Challenges in Gamma Ray Interpretation - A Case History from Rautuvaara Mine Tailins

Water is an important attenuator, amplifier and carrier of gamma radiation, especially if the radiation originates from the decay series of uranium. In mine tailings the water is often acid and it leaches uranium and transports it to new locations. One of the members of the decay series, radon, is likewise transported by flowing water. Movements of uranium or its daughters violate the secular equilibrium, and pose problems in the interpretation of field measurements. A gamma radiation anomaly at a certain position does not necessarily mean the presence of uranium, neither does the absence of radiation necessarily mean the absence of uranium. Further, the water causes characteristic changes to the gamma spectrum of bismuth, which may be used to get a rough estimation of the amount of water in the earth materials.