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Continuous measurement of radionuclide distribution off Fukushima using a towed sea-bed gamma ray spectrometer

Continuous measurement of radionuclide distribution off Fukushima using a towed sea-bed gamma ray spectrometer
Continuous measurement of radionuclide distribution off Fukushima using a towed sea-bed gamma ray spectrometer
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 1.8 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 80 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 22 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
0967-0637
10-19
Thornton, Blair
8293beb5-c083-47e3-b5f0-d9c3cee14be9
Ohnishi, Seiki
035c497a-ec02-4ce9-9879-a39a916b5d9a
Ura, Tamaki
b8fea5ba-e731-40fd-8544-1db1ca9f356b
Odano, Naoteru
acead221-760b-421e-8c06-9907c2542f9e
Fujita, Tsuneo
363e3b8e-6936-4348-9cc2-0bf9043176e6
Thornton, Blair
8293beb5-c083-47e3-b5f0-d9c3cee14be9
Ohnishi, Seiki
035c497a-ec02-4ce9-9879-a39a916b5d9a
Ura, Tamaki
b8fea5ba-e731-40fd-8544-1db1ca9f356b
Odano, Naoteru
acead221-760b-421e-8c06-9907c2542f9e
Fujita, Tsuneo
363e3b8e-6936-4348-9cc2-0bf9043176e6

Thornton, Blair, Ohnishi, Seiki, Ura, Tamaki, Odano, Naoteru and Fujita, Tsuneo (2013) Continuous measurement of radionuclide distribution off Fukushima using a towed sea-bed gamma ray spectrometer. Deep Sea Research Part I: Oceanographic Research Papers, 79, 10-19. (doi:10.1016/j.dsr.2013.05.001).

Record type: Article

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 1.8 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 80 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 22 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

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More information

Published date: September 2013
Organisations: Fluid Structure Interactions Group

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Local EPrints ID: 400017
URI: http://eprints.soton.ac.uk/id/eprint/400017
ISSN: 0967-0637
PURE UUID: 320f7b40-df3c-4d50-a6f7-d9e39763d600

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Date deposited: 09 Sep 2016 15:58
Last modified: 08 Jan 2022 06:37

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Contributors

Author: Blair Thornton
Author: Seiki Ohnishi
Author: Tamaki Ura
Author: Naoteru Odano
Author: Tsuneo Fujita

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