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PWR Pressurisers surge line weld decontamination

Remote maintenance and decontamination of PWR Pressurisers

PWR Pressurisers surge line weld decontamination



In order to allow grammagraphy of the surge line welds of PWR pressuriser,a decontamination of the bottom end and thermal shield annulus is necessary.

However, there was no access possibility for decontamination means, and it was necessary to develop methodology and tools to create holes (Ø270mm) in the intermediate plates (27mm thickness) to finally access the surge line and decontaminate it.

Service provided

EDF provided a 7 axis manipulator tool carrier and Onet Technologies designed and built 6 different machines able to be carried by the robot (limited weight and size).


Onet Technologies qualified the equipment and implemented the operation on-site with its own teams.


Main constraints for this project were :

  • Milling and UHP jetting on the primary circuit,
  • Recovery of all liquid and solid wastes generated,
  • Access to the pressurizer bottom, more than 10 m deep throught a limited diameter manhole,
  • High radiation level work environment,
  • Work carried out simultaneously in three different areas.

Key figures

  • 7 axis manipulator,
  • Six tools,
  • One control unit,
  • One HP and one UHP jetting unit
  • Team of 17 poeple for onsite implementation

Description of the installation/equipment

First phase :

  • Drilling intermediate plate to access the surge line weld.
  • Brush cleaning of the plate,
  • Weling of a hook to center the tools,
  • Ultrasonic examination to determine the thinckness with high accuracy
  • Orbital mill (Ø 270 mm) of a groove at Thickness-1mm,
  • Vacuum up all metal chips,
  • Roller cut (avoid chips) at 270 mm Ø

Second phase :

  • HP jetting for pressurizer bottom end, UHP jetting for thermal barrier annulus.
  • Plug the surge line with inflatable plug,
  • Jetting between 350 and 1000 bars,
  • Recovery and filtration of wastes for recycling.


  • EDF/UTO From 1996 to 2011
  • Development from 1995 to 1998
  • Qualification in 1998
  • Decontamination operations performed on all
  • French PWR


36, boulevard de l’Océan - CS 20280
13258 Marseille Cedex 9 - France
Tél. : +33 (0)4 91 29 18 10
Fax: +33 (0)4 91 29 18 58
ONET SA - RCS B 059 801 324 Marseille
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