Mapping large areas of radioactively contaminated land with a self adapted, handheld, GPS coupled, scintillation detector

In Belgium, during several decennia, a phosphate plant discharged radium chloride containing waste water into two small rivers. One of those is part of a hydrographically very complex ecosystem with lots of small tributaries and hundreds of hectares of flooding zones. Hence, the river banks and large parts of these flooding zones have become contaminated with radium, heavy metals and chlorides. During a foot campaign, using a home made portable data logging system, consisting of a commercial 2.5 kg NaI detector, a computer mouse sized GPS, and a small pocket PC, the radioactive contamination of about 600 ha of sometimes very rough terrain was measured and mapped. The resulting very detailed radium contamination maps shed a whole new light on the water flow patterns of the ecosystem. The apparatus can also be used for efficiently guiding sampling campaigns for investigating other types of contamination. The ground maps are also compared to existing maps from helicopter measurements, evaluating strengths and weaknesses from both methods.