Chapter 24, -NUCLEAR POWER PLANTS 



— 6 



z 



o 



u 



lU 



o 



z 

 a 



z 



EQ 



238 



— I — 

 220 



1 I 1 I I I I 

 20 40 60 80 100 120 140 



ATOMIC MASS NUMBER 



160 



180 



200 



240 260 



Figure 25-5.— Relationship between atomic mass number and 

 average binding energy per nucleon. 



147.155 



into the compound nucleus of uranium-236, 

 which fissions instantaneously. 



There are more than 40 different ways a 

 uranium-235 nuclei may fission, resulting in 

 more than 80 different fission products.^ For 

 the purpose of this discussion, let us consider 

 the most probable fission of a uranium-235 

 nucleus. In slightly more than 6 percent of 

 the fissions, the uranium-235 nucleus will split 



For a detailed discussion on nuclear fission, refer 

 to Samuel Glasstone, Sourcebook on Atomic Energy 

 (2d ed.; Princeton: D. Van Nostrand Company, Inc., 

 1958). 



into fragments having mass numbers of 95 and 

 139. The following equation is typical: 



it235 „1 

 92^ ^o"- 



,95 



39^ 



53 



1^39 . 2 



1 



0* 



where the daughter products, yttrium and iodine, 

 are toh radioactive and decay through beta 

 emission to the stable isotopes of molybdenum 

 (^2^'^ ) and lanthanum (57Lal39)^ respectively. 



One method of determining the energy re- 

 leased from the above reaction is to find the 

 difference in atomic mass units of the daughter 

 products and the original nucleus. It is also 

 necessary that we account for the neutron used 

 to bombard the uranium-235 atom and the two 

 neutrons liberated in the fission process. In 



619 



