Surveillance test of reactor vessels
Purpose of the surveillance test
Materials used in nuclear reactors are known to be irradiated with neutrons during reactor operation, increasing their tensile strength while degrading their brittleness to impact and fracture toughness. In order to investigate such changes in material characteristics, a capsule containing surveillance specimens is installed inside the reactor vessel to receive irradiation similar to that in actual nuclear power plant operation, and the specimens are removed at predetermined intervals. These specimens are used in various destructive tests and measurements at our materials hot laboratory facility, and the data obtained here are used to monitor changes in the material characteristics of reactor vessel used in nuclear reactors and to confirm the safety of the reactors. We have also established a technology for reprocessing fracture toughness specimens after surveillance tests, and are conducting research and development to improve the accuracy of data for future surveillance tests.
Examples of methods and results of surveillance tests
In addition to tensile tests, we conduct Charpy impact tests to examine changes in the material's brittleness to impact and fracture toughness tests to examine the material's resistance to fracture toughness.
Recent research trends
In recent years, in order to further improve the accuracy of surveillance test data, studies have been underway to collect and effectively utilize miniature fracture toughness specimens and tensile specimens from Charpy impact specimens, which are the most commonly contained in capsules.
Our company has developed a processing technique for taking miniature fracture toughness and tensile specimens from fractured halves of Charpy impact specimens used in surveillance tests in facilities where radioactive materials can be handled.
Appearance of each specimen
Specimen handling by remote manipulation
Sampling of miniature fracture toughness specimens and tensile specimens from
fractured halves of a Charpy impact specimen