bluuebunny/crossref_metadata_2025 huggingface dataset:
Clinical Aspects of Anesthesia Gas Monitoring
Authors: Paloheimo MPJ
Published: March 2009

Monitoring of both inspired and end-tidal concentrations of oxygen, carbon dioxide, nitrous oxide, and volatile anesthetic vapors is nowadays possible with a stand-alone unit based on infrared and paramagnetic technologies (Capnomac, Datex/Instrumentarium, Helsinki, Finland). The clinical value of the breath-by-breath information on the management of low-flow and partial rebreathing breathing circuits during various phases of general anesthesia are discussed in the light of multigas trends. It is concluded that quantitative analysis of both gases and halocarbon vapors is informative of gas delivery, uptake, and distribution, provides useful information on patient management, and enhances patient safety.
Review of Methodology in Anesthetic Gas Monitoring
Authors: Halsey MJ
Published: March 2009

This review concentrates on the underlying principles of operation of analyzers suitable for anesthetic gas monitoring. It includes any special advantage or disadvantage of a particular technique and relates these to the clinical requirements associated with patient safety. The methods available are categorized into those based on bulk properties, on spectroscopy, and on special applications such as mass spectrometry and gas chromatography. The final conclusion from the detailed considerations is that a performance standard for anesthesia gas monitoring is desirable and timely.
Is There an Anesthetic Contribution to Ozone Depletion or Greenhouse Warming?
Authors: Joyner BD
Published: March 2009

Chlorofluorocarbons (CFCs) are firmly linked with stratospheric ozone depletion and potential global atmospheric warming—the greenhouse effect. Halogenated anesthetics—halothane, enflurane, and isoflurane—are superficially similar in chemical structure to CFCs, and concern has been expressed regarding their possible contribution to the same environmental issues.

The historical development of both concerns is traced, together with the chemical structures of the highly stable CFCs and of the less stable substitute materials now under development. From this information it is shown that any conceivable contribution to either issue by halo-genated anesthetics would be absolutely minimal.

On a production volume basis alone, the annual world production of anesthetics is about one thousand times less than that of CFCs. In addition, the chemical structures of anesthetics show much more similarity with the “environment-friendly” substitutes for CFCs than with CFCs.
Anestheticography: Clinical Applications
Authors: Jantzen J-PAH
Published: March 2009

The safe practice of inhalation anesthesia requires control over the amount of volatile anesthetic delivered to the patient. This is facilitated by continuous monitoring and recording of the agents' concentration (“anestheticography”). Either the vaporizer or the circuit may be considered the “delivery system,” hence anestheticometry performed either in the fresh gas supply or in the inspiratory limb of the system is acceptable. Such monitoring practice may be expected to eliminate anesthesia-related death due to overdose of volatile agents. Besides the aspects of technical safety, anestheticometry is a useful adjunct to teaching and research. It supports a more widespread application of the minimal-flow and closed-circuit techniques, facilitates the understanding of inhalation anesthesia, and increases acceptance of low-flow systems. For minimal-flow anesthesia, anestheticometry should be considered mandatory because it provides the only means of detecting and correcting derangements of the anesthetic vapor concentration, often brought about by routine clinical maneuvers.

To demonstrate this, we recorded the course of the inspiratory and expiratory concentration of a volatile anesthetic (isoflurane) by infrared absorption and a trend recorder. Changing the carrier gas composition during high flow (fresh gas flow = 6.0 L∙ min-1) from 75 to 25 vol % nitrous oxide in oxygen resulted in a 10% increase of the inspiratory isoflurane concentration. Activating the oxygen bypass or exchanging the soda lime canisters was followed by a prolonged reduction of concentration, most pronounced with minimal flow (fresh gas flow = 0.5 L∙ min -1). Initiating emergence by closing the vaporizer during minimal flow led to a slow decrease in concentration, while at high flow the inspiratory isoflurane concentration rapidly decreased to subanesthetic levels. Integration of a charcoal filter into the inspiratory limb of the breathing circuit reduces the inspiratory concentration to undetectable levels within <3 min. Anesthe-ticography is a useful means of monitoring and documentation of inhalation anesthetic. Such monitoring should become part of ISO standards for reasons of patient safety, economy, teaching, and research.
Economics of Anesthetic Gas Monitoring
Authors: Bray CS
Published: March 2009

The purpose of this paper is to attempt to identify and quantify the cost differences in the United Kingdom (UK) between continuous-flow open anesthetic systems and low-flow closed systems. Due to the lack of reliable statistics, such an appraisal is difficult, and at best this paper can give only a likely indication of the actual costs involved. Costs will vary significantly from country to country, and a detailed study for any particular site is necessary if meaningful results are to be obtained.

Annual running costs for Raman laser, infrared, and piezoelectric type monitors have been estimated. A significant expense is the provision of the disposable gas sampling line, if it is changed in accordance with the manufacturer's recommended intervals.

An estimate is made of the money spent on volatile agents and anesthetic gases in the UK, and the potential savings from decreasing gas flow from 10 to 2 L/min. is also estimated. These figures are compared with the estimated cost of providing all operating theatres in the UK with anesthetic gas monitoring equipment.

Other factors such as additional expenditure on soda lime and savings on other monitoring equipment, e.g., oxygen analyzers, are taken into account.

The Pharmaceutical Price Regulation Scheme is briefly explained, as well as the likely effect of the scheme on savings in the use of volatile agents.
Conclusion and Summary for Standards Writing Purposes and Governmental Consideration
Authors: Thompson PW
Published: March 2009

The origins of this meeting stemmed from International Organization for Standardization (ISO) Technical Committee 121 on Anaesthetic and Respiratory Equipment, Subcommittee 3 on Lung Ventilators and Related Equipment, who sought guidance as to whether it was appropriate or indeed necessary to propose as a new work item a standard for monitoring equipment for anesthetic vapor levels in the airways of patients or at the common gas outlet of the anesthesia machine.
Suspension Systems for Today's Manufacturing Environment
Authors: Troxell JR
Published: March 2009

Manufacturing today is going through a major change; two features of this change are the reduction or elimination of inventory (Just-In-Time) and a new, plant-wide emphasis on quality (Total Quality Control). One particular technique for never-ending improvement of quality is called line-stop, where operators on the production line have the authority to stop production when an indication of quality deterioration is observed.

Suspension systems are well-suited for the line-stop technique. A suspension system is the combination of a suspension rule, designated (j,k), and a lot by lot inspection plan; suspension occurs if j lots are rejected in k or fewer lots. A simple rule such as stop production if two lots are rejected within five or fewer lots (2,5) can be used, avoiding the use of perhaps subjective impressions by the operator concerning quality.

This paper reviews the characteristics of such rules, highlighting their mean time to suspension or Average Run Length. Suspension systems are compared to cumulative sum charts. Cumulative sum charts have shorter average run lengths, but not by much; suspension systems are easier to understand and easier to use, requiring no calculations at all in their daily use.
On the Robustness of a Class of Continuous Sampling Plans under Certain Types of Process Models
Authors: Lasater HA
Published: March 2009

Harold F. Dodge in 1945 defined an acceptance sampling plan, CSP-1, for inspecting a continuous sequence of units or lots which are outputs from a process operating in statistical control. The plan is to guarantee there will be a maximum average percent of nonconforming units in the inspected units equal to a selected Average Outgoing Quality Limit (AOQL). For twenty-six plans investigated when process conditions differ from those of Dodge, the average percent nonconforming only in a finite number of units inspected will be less than or equal to the AOQL of Dodge. Also, when the process percent nonconforming is changing according to certain patterns investigated, the average percent passing inspections will be practically no larger than the AOQL under Dodge assumptions.
Sampling Terms of Reference
Authors: Proctor CH
Published: March 2009

Two aspects of a sample design that seem crucial in deciding whether specialized statistical expertise will be required to make the design work are: (1) frame versus nonframe sampling and (2) random versus patterned sampling. These terms are illustrated and some subcategories are suggested. Even a clearly defined frame may be less than adequate. Patterned sampling can yield small sampling variances but the size of this variance may be difficult to discover. The assistance of a statistician seems most needed when there is no frame, or a less than adequate one, and when a highly patterned sampling design is used.
Sampling Plans with Low Consumers' Risk
Authors: Tye JB
Published: March 2009

Most sampling activity is concerned with the Acceptable Quality Level (AQL) or Producers' Risk. There exists, however, applications for sampling schemes built around the Limiting Quality Level (LQ) or Consumers’ Risk. Examples include isolated lots or cases where the characteristic being examined in the sample is so severe that extra care must be taken to prevent nonconformances being shipped or used. When the output of nonconformances must be zero or measured in parts per million, a sampling scheme with low consumers’ risk can be effectively used to audit a process. It can be argued that this is a form of process control because rejection of a lot under this scheme is an indication of major problems. In such cases, diagnosis and corrective action are required immediately, in addition to the usual screening of the rejected lot and those immediately preceding it.

This paper provides such a sampling scheme. The determining parameter is the average outgoing quality limit (AOQL). LQ's from 0.001 to 0.05 are used. Because of the universal application and popularity of MIL-STD-105D and the ANSI Standard Z1.4 (Ref.), their format and procedure have been followed wherever possible.
A Case Study of the Use of the “Summa Canister” for Passive “Off-Gas” Vent Sampling and Analysis
Authors: Solecki MF , Syvarth HM , Campagna P , Batz W
Published: March 2009

The “SUMMA CANISTER” with a restricted flow orifice was used to collect and preserve “off-gas” vent samples from a landfill in Illinois. Since the method is rarely used for vent sampling, standard accepted methods were used to confirm the integrity of the technique. The technique presented some problems in analytical procedures. They were overcome, however, and the analysis was continued. The problems encountered are presented here with possible solutions. The method appears to have the potential to be one of the more efficient ways currently available for collecting and preserving gas samples.
Report of an Interlaboratory Study Comparing EPA SW 846 Method 3050[1] and an Alternative Method from the California Department of Health Services
Authors: Kimbrough DE , Wakakuwa J
Published: March 2009

The existing EPA method for the analysis of toxic elements in solid matrices, SW 846 method 3050, cannot accurately or precisely determine (i.e., within SW 846 quality control limits) the concentrations of either antimony or silver and can do so for barium only at lower concentrations. An alternative method was developed by the Southern California Laboratory of the Department of Health Services that could (1) simultaneously solubilize all of the above elements over a broader range of concentrations and (2) solubilize all other regulated elements with equal or better results.

As a part of the validation process for this alternative method, an interlaboratory study was conducted. Nine public and private laboratories compared the existing method with our alternative method. The results of this study clearly show statistically significant differences between method 3050 and the alternative method proposed in this paper.
Evaluation of Leachability of Radium Contaminated Soil
Authors: McNevin TF
Published: March 2009

Composite samples of radium contaminated soil were batch extracted at pH 5 and pH 3 in a modification of ASTM Test Method for Shake Extraction of Solid Waste with Water (D 3987-81) to evaluate the relative leachability of radium-226 from soil which had been blended with a non-contaminated soil, in order to achieve approximate background concentrations of radium in the soil mix. Comparisons were made between contaminated soil, diluent soil and the resulting amended mix. Analysis for radium was conducted by de-emanation of radon-222. Data from the extractions were used to evaluate a bench-scale demonstration of soil blending, which was judged to be a technically feasible disposition alternative for soil contaminated with relatively low levels of radium. Comparison of the contaminated soil extraction values of radium with the radium concentrations detected in monitoring wells placed within the area of contaminated soil, indicated a tendency for the extraction tests to overestimate the concentration of radium actually seen in groundwater associated with the soil being evaluated. Extraction values were then used in a simple analytical groundwater model, incorporating only transport and dispersion, which predicted a maximum radium value well below all concentration limits deemed acceptable by present regulatory standards.
Geochemical Basis for Predicting Leaching of Inorganic Constituents from Coal-Combustion Residues
Authors: Murarka IP , Rai D , Ainsworth CC
Published: March 2009

Pore waters, leachates, and waste-water extracts associated with electric utilities' wastes and waste disposal ponds exhibit extremely variable aqueous elemental concentrations. When ionic strength and aqueous complexation are accounted for, however, the activities of free species exhibit behavior with pH similar to those in equilibrium with known solid phases. By comparing observed ion activity products (IAPs) with calculated IAPs from thermodynamic data for selected solid phases, solubility-controlling solids may be indirectly identified or suggested for various elements. To date, AlOHSO4, Al(OH)3, BaSO4, CaSO4, Cr(OH)3/(Cr,Fe)(OH)3, CuO, SiO2, SrSO4, ZnO, and several solid solution/coprecipitates have been suggested to be the solubility-controlling solid phases for different elements over a wide range of waste compositions, waste types, and disposal conditions. These results indicate that the composition of leachates from coal-combustion wastes, with respect to several elements, can be estimated from fundamental reactions involving solubility-controlling solids of these elements. The results obtained thus far using this approach are summarized in this paper.
Modification of the TCLP Procedure to Accommodate Monolithic Wastes
Authors: Bone LI , Bricka M , Hannak P , Shah SI , Prange N , Marsden PJ , Waggener JE , Miller M , Johnson E , Robuck SJ
Published: March 2009

The current EPA Toxicity Characteristic Leaching Procedure (TCLP), SW 846 Method 1311, requires that all wastes be milled into smaller particles prior to being placed into the extractor. A multi-laboratory study has been conducted to determine if milling is necessary or if the tumbling action of the TCLP procedure will cause monolithic wastes, which are not strong enough to survive in the environment, to fall apart in the extractor. Multiple plugs of eight different solidified waste samples of variable strength were prepared. The unconfined compressive strength of a plug of each sample was measured and the environmental survivability was evaluated in two separate laboratories using the ASTM Freeze/Thaw (D4842-90) and Wet/Dry (D4843-88) testing procedures. Identical plugs of each sample were tumbled in glass bottles, equipped with a stainless cage as proposed by EPA. Additional identical plugs were tumbled in unbreakable plastic bottles following the same protocol used with the stainless steel cage. Five separate laboratories performed the stainless steel cage experiments in duplicate while three laboratories performed the plastic cage tumble, also in duplicate. No chemical analysis was performed; each laboratory simply weighed the amount of material which would not pass through a 9.5 mm sieve after the 18-hour tumble was complete. This weight compared to the initial plug weight was compared with the freeze/thaw, wet/dry and unconfined compressive strength results.

All samples that had low strength and failed the wet/dry tests fell apart when tumbled in either type of container. Comparison of the cage and plastic bottle results clearly showed the plastic bottle to be superior. The results better matched the strength data, the data were more reproducible on both an intra- and inter-laboratory basis, and a plastic bottle is easier to clean. ASTM D-34 is drafting a leaching procedure similar to the TCLP which will use a nonbreakable bottle and will not require particle size reduction of the waste prior to tumbling in the extractor.
Sampling Protocol Development for Hazardous Waste
Authors: Eatmon BS , Marcus MF
Published: March 2009

Many of the sampling devices, procedures and protocols used for hazardous waste sampling have been developed and adapted from water or soil sampling procedures. In every case significant modification and flexibility in these procedures are necessary to successfully sample hazardous waste material. A set of sampling protocols have been prepared by our operating sites to utilize our collective experience in sampling and to standardize our sampling protocols across our company. General sampling protocols were needed that address: Sample Training; Safety — Personal Protective Equipment; Chain-of-Custody/Labeling; Sample Management — Container, Preservations, Holding Times, and Sample Facilities and Decontamination.

These general protocols are the basis for development of specific sampling circumstances that are routinely encountered during the management of hazardous waste. These specific routines are called the Site Specific Protocols and they include: solids in drums; liquids in drums; bulk solids; bulk liquids; stationary tanks; surface impoundments; in-line liquids; waste piles; laboratory subsampling liquids; laboratory subsampling solids.
Early Warning Report: Automated Checking of QC Data
Authors: Peak SR , Duerksen PE , Wong KW , Szeto E
Published: March 2009

Sample log-in, work list generation, data entry, and report production are data-handling functions common to most Laboratory Information Management Systems (LIMS's). A newly developed automated review system now extends those functions to include the use of a LIMS for reviewing and evaluating quality control (QC) results. This paper delineates the four major stages involved in creating this automated review system: concept, preliminary design, programming, and testing. Although computer programming is typically system-dependent, the logic employed in QC review should have broad application to many LIMS's.

The paper also describes the daily operation of this new LIMS function on-line in three networked commercial laboratories with over 140 employees. This account of the review system's pitfalls, successes, and maintenance requirements can help other LIMS users achieve a smooth, reliable installation.
Fracture Toughness Evaluation of Heat-Treated Zr-2.5Nb Pressure Tubes
Authors: Asada T , Kimoto H , Chiba N , Kasai Y
Published: March 2009

Tests of full-size pressure tubes and compact tension specimens having several widths are carried out with emphasis on the size effect on the fracture toughness of the pressure tube material, which is made of heat-treated Zr-2.5Nb. The hydrogen concentration of the specimens ranges from 10 to 400 ppm, and the test temperature from room temperature to 573 K.

In the pressure tube burst tests at room temperature using radial hydrided materials, fracture toughness at maximum pressure KC decreased rapidly with hydrogen concentration in the region where the concentration was less than 100 ppm. In the region where the hydrogen concentration was higher than 100 ppm, KC slowly decreased with increased concentration. For materials having radial hydrides at a hydrogen concentration of 200 to 300 ppm, a steep brittle-ductile transition was observed at about 550 K.

Fracture toughness KC shows strong dependence on specimen size, increasing and approaching that of pressure tubes with increased specimen width for a ductile material. This size effect of fracture toughness can be determined by a failure assessment method in which the Dugdale model is used.
Effect of Tensile Deformation on Crystallographic Texture in Zircaloy Sheet
Authors: Mahmood ST , Murty KL
Published: March 2009

The mechanical anisotropy of recrystallized Zircaloy-4 sheet, characterized in terms of anisotropy parameters R and P obtained from contractile strain ratios measured using grid analysis method, showed no strain dependence of these parameters. This linear variation of contractile strains in Zircaloys has been observed by other investigators as well, which misleadingly points to no effect of deformation on crystallographic textures and resulting mechanical anisotropy. Since the deformation caused by slip and twinning reorients the crystallites producing changes in texture even at low strains, the purpose of this study was to investigate the texture rotations caused by tensile deformation along the rolling (RD) and transverse (TD) directions of recrystallized Zircaloy-4 sheet. Tensile deformation along the RD of the sheet showed little effect on the initial bimodal basal texture in the ND-TD plane, which became smoother and unimodal after high (∼20%) tensile strain along the RD. Tensile strain along the TD, on the other hand, exhibited strong texture rotations which resulted in 90 deg rotation of the basal pole distribution making it almost bimodal in the ND-RD plane at high (∼34%) strains, after going through a unimodal (ideal) distribution at intermediate (∼15%) strains. The observed strain independence of anisotropy is explained through combined effects of texture rotations and changes in the macroscopic stress state.
Correlation of Microstructure and Mechanical Properties of Zr-Sn Alloys
Authors: Wadekar SL , Banerjee S , Raman VV , Asundi MK
Published: March 2009

The role of tin as a solid solution strengthener and a precipitation hardener in zirconium base alloys has been examined. Mechanical properties and microstructure of Zr-Sn binary (0.5 to 8 wt% Sn) alloys were investigated in both β-quenched and tempered conditions. The yield and ultimate tensile stresses and the percentage elongation were evaluated as a function of tin content, C, in both β-quenched and tempered Zr-Sn alloys. The 0.2% yield stress shows a linear relationship with C2/3, suggesting the operation of the Mott-Nabarro model of solid solution strengthening in which clustering of solute atoms is envisaged. The presence of tin solute clusters could also be detected in TEM microstructures of β-quenched alloys. The effect of tin content on the yield and flow behavior of zirconium has been examined at temperatures between 77 and 673 K. Results indicate that the addition of tin influenced both the thermal and athermal components of flow stress. The activation volume was found to be independent of the plastic strain, while it showed an increase with temperature and a decrease with solute content. The deformation process appeared to be controlled by two ratecontrolling mechanisms: (a) dislocations overcoming the substitutional solute clusters at temperatures below 473 K, and (b) movement of jogged screw dislocations at higher temperatures. The intermetallic precipitate phase formed due to tempering was identified as Zr3Sn with A15 structure having the following orientation relationship with the matrix: (0001)α//(111)Zr3Sn <1210>α//<231>Zr3Sn Because of the good lattice registry between the precipitate and the matrix phases, partial coherency between them is maintained even after considerable growth of precipitate particles.
Growth in Zircaloy-4 Fuel Clad Arising from Oxidation at Temperatures in the Range 623 to 723 K
Authors: Donaldson AT
Published: March 2009

Tubular samples of Zircaloy-4 clad, of the standard 17 × 17 PWR design, in the cold worked, stress relieved condition, with a mean wall thickness ξ = 580 μm, and samples machined to reduce their wall thickness to 200 and 80 μm, respectively, have been oxidized in air at one bar pressure for exposure periods up to 753, 195 and 152 days, at temperatures of 623, 673 and 723 K, respectively.

Oxidation produces tube lengthening that increases with exposure time and temperature and varies inversely with clad wall thickness. The rate kinetics of oxidation induced straining mirror those of the weight gain measurements. Axial strains up to εz = 0.0265, 0.0185 and 0.0016 in the thinnest clad, and 0.0047, 0.0014 and 0.0003 in standard clad, are observed following exposure at 723, 673 and 623 K, respectively.

A model is developed in which the observed length variation, εz, is expressed in terms of the weight gain owing to oxidation, Δw, the exposure temperature, T, and clad thickness, ξ, according to (ϵz/Δw)=A⋅(ξ)m where the coefficients A and m vary with temperature.
Effects of Recrystallization and Neutron Irradiation on Creep Anisotropy of Zircaloy Cladding
Authors: Murty KL , Mahmood ST
Published: March 2009

Zirconium alloys have hcp crystal structure with low c/a ratio at and below the reactor operating temperatures and exhibit preferred orientations or textures. These textures result in anisotropic mechanical properties, which in-turn affect their in-service behavior such as in-pile creep down of the cladding tubes. The purpose of the present study has been to investigate the effects of recrystallization and neutron irradiation on the anisotropic biaxial creep behavior of Zircaloy cladding tubes. The creep anisotropies of the cold-worked and recrystallized tubes were considered using results from the closed-end internal pressurization tests superimposed with axial loading. The in situ biaxial strain measurements were made using laser and linear variable differential transformer (LVDT) extensometers. Creep data were obtained at various stress ratios, and creep loci were constructed at constant energy dissipation for both cold-worked and recrystallized tubes. X-ray diffraction techniques were used to measure the textures which were then described quantitatively in terms of crystallite orientation distribution functions (CODFs). These CODFs were employed to predict the anisotropy parameters R and P, and the anisotropic creep behavior. The creep behavior of Zircaloy tubes changed with recrystallization. The effect of neutron irradiation on the recrystallized material is modeled by invoking secondary slip systems. The considerable amount of plastic anisotropy observed in the unirradiated recrystallized tubes shows a tendency to decrease and to become isotropic at high fluences. On the other hand, neutron irradiation does not produce any significant changes in the anisotropy of the cold-worked material when radiation growth is taken into consideration.
The Contribution of Irradiation Growth to Pressure Tube Deformation
Authors: Holt RA , Fleck RG
Published: March 2009

Up-to-date growth results on Zr-2.5Nb pressure tube material from the DIDO reactor at AERE Harwell are presented. The observed temperature dependence and magnitude of growth are significantly different from the representations in a recently published model for in-reactor deformation of pressure tubes. These differences are discussed in terms of (1) the effects of stress on growth, (2) the comparability of test reactor and power reactor conditions, and (3) the relative contributions of creep and growth to pressure tube elongation.

A preliminary estimate of the anisotropic creep component of the in-service deformation suggests that the creep anisotropy may be different from that in the model (derived from small specimen stress relaxation tests). Biaxial in-reactor creep tests on specimens with microstructures and textures similar to pressure tubes are required to support this view. This would also help to resolve an apparent discrepancy in the temperature dependence of growth and pressure tube elongation.
Influence of Alloy Composition and Processing on the Nodular Corrosion Resistance of Zircaloy-2
Authors: Bradley ER , Schemel JH , Nystöm A-L
Published: March 2009

Zircaloy-2 fuel tubing with different compositions has been manufactured by a variety of thermomechanical processes to evaluate manufacturing variables that could influence nodular corrosion. The primary variables studied include: (1) alloy composition. (2) thermal annealing history, (3) tube texture, and (4) recrystallized versus stress relieved tubing. A total of 48 tubing variants were fabricated and tested.

Results from 793 K steam autoclave tests revealed that all variables examined influence the corrosion behavior with complex interactions between the variables. Alloy composition and thermal history exhibited the strongest influence. Improved corrosion resistance was observed for the material containing a lower Sn concentration and annealed at lower temperatures. The effect of thermal history was not consistent with the accumulated annealing parameter formulation. A single 1005 K anneal late in the manufacturing process produced extremely high weight gains compared to lower values when the same anneal occurred early in the process or when annealing for longer times at lower temperatures to obtain the same accumulated annealing parameter. Small improvements in corrosion resistance for the more sensitive materials were obtained from tubing produced with a more radial texture. Stress relieved tubing was generally less sensitive to nodular corrosion than comparable recrystallized tubing.

Microstructural examinations did not identify the cause for the observed variations in corrosion behavior. Particle size distributions were independent of the material or processing histories. This lack of any correlation indicates that the particles themselves do not control the corrosion behavior, but a specific microstructural feature was not found that would explain the corrosion behavior.
Oxide Growth Mechanism on Zirconium Alloys
Authors: Garzarolli F , Seidel H , Tricot R , Gros JP
Published: March 2009

In order to get a better understanding of the mechanisms governing corrosion of Zr-based alloys, several examinations have been performed on a variety of samples with uniform and nodular corrosion and different oxide layer thicknesses.

The results point to a barrier layer concept. The oxide layer becomes porous at a critical thickness. Open porosity increases from 0.01% at 10 μm to 3% at 100 μm. Between the outer porous oxide and the metal, a dense interlayer exists. This is only ≤30 nm in nodular oxide but has been found to be several hundred nm in uniform post-transition oxide.

The barrier layer is obviously influenced by the crystallization of the oxide at the interface. This crystallization leads either to a columnar monoclinic, an equiaxed tetragonal, or to a fine equiaxed monoclinic oxide. The latter, which probably forms only under the mineralizing effect of hydrogen, was found in nodular oxide. It easily cracks at the grain boundaries. Well developed columnar oxide is seen in uniform oxide, when corrosion resistance is high.

Recrystallization seems to be responsible for the pore or microcrack formation at the transition. The intermetallic precipitates influence the corrosion behavior significantly. They probably oxidize slowly. This oxidation starts with the zirconium and is accompanied by iron diffusion into the surrounding oxide.
Raman Spectroscopy Study of the Tetragonal-to-monoclinic Transition in Zirconium Oxide Scales and Determination of Overall Oxygen Diffusion by Nuclear Microanalysis of O18
Authors: Godlewski J , Gros JP , Lambertin M , Wadier JF , Weidinger H
Published: March 2009

Two allotropic forms of zirconium oxide, monoclinic and tetragonal, have been identified in the scales formed on zirconium alloys. The transition from tetragonal to monoclinic has been followed by X-ray measurements and Raman laser spectroscopy. Information on the average content of the tetragonal phase was obtained by X-ray diffraction, whereas Raman laser analyses on tapered sections revealed its distribution through the scale thickness.

Oxidation exposures were made in an autoclave, using H2O18 and D2O18 to determine the overall diffusion coefficients. In particular, oxide scales have been studied on Zircaloy-4 with three different precipitate sizes, and on a Zr-1Nb alloy, after exposure in an autoclave for between 3 and 100 days. The specimens were analyzed in detail in the vicinity of the kinetics transition point, where the acceleration of corrosion occurs.

Raman spectroscopy analyses enabled the crystallographic nature of the ZrO2 to be determined. Close to the interface, the tetragonal phase content is about 40%, when after the transition the tetragonal phase is transformed into monoclinic.

The O18 diffusion treatment was carried out in an autoclave at 400°C under pressure on specimens previously oxidized for between 3 and 100 days in natural water vapor pressure. The diffusion profiles were determined by nuclear microanalysis using the O18(p,α)→N15 reaction. Based on these profiles, the volume and grain boundary diffusion coefficients were calculated for each material and for each oxidation time.

The results show clearly that oxygen transport occurs principally by grain boundary diffusion. The boundary diffusion coefficient is 108 times higher than those for bulk diffusion (Db is equal to 10-13 to 10-15 cm2/s).

The results of these analyses are in agreement with the changes in kinetics observed at the transition point. The stabilization of the tetragonal phase by stress is discussed.
Precipitate Behavior in Zircaloy-2 Oxide Films and Its Relevance to Corrosion Resistance
Authors: Kubo T , Uno M
Published: March 2009

The a-c impedance measurements were made for oxide films formed in high temperature steam on Zry-2 with varying precipitate distributions. TEM and EDX analyses were also carried out on precipitates in oxide films. The electrical resistivity of oxide films tends to increase with an increase in nodular corrosion resistance, with the β-quenched samples having the highest resistivity. The resistivity tended to increase with a decrease in average precipitate size. EDX analyses showed that precipitates in oxide films dissolved into oxide matrix during the corrosion process in high temperature steam. Very fine precipitates in β-quenched Zry-2 would have disappeared early in the corrosion process. The improvement in corrosion resistance by β-quenching was attributed not to short-circuit effects of precipitates but to a change in oxide properties induced by an increase in the amount of alloying elements retained in the matrix.
Corrosion-Electrochemical Properties of Zirconium Intermetallics
Authors: Weidinger HG , Ruhmann H , Cheliotis G , Maguire M , Yau T-L
Published: March 2009

Alpha-zirconium is a very poor solvent for most alloying metals. Moreover, it has a high affinity for these metals. Consequently, intermetallics are easily formed and highly visible in zirconium and its alloys. Many researchers believe that the corrosion resistance of zirconium and its alloys depends strongly on the distribution and morphology of these intermetallics. Corrosion problems, such as nodular corrosion and intergranular corrosion, are often associated with intermetallics.

Numerous papers have been published concerning the role of intermetallics in nodular corrosion of Zircaloys. Several mechanisms have been proposed for nodule initiation and growth. They include one or more of the following factors: local solute depletion, electrochemical effects, oxide ductility, electronic and ionic conductivities of the surface oxide, induced stresses, and oxide structure transformation.

However, very limited studies have been directly done on the corrosion properties of these intermetallics. Therefore six intermetallics (Zr2Fe, Zr3Fe4Cr2, Zr10Fe3Ni2, Zr4Sn, ZrCr2, and 3Zr2Ni) were prepared for corrosion and electrochemical tests. These intermetallics were chosen since tin, iron, chromium, and nickel are the principal alloying elements in Zircaloys, and the selected intermetallics have been identified in the alloy matrix. In addition to these intermetallics, Zircaloy-2, Zircaloy-4, and crystal-bar zirconium were also included in this study.

Corrosion and electrochemical tests on selected materials at both ambient and elevated temperatures were performed at Teledyne Wah Chang Albany and at Siemens AG-KWU Group. Selected materials were characterized using SEM/EDX examinations, potential measurements and autoclave tests. From this information the role(s) of intermetallics on corrosion resistance in water and steam are discussed. A new electrochemical-mechanical-passivity (EMP) model is offered to explain observed oxidation of Zircaloy-2 and Zircaloy-4.
Enhancement of Aqueous Corrosion of Zircaloy-4 Due to Hydride Precipitation at the Metal-Oxide Interface
Authors: Garde AM
Published: March 2009

Long-term static autoclave corrosion tests were conducted on Zircaloy-4 tube specimens in water at 633 K. The material variables included in this investigation were: annealing parameter range 10-17 to 10-19 h (with Q/R = 40 000 K). fabrication history variation of early and late beta-quenching steps, and final heat treatment variation from several levels of stress-relief-anneal to a recrystallization anneal. Specimens were weighed at intervals of approximately 28 days for a maximum corrosion test exposure of 1160 days. The weight gain data show transitions to an accelerated corrosion rate that became apparent at exposure times greater than 300 days. The transition times varied from 141 to 253 days. Metallographic and scanning electron microscopic examination showed that the metal-oxide interface had an irregular shape and the oxidation front appeared to progress into the metal by fracture of the hydride precipitates at the interface. Hydrogen absorption fractions were calculated for each specimen and were used to estimate the hydrogen level in each specimen at the transition point. The estimated hydrogen levels at transition agreed reasonably with the hydrogen solubility in Zircaloy at 633 K. The results indicate that the corrosion rate acceleration observed in autoclaves at long times is associated with the onset of hydride precipitation and subsequent hydride fracture at the metal-oxide interface. A review of in-reactor corrosion data from the literature reveals that a similar hydride associated corrosion rate acceleration occurs in low oxygen coolant conditions in PWRs and PHWRs. Hydride precipitation at the metal-oxide interface is the probable reason for the correlation between the time of long-term autoclave corrosion rate transition and the in-PWR cladding corrosion resistance. On the basis of the effect of hydrides on the in-reactor corrosion rate, it is suggested that a better ex-reactor corrosion test to simulate the in-PWR corrosion performance would be a water test at 633 K with an imposed heat flux. The effect of hydrides on the corrosion rate is strongly related to the size, distribution, and orientation of the hydrides in the Zircaloy cross section. An alloy development program is suggested to enhance the corrosion resistance of zirconium alloys in PWRs to extended burnups.
Characteristics of Autoclave and In-Reactor Nodular Corrosion of Zircaloys
Authors: Jeong YH , Rheem KS , Chung HM
Published: March 2009

Nodular corrosion characteristics of recrystallized Zircaloy-4 were investigated in static autoclave tests at 500°C and 10.3 MPa. The roles of annealing temperature, cooling rate after beta-treating at 1050°C, cold work, and surface treatment in corrosion tests were correlated with the results of microstructural characterization by scanning and transmission electron microscopies. A good correlation was obtained between average size of intermetallic precipitates and weight gain, in contrast to nodule coverage and nodule number density. These results could be best explained by the hypothesis that nodules nucleate in local regions that are depleted of Fe and Cr alloying elements. Some observations were inconsistent with the premise that nodules nucleate on or near intermetallic precipitates. Nodular corrosion characteristics and microstructures of commercial Zircaloy-2 cladding of fuel and gadolinia rods, obtained from several boiling water reactors (BWRs) after burnup of 11 to 30 MWd/kgU, were also examined. Partial amorphization of intermetallic precipitates in BWR Zircaloy-2, and virtual dissolution, and in an extreme case spinodal-like fluctuations of dissolved alloying elements in PWR Zircaloy-4 cladding were observed. Occurrence of nodular oxidation of Zircaloy-2 in BWRs could best be correlated to average size of intermetallic precipitates before irradiation and to fuel cladding operating temperature. For an intermetallic size range of 250 to 700 nm, nodular oxides were observed at 288°C, but only thick uniform oxide was observed at 307°C. For extended-burnup operation, increased precipitation of hydrides, suboxides, and small oxide particles, apparently formed via an irradiation-induced process, is expected near the metal/oxide boundary and results in more pronounced microcracking along the metal/oxide boundary. In addition to its association with metal/oxide boundary temperature, which increases for increasing oxide thickness, boundary microcracking may be associated with accelerated corrosion of extended-burnup fuel of >45 MWd/kgU (rod-average burnup).
Amorphization of Precipitates in Zircaloy under Neutron and Charged-Particle Irradiation
Authors: Motta AT , Lefebvre F , Lemaignan C
Published: March 2009

The crystalline-amorphous transformation of the intermetallic precipitates Zr(Cr,Fe)2 and Zr2(Ni,Fe) in Zircaloy under charged-particle and neutron irradiation is studied.

In the first section, the experimental results in the literature are reviewed for the three types of irradiation: neutron, electron, and ion. It is found that the dose to amorphization in all three types of irradiation exhibits roughly the same exponential dependence with temperature but that there are important differences. The critical temperatures, above which amorphization is not practically attainable, are different for each type of irradiation, indicating the presence of different damage accumulation and annealing mechanisms in each case. Further evidence of this are the different amorphization morphologies observed under neutron and electron irradiation, and the shift in the relative susceptibility to amorphization between the two types of precipitate under high (neutron and ion) and low (electron and ion) temperature irradiation.

In the next section, the theoretical models for amorphization are reviewed and applied to the problem in an effort to obtain a coherent picture of amorphization induced by all types of irradiation in the precipitate/zirconium system. Amorphization mechanisms are proposed for each type of irradiation, based on the experimental results.

A brief conclusion indicates that different mechanisms are operative for amorphization induced by each type of irradiation and points out future areas that in our view deserve further investigation.
Oxide Characteristics and Their Relationship to Hydrogen Uptake in Zirconium Alloys
Authors: Warr BD , Elmoselhi MB , Newcomb SB , McIntyre NS , Brennenstuhl AM , Lichtenberger PC
Published: March 2009

Secondary ion mass spectrometry (SIMS) and transmission electron microscopy (TEM) have been used to investigate composition and structure of oxides on pure zirconium and Zr-2.5Nb following both in and out-reactor exposures in aqueous and gaseous environments. Thin oxides formed in steam at 400°C on Zr-2.5Nb act as excellent hydrogen permeation barriers for CANadian Deuterium Uranium (CANDU) pressure tubes. Following up to 4350 effective full power days (EFPD) exposure in-reactor in the annulus gas, and out-reactor elevated exposures to deuterium gas, these oxides generally continue to show diffusional-type through-thickness deuterium concentration profiles, with negligible deuterium contents at the metal/oxide interface. Diffusion coefficients inferred from these profiles are as low as ∼2 × 10-22m2/s at 300°C. The structure of these thin oxides on Zr-2.5Nb consists of columnar grains with amorphous regions at grain boundaries and at the metal oxide interface, and non-interconnected porosity, which implies that deuterium permeation is likely controlled by solid state diffusion through the bulk oxide. At regions containing relatively high deuterium contents in the bulk metal of removed pressure tubes, outside surface oxides showed several regions with flat deuterium concentration profiles with higher deuterium concentrations at the metal/oxide interface. Examination of thicker oxides with interconnected porosity, on pure Zr, following exposures to pure deuterium gas, also showed the presence of flat deuterium concentration profiles. This would tend to suggest that regions of high deuterium concentration dissolved in the base metal of pressure tubes may also contain oxides with interconnected porosity.