An underground oil pipe starts to leak oil - Edexcel - GCSE Physics - Question 6 - 2013 - Paper 1

To locate the leak in the oil pipe, the technician can use a gamma detector placed above the ground. As the gamma rays from the source pass through the oil, they will be absorbed more by the oil leaking out of the pipe than by the surrounding soil. By moving the detector along the surface, the technician can note where the readings are highest, indicating the position of the leak. It is important that the detector is sensitive enough to pick up the variations in gamma radiation levels.