Types of corrosion in nuclear systems. Causes and remedies for material degradation problems in nuclear reactors.

1. CORROSION IN NUCLEAR SYSTEMS
Nuzhet Nihaar Nasir Ahamed
April, 2017

2. Outline of
presentation
• Why Nuclear Power?
• How a nuclear reactor works?
• Materials used in reactors
• Challenges faced by reactors
• Why is it important to study corrosion?
• Types of corrosion
• Examples
• Ways to reduce corrosion
• Future research directions

3. Why nuclear power?
Nuclear energy – Splitting of heavy nuclei (U235) into small nuclei to produce
large amount of energy
• Carbon free source
• Less pollution
• Massive energy generation
• No CO2 emissions
• Reduces green house effect
http://www.komorasns.cz/post/archive/10

4. Countries using
Nuclear Power
Nuclear Share of Electricity Generation in 2016". IAEA. 19 April 2017. Retrieved 19 April 2017.

5. How a nuclear reactor works
http://keepvid.com/?url=https%3A%2F%2Fwww.youtube.com%2Fwatch%3Fv%3DQthg5xE196w

6. Challenges faced by reactors
• High temperature inside the reactor
• Corrosive environment due to coolants
- High temperature water
- Liquid metals
- Gas
- Liquid salts
• Intense field of high energy neutrons
• Damage from high energy particles released
• High stress states due to radiation
• Complex in reactor fuel behavior
Todd Allen, Jeremy Busby, Mitch Meyer, David Petti, Materials Challenges for nuclear systems, Materials today, December 2010 , Volume 13, number 12.

7. Why is it
important
to study
corrosion?
• Reduces performance
• Sudden failure of the plant
• Nuclear radiation is hazardous
• Present and future generations may be
affected due to radioactive nuclear radiation

8. Types of
corrosion in
nuclear
systems
• Stress corrosion cracking (SCC)
• Irradiation-assisted stress corrosion cracking
(IASCC)
• Environmentally assisted cracking (EAC)
• Intergranular attack(IGA)
• Flow-assisted corrosion (FAC)
• General corrosion (GC)
• Ammonia corrosion (AC) and
• Microbiologically influenced corrosion (MIC).
François Cattant, Didier Crusset, and Damien Féron3, Corrosion issues in nuclear industry today,
Materials today, October 2008,Volume 11, Number 10, Open access under CC BY-NC-ND license

9. Stress Corrosion
Cracking
• Corrosion due to mechanical stress
• For SCC to occur the requirements are
• A susceptible material
• an environment that causes SCC for
that material
• sufficient tensile stress to induce SCC
• Mechanisms involved
• Film Rupture mechanism
• Adsorption mechanism
Roger C. Newman , Stress-Corrosion Cracking Mechanisms, Chapter 11, Corrosion Mechanisms in Theory and Practice, Third Edition, 2011, Pages 499–

10. Mechanisms in SCC
• Film Rupture mechanism
• Plastic deformation of metal creates active
sites
• Active sites under stress promote propagation
of cracks
• Adsorption mechanism
• Involves adsorption of environmental species
• It lowers the bond strength
• It lowers the stress required for cleavage
• Crack propagation is dependent on rate of
arrival of species at the surface
SCC due to species adsorption
Roger C. Newman , Stress-Corrosion Cracking Mechanisms, Chapter 11, Corrosion Mechanisms in Theory and Practice, Third Edition, 2011, Pages 499–
544

11. Examples of SCC
• 15% Cr–Ni alloys
• alloy 600 and 182 undergo SCC in
• steam generator tubes,
• RPV head penetrations and
• pressurizer nozzles
• Remedies
• Use replacement alloys like
• alloys (690, 52, 152)
• higher Cr content.
SCC on steam generator tube made of alloy 600

12. Irradiation-assisted stress corrosion cracking
(IASCC)
• The material becomes susceptible to
SCC after neutron embrittlement
• Examples:
• 316 SS bolts in the reactor pressure
vessel internals
• Core internal structures and supports
• Baffle bolt
IASCC in PWR baffle bolts
François Cattant, Didier Crusset, and Damien Féron3, Corrosion issues in nuclear industry today, Materials today, October 2008,Volume 11, Number 10, Open access under
CC BY-NC-ND license

13. Environmentally
assisted cracking
(EAC)
• SCC is also a form of EAC.
• Also called corrosion fatigue.
• Examples:
• EAC of steels near sea water
• Especially when crack growth rates are
more than three times those observed
in air
• 403 turbine blades
François Cattant, Didier Crusset, and Damien Féron3, Corrosion issues in nuclear industry today,
Materials today, October 2008,Volume 11, Number 10, Open access under CC BY-NC-ND license

14. Intergranular attack(IGA)
• Uniform attack of grain boundaries
• Can occur without any stress
• But stress can increase IGA rate
• When stresses are high enough, IGA turns to SCC
• Examples
• Occurs in flow-restricted areas of steam generators
• Seen when mill-annealed alloy 600 tubes are used
• Remedies
• Replace alloy 600 with alloy 690
François Cattant, Didier Crusset, and Damien Féron3, Corrosion issues in nuclear industry today, Materials today, October 2008,Volume 11, Number 10, Open access under
CC BY-NC-ND license

15. Flow-assisted corrosion
(FAC)
• Requirements
• Water droplet impingement
• Presence of abrasive magnetite particles
• May lead to pipe leak or burst
• Remedies
• Adjusting the pH of the water
• Increasing the Cr content of the carbon steel
pipes
• Using SSs
François Cattant, Didier Crusset, and Damien Féron3, Corrosion issues in nuclear industry today, Materials today, October 2008,Volume 11, Number 10, Open access under
CC BY-NC-ND license

16. General corrosion (GC)
• 3 major examples of GC are
• GC of fuel cladding
• Formation of Zircon where Zr picks up Oxygen from the environment
• Remedy
• Use better GC resistant Zr alloys
• GC of steam generator tubes made of Ni alloys
• These tubes release Ni and can turn it into radioactive Co
• Remedy
• Chemically condition reactor water
• GC of feedwater carbon steel piping
• Results in loss of performance and power output
• Remedy
• Chemically condition the water using Ammonia or amines
François Cattant, Didier Crusset, and Damien Féron3, Corrosion issues in nuclear industry today, Materials today, October 2008,Volume 11, Number 10, Open access under
CC BY-NC-ND license

17. Microbiologically
influenced corrosion
• May occur in systems with
• Natural waters
• Stagnant lines conditioned with phosphate based chemicals
• These conditions are favorable for anaerobic bacteria development
• Examples:
• Pitting in SS reactor pipes
• Weld affected zones
• Remedy
• Replace steels with composite materials
François Cattant, Didier Crusset, and Damien Féron3, Corrosion issues in nuclear industry today, Materials today, October 2008,Volume 11, Number 10, Open access under
CC BY-NC-ND license

18. Some more examples
of nuclear systems
corrosion
Naus, D. J., Primer on durability of nuclear power plant reinforced concrete structures – A review of pertinent factors, NUREG/CR-6927
(ORBL/TM-2006/529),Oak Ridge National Laboratory, Oak Ridge, Tennessee, February 2007.

19. Ways to
reduce
corrosion
• Consider predictive scientific models before
selecting any material
• Use thin and highly corrosion resistant
materials like
• Carbon steel
• Stainless steels
• Ni-based alloys
• Ti alloys
• Cu in reducing environments free of
complexing agents
François Cattant, Didier Crusset, and Damien Féron3, Corrosion issues in nuclear industry today,
Materials today, October 2008,Volume 11, Number 10, Open access under CC BY-NC-ND license

20. Future Research directions
• Develop generation IV reactors
• Active research is going on to study wide range of
new materials like
• refractory alloys based on Nb, Ta, Mo or W
• oxide dispersion strengthened alloys (ODS)
• ceramics and
• composites such as SiCSiC,
• advanced coatings, etc
These are the
materials of
tomorrow’s nuclear
reactors
Carpenter, D., Assessment of innovative fuel designs for high performance light water reactors, M.S. Thesis, Massachusetts Institute of Technology,
2006

21. REFERENCES
[1] Comby Bruno, The benefits of Nuclear energy, Environmentalists For Nuclear Energy, TNR
Editions, 350 pages, (available at www.comby.org click on the Union Jack then on “Books”)
[2] Xiao Liu, Sitian Cheng, Hong Liu, Sha Hu, Daqiang Zhang and Huansheng Ning ,*A Survey
on Gas Sensing Technology, Sensors 2012, 12, 9635-9665
[3] François Cattant, Didier Crusset, and Damien Féron3, Corrosion issues in nuclear industry
today, Materials today, October 2008,Volume 11, Number 10, Open access under CC BY-NC-
ND license.
[4] World Nuclear Organization, Nuclear power reactors fact sheet, September 2010. Available
from www.world-nuclear.org/info/inf32.html.
[5] Todd Allen, Jeremy Busby, Mitch Meyer, David Petti, Materials Challenges for nuclear
systems, Materials today, December 2010 , Volume 13, number 12.
[6] Vaillant, F., et al., Assessment of PWSCC Resistance of Alloy 690: Overview of Laboratory
Results and Field Experience. Presented at EPRI International Conference on PWSCC of Alloy
600, Santa Anna Pueblo, USA, March 2005
[7] Steven J. Zinkle , Jeremy T. Busby, Structural materials for fission & fusion energy, Materials
Today, Volume 12, Issue 11, November 2009, Pages 12–19
[8] Roger C. Newman , Stress-Corrosion Cracking Mechanisms, Chapter 11, Corrosion
Mechanisms in Theory and Practice, Third Edition, 2011, Pages 499–544.
[9] Naus, D. J., Primer on durability of nuclear power plant reinforced concrete structures – A
review of pertinent factors, NUREG/CR-6927 (ORBL/TM-2006/529),Oak Ridge National
Laboratory, Oak Ridge, Tennessee, February 2007.
[10] Naus, D. J., et al., Final report inspection of aged/degraded containments program,
ORNL/TM-2005/170, Oak Ridge National Laboratory, Oak Ridge, Tennessee,August 2005.
[11] Allen, T.R. & Busby, J.T., Radiation damage concerns for extended light water reactor
service, The Journal of The Minerals, Metals & Materials Society (2009) 61: 29.
[12] World Nuclear Organization, Nuclear power reactors fact sheet, September 2010. Available
from www.world-nuclear.org/info/inf32.html.
[13] Carpenter, D., Assessment of innovative fuel designs for high performance light water
reactors, M.S. Thesis, Massachusetts Institute of Technology, 2006.