Radiotracer technology is a technique of radioactive injection into the systemand the detection is done using radiationdetector.It is alsoa tool for investigating and solving plant process problems namely process malfunctions andmechanical damages. Radiotracer is the most preferred stimulus response techniques in the industries due to its non-invasive application and on line monitoring capabilities, which avoid shut down of the plant. Radiotracer techniques have many advantages, such as high detection sensitivity, in-situ detection, availability of a wide range of compatible radiotracers for different phases, rapid response and high reliability and accuracy of the results. The residence time distribution (RTD) is one of the important parameters that can provide information on the characteristics or hydrodynamics of the nuclear reactor. In this paper, the overall review is presented in brief regarding radiotracer technology in plant operation.