The enclosed horizontal former plates are connected to the core barrel via support and/or clamping ripples and the support plates. Bolts connections are used to fasten the support plates.
In case the integrity ofthe barrel welds and of the barrel former bolts is not guaranteed, the entire structure of the core barrel would be jeopardized by the external forces which occur according to design and operation loads.
It is, therefore, of importance to inspect the barrel former bolts and barrel welds with a nondestructive inspection method and to repair them in case of a failure. Because of the high radiation in this area, all work has to be done by remote controlled manipulators
ABB Reaktor has developed and qualified a sophisticated inspection system based on the US technique which allows the accurate inspection of the barrel welds and barrel/former bolts.
The challenge is to detect cracks accurately in a relatively inaccessible area: the gap between barrel and thermal shield is only 25 to 50 mm depending from the plant construction. Additionally the high radiation dose up to 104 Rads limit the choice of materials for the construction of manipulator and probes.
Inspections have been successfully performed by MHI in Japanese nuclear power plants. The results of these inspections show the reliability of the system and confirm the performances obtained during the qualification.
The aim of this paper is to give a description of the inspection system and to summarize the results of the qualification and of the first inspection campaign.
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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