Shipboard use of californium-252 for neutron activation analysis: a new oceanographic tool

Several field tests have been made over the past three years involving the application of neutron activation analysis at sea. The neutron source was 252Cf. The initial tests were performed in the Pacific Ocean off the coast of California in which a 200 microgram 252Cf neutron source and detection systems were installed on a submersible (Westinghouse Deepstar 2000). The primary objective of these initial sea trials was to prove the reliability of the analytical system, as well as the overall feasibility of taking a neutron source to sea. All facets, including that of health physics proved positive. Subsequent investigations were also performed in the Gulf of Mexico and on the continental shelf off the southeastern U. S. coast where in situ mineral analysis was performed. In the latter tests, television equipped scuba divers and underwater sleds were used as the undersea vehicles. Early in 1972, a 1 milligram 252Cf neutron source and a more sophisticated analytical system were taken to sea for an extended cruise in the Pacific Ocean, during which the source and all support equipment remained on shipboard. The elemental content of bottom sediments and deep-sea nodules was measured from material brought to the surface by cores and grab samples. On the same cruise, sea-water samples were collected from various water depths and were analyzed immediately for trace element composition. In summary, the authors feel that the use of a 252Cf neutron source at sea will provide an important new shipboard analytical tool to the oceanographic community. (U.S.)