The effect of fabrication parameters on the inner microfissure in the Zr-lined cladding tube has been investigated. The results were as follows: 1. The Q-value during cold pilgering is an important factor for inner fissures. When the Qvalue is larger than 1.5, the tube is subject to the favorable effect on the fissure. 2. The inner fissures are dependent on grain size of the Zr liner. The smaller grain of the mother tube before cold pilgering has a good effect on the inner fissure of the tube after cold pilgering. 3. Pickling before cold pilgering has proven to be important for decreasing defects in the bore of the Zr-lined tube.
These results are very useful for improving and assuring the quality of the Zr-lined cladding tube.
A new fabrication process of high nodular corrosion-resistant Zircaloy-2 tubing for boiling water reactors (BWRs) water rods has been developed. The main features and findings are: 1. Development of a new quenching machine and method, by which tube shell can be α + β through-wall quenched at a rapid cooling rate of >50 K/s from 1173 to 1073 K. 2. High nodular corrosion-resistant tube shells, quenched at both hollow billet and tube shell stages, have less deformability, especially in the circumferential compression direction. 3. Reduction in area in combination with Q-value affect crack sensitivity during pilgering. Area reductions greater than 80% at high Q-values were proved possible with minimal or no cracking. 4. Consequently, a new fabrication process, consisting of two cold reduction passes from tube shell to final product, has been successfully developed. The final tubing showed high nodular corrosion resistance, having no nodules in the high temperature (773 K) corrosion test.
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