bluuebunny/crossref_metadata_2025 huggingface dataset:
Application of Phosphorus Bioavailability Indices to Agricultural Runoff and Soils
Authors: Sharpley AN , Smith SJ
Published: March 2009

Accelerated eutrophication of surface water is often controlled by phosphorus (P) inputs in soluble (SP) and particulate (PP) forms. While most SP is immediately available for algal uptake, PP can provide a variable but long-term source of P for aquatic plant growth. Research has shown P extracted by 0.1 M sodium hydroxide (NaOH) from lake sediments to be correlated with P uptake by the algae Selenastrum capricornutum. This study presents a modification of this procedure, where amounts of P extracted from 20 mL of unfiltered runoff by 180 mL of 0.11 M NaOH in 17 h were correlated to algal growth (r2 of 0.76 to 0.93), to allow routine measurement of potentially bioavailable P (BAP) in runoff. Bioavailable P loss in runoff from 20 agricultural watersheds in the Southern Plains was measured over a 5-year period. Losses were reduced by practices minimizing erosion and runoff, with 1.25 and 0.70 kg ha-1 yr-1 losses from conventional and no-till practices, respectively. However, as vegetative soil cover increased, BAP comprised a larger portion of total P (TP) loss (88% for no till and 19% for conventional till). As P bioavailability is a dynamic function of physical and chemical processes controlling erosion, particle-size enrichment, P desorption-dissolution, and plant residue breakdown, routine BAP measurement is recommended to more reliably evaluate the impact of agricultural management on the biological productivity of surface waters. This will also involve development of P bioavailability indices relating bioavailable soil P (NaOH- extractable, BIOP) to management. To use existing soil P test methods (for example, Bray-I, Mehlich-III, and Olsen), relationships between BIOP and soil test P were investigated for 201 soils. Although a large range in BIOP was found (1 to 712 mgP kg-1), it was not consistently related to any P form. Thus, BIOP measurement is recommended in the development of indices facilitating identification of potential agronomic and environmental risks associated with current and proposed agricultural management.
Soil Solution Assessment of the Soil Availability of Xenobiotics
Authors: Wolt JD
Published: March 2009

Soil solution displacement provides a means whereby xenobiotic availability in the soil environment can be evaluated rapidly and effectively. The displacement and analysis of soil solution provides (a) refined measurements of the bioavailability of soil active xenobiotics, (b) static measurements of phase partitioning of xenobiotics under conditions which closely mimic soil moisture regimes in field environments, and (c) dynamic measurements of xenobiotic availability as a function of residence time in the soil. The biological availability (efficacy/toxicity) and the geochemical availability (environmental fate) of biologically active molecules are both a function of the xenobiotic intensity in soil solution. Quasi-thermodynamic expression of xenobiotic effective concentration (that is, chemical activity) and solid-liquid distribution in soils is possible based on knowledge of xenobiotic pKa and mole weight, and measurement of soil solution xenobiotic intensity, pH, and ionic strength. Dynamic measures based on soil solution displacement with time offer a means to assess time domain influences on xenobiotic availability. Soil solution displacement and analysis has been employed successfully for refined assessments of leachability, phytotoxicity, and sorptivity of xenobiotics and offers a useful adjunct to more traditional whole soil extractions for determination of xenobiotic fate and behavior in soil.
Development of a Solid-Phase Extraction Method for Herbicide Residue Analysis of Soil Samples
Authors: Chirnside AEM , Ritter WF
Published: March 2009

National concern for the environment has brought about many changes for the agricultural community. The 1990 Farm Bill provided funding for water quality research that improves the understanding of the fate and transport of farm chemicals which can contaminate water and cause adverse environmental effects (United States 101st Congress 1990). Accurate models of pesticide movement and degradation require extensive monitoring in vitro and in vivo. This type of research will involve laboratory analysis of a sundry of matrices for contaminant residues. Recent method development has led to using solid-phase extraction (SPE) to concentrate and extract contaminants found within environmental samples. The objective of this study was to modify the above procedure in order to obtain adequate recovery of several herbicides from a soil matrix. Precision and accuracy determinations would be performed in order to evaluate the methodology. This paper reports on the development of analysis procedures for the herbicide alachlor [2-chloro-2,6-diethyl-N methoxymethyl acetanilide].
Testing Soils for Metals with Emphasis on Cadmium in the Food Chain
Authors: Baker DE , Lotse E , Amistadi MK
Published: March 2009

The Baker Soil Test, abbreviated BST, evolved from the concept that the availability of an ion to plants is related to its activity or relative partial molar free energy within the substrate. From the concepts of Relative Partial Molar Free Energy and the Gibbs-Duhem equation, it becomes obvious that plant availability of an ion is affected by all factors affecting ionic activity. For soil systems, these factors include water properties, mineral solubilities, ionic adsorption, and other entropy changes. A perfect soil test would measure the true ionic activity or relative chemical potential of labile ions, analogous to pH and acidity (pCd2+ and labile cadmium for cadmium).

The BST includes measurements and interpretations of the extractable amounts (Q), the negative logarithm of the activity of ions associated with diethylene triaminepenta acetic acid (pCd2+), and concentrations of cadmium and other metals by the U.S. Environmental Protection Agency (1986) method.

The determination of the intensity and buffer capacity (dI/dQ) of Cd2+ and other metals is important in order to identify soils with low potential cadmium uptake by crops, those with high cadmium uptake, and those for which the desired reduction of cadmium uptake by plants can be obtained by liming and other treatments which have been found to increase the soil buffer capacity. Reaching equilibrium after treatment takes time, and the required time can be expected to be different for different soils. The intensity and buffer capacity, predicted by the BST, should therefore be obtained repeatedly over time for soil management of cadmium and other elements for crops in the food chain.
Heavy Metals Leachability from Municipal Compost
Authors: Sawhney BL , Bugbee GJ , Stilwell DE
Published: March 2009

Municipal composts from two Connecticut towns, Fairfield and Greenwich, were analyzed for heavy metals (cadmium, chromium, copper, nickel, lead, and zinc) using nitric acid : hydrogen peroxide (HNO3 : H2O2) digestion as outlined in Environmental Protection Agency Method 3050 for digestion of solid wastes, sludges, and soils. Potential leachability of heavy metals was determined by leaching compost with water in laboratory columns, and by irrigation-leaching of compost used as growth medium for container plants in the field. Acid digests and aqueous leachates were analyzed for heavy metals by inductively coupled plasma (ICP) emission spectrometry and graphite furnace atomic adsorption (GFAA) spectrometry. Concentrations of cadmium, chromium, copper, nickel, lead, and zinc in the composts varied from 3 to 5, 43 to 118, 323 to 649, 38 to 81, 110 to 213, and 331 to 1143 mg/kg, respectively. Following the initial rapid leaching of heavy metals for 2 to 3 days in laboratory columns and 2 to 4 weeks in field containers, metals continued to leach at low concentrations, generally below the drinking water standards. The initial rapid leaching of metals is attributed to their soluble or readily exchangeable forms and the subsequent release at low concentrations is likely controlled by the solubility of the solid phases.
Representative Specimen Size for Hydraulic Conductivity Assessment of Compacted Soil Liners
Authors: Benson CH , Hardianto FS , Motan ES
Published: March 2009

An alternative to field measurement of hydraulic conductivity is to conduct laboratory hydraulic conductivity tests on specimens large enough to simulate field-scale conditions. Laboratory tests can be performed rapidly using standard procedures and with accurate control of state of stress and gradient. The objective of this research program was to identify how large a specimen must be to yield field-scale hydraulic conductivity. This objective was accomplished through field testing, laboratory testing, and statistical modeling.

Hydraulic conductivity tests were conducted on test pads at four sites that represented construction conditions ranging from poor to excellent. One test pad was deliberately constructed using poor construction methods to demonstrate “worst case” conditions. Field tests were performed with sealed double-ring infiltrometers (SDRIs) having inner rings with widths of 0.61, 0.92, 1.2, or 1.5 m. Laboratory tests were performed on block specimens with diameters ranging from 0.07 m to 0.46 m.

For the range of construction conditions that were evaluated, the test results showed that hydraulic conductivity at or near field-scale can be measured using block specimens with a diameter of 0.30 m and a thickness of 0.15 m. A probabilistic model was designed to simulate macroscopic defects in compacted soil. Results obtained with the model supported the results of the experimental study.
State-of-the-Art: Laboratory Hydraulic Conductivity Tests for Saturated Soils
Authors: Daniel DE
Published: March 2009

Hydraulic conductivity of saturated soils is measured in the laboratory with either rigid- or flexible-wall permeameters. Rigid-wall cells are preferred for granular materials, and either rigid- or flexible-wall cells are preferred for low-hydraulic conductivity materials, depending on the type of test specimen and the conditions being simulated. Procedures for selection and preparation of test specimens are critically important, even for laboratory-compacted materials. Either constant- or variable-head tests can be performed; either type of test will yield satisfactory results if used properly. For compressible materials, the head cannot change much or the test specimen will change volume. Permeation with deaired water until inflow and outflow rates equilibrate, supplemented with backpressure where appropriate, are needed to saturate test specimens. Permeation should continue until chemical equilibrium is established when testing with liquids other than water, e.g., chemical wastes.
Waste-Soil Interactions that Alter Hydraulic Conductivity
Authors: Shackelford CD
Published: March 2009

Liquid-soil compatibility of soil hydraulic conductivity is reviewed with respect to the materials and methods used in evaluating waste-soil interactions, factors influencing interpretation of test results, and the interactions that are thought to alter significantly the hydraulic conductivity of clay soils. Significant increases in hydraulic conductivity may result from flocculation of clay particles due to interactions with electrolyte solutions, shrinkage of the soil matrix in the presence of concentrated organic solvents, and acid-base dissolution of the soil. Observed effects typically are greater in rigid-wall permeameters than flexible-wall permeameters.

Considerable evidence supports the use of the Gouy-Chapman theory for describing the influence of aqueous solutions on the fabric and, therefore, the hydraulic conductivity of clay soils. However, swelling test results suggest that the Gouy-Chapman theory does not account properly for shrinkage effects which have been observed to result in large increases in hydraulic conductivity upon permeation with concentrated organic solvents.

Three mechanisms may contribute to an increase in the hydraulic conductivity of clay soils upon permeation with acid permeants: (1) flocculation of the clay, (2) dissolution of the clay minerals (aluminosilicates), and (3) dissolution of other minerals (e.g., CaCO3) in the clay soil. Dissolution and piping of clay minerals leads to increases in hydraulic conductivity. Dissolution of carbonates initially leads to buffering, re-precipitation, pore clogging, and a decrease in hydraulic conductivity. Depletion of the buffering capacity leads to a decrease in pH, dissolution of constituents, and a possible increase in hydraulic conductivity.

The measured hydraulic conductivity of a compacted sand-bentonite mixture is shown to be significantly affected by the sequence of permeation to a saturated calcium solution. The effect, termed “first exposure”, has important implications with respect to the application of laboratory test results for evaluation of the suitability of a material for a waste containment barrier.
Hydraulic Conductivity Assessment of Unsaturated Soils
Authors: Stephens DB
Published: March 2009

Predicting the direction and rate of contaminant transport in the vadose zone requires quantification of soil hydraulic properties. For many problems, the most appropriate approach is to assume that the contamination is moving with the water phase. Therefore, the unsaturated hydraulic conductivity is the most important property governing water movement in soils. There is a wide variety of methods to determine this important property including in situ methods (e.g., instantaneous profile method, crust method), laboratory methods (e.g., one-step outflow, pressure plate, long column methods), and calculations from other data (e.g., Brooks and Corey, van Genuchten models). In this paper we present a summary and brief critique of the current methods for determining unsaturated hydraulic conductivity.
In-Situ Hydraulic Conductivity Tests for Compacted Soil Liners and Caps
Authors: Trautwein SJ , Boutwell GP
Published: March 2009

The most important geotcchnical parameter for soil liners or caps for waste facilities is hydraulic conductivity. In typical practice, the vertical conductivity normally governs the barrier effect. Regulatory agencies are increasingly requiring in situ tests in addition to laboratory- tests to verify hydraulic conductivity. Many different in situ tests have been proposed; seven have some usage. These are discussed with reference to their suitability for liner/cap evaluation. Of these, the Sealed, Double-Ring Infiltrometer and the Two-Stage Borehole test have received widest acceptance and use; each has already been used on 50 to 100 projects. Both tests are examined in detail, including theoretical basis, field procedures, and data reduction. Reasons for their preference over other methods are discussed.

The Sealed Double-Ring Infiltrometer measures one-dimensional infiltration from which vertical hydraulic conductivity is determined. Testing times are comparatively long but a larger volume of soil is tested, 1000 to 3000 times that typically tested in the laboratory. It is the better of the two methods for testing thin liners (<50 cm). One test is adequate for all but the most poorly constructed test media.

The Two-Stage Borehole method involves three-dimensional infiltration, from which both vertical and horizontal conductivities are determined. A typical study involves multiple tests, the total volume of soil affected by a 5-test group being 250 to 1000 times that typically tested in the laboratory. Testing times are comparatively short, and the method is the better of the two for evaluating variability in hydraulic conductivity with depth, on slopes, and where horizontal conductivity is needed. A five-test group is adequate for all but the most poorly constructed test media.

Comparative results are presented from 15 projects. The two preferred methods yield comparable values; both have been successful in verifying well-built barriers and identifying those with defects.
Laboratory Testing to Evaluate Changes in Hydraulic Conductivity of Compacted Clays Caused by Freeze-Thaw: State-of-the-Art
Authors: Othman MA , Benson CH , Chamberlain EJ , Zimmie TF
Published: March 2009

Several laboratory studies have shown that the hydraulic conductivity of compacted clay may increase up to three orders of magnitude when subjected to freeze-thaw. In this paper, methods to freeze and thaw specimens of compacted clay are reviewed and compared. Methods to measure the hydraulic conductivity of the specimens are also reviewed. Only naturally formed clay soils are considered; soil-bentonite mixtures and other amended soils are not included.

A review of testing conditions present during freeze-thaw and their effect on hydraulic conductivity is also included. Testing conditions that are addressed include availability of an external supply of water (closed vs. open system), dimensionality of freezing (one-dimensional vs. three-dimensional), rate of freezing, ultimate temperature, number of freeze-thaw cycles, and state of stress. The rate of freezing, number of freeze-thaw cycles, and state of stress appear to have the largest effect on hydraulic conductivity.

The effect of sampling disturbance on the hydraulic conductivity of compacted clay subjected to freeze-thaw is also presented. Specimens removed in Shelby tubes may be disturbed during sampling and extrusion. As a result, the effects of freeze-thaw can be masked. Collecting block specimens of thawed clay or taking core specimens of frozen clay are suggested as alternative procedures. A method to collect block specimens is presented.
Hydraulic Conductivity of Compacted Clayey Soils Under Distortion or Elongation Conditions
Authors: Cheng S-C , Larralde JL , Martin JP
Published: March 2009

Models of fine-grained landfill cap response to differential subsidence are discussed, and experimental results are presented. Soils used include a clayey silt, a silty fine sand, and the latter with admixed kaolinite. Tests were conducted on statically compacted soils in a permeameter that induced axisymmetric distortion. Hydraulic conductivity increased with the increase in flexural stresses. Sensitivity to plasticity and compaction moisture content was observed. Tests were also conducted to obtain mechanical properties, including tensile strength (split-cylinder), unconfined compressive strength, modulus of rupture (beam flexural strength), and several deformation moduli. The results are normalized in terms of compaction moisture relative to optimum moisture content.
A Comparison Between Field and Laboratory Measurements of Hydraulic Conductivity in a Varved Clay
Authors: DeGroot DJ , Lutenegger AJ
Published: March 2009

The measurement of hydraulic conductivity using a variety of field and laboratory techniques was evaluated at a site consisting of medium stiff and soft lacustrine varved clay in western Massachusetts. Field measurements were obtained by conducting “slug” tests in both predrilled and push-in piezometers and also from pore pressure dissipation tests using the piezocone and flat dilatometer. Laboratory hydraulic conductivity values were obtained for both vertical and horizontal flow conditions using a flexible wall permeameter and by indirect estimation from 1-dimensional consolidation tests. Based on a comparison of tests conducted throughout the profile, laboratory flexible wall tests with vertical flow gave the lowest values of hydraulic conductivity whereas the predrilled piezometers yielded the highest values. Of all the field techniques, the push-in piezometers gave the lowest values. Hydraulic conductivity values interpreted from piezocone and flat dilatometer dissipation tests tended to be between those obtained from the predrilled and push-in piezometers. Results from tests in predrilled piezometers show that the hydraulic conductivity increases with increasing screen length, showing the influence of scale effects. The results of this study clearly show that estimation of hydraulic conductivity for this soil is highly dependent on scale effects, the test technique used and on the direction of flow (i.e., parallel versus perpendicular to the orientation of the varves).
Effects of Post Compaction Water Content Variation on Saturated Conductivity
Authors: Phifer MA , Drumm EC , Wilson GV
Published: March 2009

Reductions in water content after construction can produce desiccation cracking and associated aggregation of clay barriers. This produces two flow regimes within the clay barrier. Conduit flow occurs through the desiccation cracks (preferential flow paths), and matrix flow occurs through the aggregates (intact matrix). An investigation of the effect of post compaction water content variations on volumetric strain and saturated hydraulic conductivity of desiccation produced aggregates was conducted. Kaolinite samples for use in flexible wall permeameters were prepared using modified, standard, and reduced proctor methods. The initial volume and hydraulic conductivity of each sample were determined. Each sample was progressively dried back from its molding water content, and its volume and hydraulic conductivity were determined after each dry-back. Correlations between gravimetric water content, dry bulk density, volumetric strain, and saturated hydraulic conductivity were made. Significant volumetric strain occurred, which produced a decrease in the hydraulic conductivity (matrix flow) of the intact aggregate. The strain, however, while resulting in a lower matrix flow in the aggregates, should produce a higher overall flow in barriers due to conduit flow within the resulting desiccation cracks.
Influence of Polymers on the Hydraulic Conductivity of Marginal Quality Bentonite-Sand Mixtures
Authors: Haug MD , Boldt-Leppin B
Published: March 2009

The results of a two year laboratory test program demon strated that the hydraulic conductivity of a marginal quality sodium bentonite could be significantly enhanced with the addition of a small quantity of specially formulated commercial polymer. The first step in the laboratory program involved tests to establish the rheological prop erties of slurries prepared using 8 % marginal quality (MQ) and 8 % high quality (HQ) bentonite. The marginal bentonite was then modified with various percentages of polymer. A comparison of shear stress ver sus shear rate characteristics, as a function of polymer addition rate, was used to establish a range of polymer addition rates for hydraulic conductivity tests. Ten low gradient triaxial permeability/volume change tests were conducted on compacted Ottawa sand-8 % bentonite tests samples. The concentration of polymer used in these tests varied from 0 to 0.5 % based on the weight of bentonite. Approximately half of the tests were conducted on newly prepared polymer and the other half on polymer aged for one year prior to being used.
Hydraulic Conductivity of Borehole Sealants
Authors: Lutenegger AJ , DeGroot DJ
Published: March 2009

Geotechnical boreholes provide a direct conduit for the transport of surface and subsurface contaminants if left open or improperly sealed at the end of drilling operations. Current field practices used during the decommissioning of a drilled hole generally rely on a relatively small group of products to act as a sealant or barrier to contaminant transport. Slurries using mixtures of bentonite, portland cement and other materials and compacted barriers composed of native soil and other materials have been used as contaminant transport barriers in applications such as slurry trenches and compacted liners and may be well suited as workable borehole sealants. A literature review provides a summary of hydrologic properties of various materials which might have applications as borehole sealants. This summary is presented in a concise format along with a brief discussion of each of the classes of mixtures to act as permanent seals. In addition to this review, the results of laboratory hydraulic conductivity tests performed on a range of commercially processed bentonite products sold as seal materials are presented. Physical characteristics of various commercial bentonite products are also presented. Results of laboratory hydraulic conductivity tests performed on other typical sealant mixtures are also presented. The results of this study identify a number of alternatives for providing borehole seals to act as contaminant transport barriers in boreholes.
Constant-Flow and Constant-Gradient Permeability Tests on Sand-Bentonite-Fly Ash Mixtures
Authors: Shackelford CD , Glade MJ
Published: March 2009

Flexible-wall permeability (hydraulic conductivity) tests are conducted on compacted specimens consisting of 50 percent Class F fly ash with a 50 percent soil admixture (sand with 0, 6.25, 12.5, 18.75, and 25 percent bentonite). All test specimens are back-pressured before permeation with distilled water. Three specimens from each sand-bentonite-fly ash mixture are tested under high (72 or 73) and low (6.1) constant-gradient conditions as well as under constant-flow conditions for a total of 15 tests. Induced hydraulic gradients from the constant-flow tests range from 3.5 to 41. A decrease in permeability with an increase in bentonite content is evident regardless of the test method. However, the permeability is minimized at a bentonite content of 18.75 percent regardless of the test method. The overall lowest permeability value is 1.6 × 10-9 m/s. An increase in hydraulic gradient of 11.9X resulted in a 3.1X to 6.2X decrease in measured permeability values for all test specimens. A significant portion of the difference in measured permeability values is attributed to differences in applied or induced hydraulic gradients regardless of the test method.
Test Methodologies to Perform Valid Accelerated Thermomechanical Fatigue Tests of Solder Joints
Authors: Frear DR , Sorensen NR , Martens JS
Published: March 2009

Valid test parameters for performing thermomechanical fatigue tests are needed to make reasonable life prediction estimates for solder joints in electronic assemblies. We present the results of three test parameters that can be used to perform accelerated thermomechanical fatigue tests: deformation rate, hold time, and atmosphere. At deformation rates of 2.8 × 10-4 s-1 and slower, the damage mechanism in the solder does not change and is in the form of heterogeneous coarsening at cell boundaries, indicating that this is a valid testing rate. Decreasing the hold time at the temperature extremes to the point where the stress relaxes to zero at the high-temperature portion of the thermal cycle results in the same solder joint behavior as longer hold times. Accelerating the test by changing environment was found to change the damage mechanism and is not a valid means of accelerating thermomechanical fatigue tests for solder joints.
High-Cycle Fatigue of Kovar
Authors: Wasynczuk JA , Hanna WD , Ross FD , Freitag TA
Published: March 2009

Kovar®, an austenitic Fe-29Ni-17Co alloy, was tested in monotonic tension and axial fatigue at stress ratios (minimum stress/maximum stress) of R= -1 and 0.1. Two annealed microstructures, having grain sizes of 14 and 65 μm, were tested. The strainhardening exponent of tensile flow curves gradually increased with strain, and then remained constant at a value of 0.23. Long-life (>108 cycles) tests indicated that fatigue limit behavior, well known for ferritic steels, also exists in Kovar. Fatigue limits (defned as the highest stress amplitude that did not cause failure in >107 cycles) were found to be 276 MPa (53% of UTS) for the 14-μm grain size and 207 MPa (41% of UTS) for the 65-μm grain size, both at R = -1. These two data points suggest that the fatigue strength of Kovar may have a strong grain size dependence. The fatigue strength of the 65-μm grain-size material was strongly affected by stress ratio. The R = 0.1 fatigue limit of this material was found to be 103 MPa (21% of UTS). Sharply notched (Kt = 6.8, 0.04-mm notch root radius) 65-μ,m grain-size specimens were tested at R = 0.1. Metallographic evidence of a small nonpropagating fatigue crack was found at the notch root of a specimen that was tested to >108 cycles. Fracture surfaces with well-defined striations were produced when fatigue crack-growth rates were high.
Irradiation Creep due to SIPA Under Cascade Damage Conditions
Authors: Woo CH , Garner FA , Holt RA
Published: March 2009

This paper derives the relationships between void swelling and irradiation creep due to SIPA and SIG under cascade damage conditions in an irradiated pressurized tube. It is found that at low swelling rates irradiation creep is a major contribution to the total diametral strain rate of the tube, whereas at high swelling rate the creep becomes a minor contribution. The anisotropy of the corresponding dislocation structure is also predicted to decline as the swelling rate increases. The theoretical predictions are found to agree very well with experimental results.
A Model for Interstitial Loop Formation in Concentrated Alloys During Irradiation
Authors: Hashimoto T , Shigenaka N
Published: March 2009

Dislocation loop nucleation is analyzed using a rate theory based model for face-centered cubic (fcc) binary alloys containing A- and B- atoms. The model considers three types of interstitial dumbbells composed of A- and B-atoms, AA-, BB-, and AB-type dumbbells. Based on the movements of these dumbbells to the nearest neighbor lattice sites, conversion processes between their different types are introduced in the formulation. A di-interstitial is assumed to be the nucleus of a dislocation loop, and reactions of point defect production by irradiation, mutual recombination of an interstitial and a vacancy, dislocation loop nucleation, and their growth are also included. Calculations are performed, varying the composition and binding strength between the two component atoms. Different types of kinetics are obtained in accordance with the dominant loop nucleus type. Conversion between interstitial dumbbells is demonstrated to play an important role in determining the concentration of interstitials, and consequently, to affect the kinetics of loop nucleation. The present model also predicts that the average composition of the formed loops differs from that of the matrix.
Predictions of Interfacial Phosphorus Segregation in Irradiated Ferritic Steels
Authors: Faulkner RG , Little EA
Published: March 2009

A recently developed model for irradiation-induced solute segregation (IRS) is overviewed and applied to the case of phosphorus segregation to grain boundaries in a ferritic matrix. The effects on IRS of irradiation temperature, dose rate and dislocation networks acting as additional point defect sinks are examined. Phosphorus is predicted to segregate at relatively low irradiation temperatures in the range ∼ 110°–300°C, depending on dose rate, with peak segregation occurring at ∼ 120°C and ∼ 150°C at thermal and fast reactor core dose rates, respectively. The principal effect of increasing the matrix dislocation density is to reduce the magnitude of the solute segregation without change in peak temperature.
Segregation Effects in Ferritic Fe-Cr Alloys
Authors: Gelles DS
Published: March 2009

A series of alloys based on Fe-10Cr with solute additions of silicon, vanadium, manganese, tungsten, tantalum, and zirconium at 0.1 and 1.0% levels, has been examined by transmission electron microscopy following fast neutron irradiation. Marked differences in dislocation evolution and void shape following neutron irradiation were found as a function of alloying. The present study extends previous examinations by investigating microstructural response following irradiation at a lower temperature (365°C) to 30 dpa and to a higher dose, 100 dpa, at 410°C. Swelling level, void shape, and dislocation configuration continued to vary as a function of the various solutes present in the same manner as seen previously. However, two additional observations were made. Irradiation at the lower temperature promotes precipitation of chromium rich α phase and reduces microstructural evolution. Also, irradiation to higher dose, reduces the effect each solute exerts by lessening the wide variation in void shape and dislocation evolution that were found at lower dose.
Neutron Irradiation Damage and Hardness Anisotropy in Molybdenum Single Crystals
Authors: Abe K , Kanzaki M , Satou M , Arai K
Published: March 2009

This paper describes the anisotropy of Knoop hardness in olybdenum single crystals neutron-irradiated at high temperatures in the Fast Experimental Reactor (JOYO) and the Fast Flux Test Facility (FFTF/MOTA). Knoop hardness, measured on the (001) surface of the specimen, showed a maximum in the [100] indentation direction and a minimum in the [110] direction. This anisotropic behavior in body-centered-cubic metals remained the same after neutron irradiation, though the average hardness increased. The degree of relative anisotropy, i.e. the hardness ratio between [100] and [110] directions, however, decreased with increasing neutron fluence. The hardness anisotropy was analyzed using the average Taylor factor.
Strengthening of Chromium Films by 75 Mev Ni Ion Irradiation
Authors: Jain A , Loganathan S , Jaipal  , Kanjilal D , Mehta GK
Published: March 2009

Chromium coatings have technological importance due to their wear resistant properties. In the past ion implantation at keV energies has been used to enhance the performance of these films. In the present work chromium films have been irradiated with 75 MeV Ni ions and the resultant change in properties studied. It is found that there is a large increase in the integrity of these films as determined in a scratch adhesion test. This observation opens up the possibility of using high energy heavy ion beams for the modification of metallic thin films. The energy deposited by the beam in the film is largely due to inelastic processes rather than elastic processes. There is the advantage that the inelastic energy deposition profile is wide, and films of thickness on the order of a micron may be treated over their entire thickness.
Subsize Specimen Testing of a Nuclear Reactor Pressure Vessel Material
Authors: Kumar AS , Rosinski ST , Cannon NS , Hamilton ML
Published: March 2009

A new methodology is proposed to correlate the upper shelf energy (USE) of full size and subsize Charpy specimens of a nuclear reactor pressure vessel plate material, A533B. The methodology appears to be more satisfactory than the methodologies proposed earlier. USE of a notched-only specimen is partitioned into macro-crack initiation and crack propagation energies. USE of a precracked specimen provides the crack propagation energy. AUSE, the difference between the USE of notched-only and precracked specimens, is an estimate of the crack initiation energy. AUSE was normalized by a factor involving the dimensions of the Charpy specimen and the plastic stress concentration factor at the notch root. The normalized values of AUSE were found to be invariant with specimen size.
Effects Of Irradiation Temperature on Embrittlement of Nuclear Pressure Vessel Steels
Authors: Haggag FM
Published: March 2009

The effects of neutron irradiation on the steel reactor vessel for the modular high-temperature gas-cooled reactor (MHTGR) are eing investigated, primarily because the operating temperatures are low [121 to 288°C (250–550°F)] compared to those for commercial light-water reactors (LWRs) [∼288°C (550°F)]. The need for design data on the reference temperature (RTNDT) shift necessitated the irradiation at different temperatures of A 533 grade B class 1 plates, A 508 class 3 forging, and welds used for the vessel shell, vessel closure head, and vessel flange. This paper presents regular- and mini-tensile, Automated Ball Indentation (ABI), and Charpy V-notch (CVN) impact test results from five irradiation capsules of this program. The first four capsules were irradiated in the University of Buffalo Reactor (UBR) to an effective fast fluence of 1.1 × 1018 neutrons/cm2 [0.7 × 1018 neutrons/cm2 (>1 MeV)] at temperatures of 288, 204, 163, and 121°C (550, 400, 325, and 250°F), respectively. The fifth capsule (designated ORNL-7) was irradiated in the Ford Nuclear Reactor (FNR) of the University of Michigan at 60°C (140°F) to an effective fast fluence of 1.3 × 1018 neutrons/cm2 [0.8 × 1018 neutrons/cm2 (>1 MeV)]. The yield and ultimate strengths of both A 533 grade B class 1 plate materials of the MHTGR program increased with decreasing irradiation temperature. Similarly, the 41-J CVN transition temperature shift increased with decreasing irradiation temperature (in agreement with the increase in yield strength). The mini-tensile and Automated Ball Indentation (ABI) test results (yield strength and flow properties) were in good agreement with those from standard tensile specimens. The mini-tensile and ABI test results were also used in a model which utilizes the changes in yield strength to estimate the CVN ductile-to-brittle transition temperature shift due to irradiation. The model predictions were compared with CVN test results obtained here and in earlier work.
Study on the Irradiation Embrittlement of a Microalloyed Ferritic Steel
Authors: Ganguly C , Viswanathan UK , Balakrishnan KS
Published: March 2009

The embrittlement of microalloyed and grain-refined high tensile strength steel plates, which are to be extensively used as structural components in nuclear reactors in India, was studied after irradiating to neutron fluences between 1.7 x 1017 and 1.0 x 1019 n.cm2 (E > 1 MeV). The irradiations were carried out at less than 150°C. The results of room temperature tension tests and the instrumented impact tests over a range of temperature are presented. Irradiation stability of the steel is monitored by measuring the increase in yield strength and the elevation in the ductile-brittle-transition temperature after neutron irradiation. Attempts have been made to assess the extent of embrittlement as a function of neutron exposure. The results have been compared with both vintage and advanced pressure vessel steels.
Fracture Toughness and Impact Tests on Neutron Irradiated Ferritic Steels : Results and Correlations
Authors: Chatterjee S , Sriharsha HK , Viswanathan UK
Published: March 2009

Four A533B pressure vessel steels containing 0.16 wt% copper, nickel and phosphorous ranging from 0.10 to 0.82 wt% and 0.006 to 0.02 wt% respectively, and a AISI 403 stainless steel, a typical end fitting material used in pressurised heavy water reactors, in the unirradiated condition, were evaluated by instrumented impact testing to determine the crack initiation energy (CVNi), total absorbed energy (CVN), ductilebrittle transition temperature (T41J,T0.89mm), dynamic yield strength (σyd) and dynamic initiation fracture toughness (Kid). Three of these steels were irradiated at 563K to a nominal fast fluence of 1x1019, n/cm2 (E > 1 MeV) and the corresponding parameters were evaluated.

It was observed that the widely used correlation between CVN and KIC modified as (Kid/σyd)2 = 0.64[(CVN/σyd)-0.01] overpredicted the experimental Kid values by a factor of 2. However, if the CVNi was used instead of CVN, the predicted values were within ± 20%.

The irradiation induced decrease in Kid could not be correlated with increase in transition temperature. However, it could be correlated with the corresponding changes in σyd and CVNi values.
Evaluation of Thermal-Aged Plates, Forgings, and Submerged-Arc Weld Metals
Authors: DeVan MJ , Lowe AL , Wade CS
Published: March 2009

Thermal-aged surveillance material was removed from two commercial reactor pressure vessels. The material from the first reactor vessel received a thermal exposure of approximately 103,000 hours at 282°C (540°F), while the material from the second reactor vessel received a thermal exposure of approximately 93,000 hours at 282°C (540°F). The surveillance material removed consisted of SA-508, Class 2 and SA-533, Grade B, Class 1, base metals; Mn-Mo-Ni/Linde 80 flux weld metals; and SA-533, Grade B, Class 1, correlation monitor material. Charpy V-notch impact specimens were fabricated from these materials and tested. In addition, selected thermal-aged specimens were annealed at 343°C (650°F) and 454°C (850°F) and impact tested. Unaged material was tested to establish baseline data for evaluating the thermal-aged material and thermal-aged/annealed material. Small variations in the impact properties were observed for all materials. Small increases in transition temperature were observed for the forging base metal and weld metal B surveillance materials, while the upper-shelf energies exhibited small decreases. The 454°C (850°F) anneal restored the upper-shelf energy for the forging base metal and weld metal B surveillance materials.
Further Microstructural Characterization of Submerged-Arc Weld Metals - II
Authors: Lawless KR , Lowe AL
Published: March 2009

This paper presents the results of further microstructural evaluations of irradiated Mn-Mo-Ni wire/Linde 80 flux submerged-arc weld metals typically found in Babcock & Wilcox fabricated reactor vessels. Four Mn-Mo-Ni wire/Linde 80 surveillance weld metals were studied to characterize the size and distribution of micro-inclusions (< 0.26 μm).

Analytical TEM was used to characterize the carbides, coarse (0.1 to 2.0 μm) inclusions, and fine (2 to 50 run) precipitates. Thin foil and extraction techniques were used to characterize particle morphology while convergent beam diffraction and energy dispersive X-ray techniques were carried out to identify the crystal structural and chemical composition. The results are compared with previously evaluated unirradiated Mn-Mo-Ni wire/Linde 80 flux submerged-arc weld metals.
Exploratory Studies of the Effects of Irradiation Temperature on Mechanical Properties of Structural Steels amd Welds
Authors: Hawthorne JR
Published: March 2009

The influence of irradiation temperature on the extent of change in Charpy-V (Cv) notch ductility and tension test properties of low alloy structural steels and welds was explored for reactor vessel applications. Specimens were irradiated at 288°C and 316°C in temperature-controlled assemblies in the Ford Nuclear Reactor (FNR) at the University of Michigan. Irradiation at 316°C to 7.9 × 1018 n/cm2, E > 1 MeV, produced 41-J temperature elevations that were on average 51% of those produced by 260°C irradiation. Thermal aging at 316°C for 5000 h had little effect on Cv and tension test properties. NRC Regulatory Guide 1.99 Rev. 2 projections for irradiation-induced embrittlement at 288°C are compared to the experiment measurements.
The Radiation Hardening and Embrittlement of a Mild Steel Submerged-Arc Weld
Authors: Buswell JT , Bolton CJ , Wootton MR , Bischler PJE , Jones RB , Jones LT , Phythian WJ , Sinclair RR
Published: March 2009

This paper provides details of accelerated irradiation experiments on a Magnox mild steel submerged-arc weld at mean irradiation temperatures of 165°C and 269°C. The irradiation-induced changes in mechanical properties and weld microstructure have been determined. Irradiation increased the 40J transition temperature and the yield stress. The increase in transition temperature at a given dose was rather higher in the lower temperature irradiations. Irradiation-induced precipitates of about 2nm diameter were produced in both series of irradiations. Small angle neutron scattering data indicated a precipitate composition of about 75Cu25Mn (at%). Electron microscopy confirmed the presence of copper-rich precipitates of that size. The irradiation dose ranges covered the development stage of the precipitation. The directly measured and (yield stress) derived transition shift data were interpreted satisfactorily using a mechanistically based model involving a matrix damage component and a component attributable to copper precipitation.
The Effect of Flux on the Irradiation Hardening of Pressure Vessel Steels
Authors: Odette GR , Mader EV , Lucas GE , Phythian WJ , English CA
Published: March 2009

Hardening of low copper steels irradiated at 288°C increased with increasing flux in the range from about 0.6 to 50 × 1016 n/m2-s. In contrast, the hardening of high copper steels was generally less effected and, in some cases, decreased with increasing flux. Thus there are at least two competing effects of flux. The behavior of low copper alloys is attributed to a population of thermally unstable matrix defects that anneal during irradiation, hence, produce hardening that increases with flux. However, the unstable matrix defects also act as point defect sinks reducing radiation enhanced solute diffusion rates. In high copper steels, lower diffusion rates delay hardening due to precipitation. These conclusions were confirmed by low-temperature post-irradiation annealing treatments which produced rapid recovery of the unstable matrix defects. The observed data trends are consistent with a model that treats the unstable matrix defects as small cascade vacancy clusters.
Characterisation of Model Fe-Cu-Mn-Ti-N Alloys by Electron Microscopy and Positron Annihilation
Authors: Phythian WJ , de Diego N , Mace J , McElroy RJ
Published: March 2009

It has been recognised for many years that copper plays a significant role in the embrittlement process of reactor pressure vessel (RPV) steels subjected to neutron irradiation. In developing fundamental understanding, and mechanistic models to predict embrittlement, it is important to identify the microscopic mechanisms underlying this phenomena. The purpose of this paper is to discuss recent results obtained from thermal ageing experiments on model alloys doped with copper and nitrogen. These experiments were designed to characterise the material prior to receiving irradiated samples encompassing a wide range of flux, fluence and temperature conditions.

Results will be presented from a microstructural and microchemical examination using transmission electron microscopy (TEM), field emission gun scanning transmission electron microscopy (FEGSTEM) and positron annihilation (PA). Precipitation kinetics have been followed and comparison made between microstructure and measured hardness changes. In alloys containing both titanium and nitrogen, a second form of barrier hardening centre is observed. The insight these studies give into the observed macroscopic hardness increase after irradiation or thermal ageing will be discussed. In particular the implications of a potential further mechanism for embrittlement in commercial steels will be considered.
Investigation of Neutron Irradiated Soviet-type Reactor Pressure Vessel Steels by Small Angle Neutron Scattering
Authors: Brauer G , Eichhorn F , Frisius F , Kampmann R
Published: March 2009

Reactor pressure vessel steels of the Soviet-type 15Kh2MFA (Cr-Mo-V steels) are used in the VVER-440 type reactors, whereas steels of the Soviet type 15Kh2NMFA (Ni-Cr-Mo-V steels) are used in the WER-1000 type reactors. Eleven different materials, i.e. seven base metals and two weld metals of the type 15Kh2MFA, as well as one base metal and one weld metal of the type 15Kh2NMFA were available for the investigations. The small angle neutron scattering technique using the SANS-2 facility at the FRG-1 reactor in Geesthacht was employed to study the radiation-induced defect microstructure in the as-irradiated materials. The results are discussed in terms of the influence of different impurity contents and irradiation conditions on the defect microstructure.
Postirradiation Deformation Behavior in Ferritic Fe-Cr Alloys
Authors: Hamilton ML , Gelles DS , Gardner PL
Published: March 2009

It has been demonstrated that fast neutron irradiation produces significant hardening in simple Fe-(3-18)Cr binary alloys irradiated to about 35 dpa in the temperature range 365 to 420°C, whereas irradiation at 574°C produces hardening only for 15% or more chromium. The irradiation-induced changes in tensile properties are discussed in terms of changes in the power law work hardening exponent. The work hardening exponent of the lower chromium alloys decreased significantly after low temperature irradiation (< 420°C) but increased after irradiation at 574°C. The higher chromium alloys failed either in cleavage or in a mixed ductile/brittle fashion. Deformation microstructures are presented to support the tensile behavior.