338 ENVIRONMENTAL ENGINEERINGsources like mine tailings, and radon, because it is ubiquitous. Wastes are handled in
much the same manner as the hazardous wastes discussed in Chap. 15.
The United States no longer operates plutonium production reactors, and complete
shutdown of the nuclear industry is suggested from time to time by various groups.
Even if the U.S. nuclear industry were shut down, the existing waste would have to be
dealt with. Moreover, other countries throughout the world are not simply maintaining
their nuclear power production capability, but expanding it. Like virtually every other
pollution problem, radioactive waste is a worldwide concern, and not limited to the
United States or the Western Hemisphere.
In the late 199Os, the shutdown of the U.S. nuclear industry, or its decline by
attrition, was seriously considered. Localized electricity shortages, like the shortage
that forced “rolling blackouts” in California in 2000 and 2001, has led to a rethinking of
the future role of nuclear energy in the U.S. energy picture. At present, nuclear power
supplies about 20% of the electricity in the United States. In a few states the share is
about 40%, and in one state, Illinois, it is better than 60%. In the event of shutdown,
no more than about 25% of this energy could be saved by conservation. So-called
“alternative” energy sources like wind power, solar thermal generation, geothermal
energy, and small-scale hydropower have not yet been implemented on a large scale.
The adverse environmental effects of large-scale implementation are as yet unknown,
but cannot arbitrarily be assumed to be small or negligible.
Other methods of thermal generation of electricity, combustion of fossil fuels, have
quite well-understood adverse environmental effects. The adverse effects of burning
coal are particularly severe. In addition, fuel combustion contributes to the concentra-
tion of COz in the earth’s atmosphere, while nuclear electric generation does not.
Thorough and objective comparisons of electric generating methods should guide
decisions about power generation. Generating electricity, no matter how it is done,
causes irrevocable environmental damage on a scale directly proportional to the power
produced.
During the past half-century, the pendulum of public opinion swung from the ‘’pro-
nuclear” extreme of the 1950s and 1960s to the “anti-nuclear” extreme of the 1980s
and 1990s. Politics tends to follow public opinion, but political decisions, including
those about nuclear power and radioactive waste, are emotion-laden and not always
scientifically or environmentally sound. The role of engineers, now more than ever, is
to inform and influence political decisions.
PROBLEMS16.1 Show that after 10 half-lives, about 0.1% of the initial radioactive material
is left, and that after 20 half-lives, is left.
16.2 Fe-55 has a half-life of 2.4 years. Calculate the disintegration constant. If a
reactor core vessel contains 16,000 Ci of Fe-55, how many curies will be left after
100 years? How many becquerels will be left? How many grams?
163 1-13 1 is used in the diagnosis and treatment of thyroid disease, and a typical
diagnostic amount is 1.9 x lo6 Bq injected intravenously. If the physiological half-life