To assist in the development of new nuclear technologies and raise material research into highly irradiated materials to a new level, a hot cell complex has been built by the Research Centre Řež in the Czech Republic. The test data can be used to extend service life and to develop power plants with advanced technologies, with particular emphasis on high operating temperatures.
The hot cell complex consisting of 10 individual hot cells came about as part of the Sustainable Energy Project (SUSEN) supported by the European Union and the Government of the Czech Republic and is designed to cover the entire experimental area of material research, from manufacturing test specimens of irradiated materials of various shapes, through mechanical tests and the preparation of metallographic samples, to the final fractography analysis.
The electromechanical creep testing machine chosen was a ZwickRoell Kappa 50 DS with a high-temperature furnace rated up to +1,200 °C and a non-contact strain measurement system. Easy specimen changing and optimized handling were crucial, as the testing machine was inaccessibly located inside the hot cell. The semi-automated system for opening the furnace, attaching thermocouples and extensometers is of great benefit to users, who operate the testing machine using manipulators from outside the hot cell. Due to the radioactive environment inside the hot cell radiation-resistant varnish, cable coatings and grommets were used for this testing system. Operators are shielded from radiation by fixed steel shielding consisting of steel blocks up to 500 mm thick and shielding windows of 900 mm total thickness.
The high-temperature tensile creep tests according to ASTM E139 and ASTM E292 and creep crack growth tests with CT specimens at elevated temperatures as per ASTM E1457-13 generate relevant test data up to a temperature of +800 °C. This data is used as input parameters for computation models for nuclear power plant (NPP) life extension programs and more economical use of fuel.
Mechanical creep testing is necessary for the power plant research as it simulates the processes occurring in the NPP’s components. The data obtained from mechanical testing of irradiated components from the reactor core in hot cells will bring new knowledge concerning the degradation mechanisms and stability of the power plants, which is primarily of benefit to NPP operators such as ČEŽ in the Czech Republic.
For Dr. Ondřej Srba, head of the material and mechanical properties department, the main advantage of ZwickRoell’s electromechanical system is stable and user-friendly software which allows easy training of operators. The testing system is equipped with a 3-zone furnace rated up to +1,200 °C and a state-of-the art temperature controller which assists greatly in achieving precise temperature control on the sample. “The laserXtens HP/TZ is very helpful for strain control during testing of irradiated samples since it does not require specimen marking, which can be very tricky for small specimens inside the hot cell. Moreover, our system is automated, so it enables us to attach/detach extensometers and thermocouples and to close/open the furnace remotely from the operation room,” states Dr. Srba.
“Mechanical testing of irradiated materials inside the hot cell requires new advanced solutions, which were delivered by ZwickRoell,” affirms Dr. Srba and explains that the combination of price, quality and advanced techniques, together with the high level of technical support and stability, were the deciding factors in the Research Centre Řež’s decision to purchase this ZwickRoell testing system.