Thick Plates in Grade 91 for Fourth Generation Nuclear Reactors

To face the future challenge of global energy supply, taking into account the depletion of fossil fuels and global warming issues, the main nuclear energy users are strongly involved in a research program to fourth-generation reactor technology. This new generation will work at high temperatures between about 450 °C and 550 °C. Extensive studies have been launched worldwide to assess steel grades able to meet these new operating conditions. One of the candidates is Vanadium enhanced 9% Chromium steel grade (EN 10028-2 X11CrMoVNb 9-1 – ASTM A387 grade 91 class 2 – ASME SA387 grade 91 class 2). To meet the future needs in nuclear energy, Industeel improved its conventional 9Cr1MoVNb steel devoted to the fabrication of steam lines in thermal power plants. Preliminary studies revealed the feasibility of thick plates in this enhanced grade. Thick plates, 140 and 210 mm thick, have been hot rolled from a 82 metric tons ingot. Welded joints have then been prepared. Tests performed on both base metal and welded zones proved the excellent mechanical properties of the grade, especially regarding toughness property. This work demonstrated the industrial feasibility of very thick plates made of grade 91 for nuclear applications. This contribution is a review of the work done as well as the results obtained on the plates.