Technetium in Coastal Environments: Field Observations and Laboratory Experiments

By irradiating molybdenum in the cyclotron of Berkeley in 1937, Perrier and Segre discovered a new element (element 43) which they named technetium (Perrier and Segre 1937, 1947; Schriver et al. 1978). This artificial element has the properties of a metal. All of its known 21 isotopes and isomers are radioactive (Schwochau 1978, 1983). As the longest half-lives are 2.6 × 106 years (97Tc) and 4.2 × 106 years (98Tc), the earth contains no technetium formed during its origin (about 4.6 × 109 years ago). Technetium is produced in nature by spontaneous fission of uranium (238U), with smaller amounts formed by neutron-induced fission of 235 U, or by cosmic ray activation of molybdenum, niobium, ruthenium and zirconium (Boyd 1959; Kotegov et al. 1968; Till et al. 1979; Saas et al. 1980). The development of nuclear energy has considerably increased the amount of technetium in the environment, with the major source originating from the fission of uranium (233U, 235 U), thorium (232Th) and plutonium (239Pu) in nuclear weapons and in nuclear power plants (Katcoff 1958, 1960; Wildung et al. 1979).