Comparative Study of MgO, SiO₂, and Al₂O₃ Insulation Materials in Mineral-Insulated Cables Under Thermal, Electrical, Mechanical, and Radiation Stress

The long-term performance of power and insrumentation cables in nuclear, aerospace, and defense environments depends strongly on insulation stability under thermal, electrical, mechanical, and radiation stresses. Organic, and even some cross-linked, polymer insulations degrade rapidly in such conditions, accelerating the use of ceramic and mineral-based alternatives. This paper addresses magnesium oxide (MgO), silicon dioxide (SiO₂), and aluminum oxide (Al₂O₃) as cable insulation materials. Electrical, thermal, mechanical, and radiation resistance properties are reviewed based on available published data. Recent tests of nuclear-instrument cables under γ radiation (~10⁵ R/h) and elevated temperature (~450 °C) demonstrated that SiO₂ insulation achieved insulation resistances nearly two decades higher than MgO or Al₂O₃ when impurities and backfill gases were tightly controlled. Additionally, high-energy physics applications show MgO-insulated MI cables can withstand up to ~10⁹ Gy and quartz-based SiO₂ up to ~10¹⁰ Gy. Results indicate MgO provides excellent thermal stability and radiation tolerance but is moisture-sensitive, SiO₂ can outperform under specific high-radiation conditions, and Al₂O₃ achieves stability across all categories, making it the most versatile for nuclear and aerospace power applications.