Abstract
The gamma-ray back-scattering technique was utilized for measuring corrosion and scale deposit likely to be found at desalination plants. The method can be applied on hot and unprepared surfaces where the commonly used ultrasonic technique fails to produce successful results. CaSO
4 deposits inside CuNi or ion pipes and scale accumulated on the wall of superheaters underneath the aluminum cladding was successfully measured. Change in pipe wall thickness that may take place due to erosion of the carbon steel pipes was also measured accurately. In these applications an NaI(Tl) scintillation detector — with a 1024 channel multichannel analyzer and the nuclear electronics including a preamplifier, amplifier and power supply — were utilized. These are relatively inexpensive, uncomplicated equipment that can be portable. Therefore, scanning of pipes from the outside can be performed. Localized metal removal from inside the pipes that may take place due to pitting was also successfully measured by using a pure Ge detector and more powerful multichannel analyzed or 8192 channels. Cracks, voids or other defects may also be measured by this technique. Studies were made at different gamma-ray energies for the appropriate selection of a source. Radioactivity level was of an order of 10
4 Bq, giving a negligible radiation dose. It is 10
8 times less than those used in gamma radiography.