Making Bombs from Nuclear Waste


Bombs use weapons grade uranium enriched to 90% or more U-235. Lower enrichments are possible, but the bomb is technically more difficult.

Terrorists or nations could obtain uranium bombs by steal one. Alternatively, they can stealing enriched uranium, or enrich uranium to weapons grade from natural or lightly enriched uranium, and make their own bomb. Enriching uranium to weapons grade is complicated enough that it requires government leadership or sanction, so Iran could do it, Al Qaeda can’t.

It is much easier to dispose of weapons grade uranium than plutonium (Pu will be addressed in future post). It only requires diluting the weapons material with natural or depleted uranium (the U-238 left over from the enrichment process), the Megatons to Megawatts program.

Uranium bombs are not made from commercial reactor waste.


Plutonium-239 is the isotope used for weapons. Pu-240, with a half-life of 6,564 years, is a contaminant. It usually decays by alpha decay (emitting two neutrons and two protons), but can also spontaneously fission (break into two much smaller nuclei, emitting neutrons at the same time). These neutrons can start a chain reaction (predetonate) before the plutonium is fully compressed. Predetonation causes a fizzle, a smaller explosion than the bomb was designed for.

Pu-239 is made when U-238 captures a neutron to become U-239. This decays without any neutron release to become Pu-239. If the fuel is left in the reactor, some of the Pu-239 captures a neutron to become Pu-240. Taking the fuel out before long exposure minimizes the amount of Pu-240 formed.

Supergrade plutonium is 98% Pu-239, or more; the rest is Pu-240. Regular weapons grade is 94% Pu-239, 6% Pu-240, and 0.4% other. Reactor grade plutonium is 60%Pu-239, 24% Pu-240, 9% Pu-241, 5% Pu-242, and 1% Pu-238. Weapons grade produces a little over 3 times as many neutrons by spontaneous fission as does supergrade; reactor grade emits 18 times as many. While no military uses reactor grade plutonium, sophisticated bomb designers could make some sort of weapon.

Predetonation is guaranteed in a weapons using reactor grade plutonium; there is a 70% chance that the yield will be less than 10% of what the bomb was designed for. Even weapons grade plutonium has only a 50% chance of a yield more than 40% of design. Supergrade plutonium with only 1% Pu-240 has an 80% chance of exploding at full design yield.

An authoritative National Academy of Sciences report says,

[E]ven with relatively simple designs such as that used in the Nagasaki weapon—which are within the capabilities of many nations and possibly some subnational groups—nuclear explosives could be constructed that would be assured of having yields of at least 1 or 2 kilotons. Using more sophisticated designs, reactor-grade plutonium could be used for weapons having considerably higher minimum yields.

Bodansky says that it is clear that

reactor grade plutonium can be used to make an explosive device that would release a substantial amount of energy. This would be enough to create an explosion that would do great damage due to the blast itself, the heat and radiation produced in the chain reaction, and the radionuclides dispersed in its aftermath.

A national government is more likely to make a reactor particularly to irradiate the uranium for a shorter time. This is simpler, and the bomb is more likely to meet the needs of a government. A terrorist organization might take whatever is available, and worry less about uncertainties in yield.

Once reactor grade plutonium is obtained, there are several obstacles to making a bomb:

• The reactor fuel must be reprocessed to separate out the plutonium.
• The plutonium must be carefully machined, shaped, and assembled. A mistake could kill the workmen.
• The explosives must be arranged for a rapid, symmetric explosion and warm reactor grade plutonium must not overheat the explosives.

One argument against reprocessing reactor fuel is that reprocessing removes the self-protecting element of reactor fuel: fission products which are so radioactive that no one can steal it. Remote handling equipment and reprocessing could work for a national government; again, creating weapons grade plutonium would be simpler.

Some oppose reprocessing of commercial reactor fuel both because nations could make a bomb somewhat faster from reprocessed reactor fuel then from scratch and because theft is now possible. These considerations, along with the relatively high price of reprocessing, led President Carter in 1977 to forego reprocessing. This was not out of fear that the US could develop the bomb, but to discourage reprocessing elsewhere. The good example has not been completely successful. When Carter acted, France, India, Japan, and the UK reprocessed nuclear fuel. Each of these countries has expanded its reprocessing capability since then, and Russia and China have begun reprocessing.

It appears improbable that processing will be abandoned in these countries… [I]t is uncertain for how long Japan will be content to be protected by a U.S. nuclear umbrella…Although a plutonium stockpile would speed the pace of a program to develop weapons, even with no prior stockpile Japan has the personnel and facilities to develop nuclear weapons quite quickly, should it choose to do so.

While it is unlikely that the famed high school student could make a plutonium weapon, a well-organized terrorist group could acquire expertise and equipment.

It might be argued that even for such a group, it would be irrational to proceed with a plutonium bomb when there are simpler alternatives for major destruction and terror. However, it is not prudent to rely on the rationality of terrorist groups.

So good security is a must.

Also in this series
Part 1 Nuclear Bombs, Nuclear Energy, and Terrorism
Part 2 Today’s Bombs, Making a Bomb
Part 4 Terrorist Targets
Part 5 Nuclear Proliferation—International Treaties
Part 6 The Bomb Spreads
Part 7 Nuclear Power and the Weapons Threat
Part 8 Wrapup on Nuclear Power Series

One Response to “Making Bombs from Nuclear Waste”

  1. kurye says:

    very nice great post