The “Nuclear Renaissance” is at
hand and the materials community is
integral to its success. Increased reliability
of current nuclear components
and the construction of the next generation
of nuclear reactors depend on
advancements in materials knowledge.
This article introduces some of the
ways materials will enable the future of
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of this paper?
Nuclear power offers great promise
in helping to reduce greenhouse gas
emissions and in meeting increased
future energy demand. Materials
and materials engineers will play a
pivotal role in this process as many of
the critical issues facing the nuclear
power industry are related to material
…describe this work to a materials
science and engineering professional
with no experience in your
Nuclear power plants represent severe
operating conditions. An understanding
of materials processes under
radiation, including irradiation-assisted
stress corrosion cracking,
embrittlement, and creep, are critical
for the push toward higher efficiency
designs and longer reactor lives.
…describe this work to a layperson?
Nuclear reactors present unique challenges
for materials. With the predicted
expansion in the nuclear power industry,
there will be an increasing need
for new materials and a corresponding
need for materials engineers.
The renewed global interest in nuclear
power arises from balancing concerns
for global climate change with
the need to provide sufficient electricity
for a growing global population. This
means developing an energy strategy to
satisfy a projected 160 percent increase
in global electricity demand by the
year 20501 while reducing greenhouse
gas emissions. Nuclear power stands to
play an important role in such a strategy
by delivering a sustainable, large
quantity of electricity with near-zero
MATERIALS ISSUES FOR TODAY'S NUCLEAR REACTORS
Worldwide, over 130 new nuclear
plants are projected with 28 new permit
applications in the United States alone.2
The Global Nuclear Energy Partnership
(GNEP)3 and the United States Energy
Policy Act of 20054 promise a rebirth
of nuclear power in the United States;
however, the task is daunting. Much of
the emphasis in the literature has been
on the development of the next-generation,
or Generation IV, nuclear power
plant. While Generation IV reactors
promise improved efficiency and plant
simplification, including waste minimization, significant proof of concept
work is needed before any of these
designs meet regulatory approval.
Therefore, shorter-term construction
will predominantly be Generation III+
reactors, which represent incremental
improvements to current designs.
New plant construction does not occur
overnight. Significant lead time is
required for plant construction, due
in part to a limited supplier base and
necessarily stringent quality control
procedures. As such, extended lifetimes
and increased productivity of the
current fleet of nuclear power plants is planned.
Materials are the enablers for future
nuclear technologies. New alloys, improved
predictive models, and new
component quality specifications are
needed. This article highlights some
examples of the critical role materials
will play in the Nuclear Renaissance.
Materials degradation is the primary
cause of unplanned outages in the nuclear
industry. In fact, Paul Spekkans
from Ontario Power Generation states
that “managing degradation is central
to achieving business success.”5 The
U.S. Nuclear Regulatory Commission
recently conducted a survey of materials
degradation in light water reactors
(LWRs).6 As shown in Figure 1, this
study concluded that significant technology
gaps still exist. In particular,
concern was raised for those areas with
insufficient knowledge of mechanisms
and/or process interdependencies to
With the limited time available to
start bringing new capacity on line, the
current body of knowledge, including
service experience and life cycle predictions,
needs to be critically evaluated.
Recently, Peter Ford noted that
we need to do a better job than was
done 20–30 years ago when only general
corrosion, irradiation embrittlement,
and fatigue were considered in
reactor design.7 Lessons learned from
in-service performance and from laboratory
studies must form the basis for
improved risk-informed component inspection
as well as for alloy selection.
As suggested by Figure 1, fundamental
research for materials is needed. Radiation
damage, deformation of irradiated material and irradiation assisted
stress corrosion cracking (IASCC) remain
focus areas. Emphasis is needed
on understanding corrosion precursors
as well as crack growth and arrest, especially
in welded components. Andresen
and Morra8 highlighted critical
trends in high-temperature stress corrosion
cracking (SCC), including:
In the end, the results from experimental
programs need to aid in the development
of improved predictive models
for materials degradation. These
models are key inputs to fitness-for-use
analyses for reactor components as
well as tools to determine the viability
of extending reactor life. As such, the
effect of changing plant conditions, including
power uprates and water chemistry fluctuations, needs to be incorporated
into the experiments that form the
basis of material degradation models.
- Mechanistic role of silicon
- Effects of chlorine on high-temperature
SCC of low-alloy steels,
even at 5 ppb
- Rapid crack growth rates upon reloading
- Effect of residual strains at welds
MATERIALS ISSUES FOR GENERATION IV REACTORS
Generation IV reactor designs promise
higher efficiencies than Generation
III and III+ reactors. As shown in Table
I, however, the service conditions will
be more severe than those for current
reactors. The key stage gate for the construction
of a Generation IV plant will
be the development and qualification
of materials that are resistant to higher
irradiation levels, higher temperatures,
and more aggressive media.
In 2006, the United States Department
of Energy summarized materials
research needs for advanced nuclear
systems as follows:
“The fundamental challenge is to
understand and control chemical and
physical phenomena in multi-component
systems from femto-seconds to
millennia, at temperatures to 1,000°C,
and for radiation doses to hundreds of
displacements per atom (dpa).”10
This obviously is no small task. Material
system viability for Generation
IV reactors is the focal point of development
efforts. Using the supercriticial
water reactor (SCWR) as an example,
Figure 2 presents a summary of a materials
qualification program. An extensive
array of testing will be required in order to fully characterize material performance
and meet the time demands
MATERIALS ISSUES FOR ADVANCED FUEL CYCLES
Research and development programs
are underway to investigate the behavior
of candidate materials, operative
damage mechanisms, and potential materials
specifications for Generation IV
reactor designs. Recent work11–14 has
shown accelerated IASCC crack initiation
for materials in simulated SCWR
conditions; however, quantification of
crack growth behavior is still needed.
Ultimately, accurate component specifications
and robust material degradation
models will be needed to facilitate
As summarized by Steve Zinkle,16
critical materials needs for advanced
fuels include spent nuclear fuel reprocessing,
improved fuels for light water
reactors, high temperature gas-cooled
reactors and liquid metal fast burner
reactors, high performance cladding
materials, coolants for heat transfer and
transport and waste form development.
THE PATH FORWARD
In order to achieve higher efficiency
in advanced reactors, research, development,
and qualification efforts are
needed, including those for coated particle
fuel shown in Figure 3. Work is
continuing to investigate metallic, oxide,
carbide, and nitride fuel forms,17
with areas of focus being fuel fabrication
techniques, performance evaluation,
Waste disposal also remains an area
of active research. Long-term nuclear
waste repositories that will require containment
system stability for greater
than 10,000 years are an area of continued
research.18 Corrosion studies for
candidate materials for waste repository
containers are also critical. General
corrosion, hydrogen-induced cracking,
and stress corrosion cracking behavior
are being investigated and data being
extrapolated over the 10,000 year
specified timeframe based upon estimated
environmental conditions (e.g.,
ionic species accumulation, microbial
activity, radiation-induced degradation,
thermal conditions, etc.).19–23
It is obvious that much work is needed.
As summarized by Roberto and
Diaz de la Rubia, “addressing the basic
research needs (of advanced nuclear
systems) offers the potential to revolutionize
the science and technology that
underpins the development of materials.”24 The following section discusses
a few ways that the materials community
can make a difference.
Research and Development Activities
While limited work has been conducted
on materials for nuclear power
in recent decades, marked advancements
in experimental, analytical,
and computational materials science
methods have been made. Ab-initio,
thermodynamic, and multi-scale modeling
efforts are already advancing the
understanding of radiation-induced
microstructures.25–29 Orientation imaging
microscopy has also recently been
used to assist in reliability assessments
and fitness-for-service determinations.30
These and other fundamental
materials science and engineering
methodologies can greatly compliment
the traditional knowledge and research
base for materials used in the nuclear
Communication and Collaboration
Karen Gott summarized it best, stating
that “international experience will
often provide advance warnings. It is
therefore essential to participate in international
exchange of information.”31
International collaboration is at the
heart of research efforts for future reactor
designs. Likewise, it is important
that industrial experience continue to
be shared in an effort to sustain and improve
the current generation of materials
in nuclear power reactors.
With a relative hiatus in training engineers
in nuclear-related fields and
a near-term decrease in institutional
knowledge, there is concern whether
there will be enough qualified experimentalists
and analysts to meet the
challenges facing the nuclear power industry.
Academic, government lab, and
industrial organizations need to participate
in educational efforts, transferring
knowledge of intricate experimental
techniques and operative mechanisms to a new generation of scientists and
Outreach and Advocacy
The development of new materials
for advanced nuclear systems will take
a sustained effort. Governmental advocacy
efforts, such as Materials Information
Luncheons,32 should highlight
the integral role materials play in the
future of nuclear power and the need
for ongoing, stable funding. A portfolio
approach that addresses current nuclear
reactors as well as Generation III+ and
Generation IV designs should also be
advocated. Additionally outreach to the
next generation of scientists and engineers
is needed, emphasizing not only
challenges and opportunities, but also
the marked impact a career in nuclear
power can make on global energy security.
1. J.M. Deutch and E.J. Moniz, “The Nuclear Option,”
Scientific American, 295 (3) September 2006, p. 76.
2. New Reactor Licensing, United States Nuclear
Regulatory Commission, www.nrc.gov/reactors/newreactor-licensing.html.
3. Global Nuclear Energy Partnership, U.S. Department
of Energy, www.gnep.gov/.
4. United States Energy Policy Act of 2005, www.gnep. gov/pdfs/epactActOf2005Final.pdf.
5. P. Spekkans, “Material Degradation—A Nuclear
Utility’s View,” Proc. 13th International Conference on
Environmental Degradation of Materials in Nuclear
Power Systems, ed. T.R. Allen et al. (Toronto, ON,
Canada: Canadian Nuclear Society, 2007).
6. Expert Panel Report on Proactive Materials Degradation
Assessment (NUREG/CR-6923) (Washington,
D.C.: Division of Fuel, Engineering, and Radiological
Research, Office of Nuclear Regulatory Research,
United States Nuclear Regulatory Commission, 2007),
7. P. Ford, “Technical and Management Challenges
Associated with Structural Materials Degradation in
Nuclear Power Reactors in the Future,” in Ref. 5.
8. P. Andresen and M. Morra, “Emerging Issues in
Environmental Cracking in High Temperature Water,”
in Ref. 5.
9. T. Allen, “Scientific and Technological Challenges in
the Development of Materials” (2004 Frederic Joliot
and Otto Hahn Summer School, Cadarache, France,
August 25–September 3, 2004).
10. Basic Research Needs for Advanced Nuclear Energy
Systems (Washington, D.C.: Office of Basic Energy
Science Workshop, U.S. Department of Energy,
July 31 to August 3, 2006), www.sc.doe.gov/bes/reports/list.html.
11. D. Guzonas et al., “Corrosion of Candidate Materials
for Use in a Supercritical CANDU Reactor,” in Ref.
12. S. Teysseyre and G. Was, “Stress Corrosion Cracking
of Neutron-Irradiated Stainless Steels in Supercritcal
Water,” in Ref. 5.
13. E. West et al., “Influence of Irradiation Induced
Microstructure on the Stress Corrosion Cracking Behavior
of Austenitic Alloys in Supercritical Water,” in
14. A. Kruizenga, “Investigation of Stress Corrosion
Cracking in Supercritical Water Using Tubular Sample
Configuration,” in Ref. 5.
15. G. Was, “Materials: The Bridge to Future Nuclear
Power,” Materials Information Luncheon, Washington,
D.C., May 3, 2007. (See T.M. Osman and I. Anderson,
“Reawakening of United States Nuclear Energy: Materials
Challenges for a New Generation of Power Plants,”
Materials Technology@TMS, May 2007, http://materialstechnology. tms.org/TECarticle.asp?articleID=915 to view the presentation slides.)
16. S.J. Zinkle, “Fuel Systems for Future Generations
of Nuclear Power,” Materials Information Luncheon,
Washington, D.C., May 3, 2007 (See T.M. Osman and
I. Anderson, “Reawakening of United States Nuclear
Energy: Materials Challenges for a New Generation
of Power Plants,” Materials Technology@TMS, May
2007, http://materialstechnology.tms.org/TECarticle. asp?articleID=915 to view the presentation slides.)
17. R.N. Hill (Presentation at the GNEP Fuels Performance
Modeling Campaign meeting, Washington,
D.C., 8 November 2006).
18. R. Devanathan and W.J. Weber, “Radiation Effects
in a Model Ceramic for Nuclear Waste Disposal,” JOM,
59 (4) (2007), pp. 32–35.
19. K.G. Mon and F. Hua, “Materials Degradation Issues
in the U. S. High-Level Nuclear Waste Repository,”
Proc. 12th International Conference on Environmental
Degradation of Materials in Nuclear Power Systems—
Water Reactors, ed. T.R. Allen, P.J. King, and L. Nelson
(Warrendale, PA: TMS, 2005), p. 1439.
20. V. Desai, “An Overview of the Yucca Mountain Project,”
JOM, 57 (1) (2005), p. 18.
21. X. He and Y-M. Pan, “The Localized Corrosion Resistance
of Alloy 22,” in this issue.
22. F. Hua et al., “The Effect of Temperature on the
General Corrosion of Alloy 22,” in this issue.
23. R.M. Carranza, “Review on the Degradation Modes
of Alloy 22 in Repository Conditions,” in this issue.
24. J.B. Roberto and T. Diaz de la Rubia, “Basic Research
Needs for Advanced Nuclear Energy Systems,”
JOM, 59 (4) (2007), pp. 16–19.
25. A. Caro et al., “The Computational Modeling of
Alloys at the Atomic Scale: from Ab Initio and Thermodynamics
to Radiation-Induced Heterogeneous
Precipitation,” in Ref. 25, p. 50; also see www.tms.org/pubs/journals/jom/0704/caro-0704.html.
26. B. Wirth, “Multiscale Investigation of the Mechanisms
Controlling Irradiation Effects in Materials and
the Promise of Irradiation Resistant Materials” (Presentation
at the 2007 ASM/TMS Annual Symposium,
GE Global Research Center, Niskayuna, NY, August
27. J. Tucker et al., “Ab Initio-based Radiation-Induced
Segregation Predictions in Fe-Ni-Cr Alloys,” in Ref. 5.
28. D.J. Bacon and Y.N. Osetsky, “The Atomistic-Scale
Modeling of Dislocation-Obstacle Interactions in Irradiate
Metals,” in Ref. 25, pp. 40-45.
29. A. Misra, et al., “The Radiation Damage Tolerance
of Ultra-High Strength Nanolayered Composites,”
JOM, 59 (9) (2007), pp. 62–65.
30. E. Lehockey et al., “New Application of Orientation
Imaging Microscopy (OIM) to the Characterization of
Nuclear Component Failure Modes, Reliability Assessment
and Fitness-for-Service,” in Ref. 5.
31. K. Gott, “Aging Management Requirements in
Sweden” (Presentation at the 13th International Conference
on Environmental Degradation of Materials in
Nuclear Power Systems,” Canadian Nuclear Society,
Whistler, British Columbia, Canada, August 21, 2007).
32. T.M. Osman and I. Anderson, “Reawakening of
United States Nuclear Energy: Materials Challenges
for a New Generation of Power Plants” (Materials
Technology@TMS, May 2007), http://materialstechnology.tms.org/TECarticle.asp?articleID=915.
Todd M. Osman is the technical director at TMS. Dr.
Osman can be reached at email@example.com.