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Unformatted text preview: 6-12 Binary Nuclear Reactions Chap. 6 (a) How much 235Us consumedper year (in gjy) to produce enough electricity i to continuously run a 100 W light bulb? (b) How much coal (in gjy) would be needed(coal has a heat content of about 12 GJjton)? Assume a conversion efficiency of 33% of thermal energy into electrical energy. Solution: With a 33% electrical conversionprocess,the amount of thermal energy required to light the 100 W bulb for one year is E~lb = 100(Wy)jO.33 300(Wy)= 1.10x 105(Wd)= 9.46 x 109(J). =
(a) Since 1 MWd of thermal energy comes from the consumption of 1.24 g of 235U,the amount of 235Uthat is consumedto produce the thermal energy for the electricity to light the bulb is , (b) The mass of coal that must be burned is 11. An accident in a fuel reprocessingplant, caused by improper mixing of 235U, produced a burst of fissionenergyliberating energy equivalentto the detonation of 7 kg of TNT (4.2 GJjton = 4.6 kJjg). About 80% of the fission products were retained in the building. (a) How many fissions occurred? (b) Three months after the accident, what is the rate (W) at which energy is releasedby all the fission products left in the building? Solution: (a) The number of fissions, assuming200 MeV releaseper fission, is Nf = Ereleased(MeV)j200(MeVjfiss) 1 1 = 7kg(TNT) x lO3_ x 4600~ x 1.602xlO-13J/MeV x k g 200MeV jfiss g g = 1.00 X 1018 fissions. (b) From Fig. 6.9, we obtain for t = 3 months = 7.78 X 106 s F-Y+/3(t) 1.2 x 10-8 X Nt = 1.2 X 1010MeVis = 1.9 roW. = Alternatively, from Eqs. (6.44) and (6.45) we obtain for t = 7.78 X 106 s F-y+p(t) = 2.66t-1.2 x Nf = 1.14 X 1010 MeV/s = 1.8 roW. July 24, 2002 16. ...
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This note was uploaded on 02/01/2010 for the course ECE 4130 taught by Professor Cady during the Spring '06 term at Cornell University (Engineering School).
- Spring '06