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Nuclear bombs from low-enriched uranium or "spent" fuel

Nuclear Monitor Issue: 

(March 7, 2003) Conventional wisdom says that low-enriched uranium is not suitable for making nuclear weapons. However, an article in USA Today claims that "rogue" states and terrorists have discovered that this is untrue. Not only that, but terrorists could separate plutonium from irradiated fuel (often called "spent fuel") more easily than previously thought.

(584.5495) WISE Amsterdam - Low-enriched uranium (LEU) is uranium containing up to 20% uranium-235. Uranium with higher enrichment levels is classified as high-enriched, and is subject to international safeguards because it can be used to make nuclear weapons.

However, a USA Today article claims that "rogue countries and terrorists" have discovered that it is possible to make nuclear weapons with uranium of lower enrichment, according to classified nuclear threat reports (1).

The information is not entirely new. Back in 1996, a standard book on nuclear weapons material stated, "a self-sustaining chain reaction in a nuclear weapon cannot occur in depleted or natural or low-enriched uranium and is only theoretically possible in LEU of roughly 10 percent or greater" (2).

Fuel for nuclear power reactors would not be suitable - this is typically enriched to 3-5% uranium-235. However, for a "rogue state" wanting to make high-enriched uranium, it would take less work to start with nuclear fuel than with natural uranium. It could be done in a "small and easy to hide" uranium enrichment plant - perhaps similar to the plant which has recently been discovered in Iran (3). Nevertheless, it would still require a substantial operation, since the fuel would need to be converted to uranium hexafluoride, enriched and then reconverted to uranium metal.

More significantly, many research reactors use uranium of just under 20% enrichment, which according to the USA Today article can be used to make nuclear weapons.

The U.S. has long promoted a program called Reduced Enrichment for Research and Test Reactors (RERTR), offering incentives for converting research reactors from high-enriched uranium to uranium of just under 20% enrichment, as an anti-proliferation measure. The new revelations raise a question mark over the usefulness of the RERTR program, and imply that research reactors with uranium of just under 20% enrichment need to be well guarded too.

They also raise questions about the usefulness of dramatic military operations to secure high-enriched uranium at inadequately guarded research reactors, such as the operation in Serbia last year (4). This operation apparently left behind a cache of irradiated fuel containing at least 10 pounds (4.55 kg) of plutonium.

Irradiated fuel
Irradiated fuel from nuclear reactors, often described as "spent fuel" even though it still contains lots of fissile material, could also be made into weapons more easily in some cases, according to the USA Today article.

Some stocks of irradiated fuel have been sitting around for many years, and are now far less radioactive. This would mean that only "modest facilities and equipment" would be needed to reprocess the fuel to extract plutonium.

IAEA response
Challenged over the proliferation dangers from "old" irradiated fuel and LEU of just under 20% enrichment, Davis Hurt from the International Atomic Energy Agency (IAEA) told USA Today that the IAEA could only expand its monitoring too include these materials if member states provided money to boost its budget. And, it seems that the nuclear industry is reluctant to pay for the extra security measures, and would rather either ignore the problem and hope it goes away, or else get the taxpayer to foot the bill.


  1. USA Today, 27 February 2003
  2. Plutonium and Highly Enriched Uranium 1996, Stockholm International Peace Research Institute
  3. See "Iran's nuclear program" in this WISE/NIRS Nuclear Monitor.
  4. WISE/NIRS Nuclear Monitor 572.5429, "Troops seize uranium in first of 25 operations"

Contact: WISE Amsterdam