Nuclear densitometry

Nuclear densitometry is a technique used in civil construction and the petroleum industry, as well as for mining and archaeology purposes, to measure the density and inner structure of the test material.

The device uses the interaction of gamma radiation with matter to measure density, either through direct transmission or the "backscatter" method.

The device determines the density of material by counting the number of photons emitted by a radioactive source (cesium-137) that are read by the detector tubes in the gauge base.

Such instruments can help find caves or identify locations with lower density that would make tunnel construction hazardous.

Nuclear density gauges are typically operated in one of two modes:[1] Direct transmission: The retractable rod is lowered into the mat through a pre-drilled hole.

This is important to the civil construction industry specifically as both are essential to verifying suitable soil conditions to support structures, streets, highways, and airport runways.

Standard counts are the amount of radiation released by the two nuclear sources inside the machine, with no loss or leakage.

One source produces radiation that interacts with the atoms in the soil, and is then compared to the standard count, to calculate the density.

Once it has been calibrated and as long as the source detector alignment remains constant, it is possible to calculate the density of the liquid in the pipe.

Gas, oil, water and sand all have different concentrations of hydrogen atoms which reflect different amounts of slow neutrons.