The Power of Nuclear Weapons with Dr. Alex Wellerstein

Are nuclear weapons more powerful today than they were in the past? What makes a nuclear bomb so different from other bombs? Would nuclear energy lead to nuclear proliferation? Everyday Einstein gets answers from Dr. Alex Wellerstein, an expert in nuclear weapons.

Sabrina Stierwalt, PhD
12-minute read
Episode #333

I’m here today with Dr. Alex Wellerstein, a historian of science and nuclear weapons and a professor at the Stevens Institute of Technology in New Jersey. He has a Ph.D .in the History of Science from Harvard and was previously an Associate Historian with the American Institute of Physics. Alex is an expert in nuclear weapons, especially how secrecy is used to control nuclear technology. 

Thank you for being here, Alex.

I’m happy to be here. 

I think even if you don’t understand the technology completely, we all know that nuclear bombs are not like other bombs. And in your writing, you’ve called the nuclear bomb a “special bomb.” What do you mean by that and what role does science play in making it “special?” 

The question of [whether] nuclear weapons [are] totally different from everything else or ... just a regular bomb made bigger again—people have been arguing about this since before the atomic bomb was even made when people were still working on it. But at its core, nuclear weapons just have a potential that conventional weapons don’t have. And that ultimately comes down to physics.

Your average conventional chemical weapon like TNT— As a TNT molecule breaks down it releases some energy. It releases about one electron volt or so of energy. You don’t have to know what that is to know that when I tell you that a uranium atom releases 200 million electron volts, you can see that’s a big step up. The consequence of all this is that for a much smaller weapon, a much smaller amount of reacting material, you can get extreme explosive results. 

If you reacted one kilogram of uranium-235 completely, you would get about 20,000 tons of TNT-equivalent worth of explosives. That’s about the size of the Hiroshima bomb. One kg of uranium—you could hold that in your hand! That’s nothing, and to have that destroy entire cities, that changes things. And that’s not even as big as they get. 

nuclear power plant

So when people say, and when I say, there’s something different, there’s something special, there’s something unusual, that’s what they mean. There’s potential in here that’s thousands of times to millions of times more destructive than anything else out there. 

Very intimidating. So, you’ve created this incredibly interesting interactive nuclear effects simulator called NUKEMAP, and I’ve played with it. Well, played sounds like a horrible word. I’ve experimented with it bombing different cities. So, you can choose a location and what kind of (real historical) bomb that you drop and then see how widespread the damage would be. And I was surprised that there are a lot of bomb choices. I had no idea there were so many. Can you tell us about some of these bombs and how powerful nuclear weapons are today compared to in the past? 

When the United States first built nuclear weapons, it did so in the context of World War II in the context of getting this weapon done before the end of the war, what it could get done in a very short amount of time. After the war, it did a lot of research, hired a lot of scientists, spent a lot of money, did a lot of testing to get a number of different types of weapons.

In the sort of early days, it was about can we get the same amount of bang as say the Hiroshima bomb but with a lot less fuel. Or it was can we get twice the bang out of the same amount of fuel. These are sort of efficiency improvements. By the 60s, though, you get really divergent directions in weapon design. You get weapons that are about as big as you can imagine every wanting a weapon to be. In the United States, the largest weapons we built were in the tens of millions of tons of TNT equivalent, so these are megatons. 

We had a weapon that we fielded in fairly great numbers in the late 1950s that was 25 megatons, so 25 million tons of TNT. That’s over 1000 times more powerful than the Hiroshima and Nagasaki weapons. So we had these big sort of monster bombs that are physically quite large. They are the size of cars. They’re big. 

But we were also developing really small bombs. We developed a bomb by the early 1960s that we called the Davy Crockett, which is the smallest weapon the United States ever developed. It’s a nuclear artillery, basically. It’s like a cannon that shoots little tiny nuclear weapons. Each warhead weighed maybe 80 pounds, so you could carry this in a backpack. And they’re relatively small. So these may be only tens of tons of TNT—not thousands of tons, not millions of tons, but tens of tons. And these would be designed for attacking tanks and things like that. 

Over the course of the Cold War, you see these different sorts of weapon designs and different sorts of strategic ideas about what the bombs could be used for. Are they going to be used for attacking tanks, or are they going to be used to wipe out the entire Moscow metro area from the map? You get different parameters. 

The one that becomes really the most important is 'can you put it on a missile?' because we start shifting more and more of our forces into relatively compact missiles. They could be intercontinental ballistic missiles that are firing from the United States to the Soviet Union or China or they could be submarine-launched missiles which have to be very small to fit into a submarine even if the submarine is relatively large. 

We start to realize, What if we could put multiple warheads on each missile? So ,this is called MIRVing—multiple independently targetable reentry vehicle. A lot of jargon, and it basically means what if we had one missile that had, say, 12 warheads on it that could each be aimed at 12 different targets. The reason you do this is in part because you’re afraid they’ll try to shoot your missile down so you just keep adding more warheads per missile. 

nuclear missile

All of that is to say we end up optimizing a warhead that does a reasonable amount of destruction with a given amount of accuracy from a missile and can fit into a relatively compact volume. You have a warhead that’s about the size of a trash can and might be 10 to 20 times more powerful than the Hiroshima and Nagasaki bombs but not a thousand times more powerful. 

So, paradoxically, the weapons we have today— We don’t have as many types as we used to; they’re almost all these kinds of warheads and they’re also more in the hundreds of kilotons of TNT range. Not the megaton range, not the tens of kilotons range, but the hundreds of kilotons range, the sort of sweet spot for how much energy you can get out of something the size of a trash can and is useful for the amount of accuracy these missiles have. 

Sometimes, I get asked by people 'Are the weapons we have today larger than the ones we had 60 years ago?' and the answer is no, they’re actually smaller, but that’s because we deploy them differently. We have many more of them per missile. They’re much more accurate than they used to be. Again, it’s optimized not for explosive power but for this weight accuracy issue. 

So, when it comes to developing all of these different kinds of bombs, what comes first? Is it the strategy: we want something that will do this for us? Or is it the science: now that we have this technology, let’s play with it and see what we can do?

Theoretically, it’s supposed to be the strategy. The way it’s supposed to work is the government is supposed to go to the scientists and say 'We need something that can do this.' And the scientists say 'Oh, great we’ll solve it for you.' It’s not supposed to be the scientists leading the way. People thought that would just lead you into people doing things for science’s sake. 

It’s not supposed to be the scientists leading the way. People thought that would just lead you into people doing things for science’s sake.

In practice, it’s a lot of both, and it has been for a long time. The capabilities sometimes affect the strategy. And the science and the scientists often affect the imagination around the capabilities. 

For example, the idea of putting a warhead onto a submarine missile, that was suggested by the scientists. In fact, they sort of over-promised and said, ‘I bet we could do this’ even though they didn’t know if they could or not. And they sort of figured out how to do this. It took a couple generations of these before they got very reliable. That’s an example of something that’s very much pushed by the scientists. 


There were some instances of this where the military even admitted that they didn’t have a need for these things but the scientists had said it was possible so they thought they should try it out and see if a need evolved. 

In practice it’s supposed to be the government or the military guiding the development of these things. But in practice as I guess you’d expect, there’s a lot more back and forth. 

With all this potential for destruction that you’re talking about, should proponents of nuclear energy as a green energy source be worried about us investing in nuclear energy necessarily leading to the proliferation of nuclear weapons?

I have really boring opinions on nuclear power, I think, that make nobody happy. But they’re basically along the lines of: there’s better and worse ways to do nuclear power. Some of them are better for proliferation concerns. There are ways you can set up nuclear reactors where it’s very hard to get fuel out of them that you can use for bombs. 

There’s also ways in which you can use tools of diplomacy like treaties, like the nuclear nonproliferation treaty, to make sure that people are doing what they say they are going doing with these plants and they’re not going to be diverting material to a weapons program or something like that. And the track record of those is not terrible. It’s not perfect, but it’s not terrible. 

Many more countries use nuclear power than have nuclear weapons, and that’s in part because of these diplomatic and technical considerations. I do think that when you’re talking about nuclear power for other countries, there are a lot more considerations that need to take place. Sometimes, either the purely technical misses the point or the purely political or the purely economic misses the point. 

Many more countries use nuclear power than have nuclear weapons, and that’s in part because of these diplomatic and technical considerations.

There are complicated relationships where— So, in the past, one of the reasons that a lot of countries have American-style reactors is because America basically helped them get them because they reasoned that it would be better for these countries to be using American technology and American fuel than for them to develop it indiginously and then they would have total control over them. So that’s a complicated technical, political consideration that isn’t straightforward but does help countries like the United States keep an eye on other countries. 

My main take away for people for people who are thinking about nuclear power for environmental reasons is that it’s [not] the big villain that a lot of people see it as. It has some aspects that are very positive from an environmental point of view. Obviously you can mishandle a lot of it and that can be a big problem. But if you do it well, you can reduce the risk of that to pretty low. 

My main take away for people for people who are thinking about nuclear power for environmental reasons is that it’s [not] the big villain that a lot of people see it as.

But it’s also not the savior that a lot of people make it out to be. You can’t just dial up 100 times more nuclear power plant construction over night and have that make any economic sense and have that make environmental sense and power sense. It may be that well-run, well-regulated nuclear with very well-chosen technical designs needs to be part of our energy mix going forward, globally and nationally.

But at the same time, it’s not going to be the whole thing. I run into a lot of people who say if all we did was just get rid of all the environmentalists and the hippies, we’d be fine. But if you run the numbers, it’s not true! The nuclear people have even run the numbers of how many plants you’d need to put a dent in the climate … 

It’s a lot. It’s a lot more than we have conceivably in the pipeline. So, I don’t think it’s going to be the solution, but at the moment, I think we have to pursue a lot of things if we’re going to survive. 

Are there issues with the secrecy surrounding nuclear weapons that translate over into nuclear power?

So, nuclear in general has a lot more secrecy than other types of power generation. Some of that’s the legacy of it being associated with weapons. Some of it’s associated with the fact that these are what they call low probability, high consequence technologies. The probability of an accident that’s catastrophic is very low. These things run safely almost all the time. But that almost means that even for something with a very, very small potential for happening, in some cases the consequences are very very large. 

nuclear sign

Chernobyl is obviously the poster child for what can go wrong, where you contaminate a huge portion of Ukraine. I think 25 percent of Belarus is contaminated. You can calculate many tens of thousands of potential long term cancers that probably came in Europe as a result of this. 

That’s pretty bad! That’s not good. Even if it’s not as apocalyptic as some people think it is, that’s still pretty awful by any standard. Chernobyl is unusual. It’s not something that’s going to happen with a lot of reactors. It’s specific to its time and place and design. 

Still, one of the set issues, and this comes back to the earlier question about the specialness, nuclear technologies, nuclear reactions are exponential reactions. That’s how they work. That’s why they’re so amazing. That’s why they get all that power out. That same property can translate into the potential for big problems if you do it wrong. So you have to do it right. You have to get it to the right amount. 

The secrecy sometimes gets in the way of people understanding these things. It also gets in the way even in places that don’t have nuclear weapons like, say, Japan. There’s a secrecy that pervades a lot of its nuclear industry as well, and that can lead to regulatory oversight problems. Fukushima, in theory, could have been prevented if you had stronger regulatory transparency in place. That’s the kind of place where the secrecy really becomes a problem. 

This is fascinating stuff. I wonder, when you are doing your research, do you run into classified things that stop you?

I’ve just finished a book on secrecy and nuclear weapons, so yeah, all the time! A lot of the book is about me trying to get through and figure out what the blank spot is or reconstruct this history that is very hard to reconstruct because you don’t have the files or you only have part of the files. Sometimes you know that the files are out there and they won’t give them to you. Sometimes the deletion seems fairly arbitrary.

Part of it, to me as a historian, what makes it, if I can say so, a little fun—it’s a detective game. You’re trying to figure out what you don’t know, what’s out there. It’s a little different than scientific research is because I know somebody knows the answer to this. It’s not like I’m trying to find out something that nobody knows. I know that there’s a guy in DC that’s sitting there blacking out, and that can make it a very adversarial relationship. 

Part of it, to me as a historian, what makes it, if I can say so, a little fun—it’s a detective game.

So, there’s always stuff that’s missing. But I will say, in history in general, there’s always stuff that’s missing. If I’m working on something from the 19th century, there might not be any secrecy or classification but there will definitely be lost letters, damaged archives, people who have written things down that aren’t true. This is part of the historian’s repertoire is to deal with partial sources or missing information. The main difference is that that’s just maybe the ravages of time or whatever as opposed to some government bureaucrat. 

But a lot of the work that I’ve done has been to try to reconstruct how this looks from the government bureaucrat’s point of view because their point of view is rarely seen. What you see is the result of it, which is a document that says "Secret" and has all sorts of stuff crossed out. But you rarely see what they were thinking about when they did that. What I find is that most of the time, not always, but most of the time, they’re fairly benign choices that are made. There’s no necessarily right answer. There’s a lot of human judgement that plays a role in that. 

They have a system that is fairly conservative in the sense that, if you don’t let some piece of information out, nothing bad will happen to your career. If you let out the wrong piece of information out, you’ll be fired. That leads to them being overly conservative on the whole when it comes to declassifying things. 

Thank you for sharing some of your detective work with us today. You can find more from Alex about the nuclear past and present, including NUKEMAP, on his blog Restricted Data: The Nuclear Secrecy Blog or by following him @wellerstein on Twitter. 


Until next time, this is Sabrina Stierwalt with Everyday Einstein’s Quick and Dirty Tips for helping you make sense of science. You can become a fan of Everyday Einstein on Facebook or follow me on Twitter, where I’m @QDTeinstein. If you have a question that you’d like to see on a future episode, send me an email at everydayeinstein@quickanddirtytips.com


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About the Author

Sabrina Stierwalt, PhD

Dr Sabrina Stierwalt earned a Ph.D. in Astronomy & Astrophysics from Cornell University and is now a Professor of Physics at Occidental College.

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