absorbed by U-238 which then fissions by other All the above three factors are considered in the engineering design of a nuclear reactor.
So as we discussed in the hint, all the emitted neutrons triggering a fission reaction is the main reason of an uncontrolled chain nuclear reaction. So according to the options given we have been asked that whether the Size, Energy of neutron and constituent of the fuel can control the reaction or not?
Let's talk about each factor one by one.
1. Size
If the fission event takes place near the surface of the bulk Uranium material taken, there is a good chance that the neutrons produced will escape from the material without coming in contact with another U-235. The fraction of neutrons lost in this way will be larger if small pieces of Uranium fuel are used as smaller the size more the surface area hence more uranium nuclei's neutrons have a probability of being lost. Controlling the size will thus control the rate of fission.
2. Energy of neutrons
The neutrons produced in the fission have kinetic energy ≈ 2Mev. They are called fast neutrons. The U-235 has a good probability of absorbing a neutron of energy ≈ 0.04 ev which are called slow neutrons. The neutron hence may not get absorbed by a U -235 even if they collide. If the material is large enough the neutron will suffer multiple collisions in the bulk and lose its kinetic energy to become a slow neutron. It may then absorbed by a U -235.
3. Constituent of Uranium fuel
U-238 can absorb neutrons of energy 1-100 eV. If the fuel is enriched with this isotope a neutron before being absorbed by U-235 has a good chance to be absorbed by U-238 which then fissions by other All the above three factors are considered in the engineering design of a nuclear reactor.
