For tracer studies carried out with open radioisotopes, the material or materials to be tested are labeled with a radioactive isotope prior to the investigation. During

Nuclear and Radiochemistry. DOI: http://dx. doi. org/10.1016/B978-0-12-391430-9.00011-1

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the test, radiation of the isotope is detected outside the equipment, which identifies disposition of the labeled material or its rate of distribution among several branches of pipes or equipment. At the same time, intensity of the radioactive tracer is pro­portional to the quantity of the material or its concentration. With suitable calibra­tion, the intensity can be corresponded with the quantitative mass or volume of the material.