Principles of naval engineering - Historic Naval Ships Association

—Chapter 24, -NUCLEAR POWER PLANTS238— 6zoulUozazEQ1 I 1 I I I I20 40 60 80 100 120 140ATOMIC MASS NUMBER—I160 180 200 220 240 260Figure 25-5.—Relationship between atomic mass number andaverage binding energy per nucleon.147.155into the compound nucleus of uranium-236,which fissions instantaneously.There are more than 40 different ways auranium-235 nuclei may fission, resulting inmore than 80 different fission products.^ Forthe purpose of this discussion, let us considerthe most probable fission of a uranium-235nucleus. In slightly more than 6 percent ofthe fissions, the uranium-235 nucleus will splitFor a detailed discussion on nuclear fission, referto Samuel Glasstone, Sourcebook on Atomic Energy(2d ed.; Princeton: D. Van Nostrand Company, Inc.,1958).intofragments having mass numbers of 95 and139. The following equation is typical:it235 „192^ ^o"-,95 1^39 1 .39^ 2530*where the daughter products, yttrium and iodine,are toh radioactive and decay through betaemission to the stable isotopes of molybdenum(^2^'^ ) and lanthanum (57Lal39)^ respectively.One method of determining the energy releasedfrom the above reaction is to find thedifference in atomic mass units of the daughterproducts and the original nucleus. It is alsonecessary that we account for the neutron usedto bombard the uranium-235 atom and the twoneutrons liberated in the fission process. In619