Nuclide Analysis of Suspended Sediment Sampled from Rivers in Fukushima Prefecture in the Distribution Survey of Radioactive Substances
FY 2011 - FY 2014   The Ministry of Education, Culture, Sports, Science and Technology, and the Secretariat of the Nuclear Regulation Authority

In order to confirm the changing trend of the concentrations of radioactive substances in the suspended sediment in Fukushima Prefecture, we conducted surveys. The analysis results show radiation (...
In order to confirm the changing trend of the concentrations of radioactive substances in the suspended sediment in Fukushima Prefecture, we conducted surveys. The analysis results show radiation (Bq) per unit weight (kg).

Results of the Nuclide Analysis of Suspended Sediment Sampled from Rivers in Fukushima Prefecture ( From August 2014 to January 2015 )
  1. In order to confirm the changing trend of the concentrations of radioactive substances in the suspended sediment, we conducted a subsequent survey to the forth survey.
  2. The analysis results show radiation (Bq) per unit weight (kg).
  3. The observation points were 31 locations in Fukushima and Miyagi prefectures, set up on the Abukuma river and the second class river on Hamadori. 6 out of the 31 locations were long term observation points started between June 2011 and June 2011. After that, additional 24 observation points were established. In order to investigate the outflow from the urban area, we established the Oiko River observation point in Fukushima city from June, 2014.
  4. The suspended sediment sampling was conducted once or twice every month from August 2014 to January 2015.
  5. Radioactivity concentrations, errors, and detection limits values show decay-compensated values from measurement to sampling.
  6. Regarding 134Cs and 137Cs, "ND" in the column "Radioactivity Concentration", "-" in the column "Error", and Detection limit values in the column "Detection limit": The peak of relevant nuclide was not clearly detected, or calculated radioactivity concentration was equal to or below 0.0. Reference value in the column "Radioactivity Concentration" and Detection limit in the column "Detection limit": The peak of the relevant nuclide was detected even though the calculated radioactivity concentration was below detection limit.
  7. In the first survey and the second survey, radioactive cesium concentration had been measured using wet samples. Beginning with the third survey, measurement was conducted with dried samples.
Results of the Nuclide Analysis of Suspended Sediment Sampled from Rivers in Fukushima Prefecture ( From April 2013 to February 2014 )
  1. In order to confirm the changing trend of the concentrations of radioactive substances in the suspended sediment, we conducted a subsequent survey to the third survey.
  2. The analysis results show radiation (Bq) per unit weight (kg).
  3. The observation points were 30 locations in Fukushima Prefecture and Miyagi Prefecture that had been established by the end of the third survey. 6 out of the 30 locations were long term observation points started between June 2011 and August 2011. After that, additional 24 observation points were established. These new observation points were mainly located near the gauging stations and water level data was originally obtained from measured data by the Ministry of Land, Infrastructure, Transport and Tourism / Fukushima Prefecture.
  4. The suspended sediment sampling was conducted once or twice every month from April 2013 to February 2014.
  5. Radioactivity concentrations, errors, and detection limits values show decay-compensated values from measurement to sampling.
  6. Regarding 134Cs and 137Cs, "ND" in the column "Radioactivity Concentration", "-" in the column "Error", and Detection limit values in the column "Detection limit": The peak of relevant nuclide was not clearly detected, or calculated radioactivity concentration was equal to or below 0.0. Reference value in the column "Radioactivity Concentration" and Detection limit in the column "Detection limit": The peak of the relevant nuclide was detected even though the calculated radioactivity concentration was below detection limit.
  7. In the first survey and the second survey, radioactive cesium concentration had been measured using wet samples. Beginning with the third survey, measurement was conducted with dried samples.
Results of the Nuclide Analysis of Suspended Sediment Sampled from Rivers in Fukushima Prefecture ( From December 2012 to February 2013 )
  1. In order to confirm the changing trend of the concentrations of radioactive substances in the suspended sediment, we conducted a subsequent survey to the second survey.
  2. The analysis results show radiation (Bq) per unit weight (kg).
  3. In order to confirm the detailed flow characteristics of suspended sediment in Fukushima prefecture, a total 30 sampling points were chosen in the basin of Abkumagawa river and Hamadori area ( Fukushima prefecture) including the 6 points in the Second Distribution Survey. Newly chosen measurement points were mainly located near the gauging stations and water level data were originally obtained from measured data by Ministry of Land, Infrastructure, Transport and Tourism / Fukushima prefecture.
  4. The suspended sediment sampling was conducted from December 5, 2012 to December 8, 2012, from December 17, 2012 to December 19, 2012, from January 9, 2013 to January 11, 2013, from January 21, 2013 to January 23, 2013, from February 25, 2013 to February 27, 2013.
  5. Radioactivity concentrations, errors, and detection limits values show decay-compensated values from measurement to sampling.
  6. Regarding 134Cs and 137Cs, "ND" in the column "Radioactivity Concentration", "-" in the column "Error", and Detection limit values in the column "Detection limit": The peak of relevant nuclide was not clearly detected, or calculated radioactivity concentration was equal to or below 0.0. Reference value in the column "Radioactivity Concentration" and Detection limit in the column "Detection limit": The peak of the relevant nuclide was detected even though the calculated radioactivity concentration was below detection limit.
  7. In the previous survey, radioactive cesium concentration had been measured using wet samples. In this survey, measurement was conducted with dried samples to rule out the influence of water content.
Results of the Nuclide Analysis of Suspended Sediment Sampled from Rivers in Fukushima Prefecture ( March 2012 )
  1. In order to confirm the changing trend of the concentrations of radioactive substances in the suspended sediment, we conducted a subsequent survey to the first survey.
  2. The analysis results show radiation (Bq) per unit weight (kg).
  3. When selecting locations to collect river samples (river water, bottom sediment, and suspended sediment), it was taken into consideration as the selection criteria that 1) the location should have a relatively high accumulated radioactive cesium based on the results of the land-based monitoring and airborne monitoring surveys, and 2) the place would be suitable for periodically measuring flow volumes, with a view to following the movement of radioactive substances in detail in the future. Based on these criteria, 50 locations were chosen. Out of 50 locations, 10 locations were chosen geographically evenly for sampling bottom sediment and suspended sediment for the reason of survey and measurement period.
  4. The suspended sediment sampling was conducted from January 28, 2012 to February 26, 2012
  5. Radioactivity concentration, error and detection limit at time of measurement
  6. Regarding 134Cs,137Cs and 131I, "ND" in the column "Radioactivity Concentration", "-" in the column "Error", and detection limit values in the column "detection limit": The peak of relevant nuclide was not clearly detected, or calculated radioactivity concentration was equal to or below 0.0. Reference value in the column "Radioactivity Concentration" smaller than the detection limit in the column "detection limit": The peak of the relevant nuclide was detected even though the calculated radioactivity concentration was below detection limit.
  7. Regarding 110mAg, 129mTe and 136Cs, "ND" in the column "Radioactivity Concentration" and "-" in the column "Error": The peak of relevant nuclide was not clearly detected, or calculated radioactivity concentration was below three times the error.
Results of the Nuclide Analysis of Suspended Sediment Sampled from Rivers in Fukushima Prefecture ( From September 2011 to October 2011 )
  1. The analysis results show radiation (Bq) per unit weight (kg).
  2. When selecting locations to collect river samples (river water, bottom sediment, and suspended sediment), it was taken into consideration as the selection criteria that 1) the location should have a relatively high accumulated radioactive cesium based on the results of the land-based monitoring and airborne monitoring surveys, and 2) the place would be suitable for periodically measuring flow volumes, with a view to following the movement of radioactive substances in detail in the future. Based on these criteria, 50 locations were chosen. Out of 50 locations, 10 locations were chosen geographically evenly for sampling bottom sediment and suspended sediment for the reason of survey and measurement period.
  3. In order to confirm the changing trend of the concentrations of radioactive substances in the suspended sediment, we conducted samplings twice within the period between June and October.
  4. Radioactivity concentration, error and detection limit at time of measurement
  5. Regarding 134Cs,137Cs and 131I, "ND" in the column "Radioactivity Concentration", "-" in the column "Error", and detection limit values in the column "detection limit": The peak of relevant nuclide was not clearly detected, or calculated radioactivity concentration was equal to or below 0.0. Reference value in the column "Radioactivity Concentration" smaller than the detection limit in the column "detection limit": The peak of the relevant nuclide was detected even though the calculated radioactivity concentration was below detection limit.
  6. Regarding 110mAg, 129mTe and 136Cs, "ND" in the column "Radioactivity Concentration" and "-" in the column "Error": The peak of relevant nuclide was not clearly detected, or calculated radioactivity concentration was below three times the error.
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