ASME BPVC-III 5, 2023 Edition – Rules for Construction of Nuclear Power Plant Components, Division 5: High Temperature Reactors

ASME Section III, Division 5 – Division 5 of Section III of the BPVC provides construction rules for high-temperature reactors, including both High-Temperature, Gas-cooled Reactors (HTGRs) and Liquid-Metal Reactors (LMRs). These rules are for components exceeding the temperature in Division 1 and are meant for components experiencing temperatures that are equal, to or higher than, 700oF (370oC) for ferritic materials or 800oF (425oC) for austenitic stainless steels or high nickel alloys.

Importantly, Division 5 also contains the new rules pertaining to graphite core components. These new rules include general requirements, plus design and construction rules, for graphite. Irradiation effects on graphite are addressed, as are the features of probabilistic design reflected in the determination of graphite material strength properties.

Division 5 reflects new, safety-criteria approaches for nuclear power plants—accumulating rules conveniently into one, single book format. These rules have been updated and improved over those still in Code Case format.

Various industries are beginning to appreciate the unique advantages that exist with nuclear power plants that operate at elevated temperatures. For example, HTGRs can yield higher operating efficiencies, provide not only electrical power but also process heat for other industries, and can be designed to be passively-safe.

What are the key changes for 2023 BPVC Section III, Division 5 (ASME BPVC-III-5)?

Table HBB-3225-4 was revised to extend thermal aging factor for Class A, Grade 91 components from 300,000 to 500,000 hours.
Mandatory Appendix HBB-I-14 Tables were revised to extend stress rupture factor values for Grade 91 from 300,000 to 500,000 hours.
HBB-T-1800 was revised to extend isochronous stress-strain curves for Grade 91 components from 300,000 to 500,000.
HHA-3142 and HHB-3142 have been revised to remove EDN (damage dose unit) and only use dpa (displacements per atom) damage dose unit.
Nonmandatory Appendix HBB-Z added to provide guidance on constructing a suitable inelastic model from data and to offer designers an acceptable reference model for Grade 91.
Nonmandatory Appendices HHB-D and HHB-E have been developed to cover Carbon-Carbon (C-C) Ceramic Matrix Composites.