Enriching to a point

Although most of the world’s nuclear reactors rely on uranium, natural uranium cannot be used directly in a reactor because its concentration of fissile uranium-235 is too low. Natural uranium is composed of three isotopes: uranium-235, -238, and -234. The concentration of uranium-235 must be increased, or enriched, for reactor use. If that enrichment is continued to reach concentration levels common in nuclear weapons, it threatens nuclear nonproliferation efforts.

That’s where the International Atomic Energy Agency (IAEA) comes in.

The Treaty on the Non-Proliferation of Nuclear Weapons—signed by 191 nations since 1968—stipulates that the IAEA can inspect enrichment plants of signatory nations to ensure that uranium is being enriched only for energy production. The most common method used to analyze samples is thermal ionization mass spectrometry, which requires large equipment at dedicated facilities. Not only are results slow to come by, but difficult-to-dispose waste is also produced.

To streamline inspections, Los Alamos National Laboratory scientist Alonso Castro led a team that designed, built, and tested the Fieldable Atomic Beam Isotopic Analyzer (FABIA). FABIA measures the isotopic content of uranium, plutonium, and other actinides with high sensitivity, resolution, and speed. Bulk samples can be collected throughout the nuclear reactor fuel cycle to determine the purity and composition of materials. 

FABIA weighs about as much as a suitcase (around 40 pounds) and can be carried or wheeled directly to inspection sites. Results can tell inspectors in fewer than 10 minutes whether uranium has been enriched beyond reactor-grade levels. This capability also aids in the disposition and reprocessing of spent fuel. The knowledge from such quick analyses lowers the cost of energy production and increases safety at nuclear plants.

According to Castro, “FABIA makes the world a better place by aiding in verifying that nations comply with their commitments under nonproliferation treaties.”

Additional benefits include that a sample does not require preprocessing or separation, nor does it produce chemical waste. FABIA also provides flexible analysis: Simply by swapping the diode laser, the instrument can be customized to analyze most solid elements in the periodic table.

FABIA’s benefits extend to other global security applications, too. For example, if a mysterious nuclear device is detonated, FABIA could help scientists quickly and accurately understand the origin, processing history, and composition of the nuclear material before detonation, as well as the overall fission efficiency of the device. 

In addition, FABIA can determine the purity of individual isotopes used in the field of medicine. Because medical isotopes have short lifetimes, it is imperative to rapidly analyze them right at the point of production.

To develop a device with so many applications, Los Alamos needed to draw from a diverse set of skills. “We assembled a team of scientists from a variety of fields: atomic physics, spectroscopy, actinide chemistry,” says Castro. “Talent from those fields can be readily applied to nuclear nonproliferation, and it was very exciting to witness such a diverse team working together toward a common goal.” ★