Development of measurement techniques for analysing contaminated concrete structures of nuclear facilities during dismantling (joint research project KOBEKA)

Sub-Project:

Development of measurement methods for concrete porosity and moisture as well as software modules for the visualisation of findings data

Motivation:

During the sampling of the concrete structures of the reactor building at NPP Stade, contaminations were found in the concrete dome, i.e. the lower part of the containment. These were introduced by primary circuit water during plant operation. It can be assumed that this problem also affects other nuclear facilities in Germany and worldwide. For the dismantling of the concrete structures, it is necessary to determine and map the contamination. According to the current state of the art, this is done by core drilling and laboratory analyses of the core material. However, a lack of accessibility, structural boundary conditions and costs limit the number of sampling boreholes. An alternative to core drilling is drilling into the solid. With narrow boreholes, significantly more boreholes can be drilled without endangering the structural integrity. Since no drill cores are available for the analysis with this drilling method, new measurement and analysis techniques must be developed.

Objectives:

In the joint project, measurement and analysis methods as well as concepts for the electronic documentation of data from decommissioning projects are being developed. In the sub-project, the following sub-objectives will be implemented:

• Development of an in-situ analysis technique for the determination of moisture and porosity in the wall of the borehole by means of a tubular probe,
• Software for the visualisation of findings data.

Methods and results:

For the development of a tube-integrated probe for a depth-resolved determination of the dose rate, moisture and porosity, a comparative evaluation of impedance spectroscopy and radar technology as well as the construction and laboratory testing of a sensor will be carried out in the sub-project. A software module for the visualisation of findings is created on the basis of common CAD software.