Repair welding of irradiated 304 stainless steel
- Westinghouse Savannah River Co., Aiken, SC (United States)
The heat-affected zone (HAZ) of repair welds cracked when patches were welded to the tank wall of a nuclear reactor at the Savannah River Site. The cracking was caused by helium embrittlement. The presence of helium generated in irradiated type 304 stainless steel by neutron interaction with boron and nickel impairs weld repair. Welds on material with as little as one part per million helium generated by exposure to a thermal neutron fluence of 1{times}10{sup 21}n/cm{sup 2} developed substantial cracking in the weld heat-affected zone. Evaluation of conventional welds made on type 304 stainless steel containing 1 to 12 appm helium generated by neutron irradiation, or 3 to 220 appm helium generated by tritium decay, demonstrated cracking of the weld heat-affected zones. A newly developed, low penetration, weld overlay technique mitigates cracking by modifying the stress and temperature profile in the weld heat-affected zone. These results demonstrated the potential for a practical welding alternative to mechanical clamping for repair of irradiated material. The helium embrittlement process proceeds with the formation of helium bubbles, followed by agglomeration and growth of bubbles under the influence of the heat and stress of welding. To determine the effect of stress on weld quality in practical situations, a series of test welds with various conditions of mechanical restraint was evaluated. Generally, higher restraint produced greater cracking of the welds.
- DOE Contract Number:
- AC09-89SR18035
- OSTI ID:
- 234166
- Report Number(s):
- CONF-9411168-; ISBN 0-87171-444-2; TRN: IM9624%%207
- Resource Relation:
- Conference: Maintenance and repair welding in power plants V, Orlando, FL (United States), 30 Nov - 2 Dec 1994; Other Information: PBD: 1995; Related Information: Is Part Of Maintenance and repair welding in power plants 5: Proceedings; PB: 269 p.
- Country of Publication:
- United States
- Language:
- English
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