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Pressurizer heater replacement

Pressurizer maintenance operation: heater replacement

Pressurizer heater replacement


The pressurizer is the component which regulates the pressure inside the primary circuit during reactor operating.

In a joint venture with its partner HORUS, Onet Technologies is carrying out the replacement of pressurizer heaters (electrical resistor rods) for its client EDF UTO, confronted with the following environmental constraints:

  • Restricted, contaminated and irradiated environment
  • Work under containment tent and wearing ventilated leak-tight suit
  • Use of tele-operated equipment with remote control panel
  • Operations on the primary circuit
  • FME risk
  • Management of highly radioactive, contaminated waste


This service contract is a historical one for Onet Technologies, having been systematically renewed every 4 years since 1991. Guided by its trust in the company’s expertise in this field, EDF has charged Onet Technologies with the mission to manufacture a tooling system capable of rapidly extracting the heaters. 

Service provided

  1. Automated machine cutting of the heaters to be replaced
  2. Non-destructive ECT inspection of the heater well after extraction of the heaters
  3. Use of an intermediate sleeve (patented with EDF)
  4. Sleeve of heater welding operations
  5. Non-destructive gamma radiographic inspection to verify the conformity of the welding between the sleeve and the well and of the new heater on to the sleeve
  6. Cutting into sections of the 5 extracted heaters
  7. Removal and rewiring of the electricity supply to the heaters
  8. Installation of a platform: specific biological protection in order to reduce the level of radiological exposure

Core Competences

  • Coordination of  several sub-trade interventions
  • Radiation protection
  • Regulatory requirements and quality control
  • Tele operated, automated process
  • Orbital TIG welding
  • Penetrant testing / Gamma radiography / Eddy Current Testing
  • Nuclear transport


Country: France
Client: EDF UTO

Project Details:

  • Project duration: Historical service performed since 1991
  • Duration of the works: 5 weeks and equipment maintenance: 4 weeks
  • Concerns all EDF units with the exception of FES1
  • Project team: 11 peopleSite work performance team: 70 people


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


Video of chemical cleaning of the steam generators