Tc99

Technetium-99 (Tc-99) is a radioactive isotope of technetium with a half-life of about 210,000 years. It is produced predominantly as a fission product in nuclear reactors and is a long-lived component of spent nuclear fuel and high-level waste. In the environment, Tc-99 is typically found as the pertechnetate anion (TcO4−) under oxidizing conditions, which is highly soluble and mobile in groundwater. Under reducing conditions, technetium can exist in lower oxidation states (such as TcO2 or Tc(IV) compounds) that are less soluble and may sorb to minerals.

Tc-99 is not widely used in medicine; the related isotope technetium-99m (Tc-99m) is the workhorse of diagnostic nuclear medicine and is generated from the decay of molybdenum-99 in Mo-99/Tc-99m generators. Tc-99m rapidly decays to Tc-99, which then has a long half-life. The presence of Tc-99 in waste streams poses long-term radiological and environmental management challenges due to its high solubility and persistence.

Discovery and history: Technetium was discovered in 1937 by Carlo Perrier and Emilio Segrè. It is the lightest element with no stable isotopes. Production methods include nuclear fission and neutron irradiation in reactors, and it remains a focus of waste immobilization research.