The Energy-Climate Continuum by Antoine Bret

Author:Antoine Bret
Language: eng
Format: epub
Publisher: Springer International Publishing, Cham

6.5 Nuclear Energy: Fission

We now conclude our inventory of potential energy based sources by nuclear energy, which harnesses nuclear potential energy. Doing so, we jump directly from the last section on gravitational potential energy. We therefore bypass the electromagnetic potential energy category. Oil, coal, and gas are the main representatives of this category. Regarding the post-fossil fuels world, biofuels and biomass would fit in there too. Yet, they were treated in Sect. 6.2 as kinetic energy based sources, due to their direct connection with solar energy.

Nuclear reactions do not emit greenhouse gases by design. They do not have anything to do with combustion reactions at the molecular level. Here, we do not deal with the electrons around the atom nucleus. We deal with the very nucleus. The numbers reported on Table 5.​1 are another motivation to pursue this option. Because nuclear forces are by far the strongest ones, they hold, by far, the higher energy density.16 In case you are unfamiliar with nuclear physics, you can flip to Appendix C for a crash course on the basics. There, we explain, among other, why the only way to get energy out of the nuclear force is to split a big nucleus, or merge two light ones. The first option is fission. The other is fusion. Let us start with fission.

The table of nuclides represented on Fig. 6.5 displays all the known nuclei. It shows nuclei beyond 126 neutrons and 83 protons are fragile. They are simply too big to be at ease with themselves. Too many protons repel each other inside them. They are radioactive and display the full spectrum of decay types. Some of them, such as uranium-235, have the ability to split into two smaller nuclei when struck by a neutron. Here, we have one of the reactions capable of releasing energy: we start from an heavy nucleus and end up with smaller ones. Suppose our heavy weight has a total of nucleons, with more than 100 neutrons and 80 protons. From Fig. C.1 in Appendix C, we see its total binding energy should be around MeV. After fission, each fragment will be about half the size of the original. With some 50 neutrons and 40 protons, Figure C.1 gives MeV. The energy balance “after–before” reads,

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