Nuclear - Energy Policy Analysis: A Conceptual Framework - page 48

sile Pu-239, some of which will, in turn, undergo fission and produce energy. Others decay into
other nonfissionable radioactive elements such as Pu-240 and lead. Products created by nuclear
fission reactions are retained within the fuel pellets and become neutron-absorbing products that
act to slow the rate of nuclear fission and heat production. As reactor operation continues, a point
is reached at which the declining concentration of fissile nuclei in the fuel and the increasing
concentration of neutron-absorbing by-products result in lower than optimal heat generation. At
this point, a reactor must be shut down temporarily and refueled. The fraction of the reactor's fuel
core replaced during refueling is typically one-fourth for a boiling-water reactor and one-third for
a pressurized-water reactor (USEIA 2011e).
REACTOR SAFETY
The human mind is capable of infinite creativity. But is it possible for the human mind to invent
a technology so complicated and powerful it cannot be controlled by those who invented it? Or
by persons other than those who invented it, who are more likely to be operating it on a daily
basis? The continuing safety risks of utilizing nuclear fission to generate electric power were aptly
illustrated with the core meltdown at Three Mile Island near Harrisburg, Pennsylvania, in 1979,
with the core explosions in Ukraine at Chernobyl in 1986, and again with multiple core meltdowns
at the Fukushima Daiichi nuclear plant in Japan on March 11, 2011. These three lessons have
gradually increased in severity, the first two being discounted by many Americans because there
was no loss of life at Three Mile Island and because Chernobyl is located at such a great distance
from the United States and utilized a reactor design not used in this country.
Still, Three Mile Island illustrated how mechanical failures could be compounded by failure of
plant operators to understand the situation due to poor control room design and deficient training.
The result was a “partial” core meltdown (Kemeny 1979) in a 906 megawatt (MWe) pressurized-
water reactor that had become operational in 1978, only a year before its demise. This was the first
time the term “partial” meltdown was used, apparently as a public relations measure to minimize
the apparent severity of a catastrophic situation. In the nuclear industry, a meltdown is a meltdown,
partial or otherwise. It involves the distortion of metal fuel-rod assemblies in a reactor core such
that control rods cannot be inserted or removed, thus relieving plant operators of most control
over reactor core temperatures. This situation creates the possibility of a steam explosion that
may disperse highly radioactive materials over a large area and create a mess of destroyed, highly
radioactive equipment that is exceedingly difficult to clean up without harm to human life. Three
Mile Island stimulated more stringent safety regulation by the U.S. Nuclear Regulatory Commis-
sion and cancellation of many orders for nuclear reactors, which the electric utility industry had
already begun to abandon due to their exceedingly high capital costs; however, the significance
of its warning has diminished over the years as memories have faded.
At Chernobyl, poor design of a 1,000 MWe nuclear reactor and human errors during opera-
tion and testing of safety features caused an explosion and fire, releasing into the atmosphere
large quantities of radioactive contamination, which eventually spread over much of the western
Soviet Union and Europe. The disaster involved one of four 1,000 MWe reactors at the site first
operational in 1977, a light-water reactor moderated by a graphite medium, fueled with natural,
unenriched uranium dioxide. The resulting contamination of the environment with radioactive
plutonium, iodine, strontium, and cesium stimulated evacuation of more than 100,000 people
from the affected region during 1986 and relocation of another 200,000 people from Belarus, the
Russian Federation, and Ukraine. Over 5 million people continue to live in contaminated areas
(IAEA 2011a), and up to 4,000 could eventually die of radiation exposure from the Chernobyl