NDTnet 1998 Aug, Vol.3 No.8

Full-Text - Abstract

FORCE Institute has built a 6-axis manipulator, 6 meters in diameter, reaching 4 meters down from top of the core shroud in a nuclear pressure vessel. The core shroud is a stainless steel structure approximately 6 meters in diameter and 4 meters high and with a plate thickness of approximately 35 mm. Both longitudinal and vertical welds can be scanned with UT for longitudinal as well as transverse flaws. Detection of the actual weld position (ground flush) is carried out using Eddy Current. Examination takes place at a water depth of 15 to 20 meters.

The manipulator consists of a ring structure on which a so-called Docking Station can rotate 360°. The Docking Station carries a vertical moving Sword at which the UT or ET-probes are mounted in a probe fixture at the bottom. The Docking Station can move the Sword (probes) to and from the Core Shroud wall. When the examination set-up needs to be changed, the Sword is released from the Docking Station and lifted up for probe replacement. The probe fixture has 3 degrees of freedom.

The ring with the docking station is placed on top of the Core Shroud at the beginning of the fob where it stays throughout the inspection.

During scanning, all manipulator movements are simulated and visualised in real-time on a 3D model representing both the environment (Core Shroud and inside of the reactor vessel) and the manipulator. Collision detection is used to warn the operator if any part of the manipulator is coming dangerously close to an obstacle.

The manipulator is also suitable for visual examination if the probes are replaced by a radiation resistant camera. The inspection system can also be used for inspection of the inner reactor vessel surface just by mounting the camera system pointing away from the Core Shroud. The system is constructed for operation in rather high dose rate environment. Only the outer ring of fuel elements has to be removed during examination. If fuel elements are moved around in the reactor pool during the examination, the fuel block must be kept at a distance of at least one metro from the manipulator.

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:

Publication Contact:
7th ECNDT, Park Alle 345, DK-2605 Broendby, Denmark, Fax: +45 46 26 70 11, Email: 101373.3414@compuserve.com