Nuclear power certainly has its pros and cons. It is considered to be a climate-friendly energy source because it generates power without releasing carbon dioxide, which is a greenhouse gas thought to be harmful to the atmosphere. However, there are safety concerns that come with nuclear power, including the possibility that a nuclear power plant could accidentally release radiation into the environment or be targeted for a terrorist attack. There is also the issue of what to do with radioactive waste. In this lesson, we will explore the risks associated with nuclear power and discuss how radioactive waste is handled.
Most nuclear reactors are based on the concept of nuclear fission. Nuclear fission occurs when uranium nuclei are bombarded with neutrons. This bombardment breaks the uranium nuclei apart, releasing heat, radiation and more neutrons. The neutrons that are released cause a chain reaction as more uranium nuclei get bombarded, releasing massive amounts of energy. This explains how nuclear power plants can create so much electricity from only a small amount of uranium. However, it also helps explain some of the concerns governments, scientists and citizens have about the ramifications of an accident within a nuclear power plant.
Now, it's important to note that in a nuclear power plant, the uranium chain reaction is controlled. Therefore, a nuclear reactor cannot explode like an atomic bomb. This is because a nuclear bomb requires an uncontrolled chain reaction with highly-enriched uranium fuel. Uranium is a very heavy naturally-occurring element. Being an element, it can exist in different forms known as isotopes. Isotopes are different forms of the same element that contain different numbers of neutrons in their nucleus. The isotope U-235 is important because it can be used in the nuclear fission chain reaction to create a lot of energy.
Unlike the uranium used in a nuclear bomb, which is about 90% enriched with the isotope U-235, the uranium used in a nuclear reactor is only slightly enriched, to about four or five percent. This limits the amount of neutrons available for the fission chain reaction. Also, the chain reaction within the core of a nuclear reactor is controlled by control rods that absorb neutrons to control the rate of reaction. A nuclear bomb does not utilize control rods and, therefore, is an uncontrolled chain reaction.
Now, what can happen in a nuclear reactor is something called a meltdown. A meltdown is an accident in which severe overheating of the nuclear reactor results in the melting of the reactor's core. A meltdown could occur if there was a defect in the cooling system of the reactor that allowed one or more of the nuclear fuel elements to exceed its melting point. If a meltdown occurred, a nuclear power plant could release radiation into the environment.
The biggest concern associated with a nuclear power accident is the negative effects that exposure to radiation can have on the human body. It is interesting to note that we are exposed to radiation naturally just by living our lives. Natural background radiation comes from outer space, and even radiates up from the ground below us. You may also have been exposed to a medical procedure, such as a CT scan, X-ray or nuclear medicine, such as an MRI, that utilized different types of radiation to diagnose problems or treat a disease.
For most people, the low-level exposure to radiation that comes from the environment and medical procedures does not result in any detectable health problems. However, if a person were exposed to significant amounts of radiation over a period of time, this exposure could damage body cells and lead to cancer. If a person were to be exposed to an acute dose of high-levels of radiation, the result would be radiation sickness. Radiation sickness is defined as illness caused by exposure to a large dose of radiation over a short period of time. Symptoms may include skin burns, nausea, vomiting, diarrhea, hair loss, general weakness and possibly death.
In addition to personal health concerns, there are also environmental health concerns associated with nuclear power generation. Nuclear power plants use water from local lakes and rivers for cooling. Local water sources are used to dissipate this heat, and the excess water used to cool the reactor is often released back into the waterway at very hot temperatures. This water can also be polluted with salts and heavy metals, and these high temperatures, along with water pollutants, can disrupt the life of fish and plants within the waterway.
Since the World Trade Center attacks in New York City on September 11th, 2001, concerns have circulated that terrorists could target nuclear reactors with the purpose of releasing radioactive materials. While it cannot be completely predicted how a nuclear reactor would withstand a terrorist attack, it is worth noting that the containment walls that surround the nuclear reactor are typically constructed of an inner steel lining surrounded by two to five feet of reinforced concrete. Nuclear power plants within the United States are built to withstand hurricanes, tornadoes, earthquakes and small plane crashes.
But perhaps the biggest challenge that comes with nuclear power is how to deal with the disposal of the radioactive waste that is generated during nuclear fission. Radioactive waste cannot be disposed of by conventional means. This is because some of the forms of radioactive waste, such as spent nuclear fuel rods, remain radioactive for hundreds or even thousands of years. This presents a tremendous challenge when it comes to proper disposal.
Currently, storage of spent fuel is handled onsite at the nuclear power plant. The spent fuel is first cooled underwater in steel-lined, concrete pools. After this initial cooling, the waste can be moved to above-ground containers that are built with steel-reinforced concrete walls. However, long-term storage is then required to allow the radioactive materials to decay. Long-term nuclear storage facilities must be located in stable geological locations that are not prone to flooding or natural disasters.
One potential repository in the United States is Yucca Mountain Nuclear Waste Repository in Nevada, which is a proposed site designed for the permanent storage of nuclear waste. Areas that have been evaluated and deemed appropriate sites for long-term nuclear waste storage, such the Yucca Mountain location, would allow nuclear waste to be stored deep underground within rock where it could be isolated from humans and the environment for a very long time with little or no maintenance. However, public and political debates have delayed implementation of the Yucca Mountain Nuclear Waste Repository. This has left the United States with no permanent repository for spent fuel.
Let's review. A reaction within a nuclear reactor is controlled, and therefore, a nuclear reactor could not explode like a nuclear bomb. This is thanks to control rods that absorb neutrons to control the rate of reaction, as well as the fact that uranium used in a nuclear reactor is only slightly enriched.
One concern with nuclear power is the risk of a meltdown. A meltdown is an accident in which severe overheating of the nuclear reactor results in melting of the reactor's core. There is also some concern that nuclear power plants could become a target of a terrorist attack by damaging or destroying the nuclear facility, causing the population to be exposed to radiation.
Even though we are exposed to low-levels of background radiation naturally through the environment and certain medical procedures, the levels are not typically enough to negatively affect the body. However, exposure to significant amounts of radiation over a period of time could damage body cells and lead to cancer. If a person experiences exposure to sudden and high levels of radiation, the result could be radiation sickness.
An environmental concern associated with nuclear power is heat, which is a byproduct of the reaction. Local water sources are used to dissipate this heat, and these high temperatures, along with water pollutants, can disrupt the life of fish and plants within the waterway.
One of the biggest challenges facing nuclear power is storage of radioactive waste. Waste is currently stored at the nuclear plants in steel-lined, concrete pools or above-ground containers that are built with steel-reinforced concrete walls. However, long-term storage is needed to allow the waste to decay to a safe level. Yucca Mountain Nuclear Waste Repository in Nevada is a proposed site designed for the permanent storage of nuclear waste.
When this video lesson is finished, you should be able to:
- Define nuclear energy and how it works
- Identify the possibilities of radiation release concerns
- Explain the environmental concern of disposing of nuclear waste material
- Remember that nuclear plants could be targets for terrorist organizations
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Although there are many benefits to using nuclear power, there are many concerns about nuclear power plants and their resultant radioactive waste. A well known nuclear disaster occurred in 1986 at the Chernobyl Nuclear power plant. The cause of the disaster was due to a flaw in design as well as improper procedures during a safety test. This accident resulted in over 4,000 deaths and the surrounding area remains uninhabitable. In fact, it is still illegal to live in certain areas due to high radioactivity and it may be hundreds of years before it is safe to resume activities in these areas. One way to get a good understanding of how radioactive waste is difficult to manage is by considering the half-life (radioactive decay) of different materials. The half-life of a substance represents how many years it takes for half of the radioactivity to decrease. View the example below and answer the questions.
Strontium-90 has a half-life of 30 years. If the original mass was 10 grams, how much is left after 75 years?
Start by determining how many half-lives have passed by dividing the elapsed time by the half-life.
75 ÷ 30 = 2.5 half-lives elapsed
Next, take 0.5 to the power of the half-lives elapsed to determine the decimal fraction of the remaining radioactive material.
0.52.5 is approximately 0.18 (Rounding to the nearest hundredth)
Finally, multiply the starting grams by the decimal fraction to determine the remaining mass of the material.
0.18 * 10.0 = 1.8 grams remain
1. Strontium-90 has a half-life of 30 years. If the original mass was 90 grams, how much is left after 10 years?
2. Os-182 has a half-life of 21.5 hrs. If the original mass was 100 grams, how much is left after 90 hrs?
3. Are there any safety protocols you could apply to store the waste or remove it from the environment now that you understand radioactive decay?
1. 71.4 g
2. 5.49 g
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