bluuebunny/crossref_metadata_2025 huggingface dataset:
Fatigue of Small Bone Fragment Fixation Plates Made from Low-Nickel Steel
Authors: Eschbach L , Bigolin G , Hirsiger W , Gasser B
Published: April 2008

Today's implant quality stainless steels contain up to 16 wt% nickel although nickel ions are the most widespread skin contact allergens. Previously sensitized persons may develop allergic reactions when nickel is released from stainless steel medical implants. New low-nickel stainless steels combine the benefits of excellent mechanical properties with virtual absence of nickel.

Miniature bone plates and corresponding 2.0 mm screws for the fixation of small bone fragments were produced of a low-nickel stainless steel. The implants were tested in a static reverse-bending setup and under dynamic conditions, and compared to commercially pure (CP) titanium and standard 316L implant steel counterparts. The low-nickel plate could withstand over 200 cycles of bending, whereas the titanium plate broke at 26 cycles. This confirms the higher tolerance of the low-nickel plate to multiple contouring during surgery.

Nevertheless, high cycle fatigue tests under physiologic conditions showed that the low-nickel steel plates exhibit lower resistance to cyclic loads than titanium and 316L plates. SEM investigations of the fatigue fractures confirmed that the cracks preferentially propagate along grain boundaries leading to intergranular fracture of the low-nickel steel. It is suggested that the intergranular crack initiation facilitates the early failure under high cycle fatigue conditions, whereas plastic bending properties are not affected. The tendency to intergranular crack initiation in the low-nickel steel could stem from surface deformation (work hardening) introduced during machining and related embrittlement in the surface zone.
Comparison of Anodic Polarization and Galvanic Corrosion of a Low-Nickel Stainless Steel to 316LS and 22Cr-13Ni-5Mn Stainless Steels
Authors: Zardiackas LD , Williamson S , Roach M , Bogan JA
Published: April 2008

Over the years, numerous biomedical implants have been produced from austenitic stainless steels due to their exceptional mechanical and corrosion properties. High nickel content has been used to stabilize the austenitic microstructure, but the presence of these nickel concentrations has been implicated as a cause of metal sensitivity reactions in a minor portion of the population. In a partial response to the possibility of hypersensitivity reactions, low-nickel stainless steels with a high nitrogen content to stabilize the austenitic microstructure have been developed. In this study, the anodic polarization and galvanic corrosion behavior of one such low-nickel alloy (BioDur® 108 Carpenter Technology) was compared to BioDur® 316LS and BioDur® 22Cr-13Ni-5Mn. For anodic polarization, duplicate samples with a surface ground to 600 grit and duplicate samples with a metallographic polish were tested in accordance with ASTM G5 at a sweep rate of 0.6 V/hr, initiated 200 mV below the rest potential. Samples for galvanic testing were metallographically polished, the rest potentials were recorded prior to test initiation, and duplicate coupled tests were run for a period of 48 hours for each alloy combination. The galvanic current and couple potential were recorded in accordance with ASTM G71. Anodic polarization results revealed BioDur® 108 to have a pitting potential similar to BioDur® 22Cr-13Ni-5Mn and significantly higher than that of BioDur® 316LS. In addition, substantially higher pitting levels on BioDur® 316LS were also noted during post-anodic metallographic examination. None of the alloy combinations revealed substantial galvanic coupled currents indicating little susceptibility to galvanic corrosion. No evidence of pitting or crevice corrosion was found on any of the galvanically coupled surfaces.
Comparison of Notch Sensitivity and Stress Corrosion Cracking of a Low-Nickel Stainless Steel to 316LS and 22Cr-13Ni-5Mn Stainless Steels
Authors: Zardiackas LD , Roach M , Williamson S , Bogan JA
Published: April 2008

Recently, low-nickel stainless steels have been developed, in part due to concerns over patient hypersensitivity reactions. These alloys have been investigated and found to provide excellent mechanical and corrosion properties. This study compares the mechanical properties, notch sensitivity, and stress corrosion cracking (SCC) susceptibility of one such alloy, BioDur® 108, to 316LS and 22Cr-13Ni-5Mn stainless steels which have a long successful implant history. BioDur® 108 was found to have a tensile strength, yield strength, and notch tensile strength similar to 22Cr-13Ni-5Mn, and both had higher values of these properties as compared to 316LS. In addition, BioDur® 108 had the largest percentage elongation during tensile testing of the three alloys but lower reduction of area than 316LS. No evidence of SCC mechanisms was revealed in either the test results or fracture analysis on any of the materials tested. With these material properties and its very low nickel content, BioDur® 108 may be a useful alternative for certain medical implant applications.
Corrosion Behavior of Platinum-Enhanced Radiopaque Stainless Steel (PERSS®) for Dilation-Balloon Expandable Coronary Stents
Authors: Covino BS , Craig CH , Cramer SD , Bullard SJ , Ziomek-Moroz M , Jablonski PD , Turner PC , Radisch HR , Gokcen NA , Friend CM , Edwards MR
Published: April 2008

Dilation-balloon expandable coronary stents are made of implant grade stainless steels, UNS S31673, e.g., BioDur® 316LS. Boston Scientific/Interventional Technologies (BS/IVT) determined that addition of platinum to UNS S31673 could produce a stainless steel with enhanced radiopacity, which made such stents more visible radiographically. A goal of the program was to ensure the platinum additions would not adversely affect the corrosion resistance of the resulting 5–6 wt % PERSS® alloys. Corrosion resistance of PERSS and BioDur 316LS was determined using electrochemical tests for general, pitting, crevice and intergranular corrosion. Experimental methods included A262E, F746, F2129, and potentiodynamic polarization. The ∼ 6 wt % PERSS alloy (IVT 78) had a resistance to pitting, crevice and intergranular corrosion similar to base materials. IVT 78 was a single-phase austenitic PERSS alloy with no evidence of inclusions or precipitates; it was more resistant to pitting corrosion than the ∼ 5 wt % PERSS alloys. PERSS performance was not a function of oxygen content in the range 0.01 to 0.03 wt %.
Comparison of Corrosion Fatigue of BioDur® 108 to 316L S.S. And 22Cr-13Ni-5Mn S.S.
Authors: Zardiackas LD , Roach M , Williamson S , Bogan JA
Published: April 2008

Fatigue testing was performed on three austenitic stainless steels in tension-tension in distilled water and in Ringer's solution at 37°C using an MTS servo-hydraulic testing system following the guidelines of ASTM F1801. The materials chosen were BioDur® 108, BioDur® 316LS and BioDur® 22Cr-13Ni-5Mn stainless steel. Samples with a 2.5 mm diameter in the gauge length of 10 mm were prepared from 8 mm diameter bar stock using low stress grinding techniques. A minimum of three samples at each of five load levels were cycled to failure or to a maximum of 106 cycles. S/N curves for each material under each condition were plotted and fracture surfaces were examined using scanning electron microscopy (SEM). Comparison between the fatigue response of each material in distilled water and Ringer's solution as well as between alloys was evaluated. Results showed typical S/N curve response comparison of stainless steels in distilled water vs. salt solutions with curves slightly shifted in a positive direction (higher numbers of cycles to failure at equal stress values) in distilled water as compared to Ringer's solution. Additionally, although not statistically evaluated, the fatigue curves were shifted toward higher numbers of cycles to failure for the two nitrogen strengthened alloys with the number of cycles to fracture for 22Cr-13Ni-5Mn being slightly higher in distilled water at lower stress values and the fatigue curves for 22Cr-13Ni-5Mn and BioDur® 108 in Ringer's solution were essentially equivalent. Evaluation of fracture surfaces by SEM showed variations in fatigue striation spacing as a function of loading in all alloys. A difference in fracture morphology of the BioDur® 108 was noted near the area of crack initiation as compared to the other two alloys. Flutes and terraces, not normally seen in fatigue of austenitic stainless steels at in vivo temperature, were seen.
The Cemented MS-30 Steim in Total Hip Replacement, Matte versus Polished Surface: Minimum of Five Years of Clinical and Radiographic Results of a Prospective Study
Authors: Berli B , Elke R , Morscher EW
Published: April 2008

The MS-30 femoral stem is a three-dimensionally tapered, collarless implant for cement fixation in THR, manufactured from an FeCrNiMnMoNb-alloy with either a matte or polished surface. One hundred twenty-seven MS-30 stems with matte surface and 128 stems with polished surface, respectively, were implanted in an alternated manner.

The mean observation period was 5.6 years. No patients were lost to the followup. In both groups 88 patients with 108 stems were included in the clinical and radiographic follow-up examinations. Only one stem with a matte surface was revised for aseptic loosening. There was no death related to surgery and no infection.

Conclusion: Both, the clinical and radiographic evaluation (radiolucencies, osteolyses and subsidence) did not show any statistically significant difference between the two groups.

The main reason for the equally excellent performance of both the matte and the polished version of the MS-30 stem may be the design of the centralizer which resists both debonding of the stem, and subsequent subsidence as a precondition for fretting in the metal/cement interface.

Clinical relevance: Since, on the one hand, debonding of the stem/cement interface cannot entirely be excluded, we recommend the discontinuation of tapered stems with a matte surface — especially if they do not have a centralizer which resists the stem to subside.
Evaluation of the Potential Impact of Water and Sediment from National Wildlife Refuge Sites Using a Modified Frog Embryo Teratogenesis Assay- Xenopus (FETAX)
Authors: Turley SD , Eaton-Poole L , Pinkney AE , Osborn MA , Burton DT
Published: April 2008

Over the past five years, comprehensive annual surveys by U.S. Fish and Wildlife Service (USFWS) personnel have identified sites with a high prevalence of abnormal native amphibians. A number of these sites are located within National Wildlife Refuges (NWR) in the Northeast. In conjunction with the field surveys, prolonged (140-d) FETAX assays were performed with sediment and surface water samples from three potentially affected NWR sites: 1) Ferry Way Beaver Pond, Great Bay NWR, Newington, New Hampshire, 2) Brown Street Impoundment, Rachel Carson NWR, Wells, Maine and 3) Black Creek (Trails Site), Missisquoi NWR, Swanton, Vermont. Endpoints used to assess the effects of site sediment and surface water exposure on Xenopus development included survival, ability to complete metamorphosis, time to complete and size at metamorphosis, and frequency of malformations.

Exposure to Rachel Carson sediment and surface water had no significant (p > 0.05) detrimental effects on Xenopus (X. laevis) development, relative to control exposures. Exposure to Great Bay water and sediment caused a significant (p ≤ 0.05) reduction in Xenopus embryo survival, and significantly inhibited and delayed development and metamorphosis. Exposure to Missisquoi water, and sediment exposures with overlying Missisquoi water caused significant (p ≤ 0.05) embryo mortality and significantly inhibited metamorphosis in Xenopus embryos. There were no severe malformations observed in metamorphs from any of the NWR site exposures. Slight to moderate malformations were observed in embryos/tadpoles that died in the Great Bay and Missisquoi exposures.

Detectable concentrations of pesticides were measured in the Great Bay and Missisquoi sediment samples. The presence of pesticides, and low concentrations of essential ions in site water may have contributed to the adverse developmental effects observed in Xenopus in the Great Bay and Missisquoi exposures.
The Role of Multiple Stressor Causes in Declining Amphibian Populations: A Wingspread Workshop Summary
Authors: Krest SK , Linder G , Sparling DW
Published: April 2008

Numerous studies have documented the decline of amphibian populations over the past decade and no single factor has been the linked to these widespread declines. Determining the causes of declining amphibian populations worldwide has proven difficult because of the variety of anthropogenic and natural suspect agents. A Wingspread workshop, convened by The Society of Environmental Toxicology and Chemistry (SETAC), brought together individuals with expertise in the areas of amphibian biology, ecotoxicology, natural resource management, and environmental policy. This workshop had three objectives: 1) create a network for future discussions on multiple stressor causes of declines; 2) characterize and prioritize technical issues critical to the analysis of the decline problem; and 3) identify and develop resource management approaches to promote sustainable and healthy amphibian populations. The workshop proceedings will be summarized in a book entitled, “Multiple Stressors and Declining Amphibian Populations: Evaluating Cause and Effect.” This paper summarizes the results of the workshop.
Establishing Cause-Effect Relationships for Chemical Stressors in Amphibians: Providing Adequate Data for the ERA
Authors: Fort DJ , McLaughlin DW
Published: April 2008

Most studies with amphibians in the past have been designed to address either the effect or the potential cause. Thus, data collected may provide suitable documentation of field effects on local populations with little information on causality, or the data may provide suitable information on possible causes with little concrete explanation of effects on the local populations. In order to establish such a relationship at this level, a study must be designed to answer two primary questions. First, what is the effect on the local population? Second, what factors are causing this effect? To establish an effect on a local population of amphibians, population characteristics must be surveyed. This survey should include information on habitat suitability, life stage distributions, and reproductive and developmental success. Establishing the cause of the noted effects requires the collection of adequate field-based ecotoxicological data combined with well-designed and highly controlled laboratory studies, ultimately providing adequate lab-to-field extrapolation potential. Field-based ecotoxicological data can be collected using a combination in situ exposure and evaluation at various life stages, and laboratory examination of specimen collected from the field at appropriate life stages. More controlled laboratory-based studies involving the culture of indigenous species under simulated field exposure conditions should also be considered. Cross-over studies in which organisms collected from uncontaminated areas are cultured under contaminated conditions, and those from contaminated locations are cultured under uncontaminated conditions to help establish exposure and impact scenarios. Appropriate chemical analysis of environmental samples including water, sediment, soil, and tissues from field collected and laboratory-reared specimen should be performed to determine exposure concentrations relative to the effects observed in individuals and accumulation potential. Highly controlled spiking studies can then be performed to help confirm potential causes of the effects observed. Overall, in many cases a combination of parallel field and laboratory studies can be used to provide adequate data to establish causality
New and Improved Techniques for Microemulsifying Modified Seed Oils and Pesticides
Authors: Anderson TH , Abribat B , Barker P
Published: April 2008

Microemulsions are isotropic, thermodynamically stable systems consisting of surfactant, oil and water, and as necessary, additives such as alcohol or electrolytes. They are often obtained with emulsifier systems based on alkoxylated non-ionic surfactants in a certain limited temperature range. These classical microemulsions (ME) have served the pesticide industry with ready to use products for a number of years. The fine droplet size (typically 100 nm) of these emulsions enables clear, transparent products with a long shelf life.

The authors present a novel surfactant system that replaces traditional ethoxylated emulsifiers used in ME formulas. This system, based on one emulsifier, alkyl polyglycoside (consisting of a hydrophilic saccharide moiety and a long hydrophobic alkyl chain), and one co-emulsifier, glycerol monooleate, forms a transparent microemulsion. These microemulsions remain stable over a broad range of temperatures and follow the desirable trend of very low environmental impact. In this study, the systematic investigation of the phase behavior of this specific selected system is discussed for both modified seed oil formulas as well as formulas containing pesticides.
Effects of Urea and Ammonium Nitrate on Penetration of NAA Through Enzymatically Isolated Tomato Fruit Cuticular Membranes
Authors: Bukovac MJ , Fader RG , Luque P
Published: April 2008

The effects of ammonium nitrate (AMN) on penetration of foliar-applied (1-μL droplets) 1-naphthylacetic acid (NAA) through enzymatically isolated tomato (Lycopersicon esculentum Mill cv. Pik Red) fruit cuticular membranes (CM) were studied using a finite dose diffusion system. The maximum rate of penetration (Rmax) and the total amount penetrated after 120 h (P120) were used to measure the treatment effects. AMN (8 mM) increased NAA penetration significantly at pH values (5.2, 6.2) above the pKa (4.2), but had no effect at pH 3.2. Ammonium sulfate and ammonium dihydrogen phosphate were equally effective as AMN at pH 5.2, but potassium and calcium nitrate reduced NAA penetration compared to NAA alone. Alkylamine hydrochlorides were equally effective as AMN. On a relative basis, AMN had a greater effect on NAA penetration through native, nondewaxed CM (P120 172 vs. 500pmol) than through dewaxed CM (P120 503 vs. 671 pmol). The AMN effect was dependent on relative humidity (RH); both the Rmax and P120 were greater at lower (<63 %) than at higher (>64 %) RH. Droplet drying and the presence of AMN and NAA together in the donor (droplet/residue) were required for AMN enhancement of NAA penetration. We suggest that the presence of AMN in the drying droplets/residues results in protonation of the NAA anion, yielding free NAA (nondissociated), which penetrates readily. The volatilization of the ammonia produced and penetration of the nondissociated NAA into the CM favor continued formation of free NAA as long as NAA and AMN are available and the conditions in the deposit support these reactions.
Dynamic Investigations of the Formation of Phenoxy Ester Herbicide Concentrated Emulsions
Authors: Lei Y , Alexander M , Hazen JL
Published: April 2008

Dynamic interfacial tension (DIT) measurements have been employed to investigate the formation dynamics of iso-octyl 2,4-dichlorophenoxyacetate (2,4-D IOE) concentrated emulsion (EW) by citric acid alkylether ester (AEC) emulsifiers. Both of the AEC surfactants, AEC-1 and AEC-3, were found to be quite effective in reducing the interfacial tension between water and 2,4-D IOE when compared with a standard nonionic surfactant. The CMC concentrations and effective molecular areas of AEC-1 and AEC-3 have been determined at both air/water and 2,4-D IOE /water interfaces. Kinetic analysis indicated that the adsorption of AEC-1 proceeded at a faster rate than that of AEC-3 at 2,4-D IOE/water interface. But, AEC-3 is more effective in minimizing the equilibrium interfacial tension at the 2,4-D IOE /water interface. The DIT results have been contrasted with those obtained with Focused Beam Reflectance Measurement (FBRM). The results are further correlated to the rate at which 2,4-D IOE EW reaches its equilibrium particle size and longer-term physical stability. The robust physical stability exhibited by the 2,4-D IOE EW formulated with AEC-3 is attributed to the minimal interfacial tension of the system.
Glyphosate: Twenty-Eight Years and Still Growing — The Discovery, Development, and Impact of this Herbicide on the Agrichemical Industry
Authors: Magin RW
Published: April 2008

Glyphosate, discovered by Monsanto's Dr. John E. Franz in 1970, has become one of the most environmentally friendly and commercially successful herbicides in the world. Glyphosate was the result of a program at Monsanto to find a herbicide that would control perennial weeds. This narrative will take you into the Monsanto of the 1960s and early 1970s to describe the events that led to this discovery, and the people who played a part in making it a commercial reality. Key decisions and resources employed, particularly in the metabolism/residue area, are described that lead to one of the most rapid discovery to commercialization timelines on record. Formulation efforts are described along with how the commercialization of this non-selective herbicide changed Monsanto from a midwestern row crop company to a global multinational company. The marketing of glyphosate is summarized in four stages to the present ROUNDUP READY® technology, Monsanto, St. Louis, MO.
A Wind Tunnel Investigation of Airborne Liquid Particle Behavior: Adjuvant Effects on Deposition
Authors: Downer RA , Hacker JK , Hall FR
Published: April 2008

Application techniques, spray adjuvants, buffer zones, and windbreaks are all important tools for management of spray drift. However, a wide variety of vegetative types may be used for both buffer zones and windbreaks and therefore it is expected that these might capture the driftable fraction of the spray cloud differently depending on the physical properties of the spray mixture being utilized.

The studies described here set out to evaluate the influence of adjuvants on the capture efficiency of various weed species and plant densities that might be found in buffer zones. Data were generated in a wind tunnel constructed at the Laboratory for Pest Control Application Technology (LPCAT). Water sensitive papers and passive dosimetry were utilized to assess droplet interception and capture respectively. Spray clouds were generated using either a TeeJet® XR8001VS hydraulic fan nozzle or a Micron Ulva +® spinning disc sprayer placed at the opening of the tunnel. Water, an hydroxy-propyl guar (HPG polymer), two crop oil concentrates, a non-ionic surfactant, and an invert suspension were utilized to impart different physicochemical characteristics to the spray cloud. Two mL/L of Rhodamine WT were added to each mixture for fluorimetry work. Three plant species were utilized, barnyard grass (Echinochloa crus-galli), velvetleaf (Abutilon theophrasti), and smooth pigweed (Amaranthus hybridus). Each treatment was replicated five times.

The results showed that for barnyard grass, collection efficiency was different for the polymer compared to the other treatments. These results have implications for the vegetative composition of buffer zones and for drift risk assessment as applied to different crops.
Characterizing Granular Material in Aerial Application
Authors: Teske ME , Hewitt AJ , Ice GG
Published: April 2008

The ASTM Standard: Standard Test Method for Particle Size Distribution of Granular Carriers and Granular Pesticides (E726-01) is the only ASTM standard that specifically addresses the characterization of nonspherical particles. To our knowledge there is no standard for particle size distribution measurements by laser diffraction or for particle sphericity measurements by any means to complete the description of the granular material. The present paper reviews a modeling effort that effectively characterizes and then represents the behavior of nonspherical particles during aerial application, highlights the difficulties inherent in interpreting light scattering by nonspherical particles, and suggests a laboratory experiment that accurately recovers particle sphericity. Model revisions enable the user to select the granular application technique from a menu of options once the granular material has been adequately parameterized. Quantitative comparisons are made with available field data to demonstrate the implementation of the several available granular material delivery systems. Notice is made that a standard should be developed for measuring (1) particle size distributions using laser diffraction instruments, and (2) particle sphericity with a technique suggested in the paper.
Efficacy of Apogee® (prohexadione calcium) on McIntosh Apple Comparing Two Pesticide Application Technologies, a Disc-Core Type Hollow Cone Nozzle and Air Induction Nozzle
Authors: Osborne JL , Landers AJ , Schupp JR
Published: April 2008

Fruit and vegetable growers and landscapers alike are recently being pressured by neighbors and legislators to reduce drift on their orchards, vineyards, and other horticultural operations. Pesticide costs continue to rise and growers need to improve application methods if they are to minimize costs to remain competitive and avoid prosecution under increasing environmental legislation. (Landers, 2002) Spray application technology research is necessary to improve spray deposition as well as reduce drift. Recent research suggests AI nozzles can reduce drift. Air inclusion nozzles produce droplets with a size or volume median diameter (VMD) of 450 μm. Cone nozzles on average have a VMD of 220 μm. Thus, AI nozzles by nature are less susceptible to drift. (Balsari, 2001)

However, biological efficacy trials are needed to understand if new delivery methods (i.e. AI nozzles) are suitable alternatives to conventional application technologies. while the potential for drift reduction using AI nozzles has been well researched, few trials have evaluated orchard air-blast AI nozzle pesticide efficacy, and fewer have studied plant growth regulator (PGR) efficacy under these regimes. Most recently, Cross et al. (2002) in England looked at the efficacy of fungicides and insecticides using three spray drift-reducing methods in orchards, where AI nozzles were one of the treatments. The British researchers found no consistent, statistically significant differences in the biological efficacy of the drift reducing treatments evaluated, as compared to conventional hollow cone nozzles. All treatments gave equal control of disease pests such as apple scab and powdery mildew, and insect pests like rosy apple aphid. Although the efficacy results of AI nozzles appear promising, more research is warranted.

The objective of the trial was to evaluate the biological efficacy of Prohexadine Calcium, (P-Ca, Apogee®, BASF Corp., Research Triangle Park, NC) a new plant growth regulator, on McIntosh apple, comparing two types of pesticide delivery systems: conventional hollow cone nozzle, and air-induction (AI) nozzles.
Study on Ductile Fracture Strain and Fracture Toughness of Irradiated Austenitic Stainless Steels
Authors: Nishimura S , Sakamoto H , Kato T
Published: April 2008

Degradation of fracture strain and fracture toughness due to neutron irradiation in austenitic stainless steels are important issues to evaluate for plant life extension of light water reactors (LWRs). However, few efforts have been made to develop a prediction method for fracture strain and toughness. In this paper, ductile fracture of irradiated material was studied based on the irradiation-induced defects forming process combined with a ductile fracture process model i.e., void growth and coalescence model, and a model for fracture strain was developed as a function of fluence, applied stress and work hardening rate. Tensile tests of austenitic stainless steels irradiated up to about 1026 n/m2 in an LWR were conducted at room temperature and 561 K. Fracture strain decreased with the increase of neutron fluence, but no specimens showed any brittle features. The proposed model for fracture strain had good correlation with experimental results. The fracture surfaces were investigated by scanning electron microscope (SEM). Dimple diameter decreased with the increase of neutron fluence and this fact was presumed to support the propriety of the proposed fracture strain model. Fluence dependence of fracture toughness was studied based on the proposed fracture strain model. The proposed fracture toughness model agreed well with the open literature. Fracture toughness JIC of base metal and weld metal of Types 304 and 316 stainless steels neutron irradiated and tested at 673–700 K were predicted by the fracture toughness model. JIC of base metal was higher than the weld metal in the whole fluence range. JIC of base metal and weld metal decreased above the fluences of about 5×1025 n/m2 and 1×1025 n/m2 (E>0.1 MeV), respectively. Consequently, the proposed ductile fracture strain and fracture toughness models were applicable to predict those values for base metal and weld metal of neutron irradiated austenitic stainless steels.
The Effect of Void Swelling on Electrical Resistance and Elastic Moduli in Austenitic Steels
Authors: Kozlov AV , Scherbakov EN , Averin SA , Garner FA
Published: April 2008

Measurements are presented of electrical resistance and elastic moduli (Young's modulus and shear modulus) of stabilized austenitic fuel pin cladding after irradiation in the BN-600 reactor. Additional data are presented on changes in electrical resistivity of another austenitic steel irradiated in the BN-350. The elastic moduli of both steels are reduced and the electrical resistance is increased as the neutron dose and resultant swelling increase.

Dependencies of these changes in physical properties on neutron irradiation dose, temperature, and swelling level are plotted and it is shown that to the first order, the property changes are dependent on the swelling level, in agreement with earlier U.S. and Russian data. It is also observed, however, that changes in electrical resistance and elastic moduli frequently differ slightly for specimens with equal swelling, but which were obtained at different combinations of temperature and dose. These second-order differences appear to arise from contributions of other radiation-induced structural changes, especially in precipitation, which depends strongly on irradiation temperature in these stabilized steels.
Fracture Toughness and Atom Probe Characterization of a Highly Embrittled RPV Weld
Authors: Sokolov MA , Nanstad RK , Miller MK
Published: April 2008

The Heavy-Section Steel Irradiation Program at Oak Ridge National Laboratory (ORNL) includes a task to investigate the shape of the fracture toughness master curve for reactor pressure vessel steel highly embrittled as a consequence of irradiation exposure. A radiation-sensitive reactor pressure vessel (RPV) weld with intentionally enhanced copper content, designated KS-01, is characterized in terms of static initiation (KIc, KJc) and Charpy impact toughness in the unirradiated and irradiated conditions. The objective of this project is to investigate the ability of highly embrittled material to maintain the shape of the unirradiated transition fracture toughness curve, as well as to examine the ability of the Charpy 41-J shift to predict the fracture toughness shift at such a high level of embrittlement. Irradiation of this weld was performed at the University of Michigan Ford Reactor. Specimens of KS-01 weld were irradiated to about 0.74 × 1019 neutron/cm2 at 288°C. Irradiation resulted in Charpy ductile-to-brittle transition temperature (DBTT) shift of 169°C. It was anticipated that this shift would result in a fracture toughness transition temperature (at 100 MPa√m) in the irradiated condition near or slightly above the pressurized thermal shock screening criterion for weld metals, ToPTS = 129°C. The fracture toughness characterization of KS-01 weld in the unirradiated and irradiated conditions was mainly performed by testing 1T C(T), although some 0.5T C(T) and precracked Charpy specimens were used in this study. The master curve analysis showed that this material exhibited shift of reference fracture toughness transition temperature, To, of 165°C as result of radiation, which is in remarkable agreement with Charpy DBTT shift. The absolute value of To in the irradiated condition was determined to be equal to 139°C. This weld exhibited a low ductile initiation toughness (JQ) after irradiation. It left a relatively narrow temperature window to examine the shape of the transition region. Irradiated median fracture toughness values up to 148 MPa√m follow the master curve shape. However, low toughness brittle fractures occurred at temperatures further above To (To + 61°C) than expected with a leveling of the KJc data from the master curve shape. The microstructure of the weld was characterized with the ORNL's energy-compensated optical position-sensitive atom probe. Atom probe tomography revealed a high number density (∼3 × 1024m-3) of Cu-, Mn-, Ni-, Si-, and P-enriched precipitates and a lower number density (∼1 × 1023 m-3) of P clusters.
Microstructural Aspects of Irradiation Damage in A508 Gr 4N Forging Steel: Composition and Flux Effects
Authors: Burke MG , Stofanak RJ , Hyde JM , English CA , Server WL
Published: April 2008

Neutron irradiation can promote significant changes in the microstructure and associated mechanical properties of low alloy steels. In particular, irradiation can induce the formation of non-equilibrium phases and segregation, which may lead to a degradation in toughness. In this study, the microstructural changes caused by neutron irradiation have been characterized in A508 Grade (Gr) 4N-type steels (∼3.5% Ni) using a variety of state-of-the-art analytical techniques including 3D-Atom Probe Field-Ion Microscopy and Small Angle Neutron Scattering, along with post-irradiation annealing studies combining Positron Annihilation Lineshape Analysis and hardness measurements. Important differences between conventional and “superclean” A508 Gr 4N steel have been identified in this investigation. The data indicate that Ni is not the controlling factor in the irradiation damage behavior of these materials; rather, the Mn content of the steel is a dominant factor in the irradiation-induced microstructural development of solute-related hardening features.
Development of RPV Embrittlement Evaluation Technology for Charpy Upper Shelf Region
Authors: Hatano S , Sakamoto K , Osaki T
Published: April 2008

In order to develop the integrity evaluation technology for aged major components of nuclear power plants, the Japan Power Engineering and Inspection Corporation (JAPEIC) has carried out the project named “Nuclear Power Plant Integrated Management Technology (PLIM)” entrusted by Japanese Ministry of Economy, Trade and Industry since 1996 Fiscal Year (FY). One of the objectives of this project is to establish the method for integrity evaluation of aged Japanese reactor pressure vessels (RPV) by developing the prediction equations of reduction of Charpy V-notch upper shelf energy (USE) due to neutron irradiation embrittlement and the correlation equations between USE and fracture toughness. In order to study the effect of certain chemical elements, such as Cu, Ni, P and Si, and initial USE on irradiation embrittlement, nine kinds of base metal, four kinds of weld metal and one kind of heat affected zone were prepared as test materials. They were irradiated at the OECD Halden test reactor, at three fluence levels (3, 6 and 10x1019n/cm2: E>1MeV) considering total fluence estimated after 48 Effective Full Power Year (EFPY) operation of Japanese PWR plants (2 and 3 loop). Post irradiation Charpy impact tests at the upper shelf region were completed to date. This paper is an interim test report about the reduction of USE in the high fluence region.
Master Curve of Irradiated JRQ Material
Authors: Serrano M , Perosanz FJ , Lapeña J
Published: April 2008

One of the key issues concerning the structural integrity of a reactor pressure vessel (RPV) is the effect of neutron irradiation on fracture toughness. To assure the structural integrity of the RPV it is necessary to adjust the pressure-temperature operational limits. These limits depend on the fracture toughness of the RPV material, which is affected by the neutron irradiation.

The purpose of the material surveillance program, as established in ASTM E185, is to monitor changes in the fracture toughness properties of ferritic materials in the RPV. Under the surveillance program, Charpy-V notch specimens included in surveillance capsules are tested and the shift in impact energy due to irradiation is calculated. Due to the lack of standard fracture toughness specimens in the surveillance capsules, most of the codes assume that fracture toughness shift due to irradiation is the same as the Charpy-V notch shift. This correlation requires high conservative margins to reduce the uncertainty of the method. To avoid these uncertainties, several approaches have been developed during the last several years. One of the most innovative is the Master Curve approach developed by VTT, which has been adopted as a testing standard by ASTM.

In this paper, Master Curves are determined for IAEA reference material JRQ non-irradiated and irradiated on a commercial Nuclear Power Plant. Determination of the To reference temperature is done following single and multi-temperature techniques. Specimens used are pre-cracked Charpy and 1/2TCT type.
Development of International Guidelines for Application of the Master Curve Approach to Reactor Pressure Vessel Integrity
Authors: Server WL , Rosinski ST , Lott RG
Published: April 2008

The International Atomic Energy Agency (IAEA) has sponsored a series of Coordinated Research Programs (CRPs) that have been focused on integrity of reactor pressure vessel (RPV) materials. The emphasis in the last few years has been on the development of a large fracture mechanics database of three-point bend fracture toughness tests on precracked Charpy specimens and larger 1T (25.4 mm thickness) compact tension specimens, using the Master Curve approach that has been standardized in ASTM Test Method for the Determination of Reference Temperature, To, for Ferritic Steels in the Transition Range (E 1921). More than 20 international laboratories have conducted a significant amount of fracture toughness testing to allow evaluation of the Master Curve results obtained following ASTM E 1921. The current CRP also has the objective to develop international guidelines for producing adequate Master Curve data and applying the data to RPV integrity analyses. This paper will first describe a preliminary review of the data that have been produced with emphasis on the A533B-1 correlation monitor heat JRQ, which has served as a key material for the CRP. The main emphasis of the paper will be on the development of international guidelines for applying the Master Curve data that can be obtained from irradiated sample material for the most limiting RPV material.
Hardening Mechanisms in Ferritic/Martensitic Steels
Authors: Baluc N , Schäublin R , Spätig P , Victoria M
Published: April 2008

Reduced activation ferritic/martensitic steels are promising materials for the first wall of the future fusion reactors that will suffer irradiation damage from 14 MeV fusion neutrons. They have proven to be a good alternative to austenitic steels for their higher swelling resistance and their lower accumulation of damage. Unfortunately, most of these steels exhibit low temperature irradiation-induced hardening, which imposes a severe restriction on the reactor applications at temperatures below about 400°C. In the present paper, the irradiation-induced microstructures of a number of reduced activation ferritic/martensitic steels are reviewed in order to identify the key elements to hardening mechanisms.
Effect of Heat Treatment and Tantalum on Microstructure and Mechanical Properties of Fe-9Cr-2W-0.25V Steel
Authors: Klueh RL , Hashimoto N , Sokolov MA
Published: April 2008

An Fe-9Cr-2W-0.25V-0.07Ta-0.1C (9Cr-2WVTa) steel has a smaller prior-austenite grain size than this same composition without tantalum (9Cr-2WV) when the steels are given a similar heat treatment. Except for prior-austenite grain size, the microstructures of the steels are similar before irradiation, and they develop similar changes in microstructure during irradiation. Nevertheless, the 9Cr-2WVTa shows less effect of irradiation on the Charpy behavior. To determine the effect of grain size on the Charpy properties of the 9Cr-2WV and 9Cr-2WVTa, specimens of the two steels were given various normalization heat treatments to produce different prior austenite grain sizes, and the tensile and impact properties were determined. For the smaller prior-austenite grain sizes, the 9Cr-2WV steel had impact properties similar to or better than those of the 9Cr-2WVTa steel. Differences in the microstructures of the steels were used to explain the observations and what they mean for developing steels with improved properties.
Oxide Particle Stability in Oxide Dispersion Strengthened Ferritic Steels During Neutron Irradiation
Authors: Yamashita S , Oka K , Yoshitake T , Akasaka N , Ukai S , Ohnuki S
Published: April 2008

This work focused on the evaluation of the oxide particles stability in neutron-irradiated ODS ferritic steels. Two types of ODS steels were examined and both had a single ferritic phase. The neutron irradiation was conducted in the experimental fast reactor JOYO. The initial microstructure in both steels had elongated grains along the axial direction and a dislocation structure with a high density produced during a mechanical alloying (MA) consolidation process. Oxide particles were distributed finely and uniformly over the ferritic matrix. The microstructure of irradiated ODS steels exhibited no void formation and a dislocation structure with high density. After irradiation, there were slight but significant changes in the size and density of the oxide particles. This change of the oxide indicated that recoil resolution of oxide particles might occur during neutron irradiation. Chemical analysis of the oxide particles by means of Energy Dispersive X-ray Spectroscopy (EDS) revealed that some of the oxide particles observed before and after irradiation had a complex configuration, such as a double-layered structure, implying that complex oxides with such a configuration are more stable than mono-oxides like TiO2 and Y2O3.
Fracture Toughness Characterization of Irradiated F82H in the Transition Region
Authors: Sokolov MA , Klueh RL , Odette GR , Shiba K , Tanigawa H
Published: April 2008

The ferritic-martensitic steel F82H is a primary candidate low-activation material for fusion applications, and it is being investigated in the joint U.S. Department of Energy-Japan Atomic Energy Research Institute (U.S. DOE-JAERI) collaboration program. As part of this program, two capsules containing a variety of specimen designs were irradiated at two different temperatures in the Oak Ridge National Laboratory (ORNL) High Flux Isotope Reactor (HFIR). The bottom and top parts of these capsules were loaded with disk-shaped compact tension [DC(T)] specimens that were used for fracture toughness characterization. This small (12.5-mm-diam and of 4.6-mm-thick) DC(T) specimen was developed at ORNL for testing irradiated materials. Six specimens were irradiated in each “low-”and “high-” irradiation temperature capsule up to ∼3.8 dpa. Irradiation temperatures were measured by thermocouples. In the low-temperature capsule, three specimens were irradiated at an average temperature of 261°C and another three at 240°C; temperature variation during irradiation was within ±19°C for a given specimen. In the high-temperature capsule, all six specimens were irradiated at an average temperature of 377°C in the bottom part of the capsule; temperature variation during irradiation was within ±30°C for a given specimen. All irradiated specimens failed by cleavage instability. From these data, fracture toughness transition temperatures were evaluated for irradiated F82H steel and compared to unirradiated values. Specimens irradiated at the higher temperature exhibited a relatively modest shift of the fracture toughness transition temperature of ∼57°C. However, the shift of fracture toughness transition temperature of specimens irradiated at 250°C was much larger, ∼191°C. These results are compared with available tensile and impact Charpy data for this material.
Determination of the Lower Temperature Limit of Void Swelling of Stainless Steels at PWR-Relevant Displacement Rates
Authors: Porollo SI , Konobeev YV , Dvoriashin AM , Krigan VM , Garner FA
Published: April 2008

Recent studies associated with light water reactors (LWR) in both the USA and Russia have raised the question of void swelling in austenitic components of core internals. One question of particular interest is the range of temperatures over which voids can develop, especially the lowest temperature. To address this question a flow restrictor component manufactured from annealed X18H9T was removed from the reflector region of the BN-350 fast reactor, located in Kazakhstan. During operation this component spanned temperatures and dpa rates of direct interest to pressurized water reactors (PWRs) in the West and VVERs in Russia. This steel is analogous to AISI 321 and is used in Russian reactors for applications where AISI 304 would be used in the West and in Japan.

This component was sectioned on a very fine scale to determine in what range of conditions voids existed. Microstructural data were obtained for 157 separate locations, with 111 specimens showing voids over the relevant range of temperatures and displacement rates, allowing construction of a parametric map of swelling with temperature, dpa and dpa rate. These data show that swelling at doses as high as ∼50 dpa persists down to ∼306°C for dose rates in the range 0.11 × 10-7 to 1.6 × 10-7dpa/sec. Since the helium generation rate is rather low in the spectral environment of the flow restrictor, the early onset of swelling is attributed primarily to the lower displacement rate, a conclusion supported by a number of other experimental studies.
Dependence of Maximum Swelling Temperature on Damage Dose in Cold Worked 16Cr-15Ni-2Mo-1Mn Cladding Irradiated in BN-600
Authors: Kozlov AV , Portnykh IA , Bryushkova SV , Kinev EA
Published: April 2008

The experimental data comprising more than 1800 data points on swelling of fuel pin cladding specimens of cold worked austenitic steel 16Cr-15Ni-2Mo-1Mn irradiated in the BN-600 reactor are described by the equation S = Rs∙(D-D0)∙(1-exp(-p(D-D0))). Where S = swelling; D = damage dose; D0, p and Rs are parameters depending on irradiation temperature and damage dose rate.

The parameters of the equation were obtained at 40–90 dpa in the temperature range of 400 – 600 °C. Their dependencies on neutron irradiation temperature and radiation damage rate were then examined.

The dependence of swelling on neutron irradiation temperature for different values of damage dose was calculated using the derived temperature dependencies of the equation parameters. The temperature at which maximum swelling is observed was shown to increase with increasing dose in the selected model. An overview of the swelling temperature dependence on changes in the character of the equation parameters was also conducted.