Degradation of Cr-coated cladding under the simulated Loss-of-Coolant Accident phenomena

The present study focuses on the evaluation of the mechanical properties degradation of Cr-coated Zr-alloy fuel cladding. The main objective of the work is to find a suitable methodology to evaluate the mechanical properties degradation of coated cladding by performing several separate effects experiments.Apart from the many positive effects of protective coatings on the overall cladding properties, coatings’ general disadvantage is their reduced ability to tolerate plastic strain. Therefore, coating cracks might occur in the first stage of the hypothetical Loss of Coolant Accident (LOCA). The study is unique because of the consideration of coating cracks. Prior to the high-temperature (HT) oxidation, samples were subjected to either a scratch test or burst test, resulting in the creation of coating defects. The subsequent evaluation of the obtained data consisted of wavelength dispersion spectroscopy (WDS) and optical microscopy analysis and hydrogen content measurements

EXPERIMENTAL STUDY OF DAMAGED CR-COATED FUEL CLADDING IN POST-ACCIDENT CONDITIONS

To enhance the safety of nuclear power, the focus of researchers all around the world has recently mainly objected on the development of Accident Tolerant Fuels. Especially the Chromium coating of current Zirconium based cladding has been widely suggested and discussed for its immense positive effect on overall cladding properties. Nevertheless, it was observed that during the first stage of the Loss of Coolant Accident, cracks appear in the Cr coating due to its inability to tolerate higher plastic strain. Therefore, experimental methodology used in this article focuses on testing fuel cladding with damaged Cr coating after the high-temperature transient. The impact of cracks on degradation of cladding mechanical properties was observed using optical microscopy, ring compression test, microhardness, and evaluating hydrogen content and weight gain

Degradation of Cr-coated cladding under the simulated Loss-of-Coolant Accident phenomena

The present study focuses on the evaluation of the mechanical properties degradation of Cr-coated Zr-alloy fuel cladding. The main objective of the work is to find a suitable methodology to evaluate the mechanical properties degradation of coated cladding by performing several separate effects experiments. Apart from the many positive effects of protective coatings on the overall cladding properties, coatings’ general disadvantage is their reduced ability to tolerate plastic strain. Therefore, coating cracks might occur in the first stage of the hypothetical Loss of Coolant Accident (LOCA). The study is unique because of the consideration of coating cracks. Prior to the high-temperature (HT) oxidation, samples were subjected to either a scratch test or burst test, resulting in the creation of coating defects. The subsequent evaluation of the obtained data consisted of wavelength dispersion spectroscopy (WDS) and optical microscopy analysis and hydrogen content measurements

Round robin exercise of the candidate ATF cladding materials within the IAEA ACTOF project

The paper presents a summary of the round robin test activity organized within the IAEA ACTOF project. The test conditions and sample matrix were finalized during fall 2017 and the tests have been performed during the next 14 months. Two fundamental experimental tests related to normal operating conditions and accidental conditions of LWRs were defined: High-temperature steam oxidation and Long-term corrosion tests. Originally, four laboratories/institutes joined the round robin exercise - CTU in Prague, KIT, VTT, and INCT. Later, also MTA EK joined the activity. Zircaloy-2 substrate was provided by Westinghouse Electric Company and two institutes applied their protective coatings on its surface (CTU - pure Cr coating and INCT - ZrSi-Cr coating). KIT applied MAX phase coating on Zircaloy-4 substrate. Additionally, AISI 348 steel provided by USP, Brazil was tested. The geometry of the samples varied based on the needs of particular institutes. Long-term corrosion tests were performed by three laboratories in PWR and VVER chemistry for at least 63 cumulative days. High-temperature steam oxidation tests were performed by four institutes at three pre-defined conditions. Participants performed pre- and post-characterization of the material based on their standard procedures and available techniques. The paper summarizes motivation, plans, sample matrix, materials, testing conditions and preliminary results including lessons learnt. Full reports will be published in the ACTOF TECDOC under preparation.</p