A towed gamma ray spectrometer, called the RESQ hose (RESQ: Radiometric Environment Survey and Quantification), has been developed to continuously map the distribution of radionuclides in the seafloor. The instrument consists of a gamma ray spectrometer in a flexible hose that is attached to a wire or tether cable. The system is towed along the seafloor by a ship, allowing the detector to maintain continuous contact with the seafloor over long distances. Since measurements of seafloor radiation requires the device to be in contact with the seafloor, the system is equipped with accelerometers, underwater microphones and depth sensors to verify that the system is in contact with the seafloor at any given time. We describe sea trials using the RESQ hose to monitor seafloor radiation off Fukushima, within 40km of the Fukushima Dai-ichi Nuclear Power Plant (F 1 NPP) during August 2012. It is expected that data obtained using the RESQ hose will significantly improve our understanding of the distribution of radionuclides into the marine environment following their discharge from F 1 NPP between March and May 2011.
2013 Japan Society for Marine Surveys and Technology