bluuebunny/crossref_metadata_2025 huggingface dataset:
Bureau of Reclamation Experience with Construction and Control of Earth Materials for Hydraulic Structures
Authors: Farrar JA
Published: April 2008

The United States Department of the Interior, Bureau of Reclamation has a long history of development of large water supply projects in the western United States. Reclamation developed unique earthwork control techniques such as the Rapid Method of Construction Control. The Rapid Method is a three-point impact compaction test based on standard impact compaction energy level, and is performed on an adjusted wet density basis thus alleviating the need for water content determinations. Each soil sample from the in-place density test is tested using the Rapid Method to assure accurate determination of degree of compaction. Reclamation also uses the relative density for cohesionless soil and has developed a new vibratory hammer test for maximum density. Technology transfer has been accomplished through publications such as the Earth Manual, and by active participation with ASTM, resulting in standardization of many test methods. This paper will review Reclamation procedures and discuss current trends in earthwork construction control.
NRCS Experience with Field Density Test Methods Including the Sand-Cone, Nuclear Gage, Rubber Balloon, Drive-Cylinder, and Clod Test
Authors: McCook DK , Shanklin DW
Published: April 2008

Engineers of the Natural Resources Conservation Service (formerly the Soil Conservation Service), USDA, instituted a testing program to determine the reliability and reproducibility of several types of field density test methods. Tests were performed at several embankment construction sites in the Southeastern United States. Several different soil types were encountered in the embankment projects. On test pads constructed under normal field conditions, researchers measured the compacted dry density and water contents by the nuclear gage, sand-cone, drive-cylinder, and clod tests. The research compares the results of the various tests and discusses the conclusions of the researchers on reliability and accuracy of the various tests.

Conclusions of the studies include important aspects of each test that were found to explain variations and errors in the tests that were performed. The paper emphasizes errors common to the tests evaluated. Recommendations based on the studies of the NRCS are included. Advantages and disadvantages of methods are discussed. Data from the study sites is included to illustrate repeatability and comparisons of the various methods to each other. Data from the study sites are included to illustrate repeatability and comparisons of the various methods with each other.
Historical Perspectives on Earthwork Engineering and Creating a Passion for Earthwork Excellence
Authors: Hardin CD , Icenhour GD
Published: April 2008

Earthwork engineering practices have been reasonably well defined since the early 1900s. Knowledge of the historical approach to solving subsurface soil problems can be gained by reviewing the writings of the pioneers of soil mechanics. Of particular interest are the writings of Karl Terzaghi, the father of modern soil mechanics. Application of Professor Terzaghi's attitude towards consulting engineering will result in a passion for earthwork engineering excellence. The authors have observed the practical application of earthwork engineering principles in a manner which provides quality earthwork projects at a reasonable cost.
Compaction Control to Minimize Settlement of Fill Supporting a Shopping Center
Authors: Newman FB , Mazzella SG
Published: April 2008

A sloping site was regraded to a nearly level configuration for a strip shopping center. This resulted in one end of the building being underlain by rock at finished subgrade and the other end by up to 35 feet of compacted soil-rock fill. In addition, abandoned coal mine workings were present under the portion of the building with the rock subgrade. A portion of the building was supported by reinforced concrete drilled pier foundations through the abandoned mine to prevent damage due to mine subsidence. The other portion of the building was supported by spread footings bearing on compacted fill. This paper describes how ASTM testing methods were employed in controlling compaction of mixed soil-rock fill to limit total and differential settlements to tolerable values. Settlements after ten years have been minimal.
Compaction and Performance of Loess Embankments
Authors: Zhang L , Du J , Hu T
Published: April 2008

This paper summarizes the practice of highway embankment compaction in the loess plateau of northwestern China, based on a field trip and the related laboratory studies. A large number of high loess embankments were built across gullies. The compaction was based on the standard Proctor method (ASTM Test Method for Laboratory Compaction Characteristics of Soil Using Standard Effort, D698-91) during 1950 – 1985, and the modified Proctor method (ASTM Test Method for Laboratory Compaction Characteristics of Soil Using Modified Effort, D1557-91) after 1985. The performance of these embankments is described. Stability analysis and centrifuge tests are conducted to confirm the observations and improve designs. Storm water ponds are found to be critical to both stability and settlement. For embankments compacted using the standard Proctor method, progressive failure would start with any further erosion if the slopes were steeper than 1:0.75.
Comparison of Laboratory Data and Field Performance for Fills Subject to Hydrocompression
Authors: Kropp AL , McMahon DJ
Published: April 2008

Over 120 laboratory response-to-wetting (hydrocompression) tests on engineered fill samples using various procedures were compiled from the literature and from private files of geotechnical engineers in the State of California. These data were grouped into three categories according to the level of relative compaction used for the fill; these categories were 85 to 89%, 90 to 91%, and 92 to 95% relative compaction. In addition, field performance data from nine sites were compiled, which recorded the magnitude of hydrocompression in deep fills compacted with a minimum 90% relative compaction specification. Comparison of the magnitude of hydrocompression settlements calculated from the laboratory testing with the recorded values at project sites showed general agreement.
The Effect of Soil Composition and Moisture Content on Dry Density and Hydraulic Conductivity of Clays
Authors: Darban AK , Foriero A , Yong A , Yong RN
Published: April 2008

Soil composition and moisture content have significant effects on the resulting ulk density of clayey soils because of the rearrangement of the solid particles and chemical stabilization. In this study, kaolinite and kaolinite with calcium carbonate (KC), silica gel (KS), and both calcium carbonate and silica gel (KSC) were compacted at different moisture contents according to ASTM standards. These mixtures of compacted clays were then subjected to leaching by distilled water, followed by a solution of heavy metals. Experimental results indicate that the dry density and coefficient of hydraulic conductivity are significantly influenced by the soil constituents. Specifically, kaolinite exhibits a low dry density and a high coefficient of permeability when compared to the other soils (KS, KC and KSC). As permeant flow approaches a stationary regime, greater pore volumes of effluents result, and an increase in the coefficient of permeability is observed in all types of soils. Tests confirm that chemical reactions are responsible for permeability increases up to a constant value. Expressly, kaolinite mixtures with silica gel or calcium carbonate exhibit a coefficient of permeability almost one order less than that of kaolinite. Results indicate the importance of silica gel as an additive for the reduction of the permeability in clay soils.
Impact of Heavy Metals (Pb, Zn, and Cr) on the Hydraulic Conductivity of Sand/Bentonite Liner
Authors: Thériault P , Galvez-Cloutier R , Winiarski T
Published: April 2008

This research was conducted to study the changes in permeability of a sand/bentonite liner made under standard compaction conditions and permeated with solutions containing the heavy metals Pb+2, Zn+2 and/or Cr+3. The fine particle size distribution and the free swelling capacity of the bentonite were taken as indicators of the impact of contaminants on the liner's properties.

Generally, particles of bentonite were coarser when in contact with solution ontaining heavy metals. Its free swelling capacity decreased when heavy metal concentrations increased. It is shown that with heavy metal solutions the permeability of a sand/bentonite liner increased by three orders of magnitude. The ion Cr+3 which had a greater impact on the free swelling capacity may have led to a rapid change in permeability. When permeability increased rapidly, heavy metals were present earlier and in higher concentration at the outlet of the liner.
Effects of Thermal History and Physical Aging on Thermal Properties of Poly-L-Lactide
Authors: Deng M , Allan JM , Corbett JT , Shalaby SW
Published: April 2008

Poly-L-lactide (PLL) represents a major bioabsorbable polymer used in implants. Depending on its thermal history, PLL can exhibit three discernible thermal transitions upon heating: glass transition, recrystallization, and melting. These transitions are pertinent to the polymer's short- and long-term performance. Accordingly, properties of medical devices made of PLL may be altered and optimized when subjected to different thermal environments. In the present study, differential scanning carlorometry was used to study effects of thermal treatment and physical aging on thermal properties of PLL. Heat treatment was conducted at three different temperatures. Physical aging was performed at room temperature for five different time intervals. Results indicate that glass transitions and level of crystallinity were affected significantly. The polymer crystallinity can be greatly increased by thermal treatment, which may ultimately improve its mechanical properties, as well as strength retention, and absorption profile. Relevance of these results to the physical events taking place during the treatment, and their impact on post-processing and property change of fabricated articles are discussed.
Resorption Profile and Biological Response of Calcium Phosphate filled PLLA and PHB7V
Authors: Jones NL , Cooper JJ , Waters RD , Williams DF
Published: April 2008

A study was performed to assess the effects of tri-calcium phosphate filler on the tissue response, mechanical properties and degradation characteristics of injection moulded poly L-lactide (PLLA) and poly-hydroxybutyrate co valerate (7 mole % valerate) (PHB7V).

Test pieces for mechanical evaluation were prepared according to ASTM and British Standards. These were aged both in vitro, using a phosphate buffered saline solution (PBS) at pH 7.4 and 37°C and in vivo, subcutaneously using Dutch rabbits. Tensile strength of the materials was monitored, together with molecular weight (Mw) of the polymer as determined by gel permeation chromatography (GPC). The host response to intraosseous implants placed transcortically in the femurs of New Zealand rabbits, was assessed using an undecalcified, unstained, polarised light technique on resin embedded and polished sections.

The materials had good biocompatibility. The bone response to the polymers and composites was very similar. Histology showed that new bone was formed at the defect site, which grew up to the material surface and remodelled into new physiological bone tissue. The rate of degradation of the poly-L-lactide and it's composite with tri-calcium phosphate as assessed by tensile strength and Mw was found to be consistent with the rate for bone healing. Poly-hydroxybutyrate co valerate and its composite with tri-calcium phosphate degraded more slowly.
The Use of the Vibrating Particle Technique to Fabricate Highly Porous and Permeable Biodegradable Scaffolds
Authors: Agrawal CM , McKinney JS , Huang D , Athanasiou KA
Published: April 2008

This study describes the degradation behavior of biodegradable scaffolds fabricated from a copolymer of polylactic acid and polyglycolic acid using a new technique that eliminates some of the problematic issues with the salt-leaching technique. Two variations of this technique were used and the in vitro degradation characteristics of the resulting scaffolds were compared. The properties monitored included mass, molecular weight, porosity, permeability, mechanical stiffness, and polydispersity. The results indicated that the vibrating particle technique, results in scaffolds that are at least 90% porous and highly permeable. During degradation the porosity of the scaffolds initially decreased up to two weeks and then inceased. On the other hand, their stiffness first increased followed by a decrease. It was also determined that the permeability of the scaffolds can vary considerably without significant changes in the porosity.
Clinical Evaluation of a Bioresorbable Membrane for Hard Tissue Regeneration
Authors: Hutmacher DW , Kirsch A , Ackermann KL , Hürzeler MB
Published: April 2008

In the field of guided bone regeneration, biomedical engineering has been applied, more or less successfully, to the development of biodegradable and bioresorbable membranes whose chemical, physical, or mechanical properties, structure, or form permits active tissue integration of desirable cell types and tissue components. The employment of synthetic and naturally occurring polymers as well as sophisticated manufacturing technologies allow the design and fabrication of matrix configurations, so that the biophysical limitations for guided bone regeneration can be satisfied. The configuration of such a hybrid matrix can also be manipulated to vary the surface area available for cell attachment, as well as to optimize the exposure of the attached cells to nutrients. A bioresorbable membrane made of synthetic and natural polymers has been developed and manufactured. This innovative device concept has been applied as guided bone regeneration (GBR) membrane.
A Constitutive Model for Long-Term Behavior of Polymers
Authors: Skrypnyk ID , Spoormaker JL , Kandachar P
Published: April 2008

This paper describes a constitutive model for long-term behavior of plastics. The Struik theory of physical aging is adapted for use with the earlier proposed generalization of the Schapery model. Experimental data on creep and recovery behavior for different elapsed times are necessary to build the model. The parameter identification procedure is based on a minimization of the total error between experimental data and model prediction.

The model has been verified using extensive experimental data on long-term creep and recovery of polypropylene, reported by the National Physical Laboratory (NPL, Teddington, U.K.). The model has shown the ability to work with the independent data; it sufficiently describes the variation of strains in time for loading history, which contains several loading steps. The maximum deviation of the model prediction from the experimental data in a control set is less than 11% to 12%. The average deviation is less than 4%.
An Overstress Model for Solid Polymer Deformation Behavior Applied to Nylon 66
Authors: Krempl E , Ho K
Published: April 2008

Extensive experimental investigations at ambient temperature on commercial Nylon 66, PEI (Polyetherimide) and PEEK (poly(ether ether ketone)) have shown that the overstress model developed for viscoplasticity should be, in principle, capable of modeling for solid polymers the rate-dependent behavior, including creep, relaxation and cyclic motions. The viscoplasticity theory based on overstress was modified accordingly to allow for the modeling of typical solid polymer deformation behavior. Included are nonlinear rate sensitivity, curved unloading, significant strain recovery at zero stress and cyclic softening. The visco plasticity theory based on overstress for polymers (VBOP) is introduced in uniaxial formulation. It is shown that VBOP can be thought of as a modified standard linear solid with overstress-dependent viscosity and nonlinear, hysteretic equilibrium stress evolution. VBOP consists of a flow law that is easily adopted to cases where the strain or the stress is the independent variable. The flow law depends on the overstress, the difference between the stress and the equilibrium stress with the latter being a state variable of VBOP. The growth law of the equilibrium stress in turn contains the kinematic stress and the isotropic or rate-independent stress, two additional state variables of VBOP. The material constants of VBOP are determined for Nylon 66 at room temperature and various tests are simulated by numerically integrating the set of nonlinear differential equations. The simulations include monotonic loading and unloading at various strain rates, repeated relaxation, recovery at zero stress that is dependent on prior strain rate, and cyclic strain-controlled loading. Finally, the stress-controlled loading and unloading are predicted with very good results. The simulations and predictions show that VBOP is competent at modeling the behavior of Nylon 66 and other solid polymers.
Nonlinear and Dynamic Compressive Behavior of Composites with Fiber Waviness
Authors: Hsiao HM , Daniel IM
Published: April 2008

The nonlinear and dynamic behavior of unidirectional composites with fiber aviness under compressive loading was investigated theoretically and experimentally. Unidirectional carbon/epoxy composites with uniform fiber waviness were studied. Complementary strain energy was used to derive the material nonlinear stress-strain relations for the quasistatic case. Nonlinear material properties obtained from shear and longitudinal and transverse compression tests were incorporated into the analysis. An incremental analysis was used to predict the static and dynamic behavior of wavy composites using the basic strain rate characterization data. It is shown that under uniaxial compressive loading, strong nonlinearities occur in the stress-strain curves due to fiber waviness with significant stiffening as the strain rate increases. Stress-strain curves are affected less by fiber waviness under other loading conditions. The major Young's modulus degrades seriously as the fiber waviness increases. It increases moderately as the strain rate increases for the same degree of waviness. Unidirectional composites with uniform waviness across the thickness were prepared by a tape winding method. Compression tests of specimens with known fiber waviness were conducted. Experimental results were in good agreement with predictions based on the complementary strain energy approach and incremental analysis.
Accelerated Strength Testing of Thermoplastic Composites
Authors: Reeder JR , Allen DH , Bradley WL
Published: April 2008

Constant ramp strength tests on unidirectional thermoplastic composite specimens oriented in the 90° direction were conducted at constant temperatures ranging from 149°C to 232°C. Ramp rates spanning 5 orders of magnitude were tested so that failures occurred in the range from 0.5 s to 24 h (0.5 to 100 000 MPa/sec). Below 204°C, time-temperature superposition held allowing strength at longer times to be estimated from strength tests at shorter times but higher temperatures. The data indicated that a 50% drop in strength might be expected for this material when the test time is increased by 9 orders of magnitude. The shift factors derived from compliance data applied well to the strength results.

To explain the link between compliance and strength, a viscoelastic fracture model was investigated. The model, which used compliance as input, was found to fit the strength data only if the critical fracture energy was allowed to vary with stress rate. This variation in the critical parameter severely limits its use in developing a robust time-dependent strength model. The significance of this research is therefore seen as providing both the indication that a more versatile acceleration method for strength can be developed and the evidence that such a method is needed.
Hygrothermal Effects on Failure Mechanisms of Composite/Steel Bonded Joints
Authors: Roy A , Gontcharova-Bénard E , Gacougnolle J-L , Davies P
Published: April 2008

The aging in water of steel/composite glass polyester specimens bonded with an epoxy adhesive has been studied at 25° and 40°C. The damage processes are controlled by water diffusion. The main damage is due to the adhesive swelling but, when specimens are loaded during immersion, the stress gradient at the extremities of the joint accelerates the water diffusion and then the failure of specimens. A simple logarithmic relationship between the specimen life time and the applied load makes easy the life prediction.
Standard Methods for Beryllium Sampling and Analysis: Availabilities and Needs
Authors: Ashley K , Brisson MJ , Jahn SD
Published: April 2008

Conformity in methods for sampling and analysis of beryllium in workplace air and on surfaces is desired, but inconsistencies in sampling and analytical practices often occur among industrial hygienists and laboratory personnel. In an effort to address these issues, this paper gives an overview of standardized methods for sampling and analysis of beryllium in the workplace. A number of published methods is currently available to the industrial hygiene and analytical community, but shortfalls in the use of standardized practices require attention. Also, questions remain concerning the performance of some of the sampling and analytical methodologies that have been promulgated. We attempt to identify needs for new or improved standard sampling protocols, sample preparation techniques, analytical methods, and reference materials. Where applicable, performance data are summarized for standardized methods that are either published or are under development. These include not only ASTM and ISO international standards, but also methods published by government agencies in the USA and abroad. Significant gaps in standard methods and requirements for reference materials remain. For example, consistent practices are lacking for: (a) surface sampling of beryllium in dust; (b) extraction of beryllium from surface dust samples prior to instrumental analysis; and (c) reference materials containing beryllium oxide (especially high-fired BeO). These and other gaps will be identified and shortcomings addressed. An ultimate goal is to provide standard methods which will ensure comparability of data obtained from different sites around the globe.
Use of Electrically Enhanced Aerosol Plasma Spectroscopy for Real-Time Characterization of Beryllium Particles
Authors: Cheng MD , Smithwick RW , Hinton R
Published: April 2008

The best warning of human exposure to elevated toxic aerosol particles is a monitor that can provide a near-real-time alarm function. Use of surrogate indices such as particle-number concentration, mass concentration, and/or other flow-diagnostics variables is ineffective and could be costly when false positives do arise. We have developed a field-portable system specifically for monitoring beryllium particles in the air in near real-time. The prototype monitor is installed on a two-shelf handcart that can be used in workplaces involving beryllium extraction, machining, and parts fabrication. The measurement involves no sample preparation and generates no analytical waste. The operating principle of the monitor is electrically enhanced laser-induced electrical-plasma spectrometry assisted with aerosol-focusing technology. Performance data of the monitor indicate a dynamic range spanning over four orders of magnitude, and the monitor is capable of detecting an airborne beryllium concentration of 0.05 μg m−3. In reference, the Department of Energy (DOE) standard for beryllium is 0.2 μg m−3 within an 8-h average, while the Occupational Safety and Health Administration standard for beryllium is 2 μg m−3. In addition, the monitor is capable of simultaneous detection of multiple elements using an Echellette spectrometer if needed. The capability of simultaneous detection provides a convenient means for positive identification and possible quantification of multiple elements in near real time. We present the instrument development and calibration data and results from field demonstration conducted at a DOE facility in Oak Ridge, Tennessee.
ZIRLO™ — An Alloy Development Success
Authors: Sabol GP
Published: April 2008

Significant data and milestones in the development of the ZIRLO alloy for PWR applications are reviewed. From humble beginnings as an R&D program, an approach to improving the corrosion resistance of zirconium-based alloys was developed. The corrosion resistance of dilute alloys is controlled by the microstructure, and both solid solution and precipitate effects impact corrosion performance. Several transition metals are beneficial for corrosion at low concentrations, but the most favorable alloy system is zirconium-niobium, because it offers flexibility in processing options. Strength of the binary alloys can be improved by additions of tin, which, in combination with low levels of iron, provide corrosion resistance in lithium hydroxide solutions. Numerous experimental ingots, thermo-mechanical processing routes, corrosion tests, and materials characterizations were performed along the path to the final alloy composition. The resulting material, ZIRLO, has proven itself as a successful alloy for PWR fuel cladding and structural applications.
Plastic Deformation of Irradiated Zirconium Alloys: TEM Investigations and Micro-Mechanical Modeling
Authors: Onimus F , Béchade J-L , Prioul C , Pilvin P , Monnet I , Doriot S , Verhaeghe B , Gilbon D , Robert L , Legras L , Mardon J-P
Published: April 2008

TEM investigations have been performed on irradiated samples after deformation covering various testing conditions for different recrystallized Zr alloys. It is shown that for transverse tensile tests and internal pressure tests performed at 350°C, only basal channels are observed for strain levels up to uniform elongation, whereas only prismatic and pyramidal channels are observed for axial tensile test. Then, focusing on internal pressure testing, irradiation hardening and strain hardening behavior have been analyzed in detail and compared to TEM observations. It is proposed that dislocation channeling phenomenon leads to high strain incompatibility between channels and surrounding grains and therefore to high microscopic internal stresses. These high microscopic internal stresses are believed to induce strong kinematic hardening at the macroscopic scale, as suggested by the mechanical behavior analysis. Finally, a micro-mechanical model based on microscopic deformation mechanisms and using homogenization techniques is proposed, taking into account the observed channeling phenomenon.
On Secondary β-Nb Phase Precipitation within Primary α-Zr Phase in Zr-Nb Alloys During Tensile Deformation
Authors: Kapoor K , Padmaprabu C , Saroja S , Paul T , Rao SVR , Sanyal T , Rao MN , Saibaba N , Kashyap BP
Published: April 2008

Two-phase alloys of zirconium, Zr-1wt% Nb and Zr-2.5wt% Nb, are widely used in nuclear reactors as fuel-clad and structural material, respectively. Post-irradiation studies on Zr-Nb alloys have shown Nb rich β (containing more than 50wt% Nb) precipitation within the α-Zr phase. In the present study, slow deformation of the two alloys at elevated temperature was carried out on unirradiated material at different temperature up to 873 K. Secondary phase (β-Nb), identified by TEM, micro diffraction and Energy Dispersive Spectroscopy, was observed to precipitate within the primary phase (α-Zr), which is similar to the observations in the irradiated material. The precipitation was dependent on temperature and imposed strain. Measurements of the lattice parameter of the α-Zr phase using X-ray diffraction show a sharp increase in samples deformed above 550 K, where the precipitation was also observed. This change is due to Nb drawn out of the supersaturated α-Zr phase during precipitation. There is a progressive increase in the dislocation density, measured by X-ray diffraction, due to strain on elevated temperature tensile deformation (up to 723 K). No such change in lattice parameter was observed in the case of samples aged at test temperatures without deformation. Dislocations generated during deformation provide enhanced Nb diffusivity, increased preferential nucleation sites, and reduced the strain energy required for nucleation of the β-Nb phase within the existing α-Zr phase. The similarity in the secondary phase precipitation observed between slow deformation at elevated temperature and irradiation is explained on the basis of dislocation-enhanced precipitation. The change in the texture due to the uniaxial tensile deformation at elevated temperature gives information on the acting deformation mechanisms. By measurement of texture at each test temperature, the deformation mechanisms were determined, which is related to the observed precipitation behavior.
Modeling of the Simultaneous Evolution of Vacancy and Interstitial Dislocation Loops in hcp Metals Under Irradiation
Authors: Dubinko V , Turkin A , Abyzov A , Griffiths M
Published: April 2008

We present a model of the homogeneous nucleation and growth of vacancy and interstitial loops in irradiated hcp metals, which allows one to find the size distribution function, the dose dependence of the mean parameters of the dislocation system, and to describe effects due to temperature, material parameters, and initial microstructure. The model is based on a hierarchy of coupled ordinary differential equations. The first two equations are the rate equations for vacancy and interstitial concentrations. Other equations describe random walks of interstitial and vacancy clusters in a size space, i.e., the time dependence of loop densities. As an input, the model contains the capture efficiencies of point defects by loops, which depend self-consistently on the loop size and dislocation density. We have considered two possible scenarios depending on the point defect dilatation volume ratio: (i) dislocation bias for interstitial atoms and (ii) dislocation bias for vacancies. The model results are qualitatively consistent with experimental observations of a coexistence of interstitial and vacancy dislocation loops on the same habit planes in Zr and other hcp metals. The temperature dependence of the resulting loop size distributions depends strongly on the material properties and the initial microstructure.
Temperature and Strain Rate Effects on Zr-1%Nb Alloy Deformation
Authors: Bocharov O , Zavodchikov S , Belov V , Kabanov A , Kotrekhov V , Rozhdestvenski V , Filippov V , Losistskiy A , Shikov A
Published: April 2008

A series of investigations has been performed to determine the maximum plasticity of Zr1%Nb alloy material. Also, the deformation limits for Zr1%Nb alloy material were determined. Tests in tension and compression were performed. During these tests the basic value of resistance to deformation and plasticity of the Zr-1%Nb alloy was determined under the temperature and strain rate conditions typical of hot deformation processing. The best temperature range is identified for the hot deformation processing of the Zr-1%Nb alloy. Also, a mathematical model is identified for the maximum plasticity as a function of the deformation conditions. That dependence has been used for the development of the high tech processes for zirconium product manufacturing for nuclear application.
Phase Composition, Structure, and Plastic Deformation Localization in Zr1%Nb alloys
Authors: Zuev LB , Zavodchikov SY , Poletika TM , Cheremnykh GS , Filippov VB , Belov VI , Arzhakova VM , Bocharov OV , Shikov AK
Published: April 2008

The feasibility of strengthening the Zr1%Nb alloy by achieving a non-uniform solid solution oxygen distribution in the α grains is considered. Technology employing Nb2O5 as an oxygen source has been developed, which permits introduction into the alloy additional oxygen up to 0.06–0.09 wt. %. Using the method of electron microscopy, the oxygen distribution of the as-produced alloy was examined. The material was found to contain Zr and Nb oxides of non-stoichiometric compositions. The regular features of plastic deformation localization were investigated. These features as revealed by the deforming material may be regarded as forerunners of necking in the course of Zr alloy tube manufacture and are indicative of probable material fracture.
The Effect of Beta-Quenching in Final Dimension on the Irradiation Growth of Tubes and Channels
Authors: Dahlbäck M , Limbäck M , Hallstadius L , Barberis P , Bunel G , Simonot C , Andersson T , Askeljung P , Flygare J , Lehtinen B , Massih AR
Published: April 2008

The effect of β-quenching performed in the final size of Zircaloy-4 guide tubes and Zircaloy-2 sheets during fabrication process on the products' mechanical properties, crystallographic texture, microstructure, and corrosion behavior has been investigated and presented in this paper. Moreover, the impact of this processing on the irradiation growth of pressurized water reactor Zircaloy-4 guide tubes in a test reactor and Zircaloy-2 fuel channels in boiling water reactors has been evaluated. The results indicate that the irradiation growth rates of the final dimension β-quenched (FDBQ) products are substantially lower than those fabricated by conventional (Standard) techniques. BWR channels irradiated up to a fast neutron fluence of about 9 × 1025 m-2 maintain this low growth behavior. Corrosion properties of FDBQ products have been made similar to that of the Standard material by performing an αannealing step after the β-quenching. The annealing temperature and annealing time have been optimized in order to obtain good corrosion resistance. In-reactor data on Zircaloy-2 channels irradiated to a fuel assembly exposure of about 50 MWd/kgU indicate similar corrosion performance for the FDBQ and Standard materials. Finally, the in-reactor data on Zircaloy-2 channels show that bowing of the FDBQ and Standard channels is comparable up to a fast neutron fluence of about 7 × 1025 m-2.
Destruction of Crystallographic Texture in Zirconium Alloy Tubes
Authors: Grytsyna V , Stukalov A , Chernyayeva T , Krasnorutskyy V , Malykhin D , Voyevodin V , Bryk V
Published: April 2008

The paper investigates the dependence of the transformation texture of Zr-2.5wt%Nb tubes and rods on the initial texture, the method of heating (furnacing, conductive heating, inductive heating) and cooling (furnace cooling, water quenching, water shower), stress, and thermal cycling. It was demonstrated that the primary factors determining the transformation texture are the initial texture and the heating rate for quenching. From the investigation results, a method of final thermal treatment of finished zirconium reactor core components (pressure tubes, guide tubes, and cladding fuel rods) is suggested, allowing the destruction of their texture without changing the well-established manufacturing process. The suggested SHF heating includes the use of the α→β→α transformation with fast heating up to the β-phase, subsequent quenching for texture destruction, and annealing for transformation from the metastable α'-state to the equilibrium double-phase αZr + βNb state.
Improved ZIRLO™ Cladding Performance through Chemistry and Process Modifications
Authors: Yueh HK , Kesterson RL , Comstock RJ , Shah HH , Colburn DJ , Dahlback M , Hallstadius L
Published: April 2008

Since the introduction of the ZIRLO™ alloy for use in commercial nuclear light water reactors (LWRs) in the early nineties, work has continued on identifying chemistry and process changes to improve further the in-reactor corrosion performance of the alloy. Relative to the reference ZIRLO chemistry of Zr-1%Nb-1%Sn-0.1%Fe, a series of Zr-xNb-ySn-zFe alloys was fabricated to strip material and autoclave tested. The goal was to identify Zr-Nb-Sn-Fe compositions that would result in lower uniform corrosion rates in pure water and steam environments, while retaining resistance to accelerated corrosion in abnormal chemistry conditions, such as elevated lithium levels. The results of the study identified a reduction in tin content as having the greatest impact on improving the uniform corrosion performance. However, a minimum tin content was required to avoid accelerated corrosion in water containing 70-ppm Li. In the processing area, an extensive study was conducted to evaluate the relationship between thermal-mechanical processing, alloy microstructure (e.g., second phase particles), and corrosion performance. Processing variables following β-phase heat treatments included cold work, annealing temperature, and annealing time. Long-term autoclave tests performed in 633°K water containing 70-ppm lithium showed the uniform corrosion rate of the alloy is essentially optimized in cold-worked material after only 1 h of anneal at temperatures higher than 823°K. The autoclave results also showed a lower corrosion rate with decreasing processing temperatures. A low tin version of the ZIRLO alloy, with approximately 0.75 % tin content, was fabricated into fuel cladding and inserted as fuel rods in a commercial pressurized water reactor. After two 18-month cycles at high fuel duty and average burnups greater than 52 GWD/MTU, the peak oxide thickness in the low tin ZIRLO was significantly lower than reference ZIRLO.
Effect of Alloying Elements and Impurities on in-BWR Corrosion of Zirconium Alloys
Authors: Sell H-J , Trapp-Pritsching S , Garzarolli F
Published: April 2008

The data base on the corrosion behavior of Zr alloy materials under BWR conditions was evaluated with respect to the burnup target of 70 MWd/kgU. At high bumups, corrosion rate and the rate of hydrogen pickup (HPU) may increase. This onset of increase obviously depends on the material, but also seems to be significantly affected by the coolant water chemistry. Because small differences in corrosion behavior at lower burnup might become more and more important with increasing burnup, Framatome ANP has performed several studies on the separate and combined effects of (1) alloying content of the claddings, (2) cladding material condition, (3) impurity content of the cladding, and (4) the coolant chemistry. This paper focuses on the effects the concentration of alloying elements and of impurities (including microstructural differences imposed by the annealing treatment) have on corrosion. The corrosion effects were evaluated in material test irradiation programs in two BWRs. Zircaloy type materials processed at low temperatures (LTP), defined by a low particle growth parameter (PGP) value, exhibit a maximum corrosion resistance between 1.2 and 1.5 % Sn. Impurities, such as C, O, and P can increase the corrosion of Zircaloy in BWRs at high burnup. The higher the corrosion resistance of the base material, the more pronounced is the increase seen at high burnup. Above a critical PGP value, in-pile corrosion increases. At high burnups, Zry-4 shows a higher increase with increasing PGP than Zry-2, whereas at lower burnups both behave similarly. The critical PGP value varies with the chemical composition, such as Fe, Cr, and Ni content and the distribution of second phase particles (SPP). The effect of Si is more complex. Si increases in-pile corrosion at contents in excess of 140 ppm. Contents at 80 to 140 ppm can be beneficial, when the β-quench rate applied during fabrication is not high enough to ensure a uniform distribution of the SPP, and the alloying composition and the concentration of impurities is in a beneficial range. The hydrogen pickup fraction (HPUF) of Zircaloy type samples in BWRs decreases with decreasing corrosion resistance but differs from plant to plant. There are indications that the difference can partially be attributed to the Fe content in the coolant.

The results are in agreement with the irradiation experience with Zry-2 LTP cladding extending up to 73 MWd/kgU in different BWRs.
The Effect of Duplex Cladding Outer Component Tin Content on Corrosion, Hydrogen Pick-up, and Hydride Distribution at Very High Burnup
Authors: Arborelius J , Dahlbäck M , Hallstadius L , Jourdain P , Andersson T , Lisdat R , Hahn M , Toscano EH
Published: April 2008

The performance of two types of Duplex claddings irradiated to very high burnup in a German high duty pressurized water reactor (PWR) has been studied. Four fuel rods with Duplex cladding were moved from two discharged assemblies to a low-burnt assembly for further irradiation. These rods were finally unloaded after reaching a rod average burnup close to 70 MWd/kgU. The performance of these rods has been examined through pool-side inspection. Two of these rods have been studied further in a hot-cell post irradiation examination (PIE). The results of destructive and nondestructive examinations consistently show good corrosion resistance and low hydrogen pick-up for both Duplex variants. The hot-cell measurements reveal peak values of the oxide thickness of around 30 μm for both types of Duplex. Consequently, the claddings show low levels of absorbed hydrogen in the order of 300 ppm, as is indicated by metallographic cross-sections and the low axial growth of the rods. During the development of Duplex claddings, it was observed that the Sn content in the two components should not differ by more than about 0.7 wt%. A limited difference in Sn concentration implies that the two components have similar recrystallization temperatures. More important, hydriding studies of unirradiated Duplex claddings have shown that, by limiting the difference in Sn content, the amount of hydrides in the boundary zone between the inner component and the Duplex layer is reduced. There is a significant difference in the Sn concentration in the outer component of the two studied Duplex types. The effect of difference in Sn concentration on hydride distribution observed from studies of unirradiated claddings has, however, not been confirmed by the hot-cell studies presented here.
Use of the Irradiation-Thermal Creep Model of Zr-1 % Nb Alloy Cladding Tubes to Describe Dimensional Changes of VVER Fuel Rods
Authors: Rogozyanov AY , Smirnov AV , Kanashov BA , Polenok VS , Nuzhdov AA
Published: April 2008

The objective of this work was firstly to categorize the data on dimensional change of the VVER fuel rods and to identify the primary variables influencing performance, and secondly to benchmark the irradiation-thermal creep model for Zr-1% Nb alloy cladding tubes against the VVER fuel rod dimensional changes data. The creep model was developed using the results of in-pile and out-of-pile tests of tube specimens.

Data arrays on the change of fuel rod diameter and length were obtained during examination of eight VVER-440 fuel assemblies and 16 VVER-1000 fuel assemblies. Qualitative analysis was performed of the measurement results presented as dependencies of averaged axial strain on burnup.

Similar calculated dependencies were obtained using the creep model considering the irradiation growth strain. The quantitative analysis showed that differences between the calculated and actual dimensional changes of the fuel rods did not exceed 3–5 % for VVER-440 and 7 % for VVER-1000.
The Effect of Liner Component Iron Content on Cladding Corrosion, Hydriding, and PCI Resistance
Authors: Dahlbäck M , Hallstadius L , Limbäck M , Vesterlund G , Andersson T , Witt P , Izquierdo J , Remartinez B , Díaz M , Sacedon JL , Alvarez A-M , Engman U , Jakobsson R , Massih AR
Published: April 2008

This paper focuses on the effect of liner component Fe content on cladding corrosion, hydriding and Pellet-Cladding Interaction (PCI) resistance. A multitude of experimental techniques is used to evaluate the various properties. The PCI resistance is evaluated through mandrel testing of unirradiated claddings as well as by ramp tests of pre-irradiated fuel segments in the Studsvik R2 reactor. The results from the mandrel testing indicate that an increase of the iron concentration from 0.05 to 0.21 wt% has a rather small impact on the PCI properties. The ramp data, on the other hand, show a clear decrease in the PCI resistance as the Fe content approaches and exceeds 0.19 wt%. The phenomena involved in secondary degradation are complex, and separate tests are used to evaluate the corrosion resistance in steam as well as the hydriding resistance in pure hydrogen. The corrosion test includes cladding tubes with ZrSn-liner components with iron concentrations from 0.025 to 0.21 wt%. The results show that the corrosion resistance is dramatically increased as the Fe content is increased from 0.025 to 0.05–0.06 wt%, but that a further increase of the Fe concentration only has a minor impact on the corrosion resistance. However, increasing the Fe content from 0.05 to 0.21 wt% increases the hydrogen pick-up rate. The 0.21 wt% Fe liner has a significantly higher density of Secondary Phase Particles (SPPs) as well as slightly larger SPPs than the 0.05 wt% Fe liner. Consequently, it is believed that the SPPs offer sites where hydrogen can easily be absorbed into the Zr-based material, and the frequency of these sites is important for the hydrogen pick-up rate. It is finally concluded that even though the optimization of the Fe concentration in the liner is complex, an iron level regime exists that provides a good balance of resistance against PCI, corrosion, and hydriding.
Radiation-Induced Stress Relaxation of Welded Type 304 Stainless Steel Evaluated by Neutron Diffraction
Authors: Obata M , Root JH , Ishiyama Y , Nakata K , Sakamoto H , Anzai H , Asano K
Published: April 2008

The welded Type 304 stainless steel specimens were neutron-irradiated up to 2 × 1025 n/m2 (E > 1MeV) at 561K in the Japan Material Testing Reactor (JMTR). The residual stresses in the test specimens were measured by neutron diffraction, and the radiation-induced stress relaxation was evaluated from the change of stress distributions along the direction transverse to the weld bead. The magnitudes of σX (transverse to the weld) and σY (longitudinal to the weld) residual stresses decreased steadily with increasing neutron fluence. The irradiation dose dependence and the mechanism for the relaxation were examined using an equation derived from the irradiation creep equation. There was a steep stress relaxation, which might correspond to transient creep, at the early stage of neutron irradiation near the weld, and the different radiation-induced relaxation behaviors could be observed depending on the distance from the weld. The radiation-induced stress relaxation for welding-induced residual stress, which was generated under a three-dimensional restriction, indicated the tendency to be slower compared to the fundamental results for mechanically applied stress.
The Role of Grain Boundary Engineering on the High Temperature Creep of Ferritic-Martensitic Alloy T91
Authors: Gupta G , Was GS
Published: April 2008

Ferritic-Martensitic alloys are expected to play a major role in supercritical water reactor internals. These steels offer better swelling resistance than austenitic alloys but may suffer from grain boundary or matrix creep and loss of strength at higher temperatures and unacceptably low toughness at lower temperatures. The focus of this investigation is to improve the creep resistance of T91 by grain boundary engineering. By increasing the fraction of coincident site lattice (CSL), or special boundaries, the grain boundaries are strengthened against sliding and deformation, thus improving the creep resistance. Thermo-mechanical treatment for coincident site lattice enhancement of T91 has already been developed. High temperature (500°C) creep experiments in argon are conducted to assess the effectiveness of the CSL enhanced microstructure on the creep rate. Experimental analysis shows that the CSL-enhanced condition results in a lower creep rate by a factor of 3–4 as-compared to A/R condition for T91 at a temperature of 500°C and in the stress range of 200–225 MPa by reducing the effective stress.