Slender reinforced concrete walls are critical load-bearing elements in nuclear power plant buil-dings, where structural stability must be ensured over extended operational lifetimes. With theowners of the Forsmark and Ringhals nuclear power plants having decided to extend reactor ope-rational lifetimes from 60 to 80[1], a thorough stability assessment of existing structures is requi-red to support the investment decision process. This thesis investigates the stability of slenderreinforced concrete walls through a comparative study of three analysis methods prescribed inEurocode 2: the simplified method based on nominal curvature, the second-order linear elasticanalysis method based on reduced stiffness, and a general fully non-linear analysis method. Themethods are evaluated and compared with respect to accuracy, conservatism, and ease of im-plementation in commercial finite element analysis software. In addition, the influence of concretecreep on structural stability is investigated. A comparison between the provisions of EC2:2005and EC2:2023 is also conducted to identify relevant differences that may affect the evaluation ofexisting structures designed under the earlier standard. The study was carried out in collaborationwith Vattenfall Power Solutions. The results aim to support safe and sustainable lifetime extensionof nuclear power plant infrastructure by providing guidance on appropriate analysis methodolo-gy for slender reinforced concrete walls. Based on a comparison of different analytical methods,this study demonstrates that a second-order linear elastic analysis using reduced stiffness yieldsresults equivalent to a fully nonlinear analysis. Consequently, the report concludes that, underthe assumptions made in this study, the reduced stiffness method is the preferred approach forevaluating slender reinforced concrete walls.