Concrete Codes and Standards for Nuclear Power Plants (CTG)

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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 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.

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 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.

High Strength reinforcing steel

5.2.

Concrete Radiation Shielding

5.3.

Durability of concrete

5.4.

Performance based design

5.5

Ultra
-
high Performance Concrete (UHPC)

5.6

Use of lapped Splices in regions of low biaxial
tension

5.7

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 w
ider 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 high
-
strength 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.