Nuclear Physics 5

Which isotopes are fissile?

• U-235

• Pu-239

• U-233

• U-238

Which isotopes are fissionable?

• U-235

• U-238

• U-233

• Pu-239

For an isotope to undergo spontaneous fission, the critical energy must be...

• Less than or equal to the binding energy

• Higher than the binding energy

• Double the binding energy

• The binding energy

Th-232 has a critical energy of 7.5 MeV and a binding energy of 5.4 MeV, what is the minimum energy an incoming neutron must have in order for the isotope to undergo fission?

• 7.5 MeV

• 5.4 MeV

• 2.1 MeV

• 12.9 MeV

What are the most probable fission fragments from U-235?

• Kr-92 and Ba-141
• U-238 and Pu-239
• Cs-137 and Te-132
• Xe-135 and I-131

Why can all of the energy from a fission reaction not be recovered in a nuclear reactor?

• The neutrons produced have no kinetic energy.

• Gamma rays are too easily absorbed.

• Fission products are too high in energy.

• Some energy is lost as antineutrinos.

Which descriptions match prompt neutrons and which match delayed neutrons?​

Groups:

(a) Prompt

,

(b) Delayed

• >99% of fission neutrons

• Reactor must be kept subcritical in these

• Reactor criticality is controlled using these

• <1% of fission neutrons

• Emitted from fission fragments

• Emitted directly from fission of the parent nucleus

Which cross section represents the likelihood of a reaction for a single nucleus?

• Macroscopic

• Microscopic

• Absorption

• Scattering

What does the macroscopic cross section represent?

• The macroscopic cross section indicates the temperature of a material.
• The macroscopic cross section represents the likelihood of interaction between all particles in a target material.

• The macroscopic cross section measures the speed of particles.
• The macroscopic cross section defines the density of a target material.

A reaction has a macroscopic cross section of 5 cm-1. What is the mean free path?

• 0.5 cm

• 50 cm

• 0.2 cm

• 20 cm