TLO 2 Fission Process

Question 1

ELO 1 Define Excitation Energy

Answer 1

The measure of how far the energy level of a nucleus is above its ground state.

Question 2

ELO 1 Define Critical Energy

Answer 2

The minimum excitation energy required for fission to occur for a particular nuclide.

Question 3

ELO 1 If the binding energy is less than the critical energy for the nucleus…?

Answer 3

Additional energy is required to cause the nucleus to fission. This energy could be in the form of kinetic energy from the incident neutron.

Question 4

ELO 1 True or False: Excitation must be at least equal to critical energy for fission to occur.

Answer 4

True

Question 5

ELO 2 How do nuclear and electrostatic forces respond to Excitation Energy greater than Critical Energy?

Answer 5

The attractive nuclear forces reduce due to saturation while the electrostatic forces remain strong. When electrostatic forces exceed the nuclear forces, fission occurs.

Question 6

ELO 3 Define a Fissile material and give examples of a Fissile material.

Answer 6

A fissile material consists of nuclides that will fission with incident neutrons of any energy level. These are the desired nuclides for using thermal nuclear reactors. Examples are U-235, U-233, Pu-239.

Question 7

ELO 3 Define fissionable material and give examples of fissionable material.

Answer 7

A fissionable material is composed of nuclides for which fission is possible. This includes all fissile nuclides as well as nuclides that only fission from high energy neutrons. Examples that require high-energy neutrons: Th-232, U-238, Pu-240.

Question 8

ELO 3 Define a Fertile material

Answer 8

A material (nuclide) that can undergo transmutation to become a fissile material.

Question 9

ELO 3 Define Thermal Neutrons

Answer 9

Neutrons with essentially zero kinetic energy level because they are in equilibrium with the thermal energy of surrounding materials. They add no kinetic energy to a neutron absorption reaction. We want to thermalize as many neutrons as possible in a PWR.

Question 10

ELO 4 Explain Binding Energy per Nucleon

Answer 10

The average energy required to remove a single nucleon from a specific nucleus.
Total binding energy of a nuclide divided by total number of nucleons.
(BE)/A

Question 11

ELO 4 True or False: Binding energy per nucleon is independent of the specific nuclide.

Answer 11

False

Question 12

ELO 5 True or False: Less stable nuclides have a higher BE/A than the more stable ones.

Answer 12

False, it’s the opposite relationship.