To prevent the release of radionuclides, liquid metal reactor (LMR) steam generator tubing and the tubeto-tubesheet welds have to form a highly reliable sodium-to-water pressure boundary in addition to their functional performance of extracting heat from the reactor. In present commercial nuclear power plants, forced outages caused by steam generator tube leaks have exceeded all other causes combined as a cause of unplanned downtime. Therefore, an inservice inspection system is needed for the examination of liquid metal reactor (LMR) steam generator tubes and the tube-to-tubesheet welds. This project is to demonstrate a new electromagnetic method for in-service tube inspection. Two different types of in-service inspection are possible using this new method: (1) the detection and quantitative identification of loss of metallic cross-sectional area (LMA) caused by corrosion, thinning, and wastage; and (2) the detection of localized flaws (LF) such as stress corrosion cracking, pitting, denting, and mechanical damage. Feasibility will be studied by building and testing a prototype inspection system. If feasible, the planned technique will require substantially less inspection time than current ultrasonic methods. Furthermore, compared to other inspection methods, the new technique promises substantially improved signal-to-noise ratio, flaw delectability, penetration depth, and quantitative flaw identification accuracy.Anticipated Results/Potential Commercial Applications as described by the awardee:The commercial and social benefits of improved LMR steam generator tube inspection methods are substantial. They easily translate into annual cost savings of millions of dollars. These cost savings are possible through: (1) improved operating safety, (2) reduction of unscheduled equipment downtime, (3) extension of steam generator life, and (4) faster, more reliable, and less expensive tube inspections.
