The Nuclear Weapons States: Who Has Them And How Many
Forbes
Nuclear energy is growing around the world. About 70 new reactors are under construction worldwide (NEI), with more than 600 others planned by mid-century. Five reactors are under construction in the United States.
On the other hand, nuclear weapon states have declined slightly in the last twenty-five years (see figure below). Several old players have dropped their nuclear weapons programs or given their weapons back to Russia, including South Africa, Kazakhstan, Belarus and the Ukraine. The latter now regrets that decision very much.
But since 1990, only two new players have succeeded in developing nuclear weapons, Pakistan and the Democratic People’s Republic of Korea (the DPRK, formerly known as North Korea), and only because a very clever Pakistani scientist named Abdul Qadeer Khan. Khan developed Pakistan’s weapons program and sold stolen nuclear secrets to Iran, the DPRK and Libya.
While the number of countries that have commercial nuclear power has increased to 31, the number of countries that developed nuclear weapons has not increased very much, contrary to early fears. Presently, there are nine nuclear weapons states with about 10,000 weapons, but there are about 430 commercial nuclear reactors in 31 countries, depending upon what finally shakes out in Japan and Germany. Italy is the only country to completely halt its commercial nuclear energy program, although Germany will probably be the second. But new nuclear energy programs are emerging in many other states including countries like the United Arab Emirates, Vietnam, Saudi Arabia and Jordan. The only new nuclear weapons states in the last 25 years are Pakistan and the Democratic People’s Republic of Korea (the DPRK, formerly known as North Korea). South Africa, Kazakhstan, Belarus and the Ukraine dropped their nuclear weapons programs when the Soviet Union dissolved, and the old Soviet satellites gave all their nuclear weapons back to Russia. Most nuclear energy states have the knowledge and some of the infrastructure to develop a weapons program if they decide to, and the time required for them to do so is termed the latency period. Iran’s latency period is about 6 months but they are not expected to pursue the final steps to a weapon. After Scott Sagan.
Iran was threatening to enter the weapons club, but they are now unlikely to complete the final steps. Libya abandoned its weapons program under pressure from the U.S. after failing to make real progress, and has since become a failed state. Syria tried to secretly build a weapons reactor at al-Kibar with DPRK’s help several years ago, cleverly disguised as a 10th century Byzantine fortress (see figure below), but the Israelis bombed it before it got started, a fortunate move given the subsequent civil war in that country.
Therefore, the focus on weapons proliferation by the United States and the International Atomic Energy Agency has been diligent and pretty effective. This simple discussion cannot cover the total complexity of this issue, and more can be found at Stanford’s Nuclear Risk Group, especially the work by Dr. Hecker.
Presently, there are nine nuclear weapons states with about 10,000 weapons, down dramatically from the 100,000 at the height of the Cold War:
Russia 5,000 U.S. 4,400 France 290
China 240 U.K. 195 Israel 80
Pakistan 200 India 150 DPRK ~ 6
In contrast, there are 430 commercial nuclear reactors in 31 countries, assuming 10 or so in Japan are closed permanently and Germany permanently ends its nuclear program (see figure above).
The Syrians attempted to build a weapons reactor in secret at al-Kibar with North Korea’s help several years ago. They cleverly disguised the reactor (on left) as a 10th century Byzantine fortress (on right). Fortunately, the Israelis caught wind of it and bombed it before it got started. Source: Los Alamos National Laboratory
No nuclear weapons program ever came out of a nuclear energy program. It is theoretically possible, but not practical. Nations have tried, but even Argentina and Pakistan realized that if you want weapons, you develop a weapons program and pick one of the two traditional paths to the bomb. And no one is fooled by an energy front.
In fact, those countries that have the bomb developed weapons programs for that very purpose, regardless of whether they had a nuclear energy program or not.
The connection between energy and weapons is that nuclear energy states have some of the basic knowledge and some of the infrastructure to start a weapons program, but only if they decide to obtain or develop the rest of the infrastructure and knowledge (see top figure). The time required for them to produce a bomb, after they make this momentous decision, and then successfully test it, is termed the latency period (Sagan 2010).
As examples, Peru has no nuclear energy or nuclear infrastructure of any kind and so doesn’t have a latency period. Sweden has nuclear energy but insufficient infrastructure to make a weapon in less than about five years, so its latency period is about five years. Iran’s latency period is about 6 months. Through political negotiation and economic pressure, they are now not expected to pursue the final steps to a weapon. But their latency period will likely always be less than a year.
Pu and U
An atomic bomb is a containerized uncontrolled nuclear chain reaction that can be made from either U-235 and Pu-239, the two elements that can be easily split apart to release a lot of energy. Since a reliable and effective bomb requires each element to be pretty pure (over 90% of either U-235 or Pu-239), one needs to choose the specific path for each.
There are two basic approaches to building an atomic bomb. The first is enriching natural uranium until it is over 90% U-235, followed by emplacing it in a gun-type weapon (top). The second is to produce Pu in a weapons reactor, separate it from all the other elements and purify it to over 90% Pu-239, followed by emplacing it in an implosion-type weapon (bottom). The United States made both during World War II. Lately, Iran chose the U-bomb route, but has chosen not to build one. The DPRK chose the Pu-bomb, built and successfully tested two, and has enough Pu for several more.
For a U-bomb you can depend on, you just need to enrich the U-235 up to about 90%, way more then the 3% to 5% for a commercial reactor. However, in addition to needing many highly sophisticated centrifuges and associated technologies, it takes a lot of energy to enrich U-235 to weapons grade, a lot of electricity to spin that many centrifuges that fast.
To weaponize U, you need to make a big gun assembly (see figure above), put two separate globs of U-235 not large enough to go critical alone, something like 40 lbs each but when combined is more than enough, pack propellant or explosives behind one of them, and at the right moment propel it into the other so it goes critical. This is the easiest way to make an atomic bomb.
It was so easy, we didn’t even have to test it in 1945 before we used it.
For a Pu-bomb, you need a weapons reactor to produce enough Pu-239, which needs to be separated from the other elements. To weaponize it, you need to make an implosion assembly (see figure above), put a smaller glob of Pu-239, only 15 to 20 lbs since Pu-239 fissions better than U-235, but that is not dense enough to go critical. Then pack high explosives around it so that when they explode, the Pu is compressed to super high density and goes critical.
An implosion-type Pu-bomb is a lot more difficult to make than a gun-type U-bomb and we were uncertain enough about it working that we decided to make two Pu-bombs so we could test one at the Trinity Site in New Mexico on July 16, 1945 before we used the other one on August 9th.
So a U-bomb is easier to make, but a Pu-bomb is better to have.
This choice between U and Pu is reflected in the weapons programs of Iran and the DPRK. Iran decided to build a U-bomb to threaten its regional neighbors and to counter Israeli’s atomic weapons. They were never wanting to threaten the world.
Iran was using centrifuges to highly-enrich U, and got up to about 20% U-235. They did not require a weapons reactor. In fact, Iran recently completed and fired up a commercial power reactor, started with Russian fuel, and no one gave it a second thought since that is not a path to a weapon.
However, Iran is now blending down its highly-enriched U-235 stocks, and is not expected to complete the steps needed to make a bomb. They will continue to enrich to fuel levels and hopefully will take this opportunity to turn their enrichment capabilities to commercial use in producing low-enriched fuel for the region’s growing commercial nuclear programs.
On the other hand, the DPRK went for the Pu-bomb because they don’t have a lot of electricity generation, and a Pu-bomb is easier to put on missiles since they actually want to threaten the world. They built a weapons reactor, that couldn’t make energy even if they wanted it to, but that was designed specifically to produce Pu-239.
They reprocessed the fuel (see reprocessing figure in the previous post), and built an implosion-type Pu-bomb. After building at least one dud, they successfully built and tested two devices, and have enough Pu to build several more.
But what about the large amount of U and Pu that has been produced by the United States, Russia and other nations over the last 70 years? A fair amount of weapon grade U and Pu around the world is not in bombs, something like 2,000 tons, enough to make thousands of bombs (DoD Readiness Through Awareness). It is a little frightening to know that some of it may not be well-secured, but the United States and the United Nations are working to secure them and seem to be succeeding pretty well.
Finally, there are fusion bombs, or thermonuclear devices. These nuclear weapons, made from fusing hydrogen into helium, are much larger and hundreds of times more powerful than atomic bombs made from fissioning heavy elements into pieces as we’ve been discussing. Fusion bombs do require a small fission-bomb trigger, however, to initiate the second stage fusion reactions.
Fusion bombs are so difficult to make, require such large sophisticated facilities, huge nuclear workforces and enormous amounts of money, that only the most advanced nations have developed them, such as the United States, Russia, the United Kingdom, France and China. India tried but failed. We aren’t worried about anyone new like the DPRK making fusion bombs. We’re worried about them making atomic bombs which are more than enough to get respect from one’s neighbors and strike fear into everyone else.
After all, blowing up the world ten times over was a fusion fantasy of the Cold War.
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