A Precision Grinding Technology for Zirconium Alloy Tubes Based on Ultrasonic Wall Thickness Automatic Measurement System

To ensure the safety and long-term performance of nuclear fuel cladding zirconium tubes, the wall thickness uniformity of each cross section is strictly needed. Therefore, this paper presents comprehensive investigations on development of an automatic ultrasonic wall thickness measurement system for detecting the nuclear zirconium tubes. Based on the determination of overall scheme, optimization of key mechanical structures and design of control system, a series of performance testing analyses of this developed auto-measuring system were performed from aspects of measuring accuracy, measuring efficiency, stability and practicability. The results revealed that it could accurately obtain the wall thickness distribution and effectively guide the subsequent grinding process by automatically generated deviation correcting procedures to achieve the requirement of the wall thickness uniformity. The new combination method of ultrasonic auto-measuring and numerical control grinding proposed in this work would have a great significance for the development and application of nuclear reaction zirconium alloy container.

Effect of Al Concentration on Microstructure and Properties of AlNbTiZr Medium-Entropy Alloy Coatings

The AlNbTiZr medium-entropy alloy (MEA) coatings with different Al contents were prepared on N36 zirconium alloy substrates by RF magnetron co-sputtering. The morphology, microstructure, mechanical properties, surface wettability and corrosion resistance of the AlNbTiZr MEA coatings were studied to evaluate the surface protection behavior of zirconium alloy cladding under operation conditions of a pressurized water reactor. The results showed that all the coatings were composite structures with amorphous and bcc-structured nanocrystals. With the increase of Al content, both the elastic modulus and hardness decreased first and then increased. The hydrophobicity of the coatings was enhanced compared with that of the substrate. The 10.2 at.% Al AlNbTiZr coating had the best corrosion resistance and the minimum oxygen penetration depth, which originated from the formation of a denser oxide layer consisting of Nb2Zr6O17 and ZrO2. This study provides an improved idea for the design and development of Al-containing MEA coating materials for accident tolerant fuel.