Fission, Fusion & Bomb Designs Exam Click “next” to start the exam. Only one possible answer for each question. 1. Which of the following is NOT true about neutrons? a. Neutrons have a greater mass than protons or electrons b. They are located in the nucleus of an atom and do not have an electrical charge c. The number of neutrons in an atom determines its atomic number d. Atoms with the same number of protons but different numbers of neutrons are known as isotopes 2. What determines how chemically inert any element might be? a. The number of neutrons present in the nucleus b. How complete the outer electron shell is c. What the binding energy of the element is d. The element’s atomic mass e. None of the above 3. Which nuclear components are critical to chemical reactions? a. Neutrons b. Protons c. Electrons d. Isotopes e. A and B 4. What is the most important nuclear component needed to produce a nuclear reaction? a. Neutrons b. Protons c. Photons d. Alpha particles e. Gamma rays 5. When a chemical or nuclear system goes from a high to a low state of energy, what is released every time? a. Electrons b. Protons c. Neutrons d. Alpha particles e. Energy 6. What does the curve of binding energy measure? a. The energy needed to separate the nucleus of an atom into its constituent protons and neutrons b. The energy needed to separate an atom’s nucleus from its electrons c. The energy released in a chemical reaction d. The energy required to separate isotopes of uranium e. None of the above 7. What is the significance of iron on the curve of binding energy? a. Elements with nuclei heavier than iron tend to undergo fission b. Elements with nuclei lighter than iron tend to undergo fission c. Iron has the highest binding energy of all the elements d. A and C e. B and C 8. Which of the following describes uranium? a. The separation of U235 from U238 requires a demanding isotopic separation process b. The isotope U238 is less common than U235 c. Uranium fuel can only be used in gun-barrel design nuclear weapons d. B and C 9. The discovery of what nuclear component was critical to attempts to fission elements and why? a. Electrons because atoms without full outer electron shells seek stability by sharing their electrons with other atoms, which releases energy b. Neutrons because they can get past the negative charge of an atom’s electron and the positive charge of the proton and as a result can cause the nucleus to fission c. Isotopes because only certain isotopes of an element will fission d. Alpha particles because they don’t have any electrons e. None of the above 10. What element was used for the first self-sustaining nuclear fission reaction and why? a. Iron because it has the most binding energy of any element b. Hydrogen because it has the lowest binding energy of any element c. Nitrogen because it transmutes into oxygen when hit with an alpha particle d. Plutonium because it requires the least amount of material for a given yield compared to neptunium or uranium and it has relatively high spontaneous neutron emissions e. Uranium because the isotope U235 will release at least two neutrons when it fissions and it had relatively low spontaneous neutron emissions 11. The amount of energy released by the fissioning of an element: a. Is determined by the difference in mass of the material before it fissions and after it fissions b. Is determined by how many neutrons are released after the element has fissioned c. Is determined by how many photons are released after the element has fissioned d. All of the above 12. Why and how do spontaneous neutron emissions matter to bomb designers? a. Spontaneous neutron emissions can cause the fissile material to begin to fission and the weapon to blow apart before a critical mass is achieved b. The higher the level of spontaneous neutron emissions, the less fissile material is necessary to achieve criticality c. Spontaneous neutron emissions make it impossible to use even isotopes (240, 242) of plutonium to make bombs d. Materials that have higher levels of spontaneous neutron emissions must be brought together quickly in order to avoid predetonation e. A and D 13. What are the advantages to using plutonium to make bombs over uranium? a. It is easier to make plutonium in a reactor and chemically separate it from the reactor fuel than it is to separate the fissile uranium isotope 235 b. The amount of plutonium needed to make a nominal bomb is less than the amount of uranium needed c. A simple gun device can be used to assemble plutonium whereas an implosion device is needed to assemble uranium d. A and B e. B and C 14. What happens if you fail to have enough uranium or plutonium to achieve “critical size or mass”? a. The material will not fission at all b. Not enough material will fission to achieve a nominal yield c. The yield will be over a kiloton but will be very unpredictable d. All of the above 15. How might you reduce the amounts of fissile uranium and plutonium you need to produce a nuclear explosion with a yield of one kiloton or greater? a. Compress the fissionable material at the time of detonation so that the atoms are more likely to be hit by neutrons b. Use a heavy casing or tamper to decrease the bomb’s tendency to blow apart before a significant amount of the material has fissioned c. Surround the weapons material with a neutron reflector so that neutrons that pass through the material are reflected back d. Bring the weapons material together faster so more of it can fission before the bomb is blown apart e. All of the above 16. The first nuclear weapon dropped on Japan (Little Boy): a. Used a subcritical mass of plutonium as the fissile material b. Used two subcritical pieces of highly enriched uranium as the fissile material c. Used a spherical shockwave to compress the material to criticality d. A and C 17. The second nuclear weapon dropped on Japan (Fat Man): a. Relied on tritium to boost the yield of the weapon b. Was tested first to ensure the implosion mechanism produced the spherical shockwave necessary to detonate the weapon c. Had multiple crits worth of fissile material in a hollow core d. Put a space between the fissile material and the tamper to increase the efficiency of the weapon 18. Which of the following statements about the use of plutonium and uranium isotopes in weapons material is NOT accurate? a. The greater the amount of odd isotopes (Pu239 and Pu241) present in the material, the less material is needed to achieve a critical mass. b. It is possible to make a weapon using any isotopic mixture of plutonium c. The higher the percentage of U235 present, the less practical it is to make a weapon d. As the amount of U238 increases, the more material is required to achieve a critical mass 19. Tritium: a. Is produced when Lithium-6 deuteride is hit with neutrons b. Is used to produce variable yield weapons c. Has a half-life of 25 years d. A and B 20. A multiple stage weapon: a. Uses the heat and radiation created by the fission reaction in the first stage to set off a fusion reaction in the second stage b. Derives a significant portion of its energy release from fusion c. Is more powerful than a fission weapon of the same size d. All of the above 21. A levitated pit design: a. Suspends the polonium initiator within a noncritical sphere of fissile material b. Suspends the core from the tamper, pusher and explosives c. Allowed the use of less explosives and less material for the tamper, pusher and fissile core to produce the same yield d. B and C 22. A hollow core design: a. Allows the use of multiple crits worth of fissile material in a weapon, producing yields that can run as high as several hundred kilotons b. Is used in boosted weapons to increase the weapon’s yield c. Allows the use of less explosives and less material for the tamper, pusher and fissile core to produce the same yield d. All of the above e. None of the above 23. Boosted weapons: a. Were the first true thermonuclear weapons, or h-bombs b. Rely upon the injection of tritium gas c. Derives most of their yield from fission reactions d. A and B e. B and C Name Email Time's up
