TIL about nuclear energy

Episode Summary

We know how to generate tons of electricity without pumping greenhouse gases in the atmosphere, using a technology that’s already mature, widespread, and competitive with fossil fuels -- and also, very controversial: nuclear power. In this episode of TILclimate (Today I Learned Climate), Prof. Jacopo Buongiorno, Director of the MIT Center for Advanced Nuclear Energy Systems, sits down with host Laur Hesse Fisher to explore how nuclear power works, why even some climate advocates don’t agree on using it, and what role it can play in our clean energy future.

Episode Notes

We know how to generate tons of electricity without pumping greenhouse gases in the atmosphere, using a technology that’s already mature, widespread, and competitive with fossil fuels -- and also, very controversial: nuclear power. In this episode of TILclimate (Today I Learned Climate), Prof. Jacopo Buongiorno, Director of the MIT Center for Advanced Nuclear Energy Systems, sits down with host Laur Hesse Fisher to explore how nuclear power works, why even some climate advocates don’t agree on using it, and what role it can play in our clean energy future.

Jacopo Buongiorno is the TEPCO Professor of Nuclear Science and Engineering at the Massachusetts Institute of Technology (MIT), and the Director of Science and Technology of the Nuclear Reactor Laboratory at MIT.  He is also the Director of the Center for Advanced Nuclear Energy Systems (CANES), which is one of eight Low-Carbon-Energy Centers of the MIT Energy Initiative (MITEI).

Season two of TILclimate focuses on our global energy system, its relationship to climate change, and what our options are for keeping the lights on while creating a clean energy future. We're partnering with the MIT Energy Initiative, which will air longer interviews with each guest to take a deeper dive into these topics.

For more episodes of TILclimate by the MIT Environmental Solutions Initiative, visit tilclimate.mit.edu

For related energy podcasts from the MIT Energy Initiative, visit:


For the MITEI podcast episode on the Future of Nuclear Energy, visit:


For the full MITEI report on the Future on Nuclear Energy, visit:


For a deeper dive into nuclear energy, check out Prof. Buongiorno’s course on edX:


To get a sense of the USA’s energy mix, visit:


If you want to know more about how nuclear fuel is stored,visit:


For a comparison of the safety of different energy sources: 


For the landmark report on Chernobyl mentioned in the episode, written by the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR), visit:


For more details on the 2011 Fukushima accident, check out the official Fukushima Prefecture report:



Produced by the MIT Environmental Solutions Initiative at the Massachusetts Institute of Technology.

Episode Transcription

Laur Hesse Fisher: [00:00:00] Hello and welcome to TILclimate, the podcast where you learn about climate change from real scientists and experts. I’m your host, Laur Hesse Fisher, with the MIT Environmental Solutions Initiative. We’re continuing our series on energy and climate in partnership with the MIT Energy Initiative.

In our last few episodes, we’ve covered the challenges of adapting our electric grid to take on much more clean energy. But there’s another way to generate tons of electricity without pumping greenhouse gases in the atmosphere--a technology that’s already mature, widespread, and competitive with fossil fuels -- and also, very controversial.

I’m talking about nuclear power. Today, we’ll explore how nuclear power works, why even some climate advocates don’t agree on using it, and why many energy experts -- including many at MIT -- say it’s a critical part of our clean energy future.

To dig into this, we sat down with an MIT professor who has spent his career studying nuclear energy.

Jacopo Buongiorno: [00:01:15] I'm Jacopo Boungiorno, I'm a professor in the department of nuclear science and engineering, I'm also the director of the center for advanced nuclear energy systems.

Laur Hesse Fisher: [00:01:22] Let’s jump right in. What exactly is nuclear power? It all starts with a process called nuclear fission, which is where a nucleus inside an atom splits, releasing some of the energy that binds the atom together.

Jacopo Buongiorno: [00:01:39] This shows up in a form of heat and then you can convert that heat into electricity that is sent to the grid. So in that sense it's a heat source just like burning coal, natural gas or getting heat directly from the sun. But the primary energy source in this case is Uranium.

Laur Hesse Fisher: [00:01:55] Uranium is a heavy metal that’s found in rocks all over the world. For this episode, it’ll be helpful to know that most of the Uranium out there is a kind called Uranium-238. And you need to alter -- or enrich -- some of that to another type, Uranium-235, in order to use it in nuclear power plants. More about that later.

The first nuclear power plant was built in 1954, near Moscow--and for the next 30 years, power plants started popping up all around the world. At the time, many people saw nuclear power as a huge leap forward from fossil fuels. For one, Uranium is super abundant.

Jacopo Buongiorno: [00:02:42] There is an enormous amount of Uranium out there, more than enough to, to continue to use nuclear and grow it actually, and grow its use for, for centuries that essentially affords countries a certain level of energy security.

The second feature that makes nuclear attractive is that the energy density of the Uranium fuel is many orders of magnitude higher than conventional fuels. And it has to do with the fact that a nuclear reaction breaks nuclear bonds, not chemical bonds and therefore liberates a lot more energy.

Just to give you an idea, a nuclear power plant that would generate enough to power the city of Boston would require on the order of three kilograms of Uranium-235 fuel per day. And that's something that I can hold, you know, on the palm of my hand. So, that tells you how much energy there is in this material.

Laur Hesse Fisher: [00:03:38] Today, we see another very important benefit of nuclear power. These power plants don’t emit any of the greenhouse gases that are driving climate change.

Jacopo Buongiorno: [00:03:48] You have an energy source that essentially does not have any emissions into the atmosphere and so that's the first reason why people are interested in nuclear now; because of course we're trying to minimize the carbon emissions into the atmosphere to prevent massive global warming and climate change.

Laur Hesse Fisher: [00:04:04] Nuclear power could have an especially important role to play because it’s both clean and dispatchable. That means that, unlike wind and solar, nuclear power can be revved up to produce electricity exactly when we need it. If you want to dig into this topic a little more, check out our episode on renewable energy.

Today, about 20% of our electricity in the U.S. is generated using nuclear power. That’s more than solar, wind, and hydropower combined.

Jacopo Buongiorno: [00:04:37] in the US over 50%, five zero, of our carbon free electricity today comes from nuclear. So it's already the largest clean energy source that we have on the grid today.

Laur Hesse Fisher: [00:04:49] Ok, but hold on -- if nuclear power is such a great way to get cheap, clean, reliable electricity -- and we’re already using it--, why aren’t we building more? Well, many people -- and even entire countries -- are nervous about it. There are three main concerns: nuclear waste, nuclear bombs, and accidents.

Let’s start with waste--which is radioactive, and needs to be kept away from people.

Jacopo Buongiorno: [00:05:20] In our community we call it spent fuel. It's basically the material, the uranium and the products of the fission reaction that come out of the reactor when the reactor is refueled and it's usually put in water pools and it cools down for between five or ten years after which, the spent fuel is put in dry casks. So these are steel and concrete little containers and they are air cooled.

Laur Hesse Fisher: [00:05:48] In the United States, these dry casks are stored at the nuclear power plants themselves. Other countries are building underground storage facilities to store their nuclear waste. Finland is planning to store waste in a bedrock that’s been around for about 1 billion years and is not susceptible to earthquakes. They say their waste will be safe for 100,000 years.

Jacopo Buongiorno: [00:06:14] It's one of few industries I think, in the whole economy that actually takes care of its materials from cradle to grave, right? So nothing is emitted into the atmosphere or in an uncontrolled manner. 

I don't think any of the other power generation technologies do this.

Laur Hesse Fisher: [00:06:31] There’s another reason we need to be really careful about uranium, and it’s the second big fear people have about nuclear energy: the risk of nuclear proliferation.

Jacopo Buongiorno: [00:06:43] The issue is that there are materials that are used in civil nuclear power plants that potentially can be used for nuclear weapons. The fuel that is used in nuclear power plants is very low enrichment, I mentioned 5%. That material is not weapons material.

Laur Hesse Fisher: [00:07:03] As we mentioned earlier, we need to enrich some of the uranium to use it in power plants. In fact, we need to enrich 5% of it. To create a bomb, you would need to enrich way more uranium—at least 90%. There’s also an issue that the uranium could be modified into plutonium, another material that could be used for weapons. 

Jacopo Buongiorno: [00:07:27] And the way to handle it, quite frankly, is to just have a very, very tight control of all those materials throughout the overall cycle. But it is- it is a real concern and, uh, you know, it's something that has to be- that- that secure regime has to be strengthened as much as possible if nuclear is to grow internationally.

Laur Hesse Fisher: [00:07:45] And then there’s the third main concern, accidents.

When Uranium atoms are split inside a nuclear reactor, they give off radioactive particles, which in high doses can cause terrible damage to our bodies. Now, in normal conditions, that radiation stays safely inside the reactor--in fact, reactors are so well designed for this that a nuclear plant actually emits less radiation than a coal plant.

Jacopo Buongiorno: [00:08:19] The main concern that I think people have is associated with fairly spectacular, rare events, accidents.

Laur Hesse Fisher: [00:08:28] The Chernobyl accident, in 1986 in modern-day Ukraine, was by far the worst. 

Jacopo Buongiorno: [00:08:34] If you look at the, exactly at what happened at Chernobyl, the operators deliberately disabled the safety systems because they wanted to conduct an experiment. Well, you don't conduct an experiment on a commercial local power plant. 

Laur Hesse Fisher: [00:08:47] As a result, the power plant exploded, releasing the radiation that was inside the reactor.

Jacopo Buongiorno: [00:08:53] The first responders, these were soldiers of the Soviet army that were sent to basically throw sand on the burning rubble. Those were exposed to some pretty horrendous levels of radiation. And many of those died. 

Laur Hesse Fisher: [00:09:08] People who lived nearby were also exposed to radiation. The landmark report that assessed the impacts of Chernobyl found that locals who drank contaminated milk right after the accident had higher cases of cancer. And yet the same report found that the radiation that by far most people in the area experienced over their lifetime due to the accident was actually really low -- well below the levels that are known to increase your risks of getting cancer. 

The radiation exposure was even lower for the tragic Fukushima accident, which took place in Japan in 2011.

Jacopo Buongiorno: [00:09:51] The accident occurred following the earthquake and tsunamis, which devastated that area 

Laur Hesse Fisher: [00:09:57] Including flooding the power station, which led to the reactor leaking radiation. By the Japanese government’s official account, over 2,000 people died as a result -- but not from the radiation. 

Jacopo Buongiorno: [00:10:14] For Fukushima, you're looking at an integrator over a lifetime exposure of the order of 20 mSv.

What does 20 mSv mean? So just to put things in perspective, when you go to do a CT scan to your torso, or you do some kind of radiation imaging, you typically get about a third to half of that dose. And so, you know, assuming that you do a couple of CT scans over the course of your lifetime, it's about the same amount of radiation.

The evacuation of 150,000 people from the Fukushima area was a tragic mistake. The amount of damage that has been done by moving people, for example, out of, older people out of hospitals and hospices and things of that type was much, much greater than any, health, damage that would have been caused by exposure to radiation because the radiation levels were so low.

Laur Hesse Fisher: [00:11:09] Right, those 2,000 people who died from the accident passed away due to complications of evacuating the area, not from the radiation.

Jacopo Buongiorno: [00:11:24] It’s really terrible. It's unfortunate all to avoid two CT scans to the chest. 

Laur Hesse Fisher: [00:11:31] The question we’re really getting at, of course, is: is nuclear power safe?

Jacopo Buongiorno: [00:11:39] When it comes to risk and public health impact, there is no way to be particularly cheerful or positive, you have to look at the hard cold numbers and compare. And so if you compare nuclear to coal, to natural gas, to solar, wind, hydro, other ways to generate electricity, it turns out that nuclear has the the lowest actually, mortality rate per unit, energy per unit, energy generated.

Laur Hesse Fisher: [00:12:04] So how can this be? The World Health Organization estimates that over 3 million people worldwide die every year from asthma, lung cancer, and other illnesses caused by air pollution from fossil fuels. 

I was shocked to learn that if you include worker accidents in the mix too, nuclear power has actually had a lower death toll even than solar and wind. This was really surprising for me, and it might be for you, too. We’re including the studies in our show notes so you can read up on it for yourself. 

Given all of this -- the fact that nuclear power doesn’t emit CO2, that it can deliver electricity on demand, that the health risks are relatively really low, and that the technology is evolving to be safer and cleaner -- many energy experts think we need to build more nuclear as a part of a clean energy future.

Jacopo Buongiorno: [00:13:07] The intermittency that is inherent in solar and wind forces you to have backup. You, you're going to need to meet demand, right? And if it's not met by a low carbon sources like nuclear or wind then it's met by either coal or natural gas. This is not to say that we don't need renewables - we do need them. But not alone. You do need a, a, you know, a diverse portfolio.

That's what all our analysis is showing is that the best way to decarbonize is with a portfolio of low carbon technologies.

Laur Hesse Fisher: [00:13:42] If you’re hearing a running theme in this energy and climate series, it's that each clean energy technology has its benefits and its challenges. And that we can take advantage of the benefits and reduce the challenges by building a mix of different technologies. 

It’s up to us to decide what role nuclear power plays in this mix.

If you want to learn more about nuclear power, we highly recommend Dr. Buongiorno’s online course from EdX, which we’ll link to in our show notes. He also gives a great recap of the MIT Energy Initiative’s report on the future of nuclear, which you can find at energy.mit.edu/podcast.

OK so we’ve talked a lot about technologies that we can deploy immediately to clean our electricity grid. But what about new, potentially big impact technologies that are on the horizon? In our next two episodes, we’re going to dig into carbon capture and storage, and fusion energy, so stick with us.

Thanks to Dr. Jacopo Boungiorno for joining us today and thank you for listening.