Core Shroud Manipulator - T-hin
The T-hin manipulator is designed for phased array ultrasonic (PA-UT) inspection of the core shroud welds H7a+b in the Mühleberg (KKM) Nuclear Power Plant.
The KKM vessel and core shroud design features internal jet pumps, creating an extremely challenging environment for a manipulator system that’s required to cover the whole circumference of the core shroud. The minimum distance between the jet pumps and the core shroud is less than 40 mm thus the much customized design of the T-hin manipulator which has an overall thickness ≤35 mm.
The scanner is placed on the outside of the core shroud in a horizontal position on the pump deck and pushed against the shroud surface by use of clamping units, actuated against Jet Pumps or Jet Pump Dummies.
When clamped behind a Jet Pump the manipulator stroke is wide enough to reach over to the next Jet Pump and
clamp behind it. The sequence is repeated and the manipulator moves along the outside of the core shroud.
Two separate probe drives, each capable of holding two phased array probes (four probes total), are used for the welds H7a and H7b. The two weld areas (-a and -b) can be inspected from above as well as from below.
All motions are indexed and position is fed back to the control system which allows for very high accuracy and repeatability when inspecting the shroud. By use of a revolutionary small sized resolver, all electrical motions are radiation resistant to a very high degree.
Global position in the vessel is determined and verified using on-board laser aiming systems.
The small manipulator size and weight makes it easy to insert as well as retrieve into the annulus, without cranes or overhead lifting arrangements.