NRC Perspectives on AISC N690 and Appendix on Modular Composite Construction (SC)

1. NRC Perspectives on AISC N690 and Appendix on Modular Composite Construction (SC) Dr. Jose Pires Structural, Geotechnical and Seismic Engineering Branch NRC Office of Nuclear Regulatory Research Jose.Pires@nrc.gov NESCC Meeting November 29, 2012

2. ANSI / AISC N690 • The Standard Review Plan for the Review of Safety Analysis Reports for Nuclear Power Plants: LWR Edition (NUREG-0800), 2010 (SRP), refers to: • N690-1994 including Supplement 2 (2004) • In: • Section 3.8.3 – Concrete and Steel Internal Structures of Steel or Concrete Containments • Section 3.8.4 – Other Seismic Category I Structures • The Standard Review Plan for the Review of an Application for a Mixed Oxide (MOX) Fuel Fabrication Facility (NUREG-1718), 2000, refers to • N690-1984 in Section 11.4.6.1 Regulatory Guidance

3. ANSI/AISC N690 • SRP (3.8.3 and 3.8.4) refer to N690 in relation to the following for steel structures • Applicable codes, standards and specifications • Loads and load combinations • Design and analysis procedures • Structural acceptance criteria • Materials, quality control, special construction techniques and quality assurance • Example - SRP 3.8.4 - II.5 Structural Acceptance Criteria • For each of the loading combinations delineated in Subsection II.3 of this SRP section, the structural acceptance criteria appear in ACI 349 and RG 1.142 for concrete structures, and AISC N690-1994, including Supplement 2 (2004), for steel structures. • No supplemental criteria added

4. ANSI/AISC N690 • SRP references (additional examples) • SRP 3.8.4 - II.3 Loads and Load Combinations • All loads and load combinations are to be in accordance with AISC N690-1994 including Supplement 2 (2004). This specification uses the allowable stress design (ASD) method. The supplemental criteria on the use of loads and load combinations presented above for concrete structures also apply to steel structures. • SRP 3.8.3 - II.3 Structural Acceptance Criteria • ANSI/AISC N690-1994 including Supplement 2 (2004) defines the structural acceptance criteria for steel structures. This specification uses the ASD method. Use of the LRFD version of the specification (N690L) is reviewed on a case-by-case basis. • Reference is to ASD methods (as opposed to the use of LRFD for concrete structures)

5. Review of ANSI/AISC N690-2012 • Current guidance (staff review guidance) addresses the older standard • Still considered adequate for safety • Supplements to 1994 edition • Still used by end users (licensees and applicants) • Should the NRC review and endorse the new standard? • NRC has been contacted by the AISC in that regard • What are new technical and regulatory issues addressed and what are their safety significance? (previous presentations address some of this) • Examples of technical/regulatory issues • Technologies and understanding of relevant phenomena (e.g., materials, construction, analysis and characterization of loads) evolved • N690-2012 uses ANSI/AISC 360-10, Specification for Structural Steel Buildings, as the baseline document (instead of standalone document) • Discontinuation of Supplements to 1994 edition • Use of LRFD approach (with ASD as an alternative) which is consistent with the code for concrete structures (ACI-349) • Standard for Modular Composite Construction (SC) (planned Appendix N9)

6. Modular Composite Construction (SC) • Steel plate and concrete composite modular (SC) have been adopted for safety-related structures of new reactor designs • E.g., containment internal structures • SC construction is still outside the scope of existing US standards for safety-related structures • Case-by-case review is still done for current applications, license amendments and potential new applications • Standard under development by Ad-hoc subcommittee to AISC’s Task Committee 12 (TC 12) • Planned as Appendix N9 to ANSI/AISC N690 6

7. NRC Research Activities • Sponsored research at Brookhaven National Laboratory (1990s) to review technical bases for regulatory guidance (NUREG/CR-6486, 1997) • Engaged outside experts (academia and industry) to inform confirmatory reviews of certain proposed designs • Staff participates in the activities of TC 12’s ad-hoc subcommittee • Outside experts informed staff review of technical bases (2011) • Held public meeting (August 2011) • Sponsoring numerical modeling research for interpretation of testing, benchmarking and confirmatory analysis tools • Reviewing international codes and guidance • JEAC-4618 (2009) – Japan – ASD approach • KEPIC (2010) – Korea – LRFD approach

8. Review of SC Standard • Resulting designs must satisfy regulations • Resulting designs would (as examples): • Provide adequate strength and stiffness • Prevent non-ductile failure modes • Provide durability through the use of adequate materials, control of concrete cracking, prevention of steel and rebar corrosion • Provide clear load paths avoiding load path discontinuities • Other items of interest • Materials and material properties (steel plates, studs, tie bars, etc) • Type of concrete (e.g., conventional vs. self-consolidating) • Constructability • Inspection • Harmonization with international standards

9. Review of SC Standard • Challenges (examples) • Design criteria for connections and connections to other construction types, e.g., reinforced concrete • Experimental database for combined load effects • Designs should be based on sound engineering principles and validated methods • Staff continues the review of the technical bases for the provisions in the US standard under development as well as review of the scope of the provisions • Effort includes review of existing international standards (E.g., JEAC and KEPIC) • Background work is being done to review AISC’s white paper or other publicly available publication on the SC standard under development (Appendix N9)

10. Acronyms • AISC – American Institute of Steel Construction • ANSI – American National Standards Institute • ASD – Allowable Stress Design • JEAC – Japan Electric Association Code • KEPIC – Korea Electric Power Industry Code • LRFD – Load and Resistance Factor Design • SC – Modular Composite Construction (Wall modules constructed from large prefabricated sections of steel plates spaced apart and joined with intermittent steel members or tie bars, joined with other modules at the site, and then filled with concrete) • SRP – Standard Review Plan