This video segment continuous our examination of greenhouse gas emissions from electric
power plants.
It focuses on nuclear, hydroelectric, and wind power.
It's major points are number one, fears of major accidents have stalled the use of nuclear
electric power.
Number two, most of the best locations for hydroelectric power are already in use.
Number three, wind power is expanding despite difficulties in site selection.
Three major accidents have occurred at nuclear power plants.
A reactor core at Three Mile Island Nuclear Power Plant near Harrisburg, Pennsylvania,
melted down on March 28, 1979.
Fortunately, most of the radioactivity was contained, and no one experienced severe injuries.
On April twenty-sixth, 1986, a reactor at the Chernobyl nuclear power plant in Ukraine
exploded, and sent a plume of highly radioactive material over large portions of Europe.
237 people suffered from acute radiation sickness, 56 of whom died within a short period.
Millions more were exposed above normal doses of radiation.
Today, radiation levels remain so high near the plant that all residential, civil, and
business activities are forbidden within a 30 kilometer radius.
A major earthquake generated a tsunami that hit the northeast coast of Japan of the eleventh
of March, 2011.
flooding the six nuclear reactors at the Fukushima Daiichi power plant, and destroying all cooling
for the reactors.
In the days that followed three of the reactors experienced full meltdown.
Hydrogen explosions and fires damaged the containment of four reactors.
Radioactive water leaked into the ocean and contaminated ground water for kilometers around
the plant.
Most countries have advised their citizens to evacuate an 80 kilometer radius from the
plant.
Clean up of this area will require a work force of hundreds or even thousands and take
years or decades.
The accidents at Three Mile Island, Chernobyl, and Fukushima, cast appall over the nuclear
power industry.
Based together with a relatively low cost of coal power, the difficulties in disposing
of nuclear waste and the volatility of uranium prices, have deterred construction of new
facilities.
At present 435 nuclear power plants operate in 30 different countries and generate about
fifteen percent of the world's electricity.
Worldwide, only 29 new nuclear power plants are under construction and will begin operation
during the next decade.
Seven are in India, five in Russia, four in China, one or two in other countries, But
none in the United States or Western Europe.
By contrast, 6 older plants of the world closed down permanently in 2006.
The Fukushima disaster prompted Germany and Switzerland to announce their intentions to
cease use of nuclear power by 2022 and 2034 respectively.
Nuclear power plants harness the energy released during nuclear fission.
In this process, unstable isotopes of uranium or plutonium in fuel rods expel neutrons and
disintegrate, respectively, into thorium or uranium.
A tiny fraction of the mass in the original materials converts into energy.
E = MC^2.
But this releases vast amounts of energy because of the high conversion value.
Neutrons expelled from the fuel rods may strike other uranium or plutonium atoms and induce
them to expel neutrons building a self sustaining fission reaction.
The critical mass of fissionable material in the fuel rods is always below that necessary
to start a nuclear explosion.
Nonetheless, if the fission reaction accelerates too quickly, a reactor core may overheat and
melt down as they did at Three Mile Island, Chernobyl, and Fukushima.
To control the rate of the fission reaction and thereby the temperature of the core, nuclear
power plants insert control rods as neutron absorbing silver, indium, cadmium or boron
between the fuel rods.
Moreover, elaborate heat exchange systems transfer energy from the reactor core to a
steam generator that converts water to high pressure and high temperature steam.
The components outside the containment building are common to most types of electric power
plants.
Steam, which the reactor core generates, drive turbines that spin electrical generators.
Nuclear power has major advantages.
It is clean, in certain respects, because it neither releases significant amounts of
greenhouse gases, nor air pollutants such as particulates, sulfur dioxides, or nitrous
oxides.
Known reserves of fissionable materials are adequate to supply nuclear power plants, at
the current rate, for roughly 50 years.
If the price of uranium should warrant it, say above 200 dollars per kilogram, expiration
for new sources new nuclear reactor technologies, and fuel rod reprocessing, have the potential
to supply nuclear fuel for several centuries.