In-Situ Nondestructive Measurements of Key Mechanical Properties of Reactor Pressure Vessels Using Innovative SSM Technology

40345 November 12, 1996 Advanced Technology Corporation This project will develop new techniques for in-situ nondestructive measurements of key mechanical properties of reactor pressure vessels (RPVs) subjected to irradiation embrittlement. The effort will build on a recently developed stress-strain microprobe (SSM) system which tests minimal material and determines several mechanical properties of metallic structures. The SSM system utilizes a nondestructive, automated bail indentation (ABI) technique which provides a localized direct measurement of the stress-strain curve at quasi-static strain rates at room temperature. Phase I will develop testing and analytical procedures for: (1) ABI testing at high strain rates to compare with dynamic tensile test results and to develop new correlations between dynamic ABI test results and dynamic Charpy impact properties; (2) ABI testing at low and high temperatures (-130oC to 288oC); (3) development of correlations to determine fracture toughness from ABI-measured flow properties, and (4) in-situ testing of steel plates and a section from a commercial RPV (after partial removal of its inner cladding). In Phase II, numerous ABI tests will be conducted on irradiated materials (mostly from utility surveillance programs) and a new prototype of the SSM testing unit (robotistic for in-situ testing of the areas of most concern inside the beltline region of a commercial RPV) will be developed and manufactured. Anticipated Results/Potential Commercial Applications as described by the awardee: Nuclear applications should include testing of RPVs before and after their postirradiation thermal annealing, vessel supports, core internals, etc. This will ensure safe operation and avoid premature decommissioning of power plants and other expensive structural components. Furthermore, the SSM technology should be used to monitor aging and assess the integrity of structural components over their design service life and in lifetime extension evaluations in many industries.