Waterproof Underwater Gamma-ray Detector

Abstract

In-situ environmental radiation detection underwater is important to monitor the suspect radioactivity changes in the ocean. In this study, we developed a waterproof system of a commercial gamma-ray detector (Ortec 905-4 scintillation detector). Using three radioactive point sources (Ba-133, Cs-137, and Co-60), we tested its waterproofness and radiation detectability in a water tank. The detector was housed in a waterproof casing made of 9 mm thick aluminum alloy, which was sealed with O-rings to ensure water-tightness. The casing was designed to protect the gamma-ray sensor and devices of power supply and data communication and to expose the radiation sensor's scintillator to water. The waterproof underwater gamma ray detector was tested both on land and in a water tank at a depth of 1 m. We confirmed 24 hours waterproofness and the distinct peaks on underwater spectra corresponding to spectra measured on land (air spectra). Compared to the air spectra, the underwater gamma-ray spectra were attenuated by water.