High reliability monitoring cable systems
Meggitt has developed a line of SiO2 cable/connector assemblies for critical instrumentation and control systems for nuclear reactor safety-related equipment. Installed in over 66 nuclear power plants globally, these designs were developed and qualified in direct response to post accident scenarios (1E LOCA), where the environmental factors of high radiation, high temperature steam and chemical sprays quickly destroy the electrical and mechanical properties of typical organic cable and connector systems.
The resulting Meggitt cable systems range from the coaxial Quick Latch Nuclear (QLN™) connector shown in the photograph -- which significantly reduces human exposure to high radiation during installation or removal -- to various multi-conductor power, control and thermocouple cables.
Unlike organic cable, SiO2 cable is not subject to thermal and radiation aging of its dielectric material or the outer jacket. An all-welded construction delivers a highly reliable, long-life cable assembly. The silicon dioxide dielectric in the stainless steel sheathed cables eliminates any concerns about aging and the resulting deterioration of electrical properties.
The hermetically sealed connectors used to terminate the cables ensure complete isolation of the SiO2 dielectric in the cable from the humidity found in normal environments and the steam and chemical sprays of the accident environment. The result is a highly reliable cable system with a 40+ year design life.
Using this same technology for thermocouple, instrumentation and control applications, cables have been qualified for use in Appendix R applications. Typical multi-conductor cables were exposed to a 3-hour fire and hose stream test in accordance with ASTM E-119-95. The test temperature profile included 120 minutes of operation above 1750°F and a maximum temperature of 1935°F.