Neil de Grasse Tyson on Nukes and Radiation - What the Heck Is He Talking About?

Question

Last week Neil de Grasse Tyson was on Bill Maher's show and the topic of nuclear weapons came up.

Tyson said, "modern nukes don't have the radiation problem.... They're a different kind of weapon than Hiroshima and Nagasaki." When pressed by Maher, he said, no, there is no radiation issue "if it's hydrogen bombs."

With all due respect to Dr. Tyson, does anyone know what in blazes he's talking about?

My understanding is that ALL thermonuclear or "hydrogen" bombs still have a fission primary that uses at least as much fissile material as Fat Man, and therefore even the smallest TN bomb would be at least as irradiative as the original fission bombs, albeit with more "bang for the buck". However, AFAIK most also utilize a shell of additional fissile material which undergoes fission as a result of the huge neutron flux from the fusion, rendering these much dirtier than the original bombs. Wikipedia says specifically that retrofitted W87 warheads use a U235 shell to make the second fission stage even more powerful (and more radioactive).

Is there anything known about "newer" post-cold war weapons designs and/or trends that could justify what he said? My only thought was that he might have been talking about relative "dirtiness" per unit of yield being smaller with modern bombs, but I'm not even sure that much is true when you factor in the fissile shell which seems to be a common feature. Otherwise I'm at a loss to understand why he would say what he said.

Answer 1

As others have mentioned, hydrogen bombs use a fission trigger.

In addition many used a tamper made of fissile materials. This way the neutrons from the fusion reaction can create an additional fission reaction.

From Wikipedia: "The secondary's relatively massive tamper (which resists outward expansion as the explosion proceeds) also serves as a thermal barrier to keep the fusion fuel filler from becoming too hot, which would spoil the compression. If made of uranium, enriched uranium or plutonium, the tamper captures fast fusion neutrons and undergoes fission itself, increasing the overall explosive yield. Additionally, in most designs the radiation case is also constructed of a fissile material that undergoes fission driven by fast thermonuclear neutrons. Such bombs are classified as two stage weapons, and most current Teller–Ulam designs are such fission-fusion-fission weapons. Fast fission of the tamper and radiation case is the main contribution to the total yield and is the dominant process that produces radioactive fission product fallout."

(Emphasis added by me).

Many hydrogen bomb designs would have a more than 50% fission yield. And since the yield tends to be far greater than the fission only bombs of the Hiroshima and Nagasaki era, potential for radioactive fission by-products can be much worse.

Answer 2

He's not done his homework on this. There are heaps of ("over 300") fissionable and radioactive components created due to the fission initiator of a nuke. Plus gamma rays etc. To say that's not an issue to worry about is wrong. He should apologize it's giving the impression that these things are clean. Reference: https://www.britannica.com/technology/nuclear-weapon/Residual-radiation-and-fallout

Answer 3

I would rather say contrary to what Neil de Grasse has said,- Hydrogen nukes is far more dangerous in every aspect, including radioactive one. Due to much bigger blast radius, H-bomb will scatter fission initiator radioactive nuclides in fallout phase across area which approximately is $100 \times$ bigger than in A-bomb case.

Not to mention, that cyclones & air currents will spread radioactivity far more away. Just look at the table how comparatively passive nuclear leak in Chernobyl disaster has increased radioactivity in much more different countries than that one where catastrophe has happened. And in this question we are talking about deliberate spreading of radioactivity, which is far more lethal and has bigger long-term consequences.

Answer 4

Neil Degrasse tyson often talks about things as if he knows everything but often, he is just making crap up. Explained simply, a typical hydrogen bomb consists of conventional explosives arranged around a plutonium 239 core, this core usually has some kind of initiator in the center (i.e. polonium and byrillium) to produce extra neutrons to jumpstart the reaction. All of these peices essentially make up a fission bomb on their own. There also is a cylinder of lithium-deuterite encased in uranium 238 (sometimes U235) in the center of the lithium-deuterite is a plutonium 239 rod. The entire assembly is encased in (usually) Styrofoam (yes, the same stuff that your packages come in!), around this is sometimes U238 and then a steel casing. When the bomb is set off, the conventional explosives crush the plutonium down past it's critical mass, the initiator (there are varying types) releases high speed neutrons to jumpstart the fission reaction. The fission bomb creates enough heat to ionize the Styrofoam and make the lithium-deuterite undergo fusion, which in turn, creates enough heat and pressure to make the plutonium rod undergo fission this then creates more heat and a positive feedback loop of fission and fusion reactions. All while the uranium 238 casing is bouncing back neutrons and gamma rays into the core. This all happens faster than you can blink, and creates so much heat and expanding gas that you get a very large explosion.

There is still a LOT of highly radioactive plutonium, uranium, and other radioactive elements in these bombs. Nearly all of these reactions also release gamma rays and alpha particles. So yes, hydrogen bombs do in fact produce a LARGE amount of nuclear fallout. I wish that Neil Degrasse would fact check himself before he lies to millions of people.

Answer 5

Tyson said, "modern nukes don't have the radiation problem.... They're a different kind of weapon than Hiroshima and Nagasaki." When pressed by Maher, he said, no, there is no radiation issue "if it's hydrogen bombs."

With all due respect to Dr. Tyson, does anyone know what in blazes he's talking about?

Many of the answers seem to explain why Tyson is technically incorrect. However, there is a sense in which he is approximately correct.

First, note that Tyson is generally correct that H-bombs are "a different kind of weapon than Hiroshima and Nagasaki." In particular, the main source of explosive energy for an H-bomb is fusion and the main sources of explosive energy for the original atom bombs were fission.

Next, note that if you are already dead you do not care much about radiation poisoning due to fission material.

While there may be a relatively small amount of fission material that gets strewn about when the H-bomb goes off, those in the general vicinity where the fusion material gets strew about generally do not care much since they are already very much dead.

Thus, in this sense, there is not the same type of long-term radiation poisoning issue that occurred for people downwind and downstream of Hiroshima and Nagasaki.

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That being said, the characterization of "no radiation issue" is wrong because there is certainly the acute radiation issue of being burnt to a crisp during the nuclear explosion of an H-bomb.