The handling and disposal of nuclear waste is an enormous problem in the U.S. In addition to eighty thousand metric tons of spent nuclear fuel, there is also a significant quantity of nuclear waste left over from the development of nuclear weapons. The Hanford Nuclear Reservation has a great deal of contamination in the soil where radioactive liquids were just dumped into the dirt. There are also a hundred and seventy-seven buried tanks containing fifty-six million gallons of nuclear and other toxic materials. Some of those tanks are leaking. The U.S. Department of Energy is constructing a waste treatment plant which will mix the waste with powder and melt the mixture into glass logs for burial.
Technetium is a chemical element designated by the symbol "Tc" and an atomic number of 43. It is a shiny gray metal with properties similar to manganese. It is the lightest element which has only radioactive isotopes. Tc is produced naturally by fission of uranium or neutron capture by molybdenum. It is rare in nature and most existing Tc synthesized. It is used in industrial, chemical, biological and medical applications.
Tc-99 is produced during the manufacture of nuclear weapons. It is estimated that there are about two thousand pounds of Tc-99 in the buried tanks at Hanford. Tc-99 dissolves easily in water and can be spread through the environment by groundwater. It is considered one of the major problems with cleanup at Hanford, especially in view of the leaking tanks. However, there is a problem with immobilizing the Tc-99 in the glass logs because some of the Tc-99 fed into the melter volatilizes and has to be captured and recycled back to the melter.
Researchers at Washington State University led by John McCloy, associate professor in the School of Mechanical and Materials Engineering, and chemistry graduate student Jamie Weaver are studying the chemistry of Tc-99. The research was carried out at the Pacific Northwest National Laboratory in Richland, Washington, near the Hanford Nuclear Reservation. Staff at PNNL, the Office of River Protection and Lawrence Berkeley National Laboratory collaborated.
Technetium-99 compounds are hard to work with and earlier research utilized other similar compounds in their laboratory tests. However, the researchers found that Tc-99 does not behave exactly like the substitute compounds. Especially compounds of sodium and technetium have some surprising behaviors involving solubility and vaporization which are relevant to their environmental impact.
Understanding the details of the chemical behavior of dangerous radioactive isotopes such as Tc that are dangerous to the environment is critical to the cleanup at Hanford which is so far behind schedule and underfunded that the state of Washington has filed lawsuits to force the Department of Energy to commit to specific deadlines for completion of the cleanup.
Technetium: