Post irradiation examination of ~ 5m long pressure tubes removed from the Indian nuclear power reactors after irradiation is carried out in the authors' laboratory. Neutron radiography has been effectively used for the evaluation of blisters at the regions of interest. The hydride blisters are hydrogen rich regions, which have higher attenuation than the parent alloy of zirconium. This difference in the neutron interaction is exploited to image these hydride rich regions. Since the samples to be radiographed are highly radioactive, indirect technique (transfer) has been used. Thermal neutrons from a research reactor APSARA have been used to image the samples on Dysprosium foil by neutron activation. The images have then been transferred on to X-ray films by autoradiography. The neutron radiographs have been evaluated by microdensitometry and also by computer image enhancements.
A number of irradiated zircaloy pressure tube samples have been evaluated by neutron radiography. Hydride blisters have successfully been detected. As a reference standard, blisters grown on zircaloy strip artificially in the laboratory have been used.
Abstract Source:
Book of Abstracts, 7th European Conference on Non-Destructive Testing, 26-29 May 1998, ISBN: 87-986898-0-00
Full-Text Source:
Proceedings of the 7th European Conference on Non-Destructive Testing, 26-29 May 1998, ISBN:
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