Accelerator mass spectrometry of long-lived heavy radionuclides

Accelerator mass spectrometry (AMS) is presently the most sensitive technique for the environmental measurement of radionuclides with half-lives greater than about 5000 years. Traditionally, it has been used principally for light elements, of which the most familiar example is ¹⁴C. With some modifications, however, it may also be applied to elements as heavy as the actinides, and in particular to ^239,240,244Pu and ²³⁶U. Here, the principles and methodology of heavy-element AMS are described, and the ways in which these have been implemented in various laboratories around the world are detailed. Although the emphasis is on plutonium and uranium, other isotopes such as ²³⁷Np and ^226,228Ra are also considered. For completeness, the measurement of the long-lived fission products ⁹⁹Tc and ¹²⁹I by AMS is also discussed briefly. Actual or potential applications of the method in the areas of environmental science, biomedicine, and nuclear safeguards are reviewed.