Development of yttria stabilized zirconia composites for thermal insulation in nuclear reactors

Ceramics are promising insulating materials for use in nuclear reactors at high temperatures and in-core applications, but they are difficult to machine, and form into complex shapes. CanmetMATERIALS has developed a technology in the fabrication of yttria stabilized zirconia (YSZ) composites for in-core insulation that are machine-able, and can be formed into complex shape. With this technology, an insulation and support structure for the SCWR pressure tubes can be built. In this paper, the focus is geared towards the fabrication of YSZ fibrous ceramics, with a variation of fiber contents. The microstructures of the fabricated YSZ fibrous ceramics were examined and the important material properties such as thermal, and physical properties were measured and discussed. By varying the fabrication processing conditions, a low thermal conductivity of less than 0.2 W/m.K can be achieved. And this low thermal conductivity property can be maintained at a temperature range from 25 to 1000^oC. The manner which the volume fraction of the fiber influences the thermal conductivity over the fore-mentioned temperature range is discussed. (author)