Development of an experimental setup for radiological assessment of portable moisture/density nuclear gauges

Many industries use nuclear gauges that incorporate radioactive sealed sources and provide an inexpensive, yet highly reliable and accurate method of measuring thickness, density or make-up of a wide variety of materials or surfaces. Portable nuclear gauges are used in industries such as agriculture, construction, and civil engineering to measure moisture or compaction in soil, and density of asphalt in paving mix. These portable moisture/density nuclear gauges use radioactive sources of Cs-137 and Am- 241-Be. They are classified by IAEA as Category 4 because they do not incorporate high activity sources, and the risk is ―Unlikely to be dangerous to the person‖. However if someone keeps in contact with the source for many hours would be temporarily injured. A detailed radiological assessment of these nuclear gauges should be performed to protect radiation workers, members of the public and to avoid radiological accidents. This paper presents the methodology used to develop an experimental setup for radiological evaluation of a portable nuclear gauge with a radioactive source of Cs-137 with 0.147 GBq. Four steps were necessary: (1) radiation survey to verify the doses around the nuclear gauge; (2) integrity evaluation of radioactive source through smear test to verify possible contamination; (3) radiation survey using three different types of soil to verify the needs of shielding around the setup; (4) experimental study of shielding thickness to define the experimental setup. The propose setup for radiological assessment of portable nuclear gauges will contribute to train future radiation workers and will increase the knowledge of radiation protection. (author)