Performance Test of Underwater Gamma-ray Spectrometer

Abstract

There are various devices for measuring radiation dose on land, but sensors that can be used underwater are extremely limited. In this study, a underwater gamma-ray spectrometer was built with a NaI and PMT-based gamma detector, a waterproof case and a communication system. We used a Ortec’s 905-4 NaI(Tl) scintillation detector. The sensor has a 3” diameter crystal and is controlled by USB communication for the part of the scintillation detector and the communication device were placed in a 9 mm-thick rectangular aluminum waterproof box with O-rings. USB to Ethernet and PoE splitter were used as communication devices, and ethernet cable was connected to the laptop. We measured radiation spectra of three radioactive sources, Cs-137, Ba-144 and Co-60 by the developed underwater gamma-ray spectrometer. We confirmed the normal acquisition operation of the radiation spectra in water guaranteeing its waterproofing. Also, comparing to the measurement on land, it was confirmed that attenuation occurred in water. The underwater gamma-ray spectrometer will be available for continuous maritime field monitoring and regular on-site radiation monitoring.