Weld Repair of Irradiated Materials Keith J. Leonard, Zhili Feng, Wei Tang, Roger G. Miller, Brian T. Gibson, Jian Chen, Scarlett R. Clark and Jeremy T. Busby Oak Ridge National Laboratory Greg Frederick, Jonathan Tatman, Artie Peterson and Benjamin Sutton Electric Power Research Institute 4 th International Conference on Nuclear Power Plant Life Management Session 4-1 (presentation IAEA-CN-246-013) October 23 rd – 27 th , 2017 Lyon, France
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Weld Repair of Irradiated Materials
Keith J. Leonard, Zhili Feng, Wei Tang, Roger G. Miller, Brian T. Gibson,
Jian Chen, Scarlett R. Clark and Jeremy T. Busby
Oak Ridge National Laboratory
Greg Frederick, Jonathan Tatman, Artie Peterson and Benjamin Sutton
Electric Power Research Institute
4th International Conference on Nuclear Power Plant Life Management
Session 4-1 (presentation IAEA-CN-246-013)
October 23rd – 27th, 2017
Lyon, France
2 4th – International Conference on Nuclear Power Plant Life Management
Developing advanced weld technologies capable of addressing challenges associated with highly irradiated materials….
Helium generated in reactor internals
throughout the life of the plant, from boron
and nickel transmutations
Tensile stresses generated during the cooling
cycle of the weld exacerbate grain boundary
helium bubble growth, resulting in rupturing.
Diffusion and coalescence of helium occurs
at grain boundaries during welding (i.e.,
temperature in excess of 800°C)
Asano, K., et al., “Weldability of Neutron Irradiated Austenitic
Stainless Steels,” J. Nuclear Materials, Vol 264, 1999.
3 4th – International Conference on Nuclear Power Plant Life Management
Technology Gap: Controlling Grain Boundary Helium Bubble Coalescence During Welding
• Key welding factors to control the helium bubble
migration and growth at the grain boundary
during welding:
1. Controlling welding heat input and weld
thermal cycle (i.e., reduce time above 800°C)
2. Controlling the tensile stress profile during
cooling (during maximum helium bubble
growth period)
• Conventional welding processes can not be
controlled to a level that reduces or eliminates
the He-bubble growth to prevent grain boundary
cracking
200
400
600
800
1000
1200
1400
1600
1800
0 2 4 6 8 10 12 14
Time (sec)T
em
pera
ture
(K
)
-100
-50
0
50
100
150
200
250
300
Str
ess (
MP
a)
He b
ub
ble
rad
ius (
nm
)
Temperature
Stress
He bubble radius
Point of
Interest
Source: Z. Feng ORNL Report
4 4th – International Conference on Nuclear Power Plant Life Management
Advanced Welding Techniques May Provide Solutions to Repair and Mitigation Concerns
• Recent work performed on high helium
content stainless steel produced by power
metallurgy.
• Friction stir welding (FSW) suppressed voids
and cracks due to its solid state low welding
temperature. Huge voids and cracks with fusion welding
Friction stir welding and cross section
5 4th – International Conference on Nuclear Power Plant Life Management
Advanced Welding Process Development
• Overall project objectives:
1. Obtain comprehensive understanding of the metallurgical effects of
welding on irradiated austenitic materials
2. Develop and validate advanced welding processes tailored for repair of
irradiated austenitic materials
3. Provide generic welding specifications and welding thresholds for