Presentation on theme: "Chiara Ferraris, NIST Chairperson Concrete Codes and Standards for Nuclear Power Plants (CTG) in NESCC."— Presentation transcript:
Chiara Ferraris, NIST Chairperson Concrete Codes and Standards for Nuclear Power Plants (CTG) in NESCC
NESCC Nuclear Energy Standards Coordination Collaborative Joint initiative of ANSI and NIST Scope: identify and respond to the current needs of the nuclear industry Inaugural meeting June 2009 Meets at NIST 2-3 times a year Next meeting is July 28, 2011
NESCC - Mission/Purpose The NESCC is formed for the purpose of providing a cross- stakeholder forum to bring together representatives of the nuclear industry, standards developing organizations (SDOs), subject matter experts, academia, and national/international governmental organizations to facilitate and coordinate the timely identification, development and/or revision of standards that support the design, operation, development, licensing, and deployment of new nuclear power plants and other nuclear technologies, including advanced reactor concepts.
NESCC TG Formed December 2009 –Concrete Codes and Standards for NPP (CTG) – report June 2011 –Standards Database Task Group Formed in May 2010: –Structural Design and Performance –Polymeric Piping for NPP New TG proposed (July 2011) –Electrical Cable Aging and Condition Monitoring Codes and Standards for NPP –Repair of concrete of Existing NPP
Concrete Codes and Standards for NPP CTG Created December 2009 Meetings: –Monthly conference calls –in person (March 23, 2010) at the ACI convention in Chicago Final report – in print June 2011: –6 ballots to finalize the report
Membership - reviewers 37 members from : ACI, AISC, Amec, AmerenUE Callaway Nuclear Plant, AREVA, ASME, ASTM, BASF, Bechtel Power, Carrasquillo Associates, Commision Nacional de Seguridad Nuclear, DOE, Dominion Virginia Power, Duke Energy, EPRI, Exelon, FMC Lithium Division, ICA Fluor, INL, J.D. Stevenson, Los Alamos National Laboratory, NCMA, NIST, Purdue Univ., Sargent & Lundy, Savannah River Remediation, Southern Company, Unistar, University of Kansas, US- NRC, Westinghouse 34 reviewers from industry, government and SDOs
Scope Establish coordination and consistency of safety and non-safety related concrete requirements Identify new design requirements for safety related concrete components, and develop a plan to incorporate these new requirements into codes and standards. Identify and review all U.S. Nuclear Regulatory Commission (NRC) Regulatory documents related to concrete for nuclear power plant
Objectives Objective 1: Review NRC documents –Documents considered: Mattson report, NRC NUREG CR 5973, and NRC-regulatory documents –Detailed analysis of the gaps in the concrete standards, specification, and codes for all SDOs. Objective 2: Categorize and Identify –Discussion of codes and standards –A list of issues and recommendations Objective 3-4: Identify research needs –List of potential areas where research might improve or facilitate the construction
Report Table of content 1.Introduction 2.Objectives overview 3.Discussion of Standards Developing Organizations (SDO) and relevant documents 4.Issues unrelated to SDOs 5.Research Needs 6.Summary
Goal 2-3: SDO examined ACI – Amer. Concrete Institute ASTM AISC – Amer. Inst. of Steel Construction ASME – Amer. Soc. of Mechanical Engineers ANSI – Amer. National Standards Institute ASCE - American Society of Civil Engineers EPRI - Electric Power Research Institute NEI- Nuclear Energy Institute NFPA - National Fire Protection Association Foreign standards and code – exploration
SDOs Related issues Recommendation to revise not recently (more than 10 yrs) updated documents List of items that should be addressed in otherwise updated documents. –Each recommendation was structured: Title a) Status today b) What needs to be changed for application to a nuclear power plant? c) Why does it need to be changed? Provide a reference or example
Main issues uncovered ACI: –Specific recommendations for 318, 349 & 359 –Update some related ACI documents, i.e., related to Heavyweight concrete –Nuclear inspector certification program AISC/ACI: modular construction Coordination of ACI/ASME
ASTM ASTM standards were not examined in detail, because NRC does not reference them directly in their documents. Their usage is implemented by referencing other SDOs standards (codes, specifications, criteria, and guidelines)
Coordination DOE, NRC, SDOs NRC and DOE need to review any new version of SDOs documents before they are accepted for use in NPP Expedite NRC and DOE review of the most used codes and standards Resolve construction requirements in conflict with NRC current technical requirements. Better procedure for NRC to adopt SDOs documents
Goal 2-3: Issues unrelated to SDOs 4.1Materials 4.2.Implement new, mature technologies 4.3.Foreign standards and Codes
Materials Material selection for concrete mixture designs needs: –to ensure conformity to current standards and codes –sufficient material supply is locally available –commercially available concrete batch mix materials, with adequate records –enable assured concrete service life for over 60 – 75 years.
Issues to be considered Supplementary cementitious material (SCM) usage should be encouraged Aggregate sources need to be tested, e.g. ASR or enhanced mitigation procedures High density aggregates characterization Cement characterization, i.e. SCM interaction
Implement mature technologies Self consolidating concrete (SCC). There are no references to SCC in any of the NRC documents. Procedure for introduction of new technology in the nuclear construction. Performance based design of concrete Foreign codes and standards adoption
Goal 4: Research needs 5.1.High Strength reinforcing steel 5.2.Concrete Radiation Shielding 5.3.Durability of concrete 5.4.Performance based design 5.5Ultra-high Performance Concrete (UHPC) 5.6 Use of lapped Splices in regions of low biaxial tension 5.7Temperature loading concrete
High Strength reinforcing steel Advantages –Reduce cross-sectional area –Save cost of material, shipping, placement –Reduce reinforcement congestion (fewer rebars) facilitates concrete placement and consolidation Disadvantages –Higher steel stress at service load conditions potential wider cracks and larger deflections (objectionable for aesthetics and permeability) –Less deformation capacity –Better used with High strength concrete
Concrete Reinforcing Steel Institute (CRSI) – draft report Research plan in nuclear construction. –Feasibility Study for Containment/Safety-Related Structure Designs –Database of Properties –Stress-Strain Characteristics and Ductility –Development Length and Tension Lap Splices –Compression Lap Splices –Standard Hooks –Mechanical Splices –Bending and Straightening –Headed Bars –Seismic Design Requirements
Concrete Radiation Shield Neutrons and gamma photons incident on a concrete radiation shield can cause thermal gradients that can lead to stresses that cause cracking. Not addressed in standards: –Radiation and the thermal cycling of such shields –the dehydration of concrete shields caused by long term exposure to temperatures above about 90 °C –degradation in concrete's ability to shield against neutrons.
Durability of concrete Nuclear power plants would be more economical if their service life can be reliably designed for ages longer than 60 years. Models and standards should be available or developed that can quantitatively, with known uncertainty, predict the service life of the concrete materials used for their construction. Research to fill in knowledge gaps needs to be performed.
Performance based design The performance-based design of concrete is not yet fully implemented in non-nuclear construction but still should be considered for NPP. The obstacle to full implementation is the lack of test methods to measure desirable properties and the lack of models to predict performance after 50 or 100 years of service.
Ultra-high Performance Concrete (UHPC) Relatively new cementitious based materials with low permeability and incorporating fibers to obtain a very ductile and durable material. Standards and codes need to be developed to allow a wider use of this material that possibly could reduce the rebar congestion in some components of the plant.
Temperature loading concrete Lack of data on concrete subjected to temperature differential up to 100 ° F (38 ° C) Better use of slag or FA to reduce heat generation for high strength concrete
Summary Main issues –Improve process for NRC, DOE to adopt new technology and standards –Long list of research need: how can they be addressed?
Next NESCC meeting July 28, 2011 at NIST Open to all Need to register (free) to gain access to NIST campus – ANSI website: (Standards Activities – Standard panels and forum – NESCC) Agenda: –AM Keynote speakers –PM TG presentations
New TG on Repair Will be proposed that July 2011 meeting Open for members: NPP owners, SDOs Scope : –Establish coordination and consistency for safety and non-safety concrete repairs in existing NPP: evaluate the concrete structure, assess the repair strategy, design and implement the repair and monitor the repair. –Identify repair requirements.., and develop a plan to incorporate these new requirements into codes and standards. –Identify U.S. Nuclear Regulatory Commission (NRC) Regulatory documents related to concrete repair for existing nuclear power plants and identify any needs.
Questions for you How to help NRC streamline the adoption of revised/new standards and codes? How can international standards be adopted by SDOs or NRC? How to address research needs? Who and funding? What other areas are critical for NPP?
Use of lapped Splices in regions of low biaxial tension The use of welded or mechanical splices of reinforcement in regions of biaxial tension where tensile stresses perpendicular to the reinforcement are well below expected tensile crack stress in the concrete is both time consuming and expensive. It may be possible to show by comprehensive testing of this condition that lapped splices will reach the ultimate tensile capacity of the reinforcement being spliced. The testing would have to be very comprehensive. This is an area in which there is no data.
HS- reinforced steel – contd Research needs for Grade 80 and higher: 1.splice and development length design of straight bars: adequate information is available to make decisions on how to proceed 2.anchorage of hook bars no information exists
HS- reinforced steel – contd 3.use of high-strength bars for seismic loading, three areas require attention: (a) the spacing of stirrups and ties needed to limit buckling of Grade 80 bars in compression when they become plastic, (b) the inelastic cyclic performance of flexural members, and (c) bond slip through beam-column joints under cyclic loading.
HS- reinforced steel – contd 4.Use of headed reinforcing bars to develop high strength reinforcing steel: ACI 318 currently limits fy to 60 ksi for the design of headed bars. This limitation is based on a total lack of data for headed bars of higher strength, and, as a result, heads cannot be used to anchor Grade 75 or 80 headed bars. The formulation of design criteria for high- strength headed bars will require tests that develop bars to at least 80 ksi.
HS- reinforced steel – contd 5.use of mechanical splices or couplers with high strength reinforcing steel data exists on the mechanical splice performance for high-strength bars. The main task will be to consolidate that information.