The concept of residence time distribution (RTD) has become an important tool for the analysis of industrial units and reactors. The RTD of fluid flow in process equipment determines their performance. Radiotracers are method of choice for obtaining the RTD in industrial processing vessels and wastewater treatment systems. Radiotracer RTD method has been extensively used in industry to optimize processes, solve problems, improve product quality, save energy and reduce pollution. The technical, economic and environmental benefits have been well demonstrated and recognized by the industrial and environmental sectors. Though the RTD technology is applicable across a broad industrial spectrum, the petroleum and petrochemical industries, mineral processing and wastewater treatment sectors are identified as the most appropriate target beneficiaries. These industries are widespread internationally and are of considerable economic and environmental importance