2017 Accomplishments – Tritium Aging Studies on Stainless Steel Weldments and Heat-Affected Zones

Technical Report · Wed Jan 31 00:00:00 EST 2018

DOI:https://doi.org/10.2172/1419846· OSTI ID:1419846

Morgan, Michael J. ^[1]; Hitchcock, Dale ^[1]; Krentz, Tim ^[1]; McNamara, Joy ^[1]; Duncan, Andrew ^[1]

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1. Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

In this study, the combined effects tritium and decay helium in forged and welded Types 304L and 21-6-9 stainless steels were studied. To measure these effects, fracture mechanic specimens were thermally precharged with tritium and aged for approximately 17 years to build in decay helium from tritium decay prior to testing. The results are compared to earlier measurements on the same alloys and weldments (4-5, 8-9). In support of Enhanced Surveillance, “Tritium Effects on Materials”, the fracture toughness properties of long-aged tritium-charged stainless-steel base metals and weldments were measured and compared to earlier measurements. The fracture-toughness data were measured by thermally precharging as-forged and as-welded specimens with tritium gas at 34.5 MPa and 350°C and aging for approximately 17 years to build-in decay helium prior to testing. These data result from the longest aged specimens ever tested in the history of the tritium effects programs at Savannah River and the fracture toughness values measured were the lowest ever recorded for tritium-exposed stainless steel. For Type 21-6-9 stainless steel, fracture toughness values were reduced to less than 2-4% of the as-forged values to 41 lbs / in specimens that contained more than 1300 appm helium from tritium decay. The fracture toughness properties of long-aged weldments were also measured. The fracture toughness reductions were not as severe because the specimens did not retain as much tritium from the charging and aging as did the base metals. For Type 304L weldments, the specimens in this study contained approximately 600 appm helium and their fracture toughness values averaged 750 lbs / in. The results for other steels and weldments are reported and additional tests will be conducted during FY18.

• Research Organization: Savannah River Site (SRS), Aiken, SC (United States)
• Sponsoring Organization: USDOE Office of Environmental Management (EM)
• DOE Contract Number: AC09-08SR22470
• OSTI ID: 1419846
• Report Number(s): SRNL-STI-2018-00036; TRN: US1801187
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
STAINLESS STEELS
TRITIUM
HELIUM
FRACTURE PROPERTIES
FRACTURES
HEAT AFFECTED ZONE
mechanical properties
type 304L stainless steel
type 21-6-9 stainless steel
hydrogen embrittlement
J-Integral
helium embrittlement
high-energy-rate forging
neutron scattering
transmission electron microscopy
Kelvin Probe Force microscopy