Energy and Human Ambitions on a Finite Planet, 2021a

239
15 Nuclear <strong>Energy</strong>
Most of the energy forms discussed thus far derive from sunlight—
either contemporary input or fossilized storage. The fuel for nuclear
energy is truly ancient, predating the solar system. The heavy elements
participating in fission were produced by astrophysical cataclysms (most
likely merging neutron stars), while the hydrogen building blocks for
fusion originated in the Big Bang itself. In brief, fission involves the
splitting of heavy nuclei into smaller pieces, while fusion builds larger
nuclei from smaller ones.
While only fission has been successfully implemented as a source of
societal energy, both types essentially boil down to the same thing:
a source of heat to make steam <strong>and</strong> drive a heat engine. How <strong>and</strong>
why nuclear material generates heat will be a primary focus of this
chapter. Many practical concerns surround nuclear power, such as safety,
weapons, waste, <strong>and</strong> proliferation of dangerous material. Self-pride for
the impressive accomplishment of mastering nature well enough to
implement nuclear power may not adequately justify continued reliance
upon it—even if it is not a direct emitter of CO 2 .
15.1 The Nucleus .......... 239
15.2 Radioactive Decay ...... 242
15.3 Mass <strong>Energy</strong> ......... 246
15.4 Fission ............. 249
The Basic Idea ........ 250
Chain Reaction ........ 251
Fission Accounting ..... 251
Practical Implementations . 255
Nuclear Waste ......... 260
Weapons <strong>and</strong> Proliferation 262
Nuclear Safety ........ 263
Pros <strong>and</strong> Cons of Fission .. 264
15.5 Fusion ............. 264
Fuel Abundance ....... 266
Fusion Realities ....... 267
Pros <strong>and</strong> Cons of Fusion .. 268
15.6 Upshot on Nuclear ...... 269
15.7 Problems ............ 269
Underst<strong>and</strong>ing nuclear energy requires a longer journey than was
needed for hydroelectricity, wind, <strong>and</strong> solar photovoltaics. We first learn
about the nucleus <strong>and</strong> its many configurations, how nuclei transform
from one to another through radioactive decay, the role E mc 2 plays,
<strong>and</strong> finally dig into the workings of fission <strong>and</strong> fusion.
15.1 The Nucleus
First, what is a nucleus? Every (neutral) atom consists of a positivelycharged
nucleus surrounded by a cloud of negative electrons (Figure 15.1).
Cooling towers of the decommissioned Satsop nuclear power plant in Washington. Photo
credit: Tom Murphy
© 2021 T. W. Murphy, Jr.; Creative Commons Attribution-NonCommercial 4.0 International Lic.;
Freely available at: https://escholarship.org/uc/energy_ambitions.