Energy and Human Ambitions on a Finite Planet, 2021a

15 Nuclear <strong>Energy</strong> 256
In the design of Figure 15.16, called a boiling water reactor, the water acts
as both the neutron moderator <strong>and</strong> the thermal conveyance medium.
Nuclear fuel (uranium) is arranged in fuel rods, providing ample surface
area <strong>and</strong> allowing water to circulate between the rods to slow down
neutrons <strong>and</strong> carry the heat away. Neutron-absorbing control rods—
usually containing boron—set the reaction speed by lowering from the
top. 34 An emergency set of control rods can be dropped into the core in
a big hurry to shut down the reactor instantly if something goes wrong.
When the emergency rods are in place, neutrons have little chance of
235
finding a U nucleus before being gobbled up by boron.
As of 2019, the world has about 455 operating nuclear reactors, amounting
to an installed capacity of about 400 GW. 35 The average produced power—
not all are running all the time—was just short of 300 GW. The thermal
equivalent would be approximately three times this, or 1 TW out of the
18 TW we use in the world. So nuclear is a relevant player. See Table 15.8
for a breakdown of the top several countries, Fig. 7.7 (p. 109) for nuclear
energy’s trend in the world, <strong>and</strong> Fig. 7.4 (p. 107) for the U.S. trend.
Country # Plants GW inst. GW avg. % elec. global share (%)
U.S. 95 97 92 20 31
France 56 61 44 71 15
China 49 47 38 5 13
Russia 38 28 22 20 8
Japan 33 32 8 8 3
S. Korea 24 23 16 26 5
India 22 6 5 3 2
World Total 455 393 295 11 100
34: . . . always this direction, so that gravity
does the pulling rather then relying on some
other drive force
35: From this, we glean that reactors average
roughly 1 GW each.
Table 15.8: Global nuclear power in 2019
[101], listing number of operational plants,
installed capacity, average generation for
2019 (Japan currently has stopped a number
of its reactors), percentage of electricity
(not total energy), <strong>and</strong> fraction of global
production (these 7 countries accounting
for over 75%). Notice the close match between
number of plants <strong>and</strong> GW installed
for most countries, indicating that most nuclear
plants deliver about 1 GW.
Nuclear plants only last about 50–60 years, after which the material
comprising the core becomes brittle from exposure to damaging radioactivity
<strong>and</strong> must be decommissioned. The median age of reactors in
the U.S. is 40 years, <strong>and</strong> all but three are over 30 years old. Additional
challenges will be addressed in the sections that follow.
When nuclear energy was first being rolled out in the 1950s, the catch
phrase was that it would be “too cheap to meter,” a sentiment presumably
fueled by the stupendous energy density of uranium, requiring very
small quantities compared to fossil fuels. The reality has not worked
outthatway.Today,a1GWnuclear power plant may cost $9 billion to
build [102]. That’s $9 per Watt of output power, which we can compare [102]: Union of Concerned Scientists (2015),
The Cost of Nuclear Power
to the cost of a solar panel, at about $0.50 per W (Fig. 13.16; p. 215), or
utility-scale installation at $1 per Watt [89]. While it seems that solar 36
wins by a huge margin, the low capacity factor of solar reduces average
power output to 10–20% of the peak rating, depending on location.
Meanwhile, nuclear reactors tend to run steadily 90% of the time—the
off-time used for maintenance <strong>and</strong> fuel loading. So nuclear fission costs
about $10 per delivered Watt, while solar panels are $2.5–5 per delivered
36: Recall, for context, that solar is not
among the cheaper energy resources. Like solar,
nuclear power is dominated by up-front
costs, rather than fuel cost.
© 2021 T. W. Murphy, Jr.; Creative Commons Attribution-NonCommercial 4.0 International Lic.;
Freely available at: https://escholarship.org/uc/energy_ambitions.