A potential emerging issue concerning repair welding of out-of-core PWR components involving tritium exposure and 3He retention

F. A. Garner; M. N. Gussev; M. Song; G. S. Was

doi:10.1016/j.jnucmat.2025.155774

A potential emerging issue concerning repair welding of out-of-core PWR components involving tritium exposure and ³He retention

F. A. Garner, M. N. Gussev, M. Song, G. S. Was

Nuclear Fuel Element Performance

Research output: Contribution to journal › Article › peer-review

Abstract

This paper identifies a potential but previously unrecognized risk of helium-induced embrittlement and cracking during repair welding of out-of-core pressurized water reactor (PWR) components exposed to tritium-contaminated coolant. While previous weldability concerns centered on ⁴He accumulation in neutron-irradiated alloys located within the in-core or near-core regions, new measurements show that ³He generated by tritium decay can accumulate in out-of-core components. Because hydrogen isotopes readily diffuse to grain boundaries and become trapped there, significant ³He generation at grain boundaries may lead to cracking during weld repairs. Initial data from far-below-core PWR flux thimble tubes confirm the presence of ³He levels above known cracking thresholds for repair welds. These findings indicate that out-of-core regions should be considered when defining safe weld repair windows in reactors operating for 60–100 years.

Original language	English
Article number	155774
Journal	Journal of Nuclear Materials
Volume	610
DOIs	https://doi.org/10.1016/j.jnucmat.2025.155774
State	Published - May 2025

Funding

The authors would like to thank Dr. G.R. Odette (University of California, Santa-Barbara, UCSB) and Dr. M. Griffiths (Queens University, Kingston, Ontario) for valuable discussion, as well as Dr. T.S. Byun (ORNL) and Dr. J. Harp (ORNL) for their insightful reviews. The Texas A&M portion of the work by Garner was partially supported by Triad National Security, LLC, through award M2101345-01-47042-00001. The ORNL portion of the work by Gussev was supported by the Light Water Reactor Sustainability Program (LWRS) Material Research Pathway, US Department of Energy.

Keywords

Extended PWR lifetimes
Helium-induced repair weld cracking
Out-of-core weld repair challenges
Tritium-induced He embrittlement

Access to Document

10.1016/j.jnucmat.2025.155774

Cite this

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title = "A potential emerging issue concerning repair welding of out-of-core PWR components involving tritium exposure and 3He retention",

abstract = "This paper identifies a potential but previously unrecognized risk of helium-induced embrittlement and cracking during repair welding of out-of-core pressurized water reactor (PWR) components exposed to tritium-contaminated coolant. While previous weldability concerns centered on 4He accumulation in neutron-irradiated alloys located within the in-core or near-core regions, new measurements show that 3He generated by tritium decay can accumulate in out-of-core components. Because hydrogen isotopes readily diffuse to grain boundaries and become trapped there, significant 3He generation at grain boundaries may lead to cracking during weld repairs. Initial data from far-below-core PWR flux thimble tubes confirm the presence of 3He levels above known cracking thresholds for repair welds. These findings indicate that out-of-core regions should be considered when defining safe weld repair windows in reactors operating for 60–100 years.",

keywords = "Extended PWR lifetimes, Helium-induced repair weld cracking, Out-of-core weld repair challenges, Tritium-induced He embrittlement",

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AU - Garner, F. A.

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AU - Song, M.

AU - Was, G. S.

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N2 - This paper identifies a potential but previously unrecognized risk of helium-induced embrittlement and cracking during repair welding of out-of-core pressurized water reactor (PWR) components exposed to tritium-contaminated coolant. While previous weldability concerns centered on 4He accumulation in neutron-irradiated alloys located within the in-core or near-core regions, new measurements show that 3He generated by tritium decay can accumulate in out-of-core components. Because hydrogen isotopes readily diffuse to grain boundaries and become trapped there, significant 3He generation at grain boundaries may lead to cracking during weld repairs. Initial data from far-below-core PWR flux thimble tubes confirm the presence of 3He levels above known cracking thresholds for repair welds. These findings indicate that out-of-core regions should be considered when defining safe weld repair windows in reactors operating for 60–100 years.

AB - This paper identifies a potential but previously unrecognized risk of helium-induced embrittlement and cracking during repair welding of out-of-core pressurized water reactor (PWR) components exposed to tritium-contaminated coolant. While previous weldability concerns centered on 4He accumulation in neutron-irradiated alloys located within the in-core or near-core regions, new measurements show that 3He generated by tritium decay can accumulate in out-of-core components. Because hydrogen isotopes readily diffuse to grain boundaries and become trapped there, significant 3He generation at grain boundaries may lead to cracking during weld repairs. Initial data from far-below-core PWR flux thimble tubes confirm the presence of 3He levels above known cracking thresholds for repair welds. These findings indicate that out-of-core regions should be considered when defining safe weld repair windows in reactors operating for 60–100 years.

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KW - Helium-induced repair weld cracking

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