Ultrasonic Testing & Eddy Current Testing in Nuclear

Ultrasonic & Eddy Current Testing using Submarines, Rovers and Manipulators in Nuclear

Ultrasonic testing (UT) is based on the propagation of sound waves in a sample being tested. Mechanized ultrasonic testing can detect subsurface, internal and, in some cases, surface defects in different materials. DEKRA provides customers a range of mechanized ultrasonic testing solutions using the latest submarine, rover and manipulator technologies to reach the most dangerous areas in facilities. By the use of robots, the risk for the inspectors are significantly reduced and human errors can be reduced or even eliminated.
DEKRA has developed an innovative fleet of submarines and manipulators to shorten PWR Vessel examination time. Our advanced underwater robots for UT, ECT & VT examination comply with a wide range of global code demands. DEKRA’s systems are field-proven innovative manipulators designed for minimum vessel occupation time. We have the longest history and experience of working with multiple reactor vessel configurations, with record examination times.

About Advanced Ultrasonic Testing

Time is the key word for the inspection of pressurized water reactor (PWR) operators worldwide. By using three parallel manipulators, DEKRA has successfully fulfilled customer demand with a complete inspection of all vessel welds, nozzles and bottom nozzles in a world-record five days. The new manipulator concept has been used four times in the reactors Ringhals 2, 3 and 4 and Beznau with outstanding performance. DEKRA’s goal was to minimize the time in the reactor containment, offering the possibility to prepare the equipment in only one day for a full vessel exam. Furthermore, the manipulators are neutrally buoyant in water and work in parallel with ROV functions totally independent of each other and with minimum support from the crane and service bridge. No pre-installation in the vessel is needed. All control systems are identical and will thus increase the redundancy. The NDE technique has been qualified according to the ENIQ and the Swedish rules. The data gathered will be sufficient for detection, characterization and sizing.
The following objects can be inspected using mechanized ET, UT and VT:
  • BMI Nozzle and J-groove weld
  • Inlet and Outlet Nozzles, Nozzle to shell welds, inner radius and connection welds
  • Circumferential and longitudinal shell welds including the bottom dome
  • Areas with UCC (Under Clad Cracks)
  • Radial support
To execute all these tasks in the shortest time our three innovative pieces of equipment and one replica tool were designed with the focus on allowing a parallel inspection in the vessel, without obstructing or delaying the other ongoing inspections.
  • SKIDBLADNER, Manipulator for Vessel Inspection
  • SÄRIMNER, Manipulator for Nozzle Inspection
  • GUNGNER, Manipulator for BMI Nozzle and J-groove weld
  • DRAUPNER, Replica tool for BMI J-groove weld
DEKRA’s ultrasonic testing is carried out in three ways: automated, semi-automated and manual. The testing objects for mechanized NDT include:
  • Pressurized water reactors (PWR) vessel head
  • Nozzle to shell welds, nozzle inner radius, connection welds and nozzle bore
  • Circumferential and longitudinal shell welds including the bottom dome
  • Boiled water reactors (BWR) control rod shafts
  • PWR and BWR vessel shell welds and core shroud from inside of the reactor
  • PWR and BWR vessel shell welds and core shroud from outside of the reactor
  • PWR inner surface nozzle, J-groove from ID and from HAZ
For the inspection of the RVP shell welds with the core shroud installed DEKRA developed the Ringhorne manipulator. This magnetic adhered and belt driven manipulator operates on ferritic pressure vessels with cladded inner surfaces, with up to 10 mm thickness of cladding possible. The manipulator is designed to operate in narrow gaps and can maneuver to any position on a cylindrical surface. With the unique design an accurate position can be established by the “on board” laser reference beam which gives a very precise horizontal and vertical position in relation to known internal objects. The exact position is sustained by the inclinometer, immersion UT transducers and resolvers.
The manipulator Ringhorne can be configured for vertical scanning strokes with steps in the circumferential direction or configured for circumferential scan strokes and vertical steps. This makes it possible to perform scans optimized for longitudinal or transverse defects for both circumferential and vertical welds. DEKRA cover all our customer’s needs for the development of manipulators and NDT, as well as probe design. The inspection system has successfully been tested and qualified according to ENIQ requirements at our test facility before the first outage performance, resulting in an excellent customer response.
Besides the mechanized NDT solution for the scheduled vessel inspection DEKRA also supports customers during the outage tasks with a remotely controlled under water vehicle (VT Dolphin). This system is generally for visual inspection and FOSAR activities but can also execute ultrasonic testing of baffle bolts.
The range of inspections, which could be carried out by the VT Dolphin are:
  • Visual inspection of RPVs and RPV internals
  • Visual inspection of the primary loops up to the steam generator
  • Fuel element check in case of damages while unloading
  • Core mapping
  • General surveillance during unloading and reloading of the reactor
  • Ultrasonic inspection of baffle bolts
DEKRA’s ultrasonic testing experts are certified in accordance with ISO 9712 and Nordtest and our advanced ultrasonic testing meets all the latest testing standards. We also provide customers with dedicated data evaluation software packages for the evaluation of ultrasonic testing data (ultrasonic testing signal and coordinates).