Session: CS-01-02: Structural Integrity of Pressure Components

Paper Number: 80794

80794 - Non-Linear Analysis Design Rules: Recommendations for Industrial Practices 

The Cooperation in Reactor Design Evaluation and Licensing Working Group (CORDEL) of the World Nuclear Association (WNA) was established in 2007 to promote the development of a worldwide nuclear environment where internationally accepted standardized reactor designs can be deployed globally without major design changes. In practice, this would mean that safety evaluations of a reactor design and generic design certification approved by a recognized competent authority would be acceptable in other countries. The CORDEL Mechanical Codes and Standards Task Force (MCSTF) was set up in 2011 and started to collaborate closely with the Standards Development Organizations Convergence Board (SDO CB) and the Codes and Standards Working Group of the Multinational Design Evaluation Programme (MDEP) on the international convergence of mechanical codes and standards related to the design of nuclear power plant components important to safety

The MCSTF has recently completed a three part study on existing mechanical design codes and standards with the aim of proposing identifying a more harmonized approach in using non-linear analysis methods.

Major pressure vessel and piping codes design rules, nuclear and non-nuclear, are based on linear elastic methods associated with stress classification in primary (for load control), secondary (for strain control) and peak stresses (for thermal shocks). This stress classification is only straightforward to apply in simple cases, such as a cylindrical shell subjected to axisymmetric quasi-static loads. When the geometry or the loads become more complex, such classifications are not applicable, so a large part of stress is considered as primary which is extremely conservative. In such cases, non-linear analysis methods are employed. Comparison of these methods has shown that many different approaches are currently used within the industry, which gives rise to discrepancies in the analysis and assessment of designs.

Following an initial comparison of non-linear analysis design rules in nuclear mechanical codes and standards, two benchmark problems were specified for two typical nuclear components. The first benchmark problem was based on a large Class 1 low alloy steel vessel nozzle under pressure and piping loads where the aim was to analyse elastic stress, plastic collapse, plastic instability, and local failure. The second benchmark problem was based on a Class 1 reinforced stainless steel piping tee under cyclic pressure and thermal loads to perform fatigue assessment. These two benchmarks only considered non-cracked components outside of creep regime. The third and final report presents recommendations in support of international harmonization of nonlinear analysis methods following the assessments and findings of the previous reports in the series

Presenting Author: Ronan Tanguy World Nuclear Association

Presenting Author Biography: Ronan has been working in nuclear for over five years, joining the industry following his completion of a MSc in Nuclear Engineering at Imperial College London. He has experience across multiple areas of the nuclear fuel cycle from his work on decommissioning projects at Sellafield, nuclear new build at Hinkley Point C and is currently a project manager for the World Nuclear Association within CORDEL, working to harmonize reactor designs and their licensing processes. Alongside his CORDEL responsibilities, Ronan was recently appointed to the role of Technical Secretary for the SDO Convergence Board to further assist in the harmonisation of nuclear mechanical codes and standards.

Authors:

Ronan Tanguy World Nuclear Association
Byung-Chan Na World Nuclear Association