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 electronsb. They are located in the nucleus of an atom and do not have an electrical chargec. The number of neutrons in an atom determines its atomic numberd. Atoms with the same number of protons but different numbers of neutrons are known as isotopes2. What determines how chemically inert any element might be?a. The number of neutrons present in the nucleusb. How complete the outer electron shell isc. What the binding energy of the element isd. The element’s atomic masse. None of the above3. Which nuclear components are critical to chemical reactions?a. Neutronsb. Protonsc. Electronsd. Isotopese. A and B4. What is the most important nuclear component needed to produce a nuclear reaction?a. Neutronsb. Protonsc. Photonsd. Alpha particlese. Gamma rays5. When a chemical or nuclear system goes from a high to a low state of energy, what is released every time?a. Electronsb. Protonsc. Neutronsd. Alpha particlese. Energy6. What does the curve of binding energy measure?a. The energy needed to separate the nucleus of an atom into its constituent protons and neutronsb. The energy needed to separate an atom’s nucleus from its electronsc. The energy released in a chemical reactiond. The energy required to separate isotopes of uraniume. None of the above7. What is the significance of iron on the curve of binding energy?a. Elements with nuclei heavier than iron tend to undergo fissionb. Elements with nuclei lighter than iron tend to undergo fissionc. Iron has the highest binding energy of all the elementsd. A and Ce. B and C8. Which of the following describes uranium?a. The separation of U235 from U238 requires a demanding isotopic separation processb. The isotope U238 is less common than U235c. Uranium fuel can only be used in gun-barrel design nuclear weaponsd. B and C9. 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 energyb. 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 fissionc. Isotopes because only certain isotopes of an element will fissiond. Alpha particles because they don’t have any electronse. None of the above10. 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 elementb. Hydrogen because it has the lowest binding energy of any elementc. Nitrogen because it transmutes into oxygen when hit with an alpha particled. 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 emissionse. Uranium because the isotope U235 will release at least two neutrons when it fissions and it had relatively low spontaneous neutron emissions11. 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 fissionsb. Is determined by how many neutrons are released after the element has fissionedc. Is determined by how many photons are released after the element has fissionedd. All of the above12. 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 achievedb. The higher the level of spontaneous neutron emissions, the less fissile material is necessary to achieve criticalityc. Spontaneous neutron emissions make it impossible to use even isotopes (240, 242) of plutonium to make bombsd. Materials that have higher levels of spontaneous neutron emissions must be brought together quickly in order to avoid predetonatione. A and D13. 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 235b. The amount of plutonium needed to make a nominal bomb is less than the amount of uranium neededc. A simple gun device can be used to assemble plutonium whereas an implosion device is needed to assemble uraniumd. A and Be. B and C14. What happens if you fail to have enough uranium or plutonium to achieve “critical size or mass”?a. The material will not fission at allb. Not enough material will fission to achieve a nominal yieldc. The yield will be over a kiloton but will be very unpredictabled. All of the above15. 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 neutronsb. Use a heavy casing or tamper to decrease the bomb’s tendency to blow apart before a significant amount of the material has fissionedc. Surround the weapons material with a neutron reflector so that neutrons that pass through the material are reflected backd. Bring the weapons material together faster so more of it can fission before the bomb is blown aparte. All of the above16. The first nuclear weapon dropped on Japan (Little Boy):a. Used a subcritical mass of plutonium as the fissile materialb. Used two subcritical pieces of highly enriched uranium as the fissile materialc. Used a spherical shockwave to compress the material to criticalityd. A and C17. The second nuclear weapon dropped on Japan (Fat Man):a. Relied on tritium to boost the yield of the weaponb. Was tested first to ensure the implosion mechanism produced the spherical shockwave necessary to detonate the weaponc. Had multiple crits worth of fissile material in a hollow cored. Put a space between the fissile material and the tamper to increase the efficiency of the weapon18. 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 plutoniumc. The higher the percentage of U235 present, the less practical it is to make a weapond. As the amount of U238 increases, the more material is required to achieve a critical mass19. Tritium:a. Is produced when Lithium-6 deuteride is hit with neutronsb. Is used to produce variable yield weaponsc. Has a half-life of 25 yearsd. A and B20. 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 stageb. Derives a significant portion of its energy release from fusionc. Is more powerful than a fission weapon of the same sized. All of the above21. A levitated pit design:a. Suspends the polonium initiator within a noncritical sphere of fissile materialb. Suspends the core from the tamper, pusher and explosivesc. Allowed the use of less explosives and less material for the tamper, pusher and fissile core to produce the same yieldd. B and C22. 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 kilotonsb. Is used in boosted weapons to increase the weapon’s yieldc. Allows the use of less explosives and less material for the tamper, pusher and fissile core to produce the same yieldd. All of the abovee. None of the above23. Boosted weapons:a. Were the first true thermonuclear weapons, or h-bombsb. Rely upon the injection of tritium gasc. Derives most of their yield from fission reactionsd. A and Be. B and C Name Email Time is Up!
