The Materials Selection Problem as Related to Thermocouples Used to Measure Nuclear Reactor Fuel Pin Temperatures up to 2800°C

The materials that might be useful for constructing high temperature fuel pin thermocouples are reviewed. The materials selection problem is confined to three areas--i.e., sheath, electrical insulator, and thermoelement materials--with the major emphasis placed on the selection of electrical insulators. The determination of insulator properties and their effect on thermocouple performance are considered. Potential modes of thermocouple failure are illustrated, and a prototype thermocouple is described.