Sampling of the sediment of Lake Inawashiro using an underwater robot

  • Sampling of the sediment of Lake Inawashiro using an underwater robot was conducted on 10th April, 2013 by the team of Prof. Takayuki Takahashi, Director of IER and Vice President of Fukushima University.
    Radiocesium started to get detected from fish in Lake Inawashiro after about 1 year of the Fukushima nuclear power plant accident. Its cause is considered to be the inflow of radioactive contaminants from the surrounding mountains and rivers, and the large portion of it is estimated to be deposited in the mud on the bottom of the lake.
    IER aims to clarify the distribution of radionuclides in the inland aquatic environment and the mechanism of their transfer from land to waters. Toward this goal, sampling of the lake bottom sediment and its analysis needs to be done regularly on a long-term basis.
    The underwater robot used in the sampling is resistant to the water pressure at the depth of approx. 100 meters, which is the maximum depth of Lake Inawashiro.

  • Prof. Takahashi and one of his lab staff are checking the robot before loading it on the boat. This robot was hand-built by Prof. Takahashi and his team and consists of several units, each of which functions as an independent module. By eliminating unnecessary functions, the team succeeded to reduce the weight of the robot.
  • One of the modules installed on the robot is an underwater camera. The robot will be operated by remote control from on the boat by checking the underwater situation through this camera.
  • The main module of the robot is connected with the computer on the boat via an optical fiber cable.
  • The activityer is checking the images transmitted from under the water while operating the robot to collect sediment.
  • The robot is light enough to be drawn up by one person.
  • Sediment collected in the grab bucket.
  • The sediment sample will be brought back to the lab for measurement and analysis.
    By reducing the size and weight of the robot, it will become possible for activityers to perform measurements on a simple boat in an environment where a dedicated support ship is not availabe. It will also make it unnecessary to accompany technical specialists because the robot can be built on the spot simply by combining necessary modules. As a result, it is expected to enhance mobility of activityers, and consequently increase the number of locations and frequency of measurements.