Within the scope of the nuclear safety research at KIT and in cooperation with other associations (VGB, Areva-NP, GRS), LOCA (Loss Of Coolant Accident) experiments will be performed in the QUENCH facility of IMF, especially to enlarge the knowledge of the influence of the so called secondary hydrogenation on the embrittlement of cladding materials.
In the context of experimental investigations, one aim is to determine the residual strength/ductility of QUENCH-tested claddings in dependence on different test conditions. For that purpose, ring-compression and tensile tests at room temperature (RT) accompanied by metallographic investigations will be conducted.
The experiments will be performed using an universal electro-mechanical testing machine (Instron). For the ring-compression tests, the specimens will be tested between two SiC-pressure discs (very high stiffness), which are connected via Al2O3-plates with a high resolution LVDT (Linear Variable Differential Transformer) position sensor to measure the correct deflection.
For the tensile tests on cladding sections with a length of up to ca. 1000 mm, a special set-up will be used. In this case the tubes equipped with exact fitting end plugs are clamped in special grips for round bars. The deformation of a specimen during a test will be measured by a CCD-camera system. Depending on the length of a specimen 1-3 cameras will be used to determine the global - and local strains with high resolutions.
With the global deformation, the deformation and failure behavior of an entire cladding will be determined. Due to an inhomogeneous thickness of the ZrO2/a-Zr-layer along a Quench-tested cladding, in a second step small scaled specimens (ratio L0/A0 of the small specimen is comparable to the ratio of the cladding) from selected sections of the tested claddings will be used to perform additional post-tensile tests to determine the local deformation and failure behavior. This will be realized by combining the results from the tests on small specimens with the local results from the cladding tensile tests.
|Schematic illustration of the determination of the global and local deformation behavior of a cladding in a tensile test