Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
6383740 | Deep Sea Research Part I: Oceanographic Research Papers | 2013 | 10 Pages |
Abstract
Instrumentation and data processing methods to continuously map the distribution of radionuclides on the seafloor have been developed and applied to survey radioactive discharge from the Fukushima Dai-ichi Nuclear Power Plant following the M9.0 earthquake and tsunami that struck the east coast of Japan on March 11 2011. The instrument consists of a flexible rubber hose with an integrated gamma ray spectrometer that measures the full gamma spectrum between 0.1 and 1.8Â MeV while being towed along the seafloor by a ship. The data processing methods described allow for quantification of 137Cs and 134Cs concentration in marine sediments, and a technique has been developed to optimize the spatial resolution of the measurements for each radioactive species for a given level of statistical uncertainty. The system was deployed during August and November 2012 to measure the distribution of radionuclides along three transects within an 80Â km radius of the plant. Increased levels of 137Cs and 134Cs were recorded and their distributions mapped continuously over distances of 1.6, 12.5 and 22Â km respectively. The levels of 137Cs and 134Cs were found to vary significantly with location. The in situ measurements show good agreement with laboratory analyzed samples obtained during the surveys. The results demonstrate that the instrument and data processing techniques described enable high resolution, quantitative measurements of 137Cs and 134Cs in marine sediments, and provide an effective solution for rapid, low cost monitoring of radioactive material on the seafloor.
Related Topics
Physical Sciences and Engineering
Earth and Planetary Sciences
Geology
Authors
Blair Thornton, Seiki Ohnishi, Tamaki Ura, Naoteru Odano, Tsuneo Fujita,