Determination of long-lived radionuclides in biological samples collected at Mururoa by a scientific delegation headed by the IAEA

An international intercomparison exercise was conducted by the IAEA in 1994 on the edible fractions of biological samples collected in Mururoa. This article presents the results of additional measurements made on the inedible parts of marine samples, i.e., the gonads, viscera and livers of fish (groupers) and the hepatopancreas or viscera of mollusks (giant clams and turbos). The spread of data as a function of sampling locations has been investigated, while the concentration factors for several long-lived radionuclides have been determined and discussed. Plutonium-239/240 concentration data for giant clam flesh and hepatopancreas appear to be very close (approximately 0.6 Bq/kg wet weight), whereas Co-60 concentrations are 100 times less in flesh (3 Bq/kg wet weight) than in hepatopancreas. As regards groupers, Pu-239/240 and Co-60 centrations in flesh are very low and close to the detection limit. These concentration values are 100 to 500 times lower than those recorded in livers. As for turbos, plutonium and Co-60 concentrations in viscera are 5 to 10 times higher than in soft parts. Based on these data, it becomes possible to determine which fractions of marine samples should be analyzed first in order to detect minute traces of Co-60, Cs-137 and plutonium in Polynesia.