Types of Technetium Generators

Molybdenum-99 has 42 protons and 57 neutrons in its atomic nucleus, giving it an atomic weight of 99. Technetium-99 has 43 protons and 56 neutrons in its nucleus, giving it the same atomic weight as molybdenum-99. Molybdenum-99 changes into technetium-99 when one of the neutrons in its nucleus emits a negatively charged beta particle and changes into a proton. Doctors use technetium-99 as a diagnostic tool in analyzing a wide variety of pathological conditions involving the bones and organs. Various types of technetium generators produce this isotope for medical use.

Technetium Chromatographic Generator

• Splitting atoms of uranium-235 forms a variety of fission products, including molybdenum-99. A common technetium chromatographic generator uses molybdenum-99 that originates in this way. This molybdenum-99 is placed on a surface of aluminum oxide, to which it firmly adheres by a process called adsorption. As the molybdenum-99 gradually changes to technetium-99, the technetium-99 will not adhere to the aluminum oxide, so a periodic application of a salt water solution will separate technetium-99 from molybdenum-99. Chromatography is the process of separating substances by differential absorption.

Gel Technetium Generator

• A gel technetium generator employs a gel matrix such as zirconium molybdate, in which some of the molybdenum is molybdenum-99. This generator does not have to use molybdenum-99 produced by fission. It can use molybdenum produced by adding neutrons to molybdenum-98 by a process called irradiation. As the technetium-99 forms, an application of water or salt solution will remove it from the gel. This generator is less likely to produce undesirable irradiation byproducts than the technetium chromatographic generator.

Sublimation Technetium Generator

• Sublimation is a process in which a substance changes from a solid state into a gas without first becoming a liquid. The sublimation technetium generator uses this process to separate technetium-99 from molybdenum-99. This is possible because compounds such as Tc2O7 and pertechnetic acid volatilize at a temperature below the boiling point of molybdenum trioxide. According to the Journal of Inorganic and Nuclear Chemistry, a temperature of 670 degrees Celsius is sufficient to obtain technetium-99 by sublimation when separating it from a mixture of molybdenum trioxide and plumbous oxide, but higher temperatures are necessary when separating it from molybdenum trioxide alone.

Solvent Extraction Generator

• The solvent extraction technetium generator mixes molybdenum trioxide that contains molybdenum-99 with a solution of potassium hydroxide. Recovering the developing technetium-99 is a long, involved process, in which a substance called methyl ethyl bromide plays an important role. Because of the length and difficulty of this process, the fingers of the people performing the operation might suffer exposure to radiation, according to the Journal of Nuclear Medicine.