The radiation from the sulfide deposits taken at Okinawa Trough was measured on-board by a NaI gamma ray spectrometer immediately after the retrieval of the sample onto the research vessel. Gamma ray peaks were identified as those from daughter nuclei of226Ra and228Ra. The slight change with time of the radiation dose from those deposits is probably due to the geometric arrangement in measurements. As results, no change in radiation dose was observed in the time range up to 90 h after retrieval of the samples from the submarine vehicle.
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