Immediate Change of Radiation Doses from Hydrothermal Deposits

Abstract

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 of 226 Ra and 228 Ra. 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.

Design of a Prototype in-situ Gamma-ray Spectrometer for Deep Sea

“…On the other hand, although HPGe has a better energy resolution than NaI(Tl) scintillator, the disadvantages of the HPGe used in deep sea are high cost and the requirement of external cooling equipment. In these published experiments based on NaI(Tl) crystal in the depth from 110 meters to 6500 meters, the spectrometers usually have an energy range of about 100 keV to 1.8 ∼ 3.6 MeV, spectra of 240 to 2048 channels and a resolution of 7% to 10% [2,3,[7][8][9]. Moreover, only the gamma ray dose is counted without the energy spectrum in some experiments, such as an investigation in the Southern Mariana Trough [10].…”

“…The main radio-nuclides in the deep ocean are 214 Bi at 609 keV, 228 Ac at 696 keV, 137 Cs at 662 keV, 40 K at 1461 keV, 208 Tl at 2615 keV, etc. [2,4,5,7,8]. The sources for calibration are usually 137 Cs, 133 Ba, 60 Co and 22 Na.…”