, does not always produce the same products. Fission of a given nuclide, such as 238 U 238 U This is because this fission reaction produces neutrons and does not split the nucleus into two equal parts. The 171-MeV energy released is large, but a little less than the earlier estimated 240 MeV. This is about 10 times the energy per fusion reaction, and about 100 times the energy of the average α α, β β, or γ γ decay.Ī number of important things arise in this example. Thus, if a heavy nucleus splits in half, then about 1 MeV per nucleon, or approximately 240 MeV per fission, is released. The graph in Figure 32.21 shows BE / A BE / A to be about 7.6 MeV/nucleon for the heaviest nuclei ( A A about 240), while BE / A BE / A is about 8.6 MeV/nucleon for nuclei having A A about 120. The amount of energy per fission reaction can be large, even by nuclear standards. Figure 32.21 shows that BE / A BE / A is greater for medium-mass nuclei than heavy nuclei, implying that when a heavy nucleus is split, the products have less mass per nucleon, so that mass is destroyed and energy is released in the reaction. As noted in Fusion, energy is released if the products of a nuclear reaction have a greater binding energy per nucleon ( BE / A BE / A) than the parent nuclei.

(credit: Kalmthouts)įission is the opposite of fusion and releases energy only when heavy nuclei are split. The reactor is in the small domed building to the left of the towers. The cooling towers are the most prominent features but are not unique to nuclear power. About 16% of the world’s electrical power is generated by controlled nuclear fission in such plants. China is building nuclear power plants at the rate of one start every month.įigure 32.20 The people living near this nuclear power plant have no measurable exposure to radiation that is traceable to the plant. France provides over 75% of its electricity with nuclear power, while the US has 104 operating reactors providing 20% of its electricity. By the end of 2009, there were 442 reactors operating in 30 countries, providing 15% of the world’s electricity.

Whereas nuclear power was of little interest for decades following TMI and Chernobyl (and now Fukushima Daiichi), growing concerns over global warming has brought nuclear power back on the table as a viable energy alternative. Hundreds of nuclear fission power plants around the world attest to the fact that controlled fission is practical and, at least in the short term, economical, as seen in Figure 32.20. Controlled fission is a reality, whereas controlled fusion is a hope for the future. Nuclear fission is a reaction in which a nucleus is split (or fissured).

Describe controlled and uncontrolled chain reactions.

Discuss how fission fuel reacts and describe what it produces.

By the end of this section, you will be able to:

Spontaneous fission accident