21. In the induced nuclear reaction, YX+*NeHe+ O201032178→→, the reaction produces neon in an excited state, which subsequently decays into a nucleus X and a particle Y. Which one of the following Xand Y pairs is not possible? X Y (a) O178He32(b) F199H21(c) Ne2010γ(d) O168He42(e) Ne1910n10Section 32.3 Nuclear Fission Section 32.4 Nuclear Reactors 22. What is the importance of thermal neutronsin nuclear processes? (a) Thermal neutron capture results in uranium fission. (b) Thermal neutrons are released in radioactive decay. (c) Thermal neutrons are necessary in the fusion of deuterium. (d) Thermal neutrons are commonly released in fusion reactions. (e) Thermal neutrons are sources of gamma rays. 23. Which one of the following energy values would be characteristic of a thermal neutron? (a) 0.03 eV (c) 3 eV (e) 0.04 MeV (b) 0.4 eV (d) 100 eV
324 Chapter 32Ionizing Radiation, Nuclear Energy, and Elementary Particles24. A particular nuclear fission reaction produces 1.50 ×102MeV per fission. How many fissions per second are required to generate 3.00 ×108W of power? 231925. A nuclear reaction that uses one nucleus of U23692generates 170 MeV. How much energy is released when 5.0 kg of this isotope are used? 16J J 26. How many neutrons are produced in the reaction: n?+Kr + Ba U+ n108936144562359210→? 27. Identify X in the following nuclear fission reaction: X+Kr + Ba +U90361425623592→γ. (a) one alpha particle (c) three protons (e) six neutrons (b) two alpha particles (d) three neutrons 28. One example of a nuclear fission reaction involving slowly moving neutrons is n2 +La + Mo*UU+ n10139579542236922359210What is the total kinetic energy (in eV) of the products of the reaction? The relevant masses are: U23592= 235.043 924 u, Mo9542= 94.9058 u, La13957= 138.9061 u, and n10= 1.0087 u. →→29. Which one of the following processes causes the explosion of a nuclear bomb? 30. How many neutrons are produced in the following reaction: ?+Xe+ Sr U+ n1365488382359210→31. What is the function of the moderator in a fission reactor? (a) The moderator absorbs gamma rays. (b) The moderator absorbs slow neutrons. (c) The moderator decreases the speeds of fast neutrons. (d) The moderator prevents heat loss from the reactor core. (e) The moderator prevents the reactor from reaching a critical state.
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