Test and Evaluation of Monitoring Systems (TEM) - Observations & Results


Wireless monitoring

  • Within the framework of TEM a wireless magneto-inductive data transmission system was installed. Since January 2007, the data of six sensors (two water content, two pore pressure and two total pressure) has been transmitted continually to the data acquisition unit at distances of ~100 m (in the beginning) and ~30 m (since June 2007)
  • Some local magnetic noise sources of unknown origin or low battery power may be responsible for data transmission error messages. Although the error messages appear frequently, the quality of the transmitted data has not been affected. Battery power remained basically constant until the end of 2010.
  • The acquired data provides valuable additional information on the heterogeneous evolution of the water saturation and pressures within the ESDRED bentonite buffer.

Seismic tomography

  • Numerical simulations demonstrated that realistic changes in the fluid saturation of the bentonite fill can produce significant and detectable changes in seismic data recorded outside of the volume of interest.
  • A quantitative methodology to assess data quality requirements for successful monitoring has been developed. The requirements relate to repeatability, reliability and bandwidth. While the available source fulfils these requirements the repeatability of removable hydrophone recordings is limited. Firmly attached geophones show better repeatability at the expense of lower bandwidth.
  • The modelling investigations also indicated that crosshole seismic methods are likely to provide useful information for the remote monitoring of high level radioactive waste repositories over repository-scale distances. The monitoring boreholes and tunnels need not intersect the repositories, but the closer they approach the repositories, the higher the resolution and reliability of information provided by the seismic data.

 

Test and Evaluation of Monitoring Systems (ESDRED / TEM)

The GTS underground facilities are also available to interested 3rd parties for underground testing and research. The GTS offers cost-effective access to a fully developed, well characterised underground research facility with round the year logistical support - please contact Dr. Ingo Blechschmidt, Head of the Grimsel Test Site, for further details.