Fission Knowledge-Based Practice

Questions

1. 1.

   Why do the primary fragments formed by the nuclear fission of uranium-235 typically undergo successive beta-minus ($\beta^-$) decays?

   • A) They possess an atomic number greater than 83, which makes alpha emission and spontaneous fission the only viable pathways.
   • B) They capture additional prompt neutrons from the surrounding medium, which continually drives them away from nuclear stability.
   • C) They have an insufficient number of neutrons relative to protons, requiring the conversion of protons into neutrons.
   • D) They retain the high neutron-to-proton ratio of the parent nucleus, leaving them neutron-rich compared to stable medium-mass isotopes.
2. 2.

   In thermal nuclear reactors fueled by uranium-235, what is the primary function of a neutron moderator?

   • A) It absorbs excess neutrons to regulate the core temperature and halt chain reactions.
   • B) It slows down high-velocity fission neutrons to thermal energies without absorbing them to optimize further fission.
   • C) It absorbs the ionizing gamma radiation released during the decay of fission daughter products.
   • D) It converts fertile uranium-238 directly into fissile plutonium isotopes through energetic neutron capture.
3. 3.

   In the context of nuclear chemistry, which statement best defines a self-sustaining fission chain reaction?

   • A) It is the spontaneous alpha decay of daughter isotopes releasing high-energy gamma rays without external particles.
   • B) It is the complete absorption of all generated neutrons by coolant fluids to prevent thermal runaway.
   • C) It is the continuous combination of light product fragments into heavier nuclei driven by released thermal energy.
   • D) It is a process where neutrons produced by splitting nuclei induce the fission of neighboring fissile nuclei.
4. 4.

   Why does the nuclear fission of a heavy nuclide, such as uranium-235, release a large amount of energy?

   • A) The total number of nucleons increases during the reaction, creating excess mass that converts into kinetic energy.
   • B) Chemical bonds between uranium atoms are broken, liberating stored valence electronic potential energy.
   • C) The total rest mass of the resulting fission products is less than that of the reactants, converting this mass defect into energy.
   • D) The strong nuclear force is entirely destroyed, releasing the electrostatic potential energy of the surrounding orbital electrons.
5. 5.

   Which statement correctly describes the primary process of induced nuclear fission in a standard nuclear reactor?

   • A) A heavy nucleus absorbs a thermal neutron and splits into two lighter nuclei, releasing additional neutrons and energy.
   • B) Two light nuclei combine at extremely high temperatures to form a heavier nucleus, releasing energy and positrons.
   • C) An unstable nucleus spontaneously emits an alpha particle to achieve stability without capturing an external particle.
   • D) A proton-rich nucleus captures an inner orbital electron, converting a proton into a neutron and emitting a neutrino.

Answers and step-by-step solutions appear after you finish the test.