Instrument for Measuring Fuel Cladding Strain

The design and operational characteristics of a microwave frequency instrument capable of measuring strain of internally pressurized nuclear fuel cladding are described. Intended for use during the characterization of mechanical properties of advanced cladding alloys, the instrument should yield continuous strain measurements for in-core tests. Tests in a laboratory oven at 1000°F indicate the method permits strain resolution of several microinches, and accurately measures inelastic strain. Strain measurement errors attributable to physical separation of the sensor and specimen are eliminated by design of the two elements as an integral unit.