Control clusters and their control mechanisms

Maintenance of nuclear power plants (NSSS components)

Figure 1 - Cross-section of a vessel (blue) with its lower (red) and upper (green) internal fittings in the configuration of a 900 boiler.

Figure 2 - Inspection machine in service (MIS) in operational position

Figure 3 - Diagram of a guide-tube spindle: cracking at a lamella

Figure 4 - (a) Control bundle partially inserted in a fuel assembly (shortened mock-up, fuel rods removed to show assembly tubes in which bundle rods slide), (b) bundle control mechanism

Figure 5 - Cluster pencil worn by vibration and rubbing against a guide card

Figure 6 - Steam generator (originally fitted to 900 units)

Figure 7 - Stress corrosion cracks in the inner wall of the transition zone of a tube (the extracted tube has been flattened to make the cracks more visible).

Figure 8 - Number of tubes plugged per year in the EDF fleet (198 GV)

Figure 9 - Various eddy current probes used for internal inspection of HS tubes, depending on the type of damage required

Figure 10 - Replacing a GV: introducing the new GV through the material buffer

Figure 11 - Simplified exploded view of a model 100D primary pump

Figure 12 - Removal of pump hydraulics at Chooz (© Areva – Ave Multimedia)

Figure 13 - Work under the pressurizer, on the electrical connections of the heating rods (© Onet Technologies).

Figure 14 - Thermal cracking detected by dye penetrant testing (elbow of a safety injection pipe)

Figure 15 - General layout of the Fessenheim reactor building