What sampling strategy to adopt for a reliable contamination characterization? How many samples or measurements are needed? Where to locate the measuring points? How to decide on the sampling pattern and spacing? Geostatistics answers all these questions. It provides the tools to design an optimized sampling campaign for each stage of a characterization project.
Optimize the sampling design for the preliminary characterization
For this reconnaissance phase, geostatistics helps in setting a first investigation mesh based on the target dimension and expected spatial variability of the contamination level (which is assessed through a variographic analysis). A first 2D mapping is then delivered through kriging, which has the key advantage of providing information on the map quality (through the variance of kriging or other uncertainty indicators).
Develop the sampling design for the destructive sampling phase
In this phase, precise estimation, inventory, and geometry assessment of the contaminated volumes are required. An ad hoc in-depth sampling is necessary to meet the characterization’s quality objectives. The design of this second sampling program benefits from the information acquired during the reconnaissance stage where a first radiation mapping was performed. The approach uses, in particular, the correlation between 2D dose rate and in-depth activity concentration on samples.
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Refine the sampling effort for the complementary characterization
An additional sampling campaign may be needed to improve the delineation of the contaminated area and characterization quality. The previous geostatistics analysis benefits to the preparation of this additional campaign. It gives you the keys to identify areas where the uncertainty or the variability of the contamination level is the most important and to quantify and locate the extra measurement points that are needed. So, you improve your contamination characterization by reducing estimation uncertainties in an efficient way. From there, you can then assess the volume of each class of waste.