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Renovation of the IIS guide tubes

Development of a process using tele-operated devices to detect and eliminate corrosion from the IIS penetration tubes

Renovation of the IIS guide tubes


EDF has engaged in a campaign to upgrade the In-core Instrumentation System (IIS) guide tubes (located at the base of the reactor vessel) of all the 900MWe units of the French nuclear fleet. After many years of services, some tubes showed signs of corrosion.
Around 50 tubes are grouped together in this location. They enable various sensors to be inserted into the reactor. These sensors measure the neutronic activity within the reactor core and ensure control of the reactor.


Service provided

Onet Technologies has developed a remotely-controlled, fully-integrated process which enables to upgrade the corroded guide tubes by detecting and eliminating the corrosion.

The process is composed of several phases, each phase implementing the action of a specific robot:

  • A brushing and televisual inspection robot which detects and removes all deposits or traces of corrosion on the tubes,
  • A dye penetrant testing robot which detects potential sub-surface attacks on the metal (pitting),
  • A scouring robot which machines the surfaces to eliminate any pitting detected by the dye penetrant testing.

At the end of the cycle, the tube surfaces are clean and free of pitting, thus preventing any further spread of corrosion.


Travaux de mise au point du robot de ressuage télé-opéré en atelier



Country: France
Client: EDF 

Project Details:

  • 4 year contract (2014 to 2018)
  • Concerns all of EDF’s 900MWe units (33)
  • Intervention on primary circuit
  • 9 000 study hours
  • Project team: 6 members
  • Site operation team: 25 staff members in 3x8h shifts
  • Duration of one site operation: 2.5 weeks
  • Remote-controlled operations inside the controlled zone in a radiological environment with numerous constraints (orange zone )
  • Specialised skills: televisual inspection, non-destructive examination and precision machining




36, boulevard de l’Océan - CS 20280
13258 Marseille Cedex 9 - France
Phone: +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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