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Lecture21NuclearPower

Lecture21NuclearPower - Lecture 20 Nuclear Power I...

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Lecture 20 Nuclear Power I. Principles of Operation A. Review of Neutron Induced Fission Z A 0 1 Z A+1 Z A 1 + Z A 2 + X n X s X X n + Q 1 1 2 2 1    * 10 18 Bookkeeping: A + 1 = A 1 + A 2 + Z = Z 1 + Z 2 Q 180 MeV 2 10 10 kJ/mole E kinetic + E * 1 + E * 2 ~ 160 MeV ~ 20 MeV 1. IF < > 1, chain reaction possible HEAT ACTIVITY 2. Controlled conditions: power reactor 90% 10% 3. Maximum efficiency: nuclear explosion B. Fuels Only U and Th of nature's elements undergo fission readily Reaction cross sections largest for thermal neutrons (0.03 eV @ 300 K) 1. 90 232 Th (100%): (n,f) 2 10 4 b (e-e) (n, ) = 7.36 b 232 Th   92 233 U ( f =530 b) 2. 92 238 U (99.27%): (n,f) 5 10 4 b (e-e) (n, ) = 2.71 b 239 U   94 239 Pu ( =742 b) 3. 235 U (0.72%): (n,f) = 577 b (n, ) = 101 b 4. Conclusions 235 U good fuel 232 Th and 238 U – poor fuels but good feed stocks (Breeder reactors) ; v = 2.44 v = 2.89 v = 2.51
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