Transcript Concrete Codes and Standards for Nuclear Power Plants (CTG) in NESCC Chiara Ferraris, NIST Chairperson.

Concrete Codes and Standards
for Nuclear Power Plants (CTG)
in NESCC
Chiara Ferraris, NIST
Chairperson
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 crossstakeholder 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, USNRC, 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 SDO’s.
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.
2.
3.
4.
5.
6.
Introduction
Objectives overview
Discussion of Standards Developing
Organizations (SDO) and relevant
documents
Issues unrelated to SDOs
Research Needs
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 SDO’s 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
4.1 Materials
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.
5.2.
5.3.
5.4.
5.5
5.6
5.7
High Strength reinforcing steel
Concrete Radiation Shielding
Durability of concrete
Performance based design
Ultra-high Performance Concrete (UHPC)
Use of lapped Splices in regions of low biaxial
tension
Temperature 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:
www.ANSI.org (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 – cont’d
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 – cont’d
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 – cont’d
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 highstrength headed bars will require tests that
develop bars to at least 80 ksi.
HS- reinforced steel – cont’d
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.