Researchers at the Pacific Northwest National Laboratory (PNNL) have developed a way to accelerate the reprocessing of spent nuclear fuel. To do this, they applied spectroscopic monitoring methods. ACS Sensors writes about the research results.
In the United States, spent nuclear fuel is stored underground. But, contrary to popular belief, these storage facilities are not designed to get rid of this fuel forever, but to store it until it is needed again. This is because the spent fuel still contains a lot of uranium and plutonium, as well as a huge amount of extremely valuable radioactive isotopes that are in high demand in the medical and engineering circles.
But the real problem is hidden here: spent fuel consists of a complex mixture of elements, almost half of the periodic table. It is very difficult to separate them. And although nuclear fuel reprocessing is an important industry, it remains quite conservative and expensive. In addition, it increases the risks of producing pure plutonium, which in turn raises proliferation problems.
One of the main arguments in favor of nuclear power is the tiny amount of fuel required to operate a reactor. A single nuclear fuel pellet weighing only 10 grams gives off energy equivalent to a ton of coal, but surprisingly, when that pellet is “depleted”, it still contains 95% of the fissile material.
To improve the recycling process, PNNL uses Raman spectroscopy to monitor spent fuel in real time as it flows past the sensor in solution.
Raman systems are chemical analysis methods that use the interaction of light with chemical bonds in a molecule to obtain information about its chemical structure, phase and polymorphism, crystal structure, and molecular interactions.
Using this data, commercial quantities of spent fuel can be monitored as it is converted to liquid form and then sent to a centrifuge, which separates the various elements by mass. Real-time monitoring allows for more accurate control of the ratio between uranium and plutonium, as well as the removal of unwanted elements and isotopes to produce new reprocessed fuel that can be burned in advanced reactors.