Effects of process-generated hydrogen on RPV walls

1.4. Production of a reactor pressure vessel

1.4 Production of a reactor pressure vessel The production of different rings of the RPV is done in multiple successive steps. Due to the limited size of the RPV for a PWR (4 m), the rings can be produced as a whole, in contrast to RPVs for BWRs, which are larger. The starting point for the production of the RPV rings is a solidified ingot of the base material, SA-508 Class 3. From this ingot, a central “carrot” is drilled out. The diameter of this carrot depends on the amount of material necessary to produce the final product, in this case a ring. The remaining donut shaped material will be forged to obtain the proper dimensions of the ring. This is done with high power hydraulic presses, which can produce a force up to 15 MN. This process can be seen in Figure 1.3. [3] After forging, the rings are given a heat treatment. Next, there are some machining steps to obtain the correct final dimensions for the rings. Finally, different types of quality examinations are performed on the rings. These tests include non-destructive tests, e.g. ultrasonic testing and magnetic testing, and destructive tests on samples from the waste material, e.g. micrographic, mechanical and chemical analysis, conform to the ASME Code Section III regulations. [6] To complete the RPV, a cladding is weld-deposited to the different rings and the rings are welded together. Further quality examinations are performed before accepting the RPV.

Figure 1.3: Schematic representation of the forging process. The donut shaped ingot is shaped to the RPV ring dimensions.

The production of the RPV for Doel 3 and Tihange 2 was performed by multiple companies. Marrel Frères provided the plate material for the bottom cap and the vessel head. The base material for the rings was produced by Fiedrich KRUPP Hüttenwerke. KRUPP also pre-forged all the different parts of the RPV, except for the transition ring. The pre-forged parts, called blooms, were delivered to Rotterdamsche Droogdok Maatschappij (RDM) together with the ingot for the transition ring. At RDM, all of these parts were further forged to the required dimensions. RDM also 9