Design methodology
High-temperature design methodology overview
High-temperature gas-cooled reactor (HTGR) components are subject to elevated temperatures, long service lifetimes, and complex loading conditions that challenge traditional structural design approaches. High-temperature design methodology activities support the development and application of defensible ASME code–based methods for evaluating structural integrity under these conditions.
These efforts focus on improving analysis methods, validating design rules, and developing guidance that supports consistent design evaluations and regulatory review for HTGR components.
EPP+SMT code case
Developing elastic–perfectly plastic plus simplified model test (EPP+SMT) design procedures to reduce unnecessary conservatism in ASME Section III, Division 5, Class A creep-fatigue rules. This work integrates targeted testing and method development to support creation of a licensing-relevant ASME Code Case.
Fatigue design rules
Experimental testing and analysis of variable-amplitude fatigue and creep-fatigue behavior to validate and improve ASME Section III, Division 5, fatigue design rules for high-temperature reactor applications.
Universal inelastic constitutive model development
Developing unified inelastic constitutive models for ASME Class A materials to support high-temperature structural analysis. This effort responds to vendor feedback by pursuing simpler, implementable model forms compatible with commercial finite-element analysis software.
Class B rules update
Revamp ASME Section III, Division 5, Class B design rules to address the current gaps in Class B design rules for high-temperature applications. This work focuses on introducing design-by-analysis methods, strain-limit criteria, creep-fatigue evaluation, and variable design lifetimes to support emerging advanced reactor designs.
Why design methodology matters
High-temperature design methodology activities play a critical role in enabling reliable, licensable high-temperature gas-cooled reactor designs. Improving how materials behavior is represented in structural evaluations accomplishes the following:
- Reduce unnecessary conservatism while maintaining appropriate safety margins
- Improve consistency in design evaluations across components and vendors
- Provide regulators with clear, technically defensible bases for structural integrity assessments
- Support long-term structural performance and integrity considerations important to investment and licensing decisions.
Design methodology development is informed by materials testing and analysis data curated through the NDMAS.