Part 1 of 2 Parts
Many sophisticated laboratory tests have been developed for determining the composition of a material of interest. However, there are times when it is just not possible to bring a sample into the laboratory for testing. One example would be testing contents of shipping containers on the dock. Another would be analyzing a rock on the surface of Mars.
Radioactive materials such as uranium are especially difficult to analyze with respect to nuclear explosions and the debris left behind. Detection systems that can be done quickly onsite reduce human exposure that could occur during hazardous collection or laboratory analysis.
Nuclear chemistry in general and the way that uranium interacts chemically with oxygen during a nuclear explosion in particular are poorly understood. This makes it difficult to accurately identify materials involved in nuclear explosions.
The Pacific Northwest National Laboratory (PNNL) is one of the United States Department of Energy national laboratories. “It draws on signature capabilities in chemistry, earth sciences, and data analytics to advance scientific discovery and create solutions to the nation's toughest challenges in energy resiliency and national security.” Now a team of researchers at Pacific Northwest National Laboratory is working to expand our knowledge of uranium chemistry by using lasers. The leader of the PNNL team is physicist Sivanandan S. Harilal.
The work of the PNNL team is detailed in a recent report published in the Journal of Analytical Atomic Spectrometry. The PNNL team shows how the analysis of the light emitted from plasmas created by a laser can be utilized to comprehend uranium oxidation in nuclear fireballs. This method yields new insights into the uranium gas-phase oxidation during nuclear explosions. The work of the PNNL team should accelerate progress toward the creation of a reliable, non-contact method for the remote detection of uranium and isotopes. The creation of such analytical methods has serious implications for the creation of nonproliferation safeguards, nuclear explosion monitoring and verification of adherence to international treaties.
The PNNL method involves using a pulse of an extremely fast laser to blast a solid material. The laser beam excites the atoms and causes some of them to vaporize generating a tiny, brightly colored plasma plume. When the atoms jump into the superhot plasma plume, the light that is emitted is captured and studied by optical spectroscopy.
Plasmas generated from different elements at different temperatures emit different wavelengths of light. Each plasma produces a distinct color related to the element(s) and temperatures. The color of the plasma from a candle is different than the color of a plasma made in a neon sign. And both are different than the color of a uranium plasma.
The distinctive colors of light emitted by a plasma are exactly the same without regard to the size of the sample that is vaporized into a plasma. Although some material is vaporized to make a plasma in the PNNL research, the amount is so small that their method is considered to be non-destructive. The light emitted by the tiny plasma at the PNNL is similar to the chemical and nuclear transactions that are unleashed in a nuclear explosion.
Please read Part 2 next