NDTnet 1998 Aug, Vol.3 No.8

Abstract

Nuclear fuel pellets are usually loaded into zirconium tubes, which are assembled into bundles (Fig.1). In order to fulfill high safety requirements dimensions and integrity of the bundles should be periodically checked. The main tasks which arise during these chuckings the following:
• high accuracy measurement of the biggest lateral dimension (diameter) of the bundle;
• measurement of wall thickness of each tube in the bundle, including tubes in the internal layer;
• recognition of the tubes in a bundle partially filled with water.

Fig.1. Schematic view of a fuel bundle	Fig. 2. Ultrasonic C-scan image Fig.

For solution of these problems immersion ultrasonic non-destructive evaluation techniques have been developed. The diameter of a bundle and wall thickness of fuel tubes are determined using the time of the flight technique combined with a C-scan type imaging (Fig.2).

The accuracy of measurements of dimensions and wall thickness is + 50 µm. Integrity of hermetically sealed fuel tubes was evaluated analyzing the ultrasonic pulses reflected by the tubes inside a bundle. For that purpose variuos signal processing techniques, including the non-linear deconvolution, were applied.The ultrasonic techniques developed enable to perform in-service inspection of nuclear fuel bundles used in channel type nuclear reactors.

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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