Scientists have garnered greater understanding of technetium-99 nuclear waste – a byproduct of plutonium weapons production and considered to be a major U.S. challenge for environmental cleanup.
According to information provided by scientists in their study published in Inorganic Chemistry there are about 2,000 pounds of technetium-99 dispersed within approximately 56 million gallons of nuclear waste in 177 storage tanks at the Hanford Site nuclear complex in Washington state. The element can be very soluble in water and moves easily through the environment when in certain forms, so it is considered a significant environmental hazard.
While the U.S. Department of Energy is moving ahead with its plans of building a waste treatment plant at Hanford to immobilize hazardous nuclear waste in glass, the researchers have been stymied because not all the technetium-99 is incorporated into the glass and volatilized gas must be recycled back into the melter system. Because technetium compounds are challenging to work with, earlier research has used less volatile substitutes to try to understand the material’s behavior. Further some of the compounds haven’t been studied for more than five decades.
To garner a greater understanding of technetium-99, scientists at the Washington State University and colleagues from Pacific Northwest National Laboratory (PNNL), the Office of River Protection and Lawrence Berkeley National Laboratory conducted fundamental chemistry tests to better understand technetium-99 and its unique challenges for storage. They determined that the sodium forms of the element behave much differently than other alkalis, which possibly is related to its volatility and to why it may be so reactive with water.
Researchers say they are optimistic that their findings will aid in refining the understanding of technetium incorporation into nuclear waste glasses. The researchers also hope the work will contribute to the study of other poorly understood chemical compounds.