Gamma Radiation-Induced Degradation in Insulating Mineral Oil: Electrical and FTIR Characterization

Gamma radiation presents a critical challenge to the reliability of high-voltage equipment operating in radiation-prone environments. It can significantly affect the key properties of insulating materials used in such equipment. One of the most important insulating materials in high-voltage equipment is mineral transformer oils, which are essential for electrical insulation and thermal management. This study presents a comprehensive experimental investigation into the effects of gamma radiation on the electrical and molecular characteristics of transformer mineral oil. A series of controlled irradiation experiments were conducted using cobalt-60 as the gamma source, applying doses of gamma radiation ranging from 50 to 250 kGy. Various key parameters were used for evaluation, including breakdown voltage, moisture content, acidity, and density. In addition, Fourier Transform Infrared (FTIR) spectroscopy was utilized to assess structural changes in the oil’s molecular composition due to radiation exposure. All measurements were performed both before and after exposure to the controlled gamma doses to assess the extent of degradation. The FTIR spectra were analyzed in a semi-quantitative manner using the intensity ratio of the aliphatic C–H (~2920 cm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup>) to carbonyl (~1730 cm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup>) bands to reflect oxidative progression. The observed shifts in the electrical and chemical behavior of mineral oils were correlated with the extent of gamma dose exposure. The underlying mechanisms of gamma-induced degradation in transformer oil were discussed in detail to enhance understanding the key chemical and physical processes responsible for such degradation. To support correlation analysis, polynomial regression was applied to model the nonlinear relationship between gamma dose and breakdown voltage, which represents a key indicator of electrical performance.