Context and challenges

As part of the Units Conformity Reviews, numerous controls are to be carried out on the nuclear units, and in particular the control of the anchoring of the equipment to the support structures. The conformity examination consists in comparing the actual state of the installation with the safety standards and the applicable regulations, including in particular its creation authorization decree and the prescriptions of the NSA (Nuclear Safety Authority).

Anchorages refer to mechanical elements that play a role in the interface between the equipment and the support. The anchor consists of an anchor plate or lock and rods that integrate with the supporting concrete. The anchor in the broad sense includes the part of the concrete which ensures the sealing and the diffusion of the forces transmitted by the rods and the plate.

The conformity control of an anchorage currently consists for the CNPE (National Centre of Electricity Production) in:

  • Visually checking the conformity of an anchor on site with respect to the design plans
  • Justifying by calculation of the conformity of the anchor assembled on site, if non-conformity between “As Built” and the design plans
  • Making modifications and / or replacing the non-conforming anchor, if the calculation is non-conforming

As part of this project, this client, a leader in the nuclear sector, called on Assystem to carry out on-site control, calculations and follow-up of modifications to the CNPEs as part of regulatory compliance of anchors (EIPS: Equipment of Protected Interest for Safety).

Project scope

  • Establishment of justification notes for "As Built" compliance EIPS piping supports under normal and accidental operating conditions
  • In the event of non-justification of the "As Built" support compliance, proposal of a reinforcement solution supported by calculation taking into account the arrangement of the support and the problems of routing of material
  • Implementation of an equipment anchoring control methodology:
    • By calculation
    • By test, by simulating on a test bench or in situ the stresses representative of the seismic action considered for the justification of the installation
    • By comparison based on comparable calculations or by using post seismic feedback on anchors and equivalent equipment
  • For each report, submission of a study file including:
    • A description of the difference
    • The justification note (self-supporting) of the "As Built" compliance of the support plate
    • If necessary, the proposal of solutions for strengthening the support plate and the associated justification calculation

Key skills: mechanical calculations, systems for anchoring equipment to civil engineering, client repositories, etc.

Study volume of around 1000 anchors per nuclear unit

Results

  • Proactivity and availability of teams thanks to the implementation of a specific organization: obligation of result for all studies, including a response time of 4 days maximum as part of the fixed-price contract
  • Limitation of the number of anchors to be taken up by the proposal of solutions adapted to each deviation
  • Customer satisfaction who renewed the mission for 2 years on a specific nuclear power plant

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