Should We Worry About Radioactive Fallout From North Korea?

By James Conca

The Democratic People’s Republic of Korea (DPRK), often referred to as North Korea, is testing ballistic missiles capable of reaching California with a miniaturized atomic warhead. Neither component is fully developed yet.

From successful atomic bomb tests, to putting satellites into orbit and launching missiles from a submarine, DPRK’s modern weaponry has gone from a joke to something very serious.

Like their recent hydrogen bomb test that wasn’t a hydrogen bomb, their latest missile test wasn’t as long-range as the DPRK claimed. But it was an intermediate-range that could reach its neighbors easily.

It will still be some time before the DPRK can seriously threaten the United States mainland, but our allies nearby to DPRK are quite worried, especially given the scary and escalating rhetoric coming out of the White House.

If our nuclear umbrella works as designed for an attack from the DPRK on South Korea or Japan, there will be more than just a few nuclear detonations that would follow as the political, industrial, and military centers of the DPRK were obliterated.

I’ve been getting a lot of questions about what would happen after that. Even though the immediate destruction dwarfs anything that follows, most people’s minds bring up images from science fiction—that those areas would be dead zones, uninhabitable for thousands of years from radioactive fallout. And that fallout might reach Hawaii, Alaska or the U.S. mainland.

Fortunately, that’s not true. Radioactive fallout is not a common result from using nuclear weapons. It’s the pressure and the heat, the blast and the fireball, that do all the damage, not radiation.

In the decades following WWII, we spent lots of time and money researching the effects of nuclear detonations, particularly fallout. The generation of fallout is inversely proportional to destructive power, which means that if you want the biggest bang with the most destruction, which is the whole point of using such weapons, you won’t generate much fallout.

In over 200 above-ground atomic and nuclear bomb tests, fallout was minor in 99 percent of them. Residual dose rates from these test sites are very low (< 0.001 Sv/yr), less than the natural background radiation that was there before the tests.

The exception was the Castle Bravo test on Bikini Atoll that generated lots of fallout that caused radiation sickness in people of the Marshall Islands because it was incorrectly detonated too close to the ground and the yield was larger than we expected. At 15 megatons (equivalent to 15 million tons of TNT), that hydrogen bomb was the largest detonation ever by the United States, a thousand times larger than anything the DPRK has or will probably ever have.

Therefore, if an enemy wants to care about contaminating the future more than winning the present conflict, there could be areas that will be contaminated for a long time, although not thousands of years because geological and biological processes spread out and dilute contamination relatively quickly.

A good way to understand this problem is to look at the only two atomic weapon attacks in history. Little Boy, the Hiroshima U-bomb, was about 15 kilotons, and Fat Man, the Nagasaki Pu-bomb somewhat similar to DPRK’s bombs, was about 25 kilotons. There are no areas in either city, or anywhere else in Japan, that have radioactivity above background levels as a result of those detonations. There never were any dead zones.

More than 200,000 deaths occurred at Hiroshima and Nagasaki from those detonations. About 500 deaths came later from radiation-induced cancer and other long-term effects from this microsecond neutron burst. None were from fallout.

The mess this world might be heading toward is much more complicated than science fiction, but radioactive fallout is one of the least of our worries.

James ConcaDr. James Conca is a geochemist, an RDD expert, a planetary geologist and professional speaker.  He is also a regular contributor on Forbes. Follow him on Twitter @jimconca and see his book at

5 thoughts on “Should We Worry About Radioactive Fallout From North Korea?

  1. Bill Brickenstein

    While the comments are correct concerning airbursts over North Korea, those are not the only problem;
    1) Even without mastering re-entry, the electro-magnetic pulse from a light warhead above the atmosphere could affect all of southern California, little accuracy needed.
    2) A crude hydrogen device like our Mike test would be way too big to fit on a missile but could be carried by a tramp steamer or, worse, a diesel submarine into a west coast port; this would cause maximum fallout, especially if there was a lot of metal in the hull.
    The same points apply to an asymmetric Iranian attack on Israel, even more-so due to the very small size of that country.

  2. ward

    I had the pleasure of knowing Dr. Conca while at WIPP. He is a brilliant expert in this area and as a former Army NBC Officer myself I would have to say he is giving the public some reliable information.
    Al Brodsky has done the same for decades and we need a dozen more like him.
    Sales of bomb shelters are exploding right now (no pun intended), and no matter how hard we work to get people educated in this area, there will always be paranoia out there, probably until society learns the real value of harnessed nuclear energy. That is probably unfortunately not until the next century when we have fusion reactors and fusion powered space ships. It would have been this century if not for the liberal closed mind politicians and followers we have put up with for decades now. Think about it…we can’t even bury our high level waste right now because of them.

  3. Allen Brodsky, Sc.D.

    I applaud Jim Conca’s explanation and efforts.

    I have recommended his book to those who might be able to reverse the negative policies on nuclear energy. I ask that he at least download my book, Handbook for Survival:… for only $3.99, and give me a call about the suggestions in Appendix C (only 5 pages). I need his help. I have been working for over 50 years on the same missions as he, and still am. We should be in touch!! 410-641-6523.

  4. Tom Sarver

    Excellent explanation and reference point (Japan experience). One point, it assumes that the DPRK is designing for maximum destruction and not maximizing fallout. Given their leader, not clear this would be the case.

  5. Mike Patterson

    It’s rare that concepts this complex can be simplified without condescension. Nicely stated.

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