Nuclear Energy

Summary

This AP environmental sciences video explores nuclear energy, its advantages, and challenges. It discusses the INE Scale for measuring nuclear accidents, the low carbon footprint of nuclear power compared to fossil fuels, and the process of nuclear fission in reactors. The video also covers the issues of nuclear waste with long half-lives and the potential health risks of radiation exposure. It concludes by highlighting the resurgence of nuclear energy due to concerns over carbon emissions and the promise of new technologies like thorium reactors.

Takeaways

• ⚠️ The International Nuclear Event Scale (INES) measures the severity of nuclear accidents, with only two events reaching the highest level of 7, Chernobyl in 1986 and Fukushima in 2011.
• 🔋 Nuclear energy generation has remained static for decades due to fears surrounding radiation and nuclear accidents.
• 🌿 Nuclear power plants produce carbon dioxide emissions comparable to wind and hydro power, significantly less than fossil fuels.
• ⚛️ Nuclear energy is generated through the fission of radioactive material, typically Uranium-235, which splits into smaller elements and releases energy and neutrons.
• 💧 Light water reactors are a common type of nuclear reactor, using water to moderate neutrons and control the reaction.
• 🛡 Control rods in reactors absorb neutrons and are used to control the rate of the nuclear reaction.
• 🗑 Nuclear waste is a significant concern, with some radioactive materials having half-lives measured in thousands of years.
• 📉 The Three Mile Island incident in the US was the highest level of nuclear accident in the country, reaching level 5 and causing public concern.
• 🔍 The future of nuclear energy may include advancements like thorium reactors and third-generation reactors that can reuse waste.
• 🌍 As part of the effort to reduce carbon emissions and combat climate change, nuclear energy is being revisited as a potential solution.

Q & A

What is the International Nuclear Event Scale (INE Scale)?

The INE Scale is a logarithmic scale used to measure the severity of nuclear accidents, similar to how the Richter Scale measures the size of earthquakes.

What are the two instances where the INE Scale reached level 7?

The two instances were the Chernobyl disaster in 1986 and the Fukushima disaster in 2011.

What was the highest INE Scale level reached in the United States?

The highest INE Scale level reached in the United States was level 5, which occurred at Three Mile Island.

How does the amount of carbon dioxide produced by nuclear power plants compare to other energy sources?

The amount of carbon dioxide produced by nuclear power plants is comparable to that of wind generation or hydro power, and significantly less than that produced by gas, oil, and coal.

What is the primary source of energy in nuclear reactors?

The primary source of energy in nuclear reactors is the fission of radioactive material, typically Uranium-235.

How does the process of nuclear fission in a reactor differ from that in a nuclear weapon?

In a reactor, the fission process is controlled, while in a nuclear weapon, it is uncontrolled and rapid.

What are light water reactors and how do they work?

Light water reactors are a type of nuclear reactor that uses ordinary water to cool and moderate the nuclear reaction, producing heat to generate steam and electricity.

What is the role of control rods in a nuclear reactor?

Control rods are used to absorb neutrons and control the rate of the nuclear reaction in a reactor by being inserted or removed from between the fuel rods.

What are the disadvantages of nuclear energy mentioned in the script?

The disadvantages include the creation of long-lived nuclear waste and the potential for accidents that can release radiation into the environment.

How is nuclear waste typically stored after it is removed from a reactor?

Nuclear waste is initially stored in pools to cool down and then transferred to dry cask storage on concrete slabs.

What is the concept of half-life as it relates to radioactive materials?

Half-life is the time required for half of a radioactive substance to decay. It varies for different materials and determines how long the waste remains radioactive.

What are some potential future developments in nuclear energy mentioned in the script?

Some potential future developments include the use of thorium reactors and third-generation reactors that can reuse waste, as well as advances in technology to improve safety and reduce carbon emissions.

Outlines

00:00

📊 Understanding Nuclear Energy and Accidents

This paragraph introduces the International Nuclear Event Scale (INE Scale), which measures the severity of nuclear accidents on a logarithmic scale similar to the Richter Scale for earthquakes. It mentions the two level 7 accidents: Chernobyl in 1986, which resulted in 31 deaths, and Fukushima in 2011, where a reactor meltdown was triggered by an earthquake and tsunami. The paragraph also contrasts the environmental impact of nuclear power with that of fossil fuels, highlighting that nuclear power produces carbon dioxide emissions comparable to wind or hydro power. The discussion then shifts to the process of nuclear fission, where Uranium-235 decays into barium and krypton, releasing energy and neutrons that can cause further fission. The control of this chain reaction in reactors is explained, using light water reactors as an example, where fuel rods are used to generate heat and electricity through steam generation. The paragraph concludes by discussing the risks of nuclear energy, including accidents that can release radiation into the environment and the long-term issue of nuclear waste with its varying half-lives.

05:01

🔬 Nuclear Waste and the Future of Nuclear Power

The second paragraph delves into the challenges of managing nuclear waste, which remains radioactive for thousands of years. It discusses the concept of half-life and provides an example calculation for radium decay. The paragraph then recounts the accidents at Chernobyl, Fukushima, and Three Mile Island, emphasizing human error as a significant factor in these disasters. It outlines the health risks associated with radioactive materials, such as the link between radioactive iodine and thyroid cancer. The historical context of nuclear power development is provided, showing a decline in new reactor construction following these accidents. The video concludes with a look towards the future, suggesting advancements in technology like thorium reactors and third-generation reactors that can reuse waste. It posits that nuclear energy, with its low carbon emissions, will be reconsidered as part of the solution to reduce global warming.

Keywords

💡INE Scale

The International Nuclear Event Scale (INE Scale) is a logarithmic scale used to measure the severity of nuclear accidents. It is analogous to the Richter Scale for earthquakes. The scale ranges from 1 to 7, with 7 being the most severe. The video mentions that level 7 has only been reached twice: in Chernobyl and Fukushima. The INE Scale is crucial for understanding the gravity of nuclear accidents and their potential impact on the environment and human health.

💡Nuclear Fission

Nuclear fission is a nuclear reaction in which the nucleus of an atom splits into smaller parts, releasing a significant amount of energy. In the context of the video, fission is the process that powers nuclear reactors, where the fission of uranium-235 is used to generate heat, which is then converted into electricity. The video explains that fission is a controlled process in reactors, unlike in nuclear weapons.

💡Uranium-235

Uranium-235 is a radioactive isotope of uranium that is primarily used as fuel in nuclear reactors. It is noted for its ability to sustain a chain reaction during nuclear fission, making it a key component in both nuclear power generation and atomic weapons. The video discusses how uranium-235 decays into barium and krypton, releasing energy and neutrons that can trigger further fission.

💡Light Water Reactor

A light water reactor (LWR) is a type of nuclear reactor that uses ordinary water as both a coolant and a neutron moderator. The video explains that most reactors in operation today are LWRs, where fuel rods containing uranium-235 are placed in water. The heat generated by the fission process is used to produce steam, which drives turbines to generate electricity.

💡Control Rods

Control rods are used in nuclear reactors to control the rate of the nuclear fission reaction. They are made of materials that absorb neutrons, thus slowing down the fission process. By adjusting the position of control rods within the reactor core, operators can regulate the power output of the reactor. The video mentions that lowering control rods between fuel rods can slow down the reactor, preventing it from going out of control.

💡Nuclear Waste

Nuclear waste refers to the byproducts of nuclear reactions, which remain radioactive and can be hazardous for thousands of years. The video discusses the challenges of managing nuclear waste, highlighting that it has a long half-life and must be carefully contained to prevent environmental contamination. It also mentions that future technologies may be able to reuse some of this waste.

💡Half-life

The half-life of a radioactive substance is the time it takes for half of its atoms to decay. It is a fundamental concept in understanding how nuclear waste diminishes over time. The video provides an example of radium with a half-life of 1500 years, illustrating how the amount of radium decreases exponentially over time.

💡Carbon Dioxide

Carbon dioxide (CO2) is a greenhouse gas that contributes to global warming. The video contrasts the CO2 emissions of nuclear power plants with those of fossil fuel-based power plants, highlighting that nuclear energy produces a significantly lower amount of CO2. This makes nuclear energy an important part of the discussion on reducing carbon emissions and mitigating climate change.

💡Chernobyl

Chernobyl was a catastrophic nuclear accident that occurred in 1986 at the No. 4 reactor in the Chernobyl Nuclear Power Plant, near the city of Pripyat in the north of the Ukrainian SSR in the Soviet Union. The video mentions Chernobyl as the site of the first level 7 nuclear accident on the INE Scale, which resulted in a large release of radioactive material and long-term environmental and health impacts.

💡Fukushima

Fukushima refers to the nuclear disaster that occurred in 2011 at the Fukushima Daiichi Nuclear Power Plant in Japan, following an earthquake and tsunami. The video describes it as the second level 7 event on the INE Scale, where the reactors experienced meltdowns due to the loss of cooling, leading to significant releases of radioactive materials.

💡Three Mile Island

Three Mile Island is the site of a partial nuclear meltdown that occurred in 1979 at a nuclear power plant in Pennsylvania, USA. The video refers to it as the highest-level nuclear accident in the US, which reached level 5 on the INE Scale. Although it released a small amount of radioactive material, it had a significant impact on public perception of nuclear power safety.

Highlights

Introduction to the International Nuclear Event Scale (INE Scale) and its use in measuring nuclear accidents.

Only two Level 7 nuclear accidents: Chernobyl in 1986 and Fukushima in 2011.

Thirty-one people died from exposure to radiation at Chernobyl.

Fukushima disaster involved meltdowns of three reactors after an earthquake and tsunami.

The highest level of nuclear accident in the US was a Level 5 at Three Mile Island.

Nuclear accidents and radiation are feared due to their invisibility.

Nuclear energy has remained static for decades but is now being revisited due to carbon dioxide concerns.

Nuclear power plants produce carbon dioxide at levels comparable to wind or hydro power.

New technology and a decrease in carbon emissions could lead to a resurgence of nuclear energy.

Nuclear energy comes from the fission of radioactive material, typically Uranium-235.

Light water reactors are the most common type of nuclear reactor in use today.

Control rods are used in reactors to slow down the fission process and control the reaction.

Nuclear waste has a long half-life and remains radioactive for thousands of years.

Nuclear accidents can cause environmental damage and health issues such as thyroid cancer.

The advantages of nuclear power include large energy production without increasing carbon emissions.

Nuclear reactors work by controlling the chain reaction of uranium atoms splitting.

Light-water reactors use a closed system to heat fluid, create steam, and generate electricity.

Nuclear waste is stored in pools and eventually in concrete containers.

The long-term plan for dealing with nuclear waste is uncertain and will be a problem for future generations.

The concept of half-life is crucial for understanding the decay of radioactive materials.

Calculating the decay of radium over time to illustrate the concept of half-life.

Human error and design flaws have been significant factors in nuclear accidents.

Nuclear accidents have led to increased rates of thyroid cancer in affected areas.

The future of nuclear power includes advancements like thorium reactors and third-generation reactors that can reuse waste.

Nuclear energy will be part of the discussion on reducing carbon emissions.

Transcripts

Hi. It’s Mr. Andersen and this AP environmental sciences video 25. It is on nuclear energy.

You are probably familiar with the Richter Scale. It is a log scale by which we measure

the size of earthquakes. But you are not familiar with the INE Scale or the International Nuclear

Event Scale. It is also a log scale and we use it to measure the size of nuclear accidents.

We have only hit 7 twice. First time was in 1986 in Chernobyl. We had a collapse and a

meltdown of the reactor. Thirty-one people died from exposure to radiation. In 2011,

in Fukushima, we also hit a level 7. We had there of the reactors meltdown after an earthquake

and a tsunami. In the US the highest we have ever gone is a level 5, at Three Mile Island.

It released a little bit of radioactive material into the surrounding area. But it scared people.

These accidents scare people and radiation scares people because we cannot see it. And

so the amount of energy we are getting from nuclear reactors has remained static for decades.

But it is starting to be revisited again. And the reason why is there is also something

in the environment that is scary and it is also invisible. And that is carbon dioxide.

If we look at the amount of carbon dioxide being produced by nuclear power plants it

is on the level of the same as wind generation or hydro power. If we compare that to gas

and oil and coal there is way more carbon dioxide being created. So new technology and

a decrease in carbon emissions could see a resurgence of nuclear energy. Where is the

energy coming from? It comes from the fission of radioactive material, generally Uranium

235. So as it decays it breaks down into two fragments, barium and krypton. And as it does

that it gives off energy and it gives off neutrons that can trigger more fission in

more radioactive 235. So the way this is controlled, unlike in a weapon, it is controlled in a

reactor. Most of the reactors in play right now are light water reactors or normal water

reactors. What you do is you put fuel rods inside it and as they decay produces a little

bit of energy and that energy inside the water heats it up and we can use it to generate

steam and then generate electricity. Now when it melts down this goes out of control and

we get a release of that radiation into the environment. And so by having it in water

we can contain some of that energy. And we can also use control rods. These are actually

going to take in some of those neutrons and by lowering them between the fuel rods we

can slow down the reactor. Now the disadvantages are pretty apparent. Nuclear waste is going

to be created. It can be around of thousands and thousands of years, so we have to keep

track of that. Each of the radioactive materials have a different half life but it is going

to be on the order of thousands of years. And also we have these accidents where we

can have explosions, malfunctions and it releases that radiation into the environment. It can

cause things like thyroid cancer. Why do we still have it? Well the advantage is that

it creates a huge amount of energy and it can do that without increasing the amount

of carbon emissions in the environment. So if we look at uranium 235, now we are looking

just at the nucleus, and so we are looking at the protons and the neutrons. And so if

we were to hit one of those uranium atoms with a neutron, what it will do is it will

break in half. It breaks apart into these 2 fragments. And as it does that it releases

a certain amount of energy. You can see it is also liberating 3 of these neutrons. And

each of those have the potential to hit another uranium 235 and we can break it down. So it

is not an out of control chain reaction like this that we might see in a nuclear bomb,

but it goes slow over time. And so if we look at what those fuel rods are like, most of

the uranium is actually going to be uranium 238. A few of it is uranium 235. And so as

those neutrons are given off, by having it in water we can absorb some of that energy

and we can control that radiation. And also we can lower these control rods. They absorb

the neutrons and so we can slow it down. So if we look at a typical light-water reactor,

we are going to have the fuel rods and the control rods in the core. We are then going

to heat up a fluid. And that fluid is going to be in a closed system. So as it moves through

these pipes it returns back where it was. But it is bringing with it a huge amount of

heat. Now that heat moves into a separate loop. And so in this loop what we are doing

is heating up the water. It is forming steam up at the top and then that steam is moving

through a generator. So we are generating electricity. And then finally we still have

a lot of heat right here. Before we pump it back in we have to get rid of some of that

heat. And so we are going to do that by pumping the water in another loop into a cooling pond.

And so as along as we have energy contained within those fuel rods, we can generate electricity.

But what happens when we decay too much of that uranium 235? Now it becomes waste. It

is still radioactive, but it is not generating enough electricity for the plant to go. And

so now we have generated waste. So that is one form of nuclear waste. But we are also

generating a little bit of heat over here into the environment as well. And so how do

we deal with that waste? Well how do we deal with those fuel rods? We are going to put

them in a pool. And as we put them in a pool we are going to absorb some of that energy

here. But eventually we are going to have to put it in some kind of a container and

a lot of these are on these concrete slabs. And we have that nuclear waste contained inside

there. There is no real long range plan of what we are going to do with this nuclear

waste and it is going to be a problem that we will have to deal with generations down

the line. If we look at how long this could occur you have to understand what a half-life

is. A half-life is going to be the amount of time it takes for half of the material

to decay or to break apart. And so if we look at time 0, let’s say the half-life is one

year, at time 0 we would have 100 percent of the radioactive material. At time 1 we

would 50 percent of it. In other words half of it would have decayed. In another year

it would be half of that and a half of that and a half of that and a half of that. And

so in an AP environmental science class you should be able to calculate the half-life.

And let me give you a problem. Let’s say radium has a half-life of 1500 years. How

long will it take for 250 kilograms of the radium to decay down to less then 10 kilograms.

And so we are saying the mass of radium at the beginning is 250 kilograms at time 0.

And so in 1 half-life, in other words in 1500 years we would have decayed half of it down

to 125. In another 1500 years we would be down to 62.5. And you can just keep doing

this. And you can see at 7500 years we are less than 10 kilograms left. You can see a

lot of that is still going to be radioactive. Now what happens in accidents, something happens

where we are not able to contain this core. And so if we look at Chernobyl, they were

testing the reactor and it got out of control. It heated. We are having a melting or an explosion

that actually collapsed the roof. It released a lot of radiation. If we are looking at Fukushima,

it is like three levels of protection that failed. We have an earthquake but we also

have this giant tsunami. And if we are looking at Three Mile Island it was a problem with

a valve. But also a problem with user error as well. And so all of these, for the most

part, are human error. Either we had a mistake at the reactor or had a mistake in the design.

And what it does is it releases some of this radioactive material into the environment.

So for example radioactive iodine can cause thyroid cancer. So we eat it in our food.

It causes cancer years down the line. And we are going to see this wherever there is

a nuclear accident, we are going to have increases in thyroid cancer after that. So if we look

at these accidents, so this is Three Mile Island, here is Chernobyl. So we had the heyday

of nuclear reactor creation during this oil crisis. But then after these accidents you

can see the amount of reactors we have has remained static. And you can say even though

we could produce this amount of energy, we are producing less of that. And the reason

has to do with this fear of radiation and the fear of accidents as well. And so what

does the future hold for nuclear power? Well there are going to be increases in new technology.

Thorium reactors are going to be working much better than uranium light-water reactors.

And we can have these third generation reactors where we can actually reuse some of that waste.

And then finally we have to reduce carbon emissions. And nuclear energy is going to

be part of that discussion. So could you pause the video and fill-in the blanks? Let me do

that for you. Nuclear energy is the fission of something like uranium 235. We break it

apart into fragments. We also get energy in some neutrons that can cause fission in other

atoms. We have the fuel rods. That is where the radioactive material is. But we also have

these control rods. Disadvantages, nuclear waste. It takes a long time due to the half-life

of these radioactive materials for the waste to go away. We can have accidents that increase

the amount of cancer, thyroid cancer is an example of that. But the advantages again,

nuclear power can help us reduce the amount of carbon dioxide in the environment. Reduce

global warming. And that is why it is being revisited. And I hope that was helpful.