bluuebunny/crossref_metadata_2025 huggingface dataset:
High-Strength Microalloyed Pipe Steels Resistant to Hydrogen-Induced Failures
Authors: Parrini C , DeVito A
Published: March 2009

The continuing increase in oil and natural gas prices has made the utilization of sour gas reserves more and more economical. In addition, sweet gas may in time turn sour due to the action of bacteria carried in by injected seawater. Thus, future pipeline steels must be increasingly resistant to hydrogen sulfide and hydrogen-induced cracking (HIC). The present investigation on the susceptibility of steels to HIC covers pipe diameters from ∼50 to 142 cm (20 to 56 in.) and steel grades from X42 to X80. The influence of the alloying elements carbon, manganese, sulfur, chromium, molybdenum, copper, nickel, niobium, and the rare earth metals was investigated. Hydrogen effects were evaluated by means of sulfide stress corrosion (SSC) and British Petroleum (BP) tests on base metal and U-bend tests on welded joints. The effects of inclusion shape, control rolling practices and cold deformation on hydrogen susceptibility were also studied. A new welding method, able to produce joints fully resistant to HIC, was developed. Large diameter, cold expanded, submerged arc welded pipes not susceptible to hydrogen cracking have been produced.
Influence of Loading System on Crack Propagation and Arrest Behavior in a Double-Cantilever Beam Specimen
Authors: Fourney WL , Kobayashi T
Published: March 2009

Design and analysis procedures which include dynamic crack propagation and crack arrest are currently under development in order to assure the safety of such structures as nuclear pressure vessels. This type of design and analysis procedure requires a knowledge of the relationship of stress intensity factor (K) as a function of crack speed (å). The minimum value of stress intensity factor (designated as KIm) on the K versus å relationship is of particular importance because crack arrest will occur if the stress intensity factor falls below this minimum value.

Direct determination of the K versus å relationship and of the value of KIm for pressure vessel grade steels is an extremely difficult and complex task. For this reason methods have been developed to approximate KIm values. One such method was developed by Battelle Columbus Laboratory (BCL) and another by Materials Research Laboratory in Chicago. One difficulty involved in an analysis of dynamic crack propagation and arrest is the interaction of the specimen and loading system, and its effect on crack behavior.

This paper describes a series of experiments conducted to determine the influence of loading system on crack jump length and stress intensity as a function of velocity. Rectangular double-cantilever models made from Homalite 100, a birefringent polymer, were tested with two different wedge loading systems. One system used steel loading pins and aluminum wedge. The second system used both plastic pins and plastic wedge. A Cranz-Schardin high speed camera was used to photograph isochromatic fringe patterns associated with propagating and arrested cracks. Dynamic stress intensity factors were determined from the isochromatic fringe loops using a three-parameter Westergaard stress function.

The high speed photographs also were used to determine crack length as a function of time. From this relationship the crack velocity was determined. The results were compared with the predictions of a one dimensional finite difference computer code written by BCL. The crack jump for the models loaded with the plastic pins and wedge was found to be about twice the crack jump for the models loaded by metal pins and wedge for the same initial pin displacement. The amount of energy stored in pin contact stress was computed and when this additional energy was added to the computer input it was found that the proper crack length as a function of time was predicted by the BCL code.
Short Bar Specimens for KIc Measurements
Authors: Barker LM
Published: March 2009

The new short rod fracture toughness specimen with a circular cross section has already been used successfully for KIc measurements on a wide variety of materials, including brittle nonmetals. Now, a rectangular shaped “short bar” specimen which is comparable in every respect to the short rod has been developed and tested. The short bar dimensions were selected so that the geometrical constant relating KIc to the peak load in the experiment should be the same for both short rod and short bar configurations, according to a simplified compliance calculation. Careful comparison testing of short rod and short bar specimens of aluminum, aluminum oxide, and fused quartz have shown no experimentally significant difference in the geometrical constant. Therefore, these tests indicate that the short rod and short bar specimens can be used interchangeably, with no difference in the equation relating the peak load to KIc.
Zirconium Technology—Twenty Years of Evolution
Authors: Lustman B
Published: March 2009

Progress since 1955 in the technology of zirconium and its alloys is reviewed primarily from an applications viewpoint. A number of favorable features have been uncovered as their use broadened as well as problem areas which required accommodation in design or lifetime. Zirconium technology has reached its present stage of development as a result of world-wide contributions.
Review of Corrosion and Dimensional Behavior of Zircaloy under Water Reactor Conditions
Authors: Garzarolli F , Manzel R , Reschke S , Tenckhoff E
Published: March 2009

The corrosion of Zircaloy in water reactors is dependent on the water chemistry of the primary coolant and the fast neutron flux.

Under standard pressurized water reactor (PWR) coolant conditions with hydrogen overpressure, resulting in a low oxygen content in the primary coolant, the fast neutron flux has no measurable influence on the corrosion rate. Therefore, the in-pile corrosion almost follows the out-of-pile behavior. However, in some cases deviations from this general behavior have been observed. Under oxygenated coolant conditions, typically for boiling water reactors (BWRs), the corrosion is enhanced by the fast neutron flux from the early beginning. Three different types of oxide have been observed.

The dimensional behavior of Zircaloy under irradiation is governed by two processes: creep and growth. Creep is dependent on fast neutron flux and saturates with time. Total growth results from irradiation growth, anisotropic creep, and mechanical interference. Both in-pile creep and growth depend on the amount in recrystallization of the material.
Primary Creep of Zircaloy-2 Under Irradiation
Authors: Fidleris V
Published: March 2009

Primary in-reactor creep of Zircaloy-2 exhibits approximately linear plots of log(creep strain, ϵ) against log (test time, t) that fit relations of the type ϵ = βtm. For longitudinal specimens of cold-worked Zircaloy-2 at about 570 K, neutron flux of 1 × 1017 n m-2 s-1 (E > 1 MeV) and stresses σ below 310 MPa, the parameters β and m are given by β = (1.5 × 10-5) exp[(1.055 × 10-2)σ] and m = 0.24 + (4.5 × 10-4)σ Increasing the neutron flux from 1 to 3 × 1017 n m-2 s-1 or temperature from 490 to 620 K increases the value of β but has little effect on the time exponent m.

Primary creep of annealed Zircaloy-2 at temperatures between 470 and 570 K shows an abrupt decrease in the time exponent after about 10 h. Irradiation before stressing decreases primary creep strain of annealed and of cold-worked Zircaloy-2 at stresses above 300 MPa, but slightly increases primary creep of cold-worked Zircaloy-2 below about 200 MPa.
Analysis of Pressurized Water Reactor Fuel Pin Length Changes
Authors: Harbottle JE , Cornell RM
Published: March 2009

Textured Zircaloy fuel cans subjected to a net external coolant pressure will in general show a change in length due to anisotropic irradiation creep if mechanical interaction between the cladding and the fuel are negligible. Based on some recent measurements, the length increases observed in the pins of a pressurized water reactor fuel element are described to within 10 percent by a model based on irradiation growth and anisotropic creep. The model provides an adequate, quantitative explanation of the differences found between pressurized and unpressurized pins taking into account the change of hoop stress with fission gas buildup. The diametral measurements indicate that ratcheting is probably not a dominant mode of deformation in the majority of the cases.
Chemical Interaction Between Uranium Oxide and Zircaloy-4 in the Temperature Range Between 900 and 1500°C
Authors: Hofmann P , Politis C
Published: March 2009

Chemical interactions between the UO2 fuel and the Zircaloy-4 cladding material under power cooling mismatch (PCM) conditions are described. The out-of-pile uranium oxide (U02)/Zircaloy-4 reaction experiments were performed with short Zircaloy-4 tubular specimens filled with U02 pellets at temperatures between 900 and 1500°C under variable U02/Zircaloy-4 contact pressures and under inert gas conditions. The annealing periods varied between 3 and 60 min.

Due to the thermodynamic instability between U02 and Zircaloy, U02 is partially reduced by Zircaloy at the high temperatures investigated. The extent of the UO2/Zircaloy reaction as well as the composition of phases depends decisively on whether a good solid contact between U02 and Zircaloy has been established. If a solid contact exists, a (U-Zr)-alloy rich in uranium and an oxygen stabilized α-Zr(O) phase are formed.

The degree of chemical interaction between U02 and Zircaloy is determined by oxygen diffusion in the Zircaloy and the α-Zr(O)-phase formed. The UO2-Zircaloy reactions obey a parabolic rate law whose temperature dependence is given in the corresponding Arrhenius plot. The formation of oxygen-stabilized °-Zr(O) implies heavy embrittlement of the Zircaloy cladding above 1200°C. Thin oxide layers on the cladding tube inner surface prevent UO2/Zircaloy reactions from taking place below 1100°C. Simulated fission products (cesium, iodine, tellurium) in UO2 exert practically no influence on the extent of the reaction.

A comparison of the out-of-pile test results with those of in-pile experiments exhibits a very good agreement with respect to the phases formed.
Use of the Central Mudminnow (Umbra limi) in the Development and Evaluation of a Sister Chromatid Exchange Test for Detecting Mutagens in Vivo
Authors: Bishop WE , Valentine LC
Published: March 2009

Genetic toxicology is an area of scientific research which is receiving increasing attention. The increasing number of regulations regarding environmental mutagens and carcinogens has stimulated the development of numerous short-term screening test systems capable of detecting these substances. The sister chromatid exchange (SCE) test has become a popular test method both in vitro and in vivo, particularly because of its high sensitivity and relatively simple methodology. SCEs involve the symmetrical exchange of deoxyribonucleic acid (DNA) segments between homologous chromatids which can be readily visualized in appropriately treated and stained metaphase chromosomes. Though the precise mechanism or mechanisms remain unknown, SCE correlates well with, and may be predictive of, genetic damage.

The experiments reported here were designed to evaluate the use of the central mudminnow (Umbra limi) in an in vivo SCE screening test. The mudminnow's karyotype facilitates its use in the SCE test. Four known mutagens were tested: two direct acting—methyl methanesulfonate (MMS), and N-methyl-N′-nitro-N-nitrosoguanidine (MNNG)—and two indirect acting—cyclophosphamide (CP) and dimethylnitrosamine (DMN). Intraperitoneal injection of each compound produced a dose-dependent increase over control frequencies of SCEs in intestinal metaphase chromosomes. The sensitivity and efficiency of the mudminnow SCE test were confirmed and the results compared with those from other commonly used mutagenesis assays. Application of these procedures to other aquatic organisms having a broader toxicological data base should facilitate the development of a model aquatic system that is useful for studying the potential for genetic damage along with other acute and chronic effects.
Controlled Processing of Molybdenum Bearing Line Pipe Steels
Authors: Delvecchio GW , Hood JE , McCutcheon DB
Published: March 2009

Low-carbon Mn-Mo-Cb acicular ferrite steels are being used by several steel companies for higher strength line pipe above API X60. The molybdenum addition is made to achieve a continuous stress-strain curve that gives higher strength in the final pipe than that obtainable from conventional ferrite-pearlite steels. In this paper, the effects of chemistry and controlled rolling on plate and pipe properties are described for a series of steels: low-carbon Mn-Mo-Cb, low-carbon Mn-Mo-Cb-V, and low-carbon Mn-Cb-V. Low carbon Mn-Mo-Cb steels are shown to give the best combination of pipe properties for up to X70 level with thickness as high as 12 mm.
High-Hardenability Carburizing Steels for Rock Bits
Authors: Diesburg DE
Published: March 2009

High stresses experienced in rolling cutter rock bits during the drilling of large-diameter, deep oil wells require steels having extra high levels of hardenability. Nickel-molybdenum steels provide the needed hardenability and are being used successfully in the drilling industry. New EX-grades of steel were evaluated in the carburized condition by means of several laboratory tests and compared to the high-nickel SAE 4800 or SAE 9300 grades. The tests included impact fatigue, high-cycle fatigue, impact fracture stress, and plane-strain fracture toughness. In each test, the excellent performance of EX55 (0.87Mn-0.58Cr-1.85Ni-0.75Mo) was demonstrated.

Several compositional variables of EX55 were evaluated to determine their importance on mechanical properties. The variables included core carbon content as well as alloy modifications of chromium, nickel, and molybdenum. Steels having a core carbon content of 0.14 to 0.17 percent were observed to have more potential for exhibiting high impact fatigue resistance than 0.20 percent carbon steels.
Relationship Between Microstructure and Properties in Stainless Steels
Authors: Pickering FB
Published: March 2009

A review has been presented of the structure-property relationships in the major types of stainless steels, including the 12Cr transformable steels, the 17-25Cr ferritic steels, and the austenitic stainless steels. Quantitative relationships have been presented between microstructural parameters and the various mechanical properties that they control. Recent work on structure-property relationships in 12Cr steels have been summarized. Particular attention has been paid to the factors that describe the strength, toughness, and formability of the ferritic stainless steels, and attention has also been focused on the relationships that can be used to optimize the formability of the austenitic stainless steels, with particular reference to the stability of the austenite during straining.
Correlation of Sensitization with Thermomechanical History of Type 304 Stainless Steel Pipe Joint
Authors: Nakagawa YG , Kawamoto T , Fukagawa M , Saiga Y
Published: March 2009

A correlation of sensitization with thermomechanical work accumulated in a weld heat affected zone of Type 304 pipe was investigated in conjunction of heat-to-heat difference, and of a welding simulation. Highly susceptible pipe heats for stress corrosion crackings were introduced primarily through inappropriate mill practices that left pre-existing grain boundary carbides or strained subsurface layers in pipes. These undesirable heats that may have a sufficient corrosion resistance in the as-received state, most rapidly lose the resistance after being exposed to weld heat cycles. A weld simulation study was made to evaluate the thermomechanical effect on sensitization development, and distinct differences from isothermal sensitizations were confirmed by microstructure observations and some corrosion tests. The thermomechanical work and the successive continuous cooling enhance sensitization significantly.
Microstructural and Microchemical Studies in Weld Sensitized Austenitic Stainless Steels
Authors: Rao P
Published: March 2009

Considerable attention has been focused recently on understanding the detailed mechanism of intergranular stress corrosion cracking (IGSCC) in weld-sensitized austenitic stainless steels used as structural material components in light water nuclear reactors. It is well recognized that three major factors (namely, a sensitized microstructure, a stress and consequent strain-time behavior, and a corrosive environment) need to coexist in order that IGSCC may occur.This paper is only concerned with the characterization of the sensitized microstructure. In order to fully understand weld-sensitized microstructure, it is necessary to carry out detailed microstructural studies on the nature of grain boundary chromium-rich M23C6 carbides in the sensitized region adjacent to the weld bead. In addition, techniques have now been developed for performing detailed quantitative micro-structural measurements that allow the determination of carbide size, number density per unit area of grain boundary, grain boundary areal fraction coverage, and micrograms of chromium depleted from the neighboring grains. Qualitative and quantitative microstructural observations from several pipe heats, pipe diameters, and grain sizes are presented. Since the shape and depth of the chromium depletion profile in the vicinity of carbide particles is expected to govern the extent of susceptibility of the weld heat affected zone to the corrosive environment, a more realistic picture would be obtained if it were possible to map such depletion profiles. Only recently has it become possible with major developments in microanalytical instrumentation to use a combination of scanning-transmission electron microscopy (STEM) and high spatial resolution thin foil X-ray microanalysis for this purpose. Chromium depletion profiles are presented as a function of distance from austenite-austenite and austenite-carbide interfaces to demonstrate the feasibility of performing systematic sensitization studies on austenitic stainless steels used in reactor piping.
Effect of Heat Treatment and Microstructure on the Mechanical and Corrosion Properties of a Precipitation Hardenable Stainless Steel
Authors: Kosa T , DeBold TA
Published: March 2009

Custom 450 is a martensitic precipitation hardenable stainless steel. The strengthening mechanism during aging is attributed to precipitation of a very fine Laves phase. The precipitate was found to be relatively stable with respect to coarsening at aging temperatures above 811 K (1000°F). The aging reaction is accompanied by austenite reversion. The decrease in hardness and strength and increase in impact strength with increasing aging temperature and time when aging above 811 K are shown to be related to the increasing reverted austenite content of the alloy. Data are presented showing the effect of heat treatment on resistance to stress corrosion cracking. The relationship of cracking to toughness and general corrosion resistance is discussed.
Microstructural Objectives for High-Temperature Alloys in Advanced Energy Systems
Authors: Sims CT
Published: March 2009

This paper reviews six advanced systems in a broad fashion helpful in orientation of engineering and technical personnel not directly involved in such developments. These are coal utilization systems including coal liquefaction, coal gasification and pressurized fluid beds, nuclear systems including liquid metal fast breeder reactors (LMFBR), and high-temperature gas reactors (HTGR). In concert with these systems, yet cross-functioning, superalloy technologies are discussed for combined-cycle electrical plants and high-temperature heat exchangers. Then potential applications and problems for superalloys in the systems, are identified, drawing from this base examples that might typically be applied, utilizing these to discuss ideal microstructures one may find.
A Shorter Route to Steel Tire Cord
Authors: Cowlishaw FR
Published: March 2009

Processing of steel to give brass-plated high tensile cord suitable for tire reinforcement is lengthy and involves many processes, each requiring a specialized high capital cost plant and a multiplicity of technologies.

The production route adopted is necessary to provide a high quality product capable of giving trouble-free tire manufacture followed by service in tires without failure attributable to the steel cord.

Examination of the route suggests that some simplifications in the final stages of cord making is possible now that machines capable of aggregating up to four wires simultaneously at the wire drawing stage are available.

Multiple drawn wires (twins, triples, and quads) feeding final cord making machinery can give directly without any intermediate stranding operation 1 × n × 0.x mm combinations (where n = number of wires or filaments, and x = wire or filament diameter) such as 1 × 28 × 0.x mm type cords equivalent to the standard 1 × 4 + 6 × 4 × 0.x mm products.

Indications are that properties and manufacturing costs of cords made in the manner outlined compare favorably with cords made by the normal method.

In cooperation with Dunlop Limited, two such products, 3 × 10 × 0.175 mm replacing 1 × 3 + 5 × 7 × 0.15 + 1 × 0.15 mm and 1 × 14 × 0.175 mm replacing 1 × 3 + 6 × 3 × 0.15 mm, have been used successfully in truck tires for a number of years, confirming that bunch-type cords are capable of functioning and meeting the needs of a reinforcing material in tires.
Relative Importance of Cords and Rubber in Tire Rolling Resistance
Authors: Sharma RK , Kwon YD , Prevorsek DC
Published: March 2009

Experimentally measured temperature rise in tires is used to calculate tire temperature profiles and to estimate the mechanical loss of cords and rubber. These data are used to establish the relative importance of cords and rubber in tire rolling resistance. Three types of tires are examined: a bias passenger tire, a radial light truck tire, and a radial passenger tire. It is shown that the relative contribution of cords varies from 10 to 85 percent which is much more than expected on the basis of results reported in the literature. Each set of results is resolved in the rolling resistance due to: (a) the mechanical loss in tire sidewall, and (b) the loss in the shoulder-crown area. Effects of speed and load on tire are also discussed.
Fractographic Measurements of Crack-Tip Closure
Authors: Pelloux RM , Faral M , McGee WM
Published: March 2009

Relative changes in striation spacing resulting from a sudden change of the load range were used to measure crack-tip closure under plane-strain conditions. The tests were performed in a 2124-T351 aluminum alloy. The difference between the opening and closure rates of the crack tip was quantitatively measured by comparing striation spacings for two different programmed load blocks. It is concluded that crack-tip closure occurs principally in the plane-stress region of the crack front. In the center of the specimen, under plane strain, the average value of Kop/Kmax is less than 0.20 for ΔK varying from 10 to 35 MPa√m.
Direct Evaluation of J-Resistance Curves from Load Displacement Records
Authors: Joyce JA , Ernst H , Paris PC
Published: March 2009

The objective of this work was to experimentally develop a key curve for compact specimens of HY130 steel and to use this experimental function to generate the J-resistance curve from load displacement records alone using the analysis of Ernst et al. Eight 1/2T compact tension specimens with crack lengths from a/W = 0.59 to 0.94 were used to generate a series of load displacement records, which were assembled in a computer file as the key curve for geometrically similar compact specimens of this steel. Using this file, J-resistance curves (J-R curves) for 1T compact specimens were then obtained directly from the load displacement records and compared with unloading compliance J-R curves obtained for the same specimens. The critical J-values were found to be identical, but the new analysis gives much lower J-R curve slopes beyond the critical J for nonside grooved specimens. For side grooved specimens in which the crack does not tunnel, however, the J-R curves for the two methods were nearly identical. The J-R curves evaluated using the key curve method showed much less dependence on crack length than those obtained by the unloading compliance method. Agreement between the predicted and measured final crack length was excellent using the key curve method.
Estimation of J-Integral Uncertainty
Authors: Corman DE
Published: March 2009

A method for determining the effect of random experimental error on the calculation of J and crack length extension Δa is presented. Predictor-corrector equations for determining Δa are also derived and their convergence properties studied. The application to a three-point bend specimen is considered and numerical results presented.
Texture Control of Zircaloy Tubing During Tube Reduction
Authors: Nagai N , Kakuma T , Fujita K
Published: March 2009

Seven batches of Zircaloy-2 tubing with widely different textures were processed from tube shells of the same size, by different reduction routes using pilger and 3-roll mills. Based on the texture data of these tubes, the texture control of Zircaloy tubing, the texture gradient across the wall, and the texture change during annealing were studied.

The quantitative relationship between the texture parameter and the newly proposed strain ratio parameter was established using empirical equations in the case of both as-rolled and full-annealed tubing. The deformation texture of Zircaloy-2 tubing was dependent on the tool's curvature and was independent of the dimensions of the mother tubes. The different slopes of texture gradients were observed between the tubing of higher strain ratio and that of lower strain ratio. Also, the different types of the basal pole shift during annealing in the α temperature range were observed in the tested tubes.
Chemical Aspects of Iodine-Induced Stress Corrosion Cracking of Zircaloys
Authors: Cubicciotti D , Jones RL , Syrett BC
Published: March 2009

The thermodynamics of the zirconium-iodine system are summarized. In the gas phase are four stable species: ZrI4, ZrI3, ZrI2, and ZrI. Their enthalpies of formation and free-energy functions are presented. The only one of those species relevant to stress corrosion cracking (SCC) of zirconium alloys by iodine is the tetraiodide. There are also four solid compounds corresponding approximately in composition to the tetra, tri, di, and monoiodides. Ranges of solid solution composition, enthalpies of formation, and free-energy functions for those phases are given. Thermodynamic information for iodine chemisorbed on zirconium surfaces is also presented. These thermochemical results are used to analyze chemical behavior in situations related to SCC. In particular, reaction of cesium iodide with uranium dioxide in a fuel rod may produce an iodine pressure large enough to result in chemisorbtion of iodine on clean zirconium.

Crack initiation sites in commercial Zircaloy tubing were found to be associated with impurities (iron, aluminum, silicon, and chromium) in the Zircaloy surface in microsurface examination of failures produced in iodine-induced SCC tests. It is suggested that the impurity site may react with iodine to form a locally embrittled region that fails under stress and acts as a crack initiator.
Effect of Zirconium Oxide on the Stress-Corrosion Susceptibility of Irradiated Zircaloy Cladding
Authors: Mattas RF , Yaggee FL , Neimark LA
Published: March 2009

Cladding specimens were obtained from two fuel rods irradiated in the Big Rock Point Reactor to a burnup of ∼8 gigawatt days per ton. Both claddings had a uniform, thick (∼4 µm) zirconium oxide layer on the inner surface. The significant difference between the two rods was the degree of fission-gas release (0.2 versus 14.3 percent). The high-gas-release rod contained a significantly greater amount of fission-product deposits, and, in some areas, breaks in the inner-surface oxide were observed. The cladding speciments, with the fuel removed, were subjected to stress-rupture tests in an iodine environment using internal gas pressurization to evaluate their stress corrosion cracking (SCC) susceptibility. All tests were conducted at an initial iodine concentration of 0.6 mg/cm2 and a temperature of 325°C. Specimens from the high-gas-release rod exhibited signifciantly increased susceptibility to iodine SCC, with a threshold stress level of ∼200 MPa as compared with ∼280 MPa in the specimens from the low-gas-release rod. The results suggest that the inner-surface oxide provides a barrier to iodine penetration. Hence, the thick unbreached oxide on the low-gas-release rod provided greater resistance to iodine SCC than the breached oxide on the high-gas-release rod.
Waterside Corrosion of Zircaloy-Clad Fuel Rods in a PWR Environment
Authors: Garzarolli F , Jorde D , Manzel R , Politano JR , Smerd PG
Published: March 2009

Waterside corrosion of fuel rods has generally not been a problem under normal pressurized-water reactor (PWR) operating conditions, although some instances of accelerated corrosion have been reported. However, an incentive exists to extend the average fuel rod discharge burnups to about 50 000 MWd/Mtu. To minimize corrosion at these extended burnups, the factors which influence Zircaloy corrosion need to be better understood.

A data base of Zircaloy corrosion behavior under PWR operating conditions has been established. The data are compiled from previously published reports as well as from new Kraftwerk Union (KWU) fuel examinations.

This PWR data base has been compared with the predictions of a corrosion model derived from ex-reactor data. In order to predict the in-reactor corrosion behavior from ex-reactor corrosion models, a fitting factor (F) is required. The calculated fitting factor will depend on the corrosion models used to represent the ex-reactor kinetics; for the data analyzed, it was found to vary from 0.8 to 2.8. The data show that the reactor environment increases the corrosion. For a given corrosion model, the fitting factor varies from reactor to reactor, and within a given reactor it varies from cycle to cycle.

ZrO2 film thermal conductivity is another major factor that influences corrosion behavior. The thermal conductivity of the oxide layer has been determined only in out-of-pile tests on unirradiated specimens having a variety of oxide film microstructures. There is relatively large scatter in the measured data, and no such measurements exist for representative irradiated specimens. It was inferred from KWU film thickness data that the oxide film thermal conductivity may decrease once circumferential cracks develop in the layer. Measurements on irradiated specimens are needed to better evaluate the effect of the thermal conductivity of oxide films formed in-reactor on the in-reactor corrosion rate.

The corrosion mechanisms and the factors influencing the waterside corrosion of PWR fuel rods are not known precisely enough to allow for a reasonable extrapolation of current operating experience to rod average burnups of 50 000 MWd/Mtu.
In-Reactor Stress Relaxation of Type 348 Stainless Steel In-Pile Tube
Authors: Beeston JM , Burr TK
Published: March 2009

The results of a slit tube test, which show that large residual stresses do not develop during irradiation of in-pile tubes at operating temperatures of 573 to 698 K are presented. The slit width measurement at ambient conditions indicates that the predicted stress gradient due to irradiation growth was completely relaxed, and the residual stress that opened the slit was caused by the tube wall temperature change (hot to cold) when the reactor was shut down. No voids were detected and no immersion density gradient or difference in transmission electron microscopic (TEM) observations of irradiation-produced defects was found through the wall thickness. The microstructural mechanism for plastic flow through irradiation creep could explain the relief of the differential swelling stresses.
Effect of Texture on Hydride Reorientation and Delayed Hydrogen Cracking in Cold-Worked Zr-2.5Nb
Authors: Coleman CE
Published: March 2009

Hydride reorientation and delayed hydrogen cracking have been evaluated in specimens cut from the longitudinal and circumferential directions of cold-worked Zr-2.5Nb pressure tubes. In this material basal plane normals were highly concentrated in the circumferential direction. In longitudinal specimens hydrides did not reorient, cracks were not initiated, and artificial cracks grew slowly and only at KI>15MPa·m, whereas in circumferential specimens hydrides reoriented easily, cracks could be initiated, and grew at KI>4.5MPa·m25 25 times faster than cracks at the same KI in longitudinal specimens. Reorientation of hydrides is not necessary for delayed hydrogen cracking, but the degree of reorientation controls cracking susceptibility. Crystallographic texture regulates hydride reorientation and a rotation of basal plane normals from the circumferential to radial direction should reduce the susceptibility of Zr-2.5Nb and other zirconium alloys to delayed hydrogen cracking.
Anodic Dissolution and Crack Growth Rate in Constant Strain-Rate Tests at Controlled Potentials
Authors: Hishida M , Begley JA , McCright RD , Staehle RW
Published: March 2009

A theoretical analysis is presented of the constant strain-rate test. The rate of reduction of the cross-sectional area caused by straining is compared with the loss of cross section due to metal dissolution or crack growth, or both. The relationship between the environmental deterioration rate and the strain at which a maximum load is obtained in a constant strain rate test is developed as a function of strain rate. Experimental results of constant strain-rate tests of Type 304 stainless steel conducted in a 10 N sulfuric acid (H2SO4) + 0.1 M sodium chloride (NaCl) solution at various rates are discussed. Measured and calculated crack growth rates show good agreement.
Slow Strain-Rate Stress Corrosion Testing of Metals in Gaseous Atmospheres at Elevated Temperatures
Authors: Ugiansky GM , Johnson CE
Published: March 2009

A total of six different alloys—stainless steel (SS) Types 310, 310S, 347, and 446, and nickel alloys 800 and 671—were tested using the slow strain-rate test technique in oxidizing/sulfidizing and in oxidizing/sulfidizing/carburizing simulated coal gasification environments, and in helium (and other inert environments) at both 450 and 600°C at a strain rate of 10-6/s. Of the six alloys, four (Types 310 stainless steel and 310S stainless steel, nickel alloy 800, and nickel alloy 671) were found to be susceptible to cracking at 600°C by possibly different mechanisms, however, all were detected by the slow strain-rate technique.

For cracking, the nickel alloy 671 required no reactive environment; it suffered internal cracking in helium and all other test environments used. However, the stainless steel Type 310, Type 310S, and nickel alloy 800, all of which failed through surface initiated cracking, required increasingly severe environments for cracking. The Type 310 stainless steel required very little reactive environment; it cracked not only in the simulated coal gasification gases but also in low vapor pressure O2 or water (H2O) environments, or both (for example, helium), as did the Type 310S stainless steel, although with greater ductility than the Type 310 stainless steel. The nickel alloy 800 required the rather reactive environment of the simulated coal gasification gases; it did not crack in the low vapor pressure O2 and H2O environments.

The detection of the environmentally independent failure of Alloy 671 shows that the use of the slow strain-rate technique need not be limited to use for testing for susceptibility to cracking by stress corrosion cracking. The slow strain-rate technique is shown to be a viable testing method for detecting an alloy's propensity to premature failure in simulated coal gasification environments.
Slow Strain-Rate Testing in High Temperature Water
Authors: Solomon HD , Povich MJ , Devine TM
Published: March 2009

The apparatus and technique employed in slow strain-rate testing of stainless steels in high temperature high purity water are described and discussed. Typical results from work in progress on the influence of heat treatment and surface treatment on the intergranular stress corrosion cracking of Types 304 and 308 stainless steel and Alloy XM-19 are described. The correspondence between strain-rate tests varies from alloy to alloy. The minimum strain rate required to cause intergranular cracking varied significantly with the alloy and with the surface treatment. It is suggested that reduction of area and observation of the fracture mode provide better measures of environmental interactions than measures of tensile parameters obtained from the test records.
Design and Construction of an Inexpensive Multispecimen Slow Strain-Rate Machine
Authors: Nutter WT , Agrawal AK , Staehle RW
Published: March 2009

The general considerations required in the design and construction of a slow strain-rate machine are discussed. A multispecimen machine built at the Ohio State University is illustrated, and the principal components used in this machine are listed. A four-specimen machine with a crosshead speed adjustable between 10-4 and 10-8 cm/s can be built for about $5000.00.
General Discussion—Historical Note on the Slow Strain Testing of Solder
Authors: Treseder RS
Published: March 2009

This is a historical note describing an early experience of Aaron Hachter, Ross Miller, and the writer with slow strain-rate stress corrosion testing. In 1945 there was some concern about the possibility of stress-related corrosion effects on the soldered joints in automobile radiators when sodium nitrite was used as a corrosion inhibitor in the radiator coolant. The accepted method of determining stress corrosion cracking (SCC) susceptibility in those days was to make tests using U-bend specimens. Obviously, this technique was not compatible with the mechanical properties of solder. Therefore, a test method was devised; this method was called a creep corrosion test. The specimen was a 50.8 mm long by 3.2 mm (2 by ⅛ in.) diameter rod of 50-50 solder (50Sn, 50Pb) with brass end pieces. The specimen was loaded in tension by a 0.34 kg (0.75 lb) steel weight. Figure 1 shows the simple apparatus that was used.
A Modified Spread Plate Technique for the Determinations of Concentrations of Viable Heterotrophic Bacteria
Authors: Young M
Published: March 2009

Four techniques for the enumeration of viable heterotrophic bacteria were evaluated for use with environmental samples. Factors being sought were an economical use of materials and time and a superior level of bacterial recovery. The techniques compared in this study were pour plate, spread plate, membrane filtration, and the modified spread plate technique (spot plate).

Eighty-four water and thirty-two sediment samples were analyzed for heterotrophic bacterial concentrations using the four methods under study. A statistical analysis of the data by a factorial analysis of variance and a t test indicated that there was no significant difference in the recoveries of the spread plate and spot plate techniques. Both of these produced superior recoveries to the membrane filter and pour plate methods. Poorest recoveries were obtained with the pour plate for water and membrane filter for sediment.

The spot plate method was determined to be the most appropriate method for our purposes, since it was superior in most areas of interest to the other methods tested.
Determining the Sediment Distribution of Methanogenic Bacteria by Direct Fluorescent Antibody Methodology
Authors: Ward TE , Frea JI
Published: March 2009

A direct fluorescent antibody (FA) methodology was devised to accurately quantitate a select number of known methanogenic bacteria in the sediments of Lake Erie. The specificity of the respective fluorescent antibodies was evaluated against a limited number of hetero- and methylotrophic bacteria. The fluorescent antibodies for each of the surveyed methanogens were specific in that no cross reactions with the other methanogenic species could be shown. The autofluorescence of the methane bacteria and nonspecific absorption were masked by rhodamine isothiocyanate conjugated bovine serum albumin (RhoITC-BSA). The FA methodology devised permitted the detection of the specific methanogens in numbers as low as 106 cells per gram of lake sediment. The FA method worked equally well when applied to fine silt, sand-silt, or sand sediments. The presence of large numbers of other microorganisms did not interfere with the staining process. To increase the sensitivity of this sediment analysis, organic and inorganic enrichments were pursued. These procedures permitted the selective enrichments of specific methanogens to population sizes (106/ml or greater) large enough for direct FA observation. Thus, this direct FA staining methodology can specifically and accurately quantitate the known methanogenic bacteria in lake sediments. This procedure can be combined with concentration techniques to increase the sensitivity of the FA procedure. Also, this staining procedure could be adapted to other methanogenic bacteria, either known pure cultures or natural isolates, which could be obtained from lake sediments.

The greatest advantage this enumeration has over other methods of enumerating methanogens [most probable number (MPN), substrate limitations, or general cellular morphology] is that it is a direct count that is species specific.
Lipid Analysis of Sediments for Microbial Biomass and Community Structure
Authors: White DC , Bobbie RJ , King JD , Nickels J , Amoe P
Published: March 2009

The microbial ecology of sediments has proved notoriously difficult to analyze because of the complex composition of nonliving structures. Examination of the lipid extracts of lyophilized core samples has proved a feasible method of biomass determination. Extractable lipid phosphate, shown in previous work to correlate well with other measures of the microbial biomass and to correlate with sedimentary extractable adenosine triphosphate (ATP), can be reproducibly determined from sedimentary materials. Labeled lipids and poly-β-hydroxybutyrate (PHB) added to the sediments can be recovered in reasonable yields, and analysis from a single estuarine station shows reasonable reproducibility between different core samples.

The community structure as measured by the proportion of diacyl phospholipids, plasmalogens, phosphonolipids, and characteristic fatty acids as well as the bacterial endogenous storage material PHB shows differences between the different horizontal horizons in a sedimentary core that are consistent with expected changes based on predictions from bacterial monocultures.
Toughness of 18Cr-2Mo Stainless Steel
Authors: Redmond JD
Published: March 2009

The effect of residual and stabilizing elements on toughness has been investigated for a series of 18Cr-2Mo ferritic stainless steels which contained 0.015C and 0.015N. The residual elements varied were sulfur, manganese, and silicon. The stabilization variables were niobium, titanium, (Nb + Ti), and (Nb + Al).

The impact transition temperature was determined in the base metal and weld deposit for all steels. Crack opening displacement (COD) measurements were made on selected steels in the welded condition and a COD transition temperature was determined for these.

Over the ranges investigated, sulfur, manganese, and silicon had only minor effects on the base metal and welded impact toughness.

The best base metal impact toughness was achieved with a combination of (Nb + Al) stabilization. A niobium-stabilized steel to which 0.5 percent aluminum had been added exhibited a FATT50 (fracture appearance transition temperature) of -60°C. Niobium stabilization and (Nb + Ti) stabilization gave transition temperatures intermediate between (Nb + Al) combination and titanium-stabilization.

The (Nb + Al) stabilizer combination also gave the best weld metal impact toughness with a FATT50 of approximately 25 °C; however, the steel had limited weld ductility. The niobium-stabilized steels had higher weld impact transition temperatures than the titanium-stabilized steel, with the mixed (Nb + Ti) combination being intermediate between them.

The (Nb + Ti) stabilized steel had the best COD fracture toughness and seems to be the best stabilizer choice for a combination of base metal and welded toughness and ductility.
Effect of Residual Elements and Molybdenum Additions on Annealed and Welded Mechanical Properties of 18Cr Ferritic Stainless Steels
Authors: Wood JR
Published: March 2009

The annealed and welded mechanical properties of titanium-stabilized 18 percent chromium (18Cr) ferritic steels were studied as functions of molybdenum content (0, 1, and 2 percent) and residual levels. The residual elements carbon, nitrogen, manganese, silicon, nickel, copper, and molybdenum were evaluated at low levels typical of virgin-charge, vacuum melt practice and at moderate levels typical of electric-arc furnace melt practice. It was found that the residual elements manganese, silicon, nickel, and copper and excess titanium [defined as total titanium minus that necessary for stabilization of carbon plus nitrogen (C + N)] influenced annealed and welded tensile properties to the greater degree, whereas titanium, (C + N), and molybdenum additions of 1 and 2 percent were more influential on as-welded toughness. Impact transition temperatures of welds were lowered by as much as 100 deg F (55 deg C) in 18Cr alloys by decreasing residual, titanium, and (C + N) levels from typical to very low levels. Titanium was found to be the most potent solid solution strengthening element. Titanium was approximately twice as effective as molybdenum and slightly more effective than the combined effects of other substitutional residual elements. For light-gage applications such as sheet, strip, or welded tubing, a good combination of strength, ductility, and toughness was found with a low (C + N), low-titanium, low-residual analysis at all molybdenum levels studied. For heavier-gage applications such as plate or piping, where ductility and toughness are probably more sensitive to grain size and annealing and welding variables, it is also implied that a low-residual, low-titanium, low (C + N) analysis would be beneficial for a good combination of toughness and ductility.
Vapor Retarders in Roofing Systems: When Are They Necessary?
Authors: Condren SJ
Published: March 2009

Despite continuing debate about the need for, and efficacy of, vapor retarders as part of a roofing system, little information has been published on the specifics governing their use. This paper proposes criteria and computation methods to determine the need for vapor retarders.

We evaluate vapor diffusion as a source of condensation. We present a procedure to calculate moisture migration by diffusion, using typical interior and exterior temperature and moisture parameters, to determine the vapor migration into a roofing system. Our methods include provisions for calculating moisture accumulation in the roofing system during winter conditions, and its drying out during the summer when vapor pressures reverse direction to the interior. We propose allowable limits for moisture accumulation at any time, which are designed to prevent loss of insulating value and degradation of the roofing system from excessive moisture. This analysis, when coupled with design limits, provides a rational basis for the incorporation of vapor retarders into the roofing system.

We also consider the problem of air leakage through the building envelope as the more frequent cause of condensation problems. We discuss the mechanisms by which condensation problems arise, and provide guidelines to minimize this problem through the use of vapor retarders and other air seals. Condensation through air leakage is best controlled by proper detailing of the roofing components to prevent air leakage. Calculations are unnecessary.