By Jessica Riedmueller
Nuclear energy. The words bring to mind a host of images: an atom with electrons orbiting in rings around a nucleus, the artificial cloud of a plant’s steam tower, a concrete shelter housing the post-meltdown Chernobyl reactor, a mushroom cloud filling the sky.
Nuclear fuel has a complex history. From the secrecy of the Manhattan Project and its devastating outcome to the Cold War to modern-day North Korea, nuclear energy seems inextricably linked with the threat of nuclear war.
Nuclear power is one of the biggest issues facing the new president and the world today. There is a strong cry to reduce our dependence on fossil fuels and imported oil. Some believe that nuclear power is a ready and reliable source of clean energy and must be considered as part of any plan to reduce dependence on fossil fuels. Others, many who protested the construction of plants decades ago, say there are still unanswered questions that need to be addressed before more plants are built.
How It Works
Shrouded in physics, the understanding of nuclear energy came through the experiments of a long list of scientists in the early 20th century, from the discovery of the nucleus to the Manhattan Project. The history of nuclear energy is fascinating and complex, but the reason it works is simple.
The nuclei of the large nuclear elements are held together by substantial binding energy. The breaking apart of the nucleus, which is what a nuclear reaction is, frees this energy. The two types of nuclear reactions lead to the release of energy are fusion and fission.
Fusion is nature’s favorite reaction. It drives the universe, and without it we would have no stars, no sun, no life. Fusion works by binding two like-charged nuclei to create a heavier nucleus.
In the process neurons are freed along with the energy holding them to the original nucleus. In the cosmos, the heavier elements from carbon to iron are “cooked” in the stars through the fusion of hydrogen and helium and released into the universe.
“Nature’s fusion” is a process that has worked smoothly for billions of years leading to the universe we know today. Man-made fusion, on the other hand, is not quite as smooth. Though we can achieve nuclear fusion, it is not exactly controllable.
Fission is considered controllable and used in the nuclear reactors that are operating today. Fission reactions involve the splitting of the nucleus of a heavy element, usually uranium and sometimes plutonium, by hurtling a neutron at high speed directly at it. The nucleus absorbs the neutron splitting into various fission products and releasing a few neutrons. The one reaction alone releases a great deal of energy in a control reactor in a chain reaction. As the nuclei split, the fragment neutrons bombard other particles, those bombard still more particles, and on and on to create more energy. Power plants then use the heat created in the reactions to boil water into steam that turns turbines, thereby converting heat into the electricity that flows through our houses.
The only reactors commercially operating today are fission reactors, and the most common type is the Pressurized Water Reactor (PWR). Better known in The Natural State as Arkansas Nuclear One. Unit One came online in 1974 and its license will expire in 2034. Unit Two began operation in 1980 and its license will expire in 2038.
As the name suggests, pressurized water reactors use water under high pressure to both remove the heat from the nuclear reactions and to moderate the chain reaction. The fuel used in these reactions is low-enriched uranium containing a small percentage of fissile uranium. The uranium is formed into pellets and housed in metal rods.
PWRs use two coolant loops of water to transfer heat energy from the nuclear reactor to electricity fed into the grid. The primary coolant loop is pressurized and runs through the reactor. After it is heated in the core, the primary coolant runs through a steam generator containing the lower pressure secondary coolant creating pressurized steam. The steam flows through a turbine that turns a generator to produce electricity. The steam is run through a condenser and the resulting water is fed back into the steam generator.
The radioactive primary loop is housed in a containment building meant to prevent the escape of radiation into the environment. The radioactive primary coolant and the non-radioactive secondary coolant remain separate throughout the process.
Another reactor type of particular interest to those in Northwest Arkansas is the Fast Breeder Reactor (FBR). The Southwest Experimental Fast Oxide Reactor or SEFOR, which is located south of Fayetteville, is a deactivated test reactor. It is currently owned by the University of Arkansas and is a Nuclear Historic Landmark. Fast breeder reactors are able to use an isotope of uranium that is not viable as a fuel in PWRs. From this isotope, a plutonium fuel can be bred.
Why Some Say ‘No’
So what’s wrong with nuclear energy? Waste for one. The issues that were being debated decades ago, still exist. There is no place for the radioactive waste. Arkansas Nuclear One stores its spent fuel onsite.
SEFOR is still contaminated and the University of Arkansas, which agreed to accept the site when it was decommissioned, is now plagued with the cost of keeping it secure. Sen. Blanche Lincoln D-Ark. has been working unsuccessfully for several years to secure federal funding to properly shut it down.
Once the uranium rods are spent, they are a highly radioactive mix of fission products. This used fuel currently has no where to go and is stored at the reactors, either in pools of water or in dry casks made of concrete or some other insulating material.
Scientists and governmental officials have considered burying the uranium under the ocean floor or ejecting it into outer space. But the current option is burying it underground and on the earth.
The Department of Energy has submitted an application to the Nuclear Regulatory Commission to create a repository at Yucca Mountain in the Mojave Desert. The thought is that if spent nuclear fuel is buried in strategic geological locations, it will isolate the dangerous radioactivity from people and the environment. This option is still controversial. The “not in my backyard” mentality is not unexpected.
The biggest fear about nuclear energy is meltdown. Meltdown occurs when the reactor core overheats and the nuclear fuel melts. Two nuclear accidents are famous for meltdown, Three Mile Island in the U.S. and Chernobyl in Russia.
The Three Mile Island accident remains to America a frightening reminder of the dangers of nuclear energy. In the early morning hours on March 28, 1979, the feedwater pumps in the secondary loop stopped working. Through a series of events, this lead to a loss of coolant and subsequently a partial meltdown of the reactor core. The radiation did not breach the containment unit and there were no immediate injuries.
Chernobyl was a different story. Because of a power increase accident, the reactor in Unit Four of the plant was destroyed, and massive radiation was released into the environment. An 18-mile zone around the reactor was evacuated. Fires rampaged through the reactor threatening to release more radiation. Thirty-one people died, and thousands of people have been subsequently treated for thyroid cancer. The destroyed reactor was entombed in concrete to prevent the release of more radiation, and the surrounding area was cleaned to reduce the contamination around the site. The remaining reactors were restarted, but have been closed since. Chernobyl was avoidable. The reactor was of a flawed design, one that has not been used in the United States.
From Nuclear Plants To Nuclear Weapons
Today, nuclear disasters of a different kind eclipse the fears of a meltdown. Nuclear war and nuclear terrorism are chilling threats. Though power plants use enriched uranium, it is not weapons-grade. But the technology used to make civilian use uranium can be converted to make the highly enriched uranium used in weapons. The world has acknowledged this, prompting the creation of the Nuclear Nonproliferation Treaty and the United Nation’s International Atomic Energy Agency.
The Future Of Nuclear Energy
Nuclear technology offers two visions of the future. The first a bleak apocalyptic landscape, entire towns, cities, countries leveled by nuclear war, the second a near utopian vision of clear blue skies, flying cars and people in silver spandex jumpsuits. Well, maybe not the spandex. Can nuclear power offer a clean, safe alternative energy source or is it still too dangerous to consider?