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HYDROGEN EFFECTS ON THE FRACTURE TOUGHNESS PROPERTIES OF FORGED STAINLESS STEELS

Description: The effect of hydrogen on the fracture toughness properties of Types 304L, 316L and 21-6-9 forged stainless steels was investigated. Fracture toughness samples were fabricated from forward-extruded forgings. Samples were uniformly saturated with hydrogen after exposure to hydrogen gas at 34 MPa or 69 and 623 K prior to testing. The fracture toughness properties were characterized by measuring the J-R behavior at ambient temperature in air. The results show that the hydrogen-charged steels have fracture toughness values that were about 50-60% of the values measured for the unexposed steels. The reduction in fracture toughness was accompanied by a change in fracture appearance. Both uncharged and hydrogen-charged samples failed by microvoid nucleation and coalescence, but the fracture surfaces of the hydrogen-charged steels had smaller microvoids. Type 316L stainless steel had the highest fracture toughness properties and the greatest resistance to hydrogen degradation.
Date: March 28, 2008
Creator: Morgan, M
Partner: UNT Libraries Government Documents Department

2012 ACCOMPLISHMENTS - TRITIUM AGING STUDIES ON STAINLESS STEELS

Description: This report summarizes the research and development accomplishments during FY12 for the tritium effects on materials program. The tritium effects on materials program is designed to measure the long-term effects of tritium and its radioactive decay product, helium-3, on the structural properties of forged stainless steels which are used as the materials of construction for tritium reservoirs. The FY12 R&D accomplishments include: (1) Fabricated and Thermally-Charged 150 Forged Stainless Steel Samples with Tritium for Future Aging Studies; (2) Developed an Experimental Plan for Measuring Cracking Thresholds of Tritium-Charged-and-Aged Steels in High Pressure Hydrogen Gas; (3) Calculated Sample Tritium Contents For Laboratory Inventory Requirements and Environmental Release Estimates; (4) Published report on “Cracking Thresholds and Fracture Toughness Properties of Tritium-Charged-and-Aged Stainless Steels”; and, (5) Published report on “The Effects of Hydrogen, Tritium, and Heat Treatment on the Deformation and Fracture Toughness Properties of Stainless Steels”. These accomplishments are highlighted here and references given to additional reports for more detailed information.
Date: January 31, 2013
Creator: Morgan, M.
Partner: UNT Libraries Government Documents Department

TRITIUM AGING EFFECTS ON THE FRACTURE TOUGHNESS PROPERTIES OF FORGED STAINLESS STEEL

Description: The fracture toughness properties of Type 21-6-9 stainless steel were measured for forgings in the unexposed, hydrogen-exposed, and tritium-exposed-and-aged conditions. Fracture toughness samples were cut from conventionally-forged and high-energy-rate-forged forward-extruded cylinders and mechanically tested at room temperature using ASTM fracture-toughness testing procedures. Some of the samples were exposed to either hydrogen or tritium gas (340 MPa, 623 K) prior to testing. Tritium-exposed samples were aged for up to seven years and tested periodically in order to measure the effect on fracture toughness of {sup 3}He from radioactive tritium decay. The results show that hydrogen-exposed and tritium-exposed samples had lower fracture- toughness values than unexposed samples and that fracture toughness decreased with increasing decay {sup 3}He content. Forged steels were more resistant to the embrittling effects of tritium and decay {sup 3}He than annealed steels, although their fracture-toughness properties depended on the degree of sensitization that occurred during processing. The fracture process was dominated by microvoid nucleation, growth and coalescence; however, the size and spacing of microvoids on the fracture surfaces were affected by hydrogen and tritium with the lowest-toughness samples having the smallest microvoids and finest spacing.
Date: April 14, 2008
Creator: Morgan, M
Partner: UNT Libraries Government Documents Department

TRITIUM AGING EFFECTS ON THE FRACTURE TOUGHNESS PROPERTIES OF STAINLESS STEEL BASE METAL AND WELDS

Description: Tritium reservoirs are constructed from welded stainless steel forgings. While these steels are highly resistant to the embrittling effects of hydrogen isotopes and helium from tritium decay; they are not immune. Tritium embrittlement is an enhanced form of hydrogen embrittlement because of the presence of helium-3 from tritium decay which nucleates as nanometer-sized bubbles on dislocations, grain boundaries, and other microstructural defects. Steels with decay helium bubble microstructures are hardened and less able to deform plastically and become more susceptible to embrittlement by hydrogen and its isotopes. Ductility, elongation-to-failure, and fracture toughness are reduced by exposures to tritium and the reductions increase with time as helium-3 builds into the material from tritium permeation and radioactive decay. Material and forging specifications have been developed for optimal material compatibility with tritium. These specifications cover composition, mechanical properties, and select microstructural characteristics like grain size, flow-line orientation, inclusion content, and ferrite distribution. For many years, the forming process of choice for reservoir manufacturing was high-energy-rate forging (HERF), principally because the DOE forging facility owned only HERF hammers. Today, some reservoir forgings are being made that use a conventional, more common process known as press forging (PF or CF). One of the chief differences between the two forging processes is strain rate: Conventional hydraulic or mechanical forging presses deform the metal at 4-8 ft/s, about ten-fold slower than the HERF process. The material specifications continue to provide successful stockpile performance by ensuring that the two forging processes produce similar reservoir microstructures. While long-term life storage tests have demonstrated the general tritium compatibility of tritium reservoirs, fracture-toughness properties of both conventionally forged and high-energy-rate forged are needed for designing and establishing longer tritium-reservoir lifetimes, ranking materials, and, potentially, for qualifying new forging vendors or processes. Measurements on the effects of tritium and decay helium on ...
Date: July 30, 2009
Creator: Morgan, M.
Partner: UNT Libraries Government Documents Department

The effects of hydrogen on the fracture toughness properties of upset welded stainless steel

Description: The effects of hydrogen on the fracture toughness properties of upset welded Type 304L stainless steel were measured and compared to those measured previously for as-received and as-welded steels. The results showed that the upset welded steels had good fracture toughness properties, but values were lower than the as-received material. The fracture toughness value of the base material was 6420 in-lbs/sq. in., while the welded steels averaged 3660 in-lbs/sq. in. Hydrogen exposure lowered the fracture toughness values of the as-received steel by 43 % to 3670 in-lbs/sq. in. and the welded steels by 21 % to 2890 in-lbs/sq. in. The fracture morphologies of the unexposed steels showed that ductile fracture occurred by the microvoid nucleation and growth process. The size of the microvoids on the fracture surfaces of the welded steels were much smaller and more closely spaced that those found on the base material fracture surfaces. The change in the size and spacing of the microvoids indicates that the fracture toughness properties of the welded steels were lower than the base steels because of the higher concentration of microscopic precipitates on the weld plane. The welds examined thus far have been {open_quotes}good{close_quotes} welds and the presence of these precipitates was not apparent in standard {open_quotes}low{close_quotes}-magnification metallographic sections of the weld planes. The results indicate that hydrogen did not weaken greatly the solid-state welds but that other inclusions or impurities present prior to welding did. Improvements in surface cleaning and preparation prior to welding should be explored as a way to improve the strength of solid-state welded joints.
Date: June 1, 1995
Creator: Morgan, M.T.
Partner: UNT Libraries Government Documents Department

Electric-Discharge Machining Techniques for Evaluating Tritium Effects on Materials

Description: In this investigation, new ways to evaluate the long-term effects of tritium on the structural properties of components were developed. Electric-discharge machining (EDM) techniques for cutting tensile and fracture toughness samples from tritium exposed regions of returned reservoirs were demonstrated. An existing electric discharge machine was used to cut sub-size tensile and fracture toughness samples from the inside surfaces of reservoir mockups. Tensile properties from the EDM tensile samples were similar to those measured using full-size samples cut from similar stock. Although the existing equipment could not be used for machining tritium-exposed hardware, off-the shelf EDM units are available that could. With the right equipment and the required radiological controls in place, similar machining and testing techniques could be used to directly measure the effects of tritium on the properties of material cut from reservoir returns. Stress-strain properties from tritium-exposed reservoirs would improve finite element modeling of reservoir performance because the data would be representative of the true state of the reservoir material in the field. Tensile data from samples cut directly from reservoirs would also complement existing shelf storage and burst test data of the Life Storage Program and help answer questions about a specific reservoir's processing history and properties.
Date: November 7, 2003
Creator: Morgan, M. J.
Partner: UNT Libraries Government Documents Department

The effects of hydrogen isotopes and helium on the tensile properties of 21-6-9 stainless steel

Description: High-energy-rate-forged (HERF) stainless steels are used as the materials of construction for tritium and deuterium reservoirs. Hydrogen and helium, the decay product of tritium, are known to embrittle stainless steels (1--4). The resistance to hydrogen and helium induced embrittlement is relatively good for HERF stainless steels when compared to annealed stainless steels due to their high number density of dislocations, which act as traps for hydrogen and helium. However, the degree of the embrittlement in these materials can vary considerably because of microstructure and yield strength variations introduced during the forging process. In this study the effect of hydrogen and tritium on the room temperature tensile properties of 21-6-9 stainless steel was measured as a function of HERF yield strength in the range of 500 to 918 MPa. The effect of a microstructures was studied also by conducting tensile tests with both HERF samples and annealed samples.
Date: January 1, 1990
Creator: Morgan, M.J.
Partner: UNT Libraries Government Documents Department

The effects of tritium and decay helium on the fracture toughness properties of stainless steels

Description: J-integral fracture mechanics techniques and scanning electron microscopy observations were used to investigate the effects of tritium and its decay product, helium-3, on Types 304L, 316L, 21-6-9, A286, and JBK-75 (Modified A286) stainless steels. Tritium-exposed samples of each steel had lower fracture toughness values and less resistance to stable crack growth than control samples. Type 316L stainless steel was more resistant to the embrittling effects of tritium and decay helium than the other steels.
Date: January 1, 1991
Creator: Morgan, M.J.
Partner: UNT Libraries Government Documents Department

MICROSTRUCTURAL FEATURES AFFECTING PROPERTIES AND AGING OF TRITIUM-EXPOSED AUSTENTIC STAINLESS STEEL

Description: A project to implement a life-cycle engineering approach to tritium reservoirs has been initiated through the DOE - Technology Investment Projects. The first task in the project was to develop a comprehensive list of microstructural features that impact the aging performance of the tritium reservoirs. Each of the participating sites (SRNL, SNL, LANL, KCP) independently developed a list of features deemed integral to tritium reservoir performance based upon operational and design experience. An integrated list of features was ultimately developed by the project team that could be included in the modeling process. The features of interest were chosen based upon their impact on the following key factors in controlling crack growth: (1) the H/He solubility or diffusivity within the materials, (2) the stress/strain state at the crack tip, (3) material threshold for crack extension, and (4) microstructure based fracture distance, commonly estimated by grain size for intergranular fracture. Wherever possible, key references were identified to substantiate the effects on the tritium embrittlement phenomenon of the various microstructural features. Each of these features was chosen based upon their impact to the cracking phenomenon of interest. The features chosen were typically associated with orientation, morphology, and distribution of phases and inclusions, grain and grain boundary characteristics, and initial mechanical properties. Phase and inclusion content and distribution were determined to play a key role in the cracking phenomenon. The presence of {delta}-ferrite in the weld and strain-induced martensite in the primarily austenitic matrix are known to facilitate hydrogen diffusion and the interfaces have been observed as a hydrogen assisted fracture path. The morphology, size, and distribution of inclusions and precipitates, particularly on the grain boundaries, influence cracking since they trap hydrogen and facilitate intergranular fracture. Compositional banding and nitrogen concentration were also included as features of interest. The microstructural features of interest included ...
Date: January 10, 2004
Creator: Subramanian, K & Michael Morgan, M
Partner: UNT Libraries Government Documents Department

PERMEABILITY, SOLUBILITY AND DIFFUSIVITY OF HYDROGEN ISOTOPES IN STAINLESS STEELS AT HIGH GAS PRESSURES

Description: The Defense Waste Processing Facility (DWPF) is about to process High Level Waste (HLW) Sludge Batch 4 (SB4). This sludge batch is high in alumina and nepheline can crystallize readily depending on the glass composition. Large concentrations of crystallized nepheline can have an adverse effect on HLW glass durability. Several studies have been performed to study the potential for nepheline formation in SB4. The Phase 3 Nepheline Formation study of SB4 glasses examined sixteen different glasses made with four different frits. Melt rate experiments were performed by the Process Science and Engineering Section (PS&E) of the Savannah River National Laboratory (SRNL) using the four frits from the Phase 3 work, plus additional high B2O3/high Fe2O3 frits. Preliminary results from these tests showed the potential for significant improvements in melt rate for SB4 glasses using a higher B2O3-containing frit, particularly Frit 503. The main objective of this study was to investigate the durability of SB4 glasses produced with a high B2O3 frit likely to be recommended for SB4 processing. In addition, a range of waste loadings (WLs) was selected to continue to assess the effectiveness of a nepheline discriminator in predicting concentrations of nepheline crystallization that would be sufficient to influence the durability response of the glass. Five glasses were selected for this study, covering a WL range of 30 to 50 wt% in 5 wt% increments. The Frit 503 glasses were batched and melted. Specimens of each glass were heat-treated to simulate cooling along the centerline of a DWPF-type canister (ccc) to gauge the effects of thermal history on product performance. Visual observations on both quenched and ccc glasses were documented. A representative sample from each glass was submitted to the SRNL Process Science Analytical Laboratory (PSAL) for chemical analysis to confirm that the as-fabricated glasses corresponded to the defined ...
Date: September 12, 2005
Creator: Subramanian, K & Michael Morgan, M
Partner: UNT Libraries Government Documents Department

THE EFFECTS OF HYDROGEN, TRITIUM, AND HEAT TREATMENT ON THE DEFORMATION AND FRACTURE TOUGHNESS PROPERTIES OF STAINLESS STEEL

Description: The deformation and fracture toughness properties of forged stainless steels pre-charged with tritium were compared to the deformation and fracture toughness properties of the same steels heat treated at 773 K or 873 K and precharged with hydrogen. Forged stainless steels pre-charged with tritium exhibit an aging effect: Fracture toughness values decrease with aging time after precharging because of the increase in concentration of helium from tritium decay. This study shows that forged stainless steels given a prior heat treatment and then pre-charged with hydrogen also exhibit an aging effect: Fracture toughness values decrease with increasing time at temperature. A microstructural analysis showed that the fracture toughness reduction in the heat-treated steels was due to patches of recrystallized grains that form within the forged matrix during the heat treatment. The combination of hydrogen and the patches of recrystallized grains resulted in more deformation twinning. Heavy deformation twinning on multiple slip planes was typical for the hydrogen-charged samples; whereas, in the non-charged samples, less twinning was observed and was generally limited to one slip plane. Similar effects occur in tritium pre-charged steels, but the deformation twinning is brought on by the hardening associated with decay helium bubbles in the microstructure.
Date: September 6, 2013
Creator: Morgan, M.; Tosten, M. & Chapman, G.
Partner: UNT Libraries Government Documents Department

HYDROGEN EFFECTS ON FRACTURE TOUGHNESS OF TYPE 316L STAINLESS STEEL FROM 175 K TO 425 K

Description: The effects of hydrogen on the fracture-toughness properties of Type 316L stainless steel from 175 K to 425 K were measured. Fracture-toughness samples were fabricated from Type 316L stainless steel forgings and hydrogen-charged with hydrogen at 34 MPa and 623 K for two weeks prior to testing. The effect of hydrogen on the J-Integral vs. crack extension behavior was measured at various temperatures by fracturing non-charged and hydrogen-charged samples in an environmental chamber. Hydrogen-charged steels had lower toughness values than non-charged ones, but still retained good toughness properties. The fracture-toughness values of hydrogen-charged samples tested near ambient temperature were about 70% of non-charged values. For hydrogen-charged samples tested at 225 K and 425 K, the fracture-toughness values were 50% of the non-charged values. In all cases, fracture occurred by microvoid nucleation and coalescence, although the hydrogen-charged samples had smaller and more closely spaced microvoids. The results suggest that hydrogen effects on toughness are greater at 225 K than they are at ambient temperature because of strain-induced martensite formation. At 425 K, the hydrogen effects on toughness are greater than they are at ambient temperature because of the higher mobility of hydrogen.
Date: May 4, 2009
Creator: Morgan, M & Glenn Chapman, G
Partner: UNT Libraries Government Documents Department

HYDROGEN EFFECTS ON STRAIN-INDUCED MARTENSITE FORMATION IN TYPE 304L STAINLESS STEEL

Description: Unstable austenitic stainless steels undergo a strain-induced martensite transformation. The effect of hydrogen on this transformation is not well understood. Some researchers believe that hydrogen makes the transformation to martensite more difficult because hydrogen is an austenite stabilizer. Others believe that hydrogen has little or no effect at all on the transformation and claim that the transformation is simply a function of strain and temperature. Still other researchers believe that hydrogen should increase the ability of the metal to transform due to hydrogen-enhanced dislocation mobility and slip planarity. While the role of hydrogen on the martensite transformation is still debated, it has been experimentally verified that this transformation does occur in hydrogen-charged materials. What is the effect of strain-induced martensite on hydrogen embrittlement? Martensite near crack-tips or other highly strained regions could provide much higher hydrogen diffusivity and allow for quicker hydrogen concentration. Martensite may be more intrinsically brittle than austenite and has been shown to be severely embrittled by hydrogen. However, it does not appear to be a necessary condition for embrittlement since Type 21-6-9 stainless steel is more stable than Type 304L stainless steel but susceptible to hydrogen embrittlement. In this study, the effect of hydrogen on strain-induced martensite formation in Type 304L stainless steel was investigated by monitoring the formation of martensite during tensile tests of as-received and hydrogen-charged samples and metallographically examining specimens from interrupted tensile tests after increasing levels of strain. The effect of hydrogen on the fracture mechanisms was also studied by examining the fracture features of as-received and hydrogen-charged specimens and relating them to the stress-strain behavior.
Date: December 11, 2008
Creator: Morgan, M & Ps Lam, P
Partner: UNT Libraries Government Documents Department

TRITIUM RESERVOIR STRUCTURAL PERFORMANCE PREDICTION

Description: The burst test is used to assess the material performance of tritium reservoirs in the surveillance program in which reservoirs have been in service for extended periods of time. A materials system model and finite element procedure were developed under a Savannah River Site Plant-Directed Research and Development (PDRD) program to predict the structural response under a full range of loading and aged material conditions of the reservoir. The results show that the predicted burst pressure and volume ductility are in good agreement with the actual burst test results for the unexposed units. The material tensile properties used in the calculations were obtained from a curved tensile specimen harvested from a companion reservoir by Electric Discharge Machining (EDM). In the absence of exposed and aged material tensile data, literature data were used for demonstrating the methodology in terms of the helium-3 concentration in the metal and the depth of penetration in the reservoir sidewall. It can be shown that the volume ductility decreases significantly with the presence of tritium and its decay product, helium-3, in the metal, as was observed in the laboratory-controlled burst tests. The model and analytical procedure provides a predictive tool for reservoir structural integrity under aging conditions. It is recommended that benchmark tests and analysis for aged materials be performed. The methodology can be augmented to predict performance for reservoir with flaws.
Date: November 10, 2005
Creator: Lam, P.S. & Morgan, M.J
Partner: UNT Libraries Government Documents Department

TRANSMISSION ELECTRON MICROSCOPY STUDY OF HELIUM BEARING FUSION WELDS

Description: A transmission electron microscopy (TEM) study was conducted to characterize the helium bubble distributions in tritium-charged-and-aged 304L and 21Cr-6Ni-9Mn stainless steel fusion welds containing approximately 150 appm helium-3. TEM foils were prepared from C-shaped fracture toughness test specimens containing {delta} ferrite levels ranging from 4 to 33 volume percent. The weld microstructures in the low ferrite welds consisted mostly of austenite and discontinuous, skeletal {delta} ferrite. In welds with higher levels of {delta} ferrite, the ferrite was more continuous and, in some areas of the 33 volume percent sample, was the matrix/majority phase. The helium bubble microstructures observed were similar in all samples. Bubbles were found in the austenite but not in the {delta} ferrite. In the austenite, bubbles had nucleated homogeneously in the grain interiors and heterogeneously on dislocations. Bubbles were not found on any austenite/austenite grain boundaries or at the austenite/{delta} ferrite interphase interfaces. Bubbles were not observed in the {delta} ferrite because of the combined effects of the low solubility and rapid diffusion of tritium through the {delta} ferrite which limited the amount of helium present to form visible bubbles.
Date: December 12, 2008
Creator: Tosten, M & Michael Morgan, M
Partner: UNT Libraries Government Documents Department

Scrubbing of iodine from gas streams with mercuric nitrate-conversion of mercuric iodate product to barium iodate for fixation in concrete

Description: A bench-scale model of a mercuric nitrate scrubber for removal of iodine from off-gas streams was constructed and operated in conjunction with a mercuric iodate-to-barium iodate conversion system to determine the feasibility of total recycle of all processing solutions. The two main aspects of the system examined were (1) the extent of contamination of the barium iodate product, and (2) the effect of cross-contamination of various process solutions on the efficiency of the process. The experimental evidence obtained indicates that, with appropriate control, all solutions can be recycled without significant contamination of the product that would be harmful to the host concrete or to the environment. Mercury contamination was found to be less than or equal to 0.5 wt % of the barium iodate product. The most significant effect on system efficiency was determined to be barium hydroxide contamination of the sodium hydroxide solution used to convert mercuric iodate to sodium iodate. A mole ratio of barium hydroxide to sodium hydroxide of about 1:225 caused a decrease in conversion efficiency of about 45%.
Date: June 1, 1980
Creator: Rogers, G.C.; Moore, J.G. & Morgan, M.T.
Partner: UNT Libraries Government Documents Department

The Effects of Helium Bubble Microstructure on Ductility in Annealed and HERF 21Cr-6Ni-9Mn Stainless Steel

Description: This study examined the effects of microstructure on the ambient temperature embrittlement from hydrogen isotopes and decay helium in 21Cr-6Ni-9Mn stainless steel. Hydrogen and tritium-exposed 21Cr-6Ni-9Mn stainless steel tensile samples were pulled to failure and then characterized by transmission electron microscopy (TEM) and optical microscopy. This study determined that ductility differences between annealed and high-energy-rate-forged (HERF) stainless steel containing tritium and its decay product, helium, could be related to differences in the helium bubble microstructures. The HERF microstructures were more resistant to tritium-induced embrittlement than annealed microstructures because the high number density of helium bubbles on dislocations trap tritium within the matrix and away from the grain boundaries.
Date: January 1, 1998
Creator: Tosten, M.H. & Morgan, M.J.
Partner: UNT Libraries Government Documents Department

Savannah River Restart Peer Evaluation Program final examination report

Description: During the period of August 13, 1990 through September 6, 1991 the Savannah River Peer Evaluation Program was administered during three distinct phases to 73 certified Central Control Room Operators, Central Control Room Supervisors, and Shift Technical Engineers assigned to the K Reactor, on the Savannah River Site (SRS). This program was conceived and developed by the Department of Energy (DOE) and it's implementation satisfies recommendations made by the Defense Nuclear Facilities Safety Board. The review identified both strengths and weaknesses of the procedures and personnel.
Date: December 1, 1991
Creator: Morgan, M.P. & Draper, D.G.
Partner: UNT Libraries Government Documents Department

Mapping of upper electronic reaction surfaces by tuned laser photolysis and by absorption and emission spectroscopies

Description: Potential energy surfaces for photorotamerization of two intramolecularly hydrogen-bonded molecules, o-hydroxybenzaldehyde (OHBA) and methyl salicylate (MS), isolated in cryogenic matrices have been spectroscopically mapped. In addition, the external heavy atom effect of krypton and xenon matrices on the coupling between the S{sub 1} and T{sub 1} surfaces of 4-(dimethylamino)benzonitrile has been examined. Heavy atom matrices are known to increase rates of spin-forbidden processes. The phosphorescence intensity of DMABN increases in krypton and xenon matrices, while the fluorescence intensity, and phosphorescence and fluorescence lifetimes, decrease. These effects are interpreted in terms of a model in which the phosphorescence rate constant increases 300-fold in xenon compared to argon, while the rate constants for intersystem crossing and nonradiative relaxation from the triplet state increase by factors of less than 5. Lifetime measurements in argon matrices doped with heavy atoms indicate that even one heavy atom neighbor has a significant effect on both singlet and triplet lifetimes. 78 refs., 35 figs., 15 tabs.
Date: July 1, 1989
Creator: Morgan, M.A.
Partner: UNT Libraries Government Documents Department

The effect of hydrogen isotopes and helium on the tensile properties of 21-6-9 stainless steel

Description: High-energy-rate-forged (HERF) stainless steels are used as the materials of construction for pressure vessels designed for the containment of hydrogen and its isotopes. Hydrogen and helium, the decay product of tritium, are known to embrittle these materials. HERF stainless steels have a relatively good resistance to hydrogen-and-helium-induced embrittlement when compared to annealed stainless steels due to their high number density of dislocations, which act as traps for hydrogen and helium. However, the degree of embrittlement in these materials can vary considerably because of microstructure and yield strength variations introduced during the forging process. In this study the effect of hydrogen and tritium on the tensile properties of 21-6-9 stainless steel was measured as a function of HERF yield strength in the range of 660 to 930 MPa. The effect of microstructure was studied also be conducting tensile tests with HERF and annealed samples.
Date: January 1, 1990
Creator: Morgan, M.J. & Lohmeier, D.
Partner: UNT Libraries Government Documents Department

TRITIUM AND DECAY HELIUM EFFECTS ON THE FRACTURE TOUGHNESS PROPERTIES OF STAINLESS STEEL WELDMENTS

Description: J-Integral fracture toughness tests were conducted on tritium-exposed-and-aged Types 304L and 21-6-9 stainless steel weldments in order to measure the combined effects of tritium and its decay product, helium-3 on the fracture toughness properties. Initially, weldments have fracture toughness values about three times higher than base-metal values. Delta-ferrite phase in the weld microstructure improved toughness provided no tritium was present in the microstructure. After a tritium-exposure-and-aging treatment that resulted in {approx}1400 atomic parts per million (appm) dissolved tritium, both weldments and base metals had their fracture toughness values reduced to about the same level. The tritium effect was greater in weldments (67 % reduction vs. 37% reduction) largely because the ductile discontinuous delta-ferrite interfaces were embrittled by tritium and decay helium. Fracture toughness values decreased for both base metals and weldments with increasing decay helium content in the range tested (50-200 appm).
Date: August 31, 2007
Creator: Morgan, M; Scott West, S & Michael Tosten, M
Partner: UNT Libraries Government Documents Department

EFFECT OF TRITIUM AND DECAY HELIUM ON WELDMENT FRACTURE TOUGHNESS

Description: The fracture toughness data collected in this study are needed to assess the long-term effects of tritium and its decay product on tritium reservoirs. The results show that tritium and decay helium have negative effects on the fracture toughness properties of stainless steel and its weldments. The data and report from this study has been included in a material property database for use in tritium reservoir modeling efforts like the Technology Investment Program ''Lifecycle Engineering for Tritium Reservoirs''. A number of conclusions can be drawn from the data: (1) For unexposed Type 304L stainless steel, the fracture toughness of weldments was two to three times higher than the base metal toughness. (2) Tritium exposure lowered the fracture toughness properties of both base metals and weldments. This was characterized by lower J{sub Q} values and lower J-da curves. (3) Tritium-exposed-and-aged base metals and weldments had lower fracture toughness values than unexposed ones but still retained good toughness properties.
Date: September 26, 2006
Creator: Morgan, M; Scott West, S & Michael Tosten, M
Partner: UNT Libraries Government Documents Department

EXTRACTION OF FRACTURE-MECHANICS AND TRANSMISSION-ELECTRON-MICROSCOPY SAMPLES FROM TRITIUM-EXPOSED RESERVOIRS USING ELECTRIC-DISCHARGE MACHINING

Description: The Enhanced Surveillance Campaign is funding a program to investigate tritium aging effects on the structural properties of tritium reservoir steels. The program is designed to investigate how the structural properties of reservoir steels change during tritium service and to examine the role of microstructure and reservoir manufacturing on tritium compatibility. New surveillance tests are also being developed that can better gauge the long-term effects of tritium and its radioactive decay product, helium-3, on the properties of reservoir steels. In order to conduct these investigations, three types of samples are needed from returned reservoirs: tensile, fracture mechanics, and transmission-electron microscopy (TEM). An earlier report demonstrated how the electric-discharge machining (EDM) technique can be used for cutting tensile samples from serial sections of a 3T reservoir and how yield strength, ultimate strength and elongation could be measured from those samples. In this report, EDM was used successfully to section sub-sized fracture-mechanics samples from the inner and outer walls of a 3T reservoir and TEM samples from serial sections of a 1M reservoir. This report fulfills the requirements for the FY06 Level 3 milestone, TSR 15.1 ''Cut Fracture-Mechanics Samples from Tritium-Exposed Reservoir'' and TSR 15.2 ''Cut Transmission-electron-microscopy foils from Tritium-Exposed Reservoir'' for the Enhance Surveillance Campaign (ESC). This was in support of ESC L2-1870 Milestone-''Provide aging and lifetime assessments of selected components and materials for multiple enduring stockpile systems''.
Date: August 31, 2006
Creator: Morgan, M; Ken Imrich, K & Michael Tosten, M
Partner: UNT Libraries Government Documents Department