bluuebunny/crossref_metadata_2025 huggingface dataset:
Relationship of Automated Weather Observations to Subjective Elements
Authors: Lefkowitz M , Bradley JT
Published: March 2009

Traditionally, surface weather observations have been made by human observers. It has been their difficult task to estimate subjective elements such as sky cover (in tenths) and the heights of clouds (often to the nearest 100 ft). Automation has moved slowly to replace subjective methods in the field and, even then, usually only in special areas such as runway visual range (RVR) and runway visibility (RVV). Recent work has demonstrated that automated observations of other subjective elements are feasible and are already operational at two points in the United States.

The paper reviews the concepts of RVR and RVV, and discusses in detail new methods for the automation of cloud and visibility observations. The automated observations are compared with human products made at the same time and location. The paper points out the difficulties of assessing the success of objective techniques in comparison with subjective methods.
Inadequacies of Atmospheric Stability Measurements and Recommendations for Improvement
Authors: Carlson JH , Hollister RA , Smith ME , Castelli FP
Published: March 2009

Three of the most commonly used atmospheric dispersion classification schemes—STAR, Delta-T, and Brookhaven National Laboratory (BNL) gustiness— are compared at shore and inland stations. Large inconsistencies were found between the three systems for all major stability groups. The STAR program consistently gave higher percentages of neutral cases as compared to the BNL and Delta-T systems. Similarly, the BNL scheme gave the highest estimate of unstable conditions and the Nuclear Regulatory Commission (NRC) Delta-T gave the highest estimate of stable cases. Limitations of these three systems are discussed and recommendations for improvement are suggested.
Useful and Useless Data for Judging Air Pollution Effects on Climate
Authors: Landsberg HE
Published: March 2009

Present observations for assessing man's effect on the climate are inadequate. Although global temperature and radiosonde records are beginning to fill data needs, precipitation records in and near urban heat islands and major industrial zones with heat rejection and nuclei production are not sufficiently dense. Atmospheric observations of carbon dioxide (CO2) are satisfactory, but more information on CO2 sinks in the ocean and the biomass are needed. Atmospheric levels of other infrared absorbers have to be systematically watched. The total particulate load is a useless measure and needs to be replaced by regular and widespread observations of the size spectra of particulate matter. Adequate inventories of anthropogenic heat and water vapor emissions are required. Better inventories of man-made cloudiness have to be established. Additional atmospheric electric observations are also needed.
Dispersion from Individual Sources
Authors: Pasquill F
Published: March 2009

A brief survey is given of the present position in the specification of atmospheric dispersion parameters for use in estimating pollutant concentration from a continuous-point release.

The theorectical indications of the distribution to be expected across a time-mean plume are reviewed, with particular reference to the existence of the Gaussian form. Observational evidence, especially on vertical distribution from a surface release, is also recalled, and the practical significance of departure from an assumed Gaussian form is noted.

The use of the Taylor statistical theory in the generalized estimation of crosswind spread in quasi-ideal boundary-layer flow is briefly summarized. Recent considerations of the behavior of the crosswind component of turbulence in the surface layer and new developments from laboratory modeling of horizontal dispersion in convective mixing are noted.

A brief survey is given of the achievements of the gradient-transfer theory and the Lagrangian similarity theory in calculating vertical spread from a surface release. New tests against previous dispersion data underline inadequacies in the present approaches in very unstable conditions. Promising developments from laboratory modeling of a convectively mixed layer and from the second-order-closure modeling of the turbulent fluctuation equations are summarized.

The assimilation of theory and experience into practical systems for the specification of σy and σz is briefly reconsidered. For σy a practical procedure, based on wind direction fluctuation data, is reaffirmed. For σz a new format, which may be envisaged for future composite curves, is suggested. Finally, the inherent limitations of practical systems for estimating concentration levels are reiterated.
Urban Modeling of Inert Substances
Authors: Hanna SR
Published: March 2009

The physical assumptions in various models for the diffusion of inert substances in urban areas are critically reviewed. It is suggested that there are no significant differences among the predictions of the models, and that often simple integral models have more valid physical assumptions than do complex computer models. Correlations between observed and predicted concentrations of carbon monoxide (CO), sulfur dioxide, and suspended particles are typically in the range of 0.4 to 0.8. The magnitude of the prediction can be expected to be within a factor of two of the observation.

Mixing depth and pollutant concentration are not well correlated (R ≃ -0.2) because local pollutant plumes do not as a rule reach the capping inversion. Inverse wind speed and pollutant concentration are better correlated (R ≃ 0.6). A method for accounting for stability in the simple Atmospheric Turbulence and Diffusion Laboratory model is suggested, based on observations of CO emissions and concentrations and of wind speeds at numerous stations.
Applications of General Meteorological Models to Air Quality Problems
Authors: Anthes RA , Warner TT
Published: March 2009

Some of the potential applications of general meteorological models to air quality problems of mesoscale flows are discussed. Although general models are relatively expensive, they are easily modified to treat many complicated problems that are not amenable to solution by simpler methods.

Results from two meteorological models are presented to illustrate the versatility of the models. The first is a relatively simple model of the atmospheric mixed layer. A 6-h, real-data forecast is shown. The second model is a more general three-dimensional model which is capable of treating a variety of meteorological problems. A 12-h, real-data forecast of flow and precipitation over the United States is summarized. Then the model is applied to a regional-scale simulation of light wind conditions. Finally, the model is applied to small-scale flow under stable conditions over complex terrain.
Effects of Weather Fronts on Ozone Transport
Authors: Ludwig FL , Shelar E
Published: March 2009

The object of the research discussed in this paper has been to define special meteorological conditions that are conducive to the long-range transport of ozone and its precursors, especially in highly urbanized areas like the northeastern United States. Long-range transport is an important factor in the design of ozone control strategies.

Routinely collected air quality data, special data from the Northeast Oxidant Study, and National Weather Service data and analyses were combined to determine relationships among source areas, areas of high ozone concentration, and air movement associated with different weather systems.

In the eastern United States, the warm, southwesterly winds preceding weather fronts were found to provide favorable conditions for ozone formation and transport. The alignment of the coastal source areas is such that particularly dramatic buildups of ozone result, followed by abrupt decreases in concentration as colder, cleaner air behind a front replaces the polluted air ahead of it. Examples of several such events have been analyzed.

Although air movement associated with frontal passages is only one of the important situations causing long-range transport and ozone buildup in the Northeast, the events are sufficiently common that they must be considered in the design of control strategies. Furthermore, the fact that ozone buildups are found in conjunction with frontal passages belies the common assumption that stagnating high pressure systems are required for important violations of ozone standards in the eastern United States. The results show that extended source areas, when aligned with the air flow, may lead to significant ozone concentrations even in the decidedly unstagnant air ahead of frontal zones.
Weekday-Weekend Ozone Concentrations in the Northeast United States
Authors: Cleveland WS , McRae JE
Published: March 2009

Ozone concentrations at sites downwind of the New York City metropolitan region decrease on weekends. Concentrations within and upwind of the region are very nearly the same on weekdays and weekends, which agrees with earlier analyses of data in this region. For concentrations above the Federal Standard of 80 ppb, the reduction in Connecticut, which has the highest ozone concentrations in the Northeast, is approximately 20 percent. This weekend reduction carries over into Monday, which has concentrations approximately the same as those on weekends. This is then followed by a gradual increase from Tuesday to Friday. The reductions in ozone concentrations on Saturdays, Sundays, and Mondays correspond to reductions in traffic which occur on these days of the week. The fitting of a time series model with periodic means, variances, and autocorrelations shows the observed reductions are statistically significant.
Formation and Transport of Ozone in the Northeast Quadrant of the United States
Authors: Wight GD , Wolff GT , Lioy PJ , Meyers RE , Cederwall RT
Published: March 2009

The very high concentrations of ozone measured in Connecticut and elsewhere along the Northeast and Mid Atlantic Coast were investigated through the analysis of data from the entire 1976 ozone season from 19 northeastern and midwestern states, National Weather Service meteorological data, and air parcel trajectories. For several high ozone episodes, the relationship between the movement of and circulation within a high pressure system across the northeast quadrant of the United States and the buildup of ozone concentrations was clearly demonstrated. Air parcel trajectory analysis, coupled with source density information, was utilized for several well-defined episodes in 1976 to show that ozone measured at various locations throughout the study area is partially generated locally and partially transported from substantial distances.
Global Atmospheric Sampling Program: Prospects for Establishing a Tropospheric Ozone Budget from Commercial Aircraft Data
Authors: Falconer PD
Published: March 2009

A preliminary analysis of zonally averaged, ozone concentration data obtained from commercial (GASP) aircraft between the equator and 60 deg North indicates that ozone in the upper troposphere exhibits a primary maximum during the spring, and, in middle latitudes, a secondary maximum in the summer of both 1975 and 1976. A late-fall/early-winter minimum also appears and seems consistent with previous upper air measurements. The April ozone maximum has been well documented and appears at the time when the stratospheric ozone content is greatest and cyclogenetic activity is most vigorous. However, the secondary maximum in June has not been widely observed or quoted as a unique feature. It is hypothesized that the rapid ascent of the tropopause between midspring and summer could account for the incorporation of ozone-rich, stratospheric air into the upper troposphere with a subsequent dilution during the following months. This may explain certain aspects of the annual ozone cycle in the lower troposphere which occasionally exhibit a bimodal distribution during the warm season.
Ozone Trends Determined from the Dobson Ozone Network
Authors: Angell JK
Published: March 2009

Based on a regional weighting technique, it was found that the Northern Hemisphere had a significant 5 percent increase in total ozone (O3) between the early 1960s and about 1970, a barely significant 1 to 2 percent decrease in total O3 between 1970 and 1971–1972, and little change thereafter, though rather low levels were observed temporarily in early 1976. In the southern hemisphere the total O3 increased slightly prior to 1968 and has decreased slightly since, but neither change approaches significance. Umkehr measurements indicate about a 12 percent increase in O3 amount in the 32 to 46-km layer in north temperate latitudes between 1964 and 1972, with the evidence for a slight decrease thereafter controversial due to the uncertainties introduced into the Umkehr technique by aerosols from the Fuego, Guatemala eruption. It is shown that for the past 12 years the trend in total O3 amount in north temperate latitudes has been closely related to the trend in stratospheric water vapor in Washington, D. C. and equatorial tropopause temperature, but inversely related to the trend in stratospheric temperature in north temperate latitudes.
Ozone Measurements at Several Rural and Urban Sites in New York State
Authors: Coffey PE , Whitby RA , Stasiuk WN , Husain L , Mohnen VA
Published: March 2009

Since the early 1970s, research to evaluate ozone levels in ambient air has been in progress at several rural and urban site in New York State. The sites were chosen to provide ozone data above and below the nocturnal inversion layer.

Ozone from upwind sources has been shown to significantly affect both the urban and remote rural areas. Concentration isopleths show that ozone created in the urban plume of the larger urban areas significantly affects areas downwind under the plume.

The sources of ozone in the remote rural areas are still not clear. Principal ozone sources are stratospheric ozone, photochemical production from terpenes and hydrocarbons emitted from local vegetation, and ozone transported via urban plumes. Each of these three sources can be a significant contributor.
A Review of Ozone Toxicology Studies
Authors: Parent RA
Published: March 2009

Various aspects of ozone toxicity are discussed, including pulmonary function testing on humans, morphological alterations in the lungs of model animals, effect on bacterial clearance from the lungs, biochemical changes, and mutagenic effects. Although not a complete review of ozone toxicology, this paper does provide insight into the problem of setting an occupational exposure limit on ozone and does point out deficiencies in available data. An occupational exposure limit of 0.1 ppm, with peak exposure at 0.2 ppm is recommended.
Controlled Studies of Ozone‘s Effects on Human Health
Authors: Hackney JD , Linn WS , Bell KA
Published: March 2009

Human health is probably the most important reason for concern over atmospheric ozone pollution. Controlled studies of humans cannot answer some questions concerning possible long-term harmful effects, but they can provide the most definitive means of documenting short-term, adverse effects which are likely to occur in ambient exposures. Lung function tests, biochemial analyses of red blood cells, and clinical evaluations have revealed harmful short-term effects in some volunteers exposed to ozone concentrations of 0.4 to 0.5 ppm under conditions simulating ambient exposures. One laboratory has reported adverse changes after exposures to 0.1 ppm, but these findings have not been independently confirmed as yet. Factors which may modify toxic responses to ozone include preexisting disease, biological adaptation, and coexisting pollutants which may enhance toxicity.
Standards in Meteorology
Authors: Morris AL
Published: March 2009

Beginning in the late 16th century, when Fludd and Galileo resurrected the thermoscope and started using it as a thermometer, standards in meteorology became essential. It was necessary to adopt standard materials, manufacturing techniques, and scales if one instrument was to be compared with another. When it became practical to collect weather observations rapidly enough to assemble them into weather maps, another step toward standardization became necessary. Observations had to be taken in a standard way at a standard time. Since weather does not respect national boundaries, it was important that these standards be accepted internationally. With the development of concern about the quality of the atmosphere, engineers and chemists became increasingly interested in meteorological measurements, and a new branch of meteorology developed with attendant new measurement requirements. New instruments evolved. These need to be described and used in standard ways if they are to be most effective. Subcommittee D22.11 on Meteorological Measure|ments, of ASTM Committee D-22 on Methods of Sampling and Analysis of Atmospheres, is writing new ASTM standards to meet these needs.
The National Fire Incident Reporting System: A Key to Fire Hazard Quantification
Authors: Tovey H
Published: March 2009

The National Fire Incident Reporting System is the collection of national fire loss data for fires attended by the fire service. It includes information on factors involved in fire ignition, spread, and extinguishment. It has been developed with recognition of the importance of serving the needs of state, regional, municipal, and local fire jurisdictions, as well as those at the Federal level. A representative selection of states has been identified for cooperative preliminary studies of this system. The system is based on use of the fire data reporting procedures developed by the National Fire Protection Association. Data elements have been selected as usual with many compromises to provide the most versatile use of data readily available. A review is presented of the way in which the data collected could be used in locating and analyzing fire problem areas as they occur. Brief mention is included on work under way to report and classify fire incidents on an international scale.
Fire-Related Fatalities: An Analysis of Their Demography, Physical Origins, and Medical Causes
Authors: Berl WG , Halpin BM
Published: March 2009

Data are presented and analyzed on the demographic variables (location, age, sex, and race) of people perishing in fires in the state of Maryland in 1972/1973, on the physical causes of these fires, and on the most likely medical effects. Carbon monoxide as asphyxiant, cigarettes as ignition source, and the disproportionately large involvement of children and the elderly are pointed up. The contributory effects of alcohol ingestion, particularly in men in the 40 to 60 years age group, are described.
Estimating Injury from Burning Garments and Development of Concepts for Flammability Tests
Authors: Bercaw JR , Jordan KG , Moss AZ
Published: March 2009

Part of the flammability research at Du Pont has been concerned with understanding the way various garments ignite and transfer heat under simulated conditions of use. The objective is to develop basic principles which will aid in the definition of improved products and guide the development of more appropriate test methods. To this end, we have acquired Thermo-Man, a thermally instrumented manikin and heat sensing system which produces detailed estimates of injury from burning garments. The highly sophisticated system and procedure for injury evaluation to give accurate estimates of area burned and burn depth through the human skin is reviewed. Burn injury data are presented which predict injury potential from common apparel, including fabrics from both man-made and natural fibers. Effects of garment type on potential injury and injury-time propagation are also discussed.

Thermo-Man provides a unique basis for development of concepts for more relevant and predictive flammability tests applicable to general apparel fabrics. The essential aspects of burn injury production are fabric ignition and heat transfer. Research at the National Bureau of Standards (NBS) and Du Pont is aimed at developing a heat transfer concept for possible consideration as part of a general apparel fabric flammability test method.
Some Problem Aspects of Fully Developed Room Fires
Authors: Thomas PH
Published: March 2009

The knowledge of fully developed room fires is reviewed fairly frequently, and research in this field is increasingly applicable to building design for designers who need to predict fire severity. In addition, there are several problems of general interest with relevance to other fields of fire safety, for example, stability of the system and the properties of the flame emerging from the window opening. This paper discusses these and other problems, along with some wider theoretical aspects of fully developed fires.
Growth of Fire in Building Compartments
Authors: Quintiere J
Published: March 2009

A review was made of both full-scale and scale model experiments concerned with fire growth and spread in building compartments. It appears that “flashover,” that is, the rapid transition to a fully developed room fire, could be initiated by a fully involved chair fire alone or by a large waste container ignition source against a combustible lining material. Scale model results continue to provide valuable insight, but the validity of partial scaling results must be considered for each type of experiment. A quasi-steady idealized mathematical model was developed to analyze the various parameters of fire development in a room. These theoretical results show the significance of fuel properties, fire size and location, room and doorway dimensions, and wall thermal properties. The limitations of a mathematical approach are also discussed.
The Role of Tests in Defining Fire Hazard: A Concept
Authors: Roux HJ
Published: March 2009

Recent increased concern about life safety by various interested public agencies has led to questioning the credibility of small-scale fire tests in predicting the performance of a product or system in a real-fire situation.

It is proposed that many of these fire test methods, though, can be upgraded to fire-characteristic test methods by the application of appropriate criteria. Furthermore, the results from one or more fire-characteristic test methods, plus other parameters, could then be integrated to establish the potential for harm (PH) of a product or a system. The fire hazard of a product or system can then be established by combining the potential for harm with the degree of exposure.

One pragmatic approach to establishing the integration equation for the PH of a product or system is to start with the available fire statistics for that product or system and to prepare a scenario that describes the involvement and the effects of the subject item in a fire situation. Then an integration equation that fits this scenario can be written. This approach would identify the fire-characteristic test methods and parameters that are needed to assess the PH of that product or system. Included in this concept is the idea of using full-scale fire tests either to prove the integration equation for a given product or system or to assess directly the PH of that given product or system.

Alternatively, full-scale fire tests can be used to derive the integration equation for a given product or system when no fire statistics are available for that product or system.
Building and Fire Codes: The Regulatory Process
Authors: Bihr JE
Published: March 2009

The complete regulatory process involves the application and enforcement of building and fire codes. Building codes govern new construction and embody standards designed to protect occupants and property from the hazards of fire. Fire codes are intended to preserve fire safety features of building codes and to govern fire safety practices involving the processes and uses within buildings. These codes must be compatible. Additional research is needed to address some of the newer fire problems now confronting regulatory officials.
National Mandatory Fire Safety Standards
Authors: Thomas W , Willis CL
Published: March 2009

The Consumer Product Safety Commission has broad regulatory authority over thousands of consumer products. Mandatory safety standards for matchbooks, aluminum wire systems, and television receivers are being developed or planned under the Consumer Product Safety Act, and two other standards will have significant fire safety aspects. Regulation under the Flammable Fabrics Act has resulted in mandatory standards for children's sleepwear, clothing, carpets and rugs, and mattresses.
Sampling and Analysis of Fire Atmospheres
Authors: Fristrom RM
Published: March 2009

The characterization of fire atmospheres is discussed. A complete description would require more than 1017 measurements. This is beyond present capabilities, but the requirements could be reduced by separating the problem into three regimes, each characterized by a minimum volume-time (v, t) increment. They are: (a) overall fire atmospheres (v = 1 m3, t = 10 s) for hazard and detection, (b) fire plumes (v = 10−6 m3, t = 10−1 s) for heat transfer and fire propagation, and (c) flames (v = 10−15 m3, t = 10−4 s) for microscopic and molecular combustion processes. By systematically applying these characterizations to the regions where they are required, the data base can be reduced to 106 measurements for a typical small fire. This is feasible with present technology. However, the application would require a substantial investment in facilities and the development of sampling and analytical technique. Some sampling and analytical problems associated with characterizing fire atmospheres are discussed. The current status is illustrated using several recent studies.
Introduction
Authors: Bartnikas R , McMahon EJ
Published: March 2009

The ASTM book series on Engineering Dielectrics is devoted to a comprehensive presentation of topics related to electrical insulating materials, concerning their dielectric properties, their use, and evaluation for application in electrical power and communication apparatus structures and devices. It has been deemed proper that the first volume of the series should deal with corona or partial discharge measurements, since the subject matter is of great interest to electrical insulation engineers and scientists. At the same time, it was felt that a monograph on corona discharges would fill in a gap in the scientific literature, which has now been long overdue.
Fundamentals of Partial-Discharge Detection: System Sensitivity and Calibration
Authors: Curdts EB
Published: March 2009

The sensitivity and calibration of partial-discharge detection systems is an important aspect of the general subject of partial-discharge measurements of products or structures involving electrical insulating materials. The primary objective is to perform a measurement, using a detection system having a sensitivity adequate to the purposes of the test, in the presence of inevitable electrical noise. Of equal importance is the matter of calibration which requires that fairly-accurate information be obtained as to the magnitudes of the changes that take place in the insulation system when it is stressed at some particular voltage.
Partial Discharge Measurements in Distributed Parameter Systems: Cables
Authors: Timpe NB
Published: March 2009

Problems of partial or corona discharges in cables were recognized by a number of electrical engineering pioneers. As early as 1898, Fessenden performed experiments that showed the danger of air bubbles in solid insulation. Perrine reported in 1902 that the failure of cable insulation sometimes was due to the presence of spaces filled with ratified gases [1]. In 1912, Petersen called attention to the fact that air films in a dielectric of specific inductive capacity or dielectric constant, k, are subjected to a stress of k times that in the surrounding medium, and ionization may therefore occur therein at comparatively low voltages [2]. He also stated that ions are shot from these films into the surrounding medium. Dubsky reported in 1919 that he had measured the dielectric strength of thin air films between glass plates [3]. He then applied these data theoretically to assumed gas spaces in solid dielectrics and showed the possible conditions under which partial discharge was likely to occur. Shanklin and Matson also reported in 1919 that they had measured the ionization voltage in actual insulation designs by the dielectric loss method [4]. In the case of paper cables, evidence was given showing that a true ionization occurs. However, the exact nature of this ionization, its position, and the possibilities of serious damage were not shown. Many of the studies into the nature of the partial or corona discharges began with the advent of the cathode ray tube application in the 1930's. The purpose of this chapter is to briefly describe the early experiences of partial discharge problems in cables with the subsequent developments of methods of detection, and then to discuss the techniques used to standardize partial discharge testing, the measurement limitations, and finally to provide guidance for interpretations of present-day measurements in cable systems.
Corona Pulse Counting and Pulse-Height Analysis Techniques
Authors: Bartnikas R
Published: March 2009

In the detection of pulse-type corona discharges in voids occluded within the insulating systems of electrical apparatus, the corona pulse amplitude and repetition or discharge rate represent two basic quantities upon which much of the present state-of-the-art of corona measurement and interpretation rests. In the past, however, much more attention has been paid to the measurement of the corona discharge pulse amplitude than to that of the pulse recurrence rate. This underlying fact is well borne out by the present specifications, concerning commercially available corona detection sets for use on transformers, capacitors, and cables, which are based in their entirety upon the detectable apparent corona pulse charge expressed in picocoulombs. In so far as the corona testing techniques presently in use invoke the measurement of the corona inception and extinction voltages, they must be regarded ipso facto as go no-go type test methods in the sense that they merely indicate the presence or absence of corona pulse discharges above certain preset sensitivity levels expressed in picocoulombs. In order to characterize the corona discharge pulse behavior in a given insulating system, it is necessary to go further and measure the discharge quantities of both the corona pulse amplitude and repetition rate. Quantitative information concerning the corona pulse pattern density is obtained in terms of the overall corona discharge rate measurements. However, additional meaningful data is readily obtained if the corona discharge rate is measured as a function of the corona pulse amplitude. The resulting corona pulse-height distribution spectrum is proportional to the total discharge energy dissipated and, therefore, represents essentially a fingerprint typical of the corona discharge behavior in the insulating system under the given applied voltage and elapsed time conditions of the test. Evidently, this form of corona pulse-height analysis constitutes a very powerful tool for assessing the corona discharge intensity in the insulating systems of electrical apparatus.
Partial Discharges Under Direct-Voltage Conditions
Authors: Densley RJ
Published: March 2009

The following symbols are commonly used in d-c corona or partial discharge terminology. These symbols will be used throughout the course of this chapter.
Partial Discharges Under Impulse-Voltage Conditions
Authors: Densley RJ
Published: March 2009

Throughout this chapter, the following symbols will be used.
Effects of Prior Stress History on Irradiation-Induced Creep
Authors: Wire GL
Published: March 2009

The purpose of this paper is to report the results of an experimental study to determine the effects of previous irradiation history on the fast-flux neutron irradiation creep behavior of 20 percent cold-worked Type 316 stainless steel for liquid metal fast breeder reactor (LMFBR) application. Previous irradiation creep experiments have involved monitoring the irradiation creep strain of specimens held at constant stress while irradiated at approximately constant temperature and flux. Under these conditions, the irradiation creep rates have been observed to vary with neutron exposure. Application of these “creep curve” data to design and analysis of reactor core structural materials requires some knowledge of how the creep rate at a given point in time depends upon the previous stress history.

In the present experiment, in-reactor stress relaxation tests were performed on specimens which had previously been irradiated in the stress-free condition to various exposures ranging from 0 to 4 × 1022 (n)/cm2 (E > 0.1 MeV) at 800 and 1000 °F (427 and 538 °C). It was found that the creep coefficients derived from this experiment were essentially the same as that obtained from the constant-load in-reactor test when allowance was made for thermal deformations. Thus it is concluded that, for the materials and conditions studied, the irradiation creep rate is essentially independent of previous stress history. This result may be rationalized if the microstructural development during irradiation is influenced predominantly by the irradiation flux and temperature variables and only to a minor extent by the irradiation creep deformation.

The sensitivity of the experimental technique to in-reactor effects coupled with supplementary thermal control studies led to a new insight into what has been called transient irradiation creep. The results of this experiment suggest that thermal effects can account for the initially higher creep rate portion of the total in-reactor behavior observed. The thermal component was observed to recur upon reloading, giving rise to a significantly enhanced creep rate for cyclic loadings.
Analysis of In-Reactor Stress Relaxation Using Irradiation Creep Models
Authors: Foster JP
Published: March 2009

Irradiation creep and stress relaxation data are available from the United Kingdom for 20 percent cold-worked Type M316, 20 percent cold-worked Type FV548, and FHT Type PE-16 using pure torsion in the absence of swelling at 300 °C (572 °F). Irradiation creep models were used to calculate the relaxation and permanent deflection of the stress relaxation tests. Two relationships between irradiation creep and stress relaxation were assessed by comparing the measured and calculated stress relaxation and permanent deflection. The results show that for Types M316 and FV548 the stress relaxation and deflection may be calculated using irradiation creep models when the stress rate term arising from the irradiation creep model is set equal to zero. In the case of Type PE-16, the inability to calculate the stress relaxation and permanent deflection from the irradiation creep data was attributed to differences in creep behavior arising from lot-to-lot variations in alloying elements and impurity content.

A modification of Types FV548 and PE-16 irradiation creep coefficients was necessary in order to calculate the stress relaxation and deflection. The modifications in Types FV548 and PE-16 irradiation creep properties reduces the large variation in the transient or incubation parameter predicted by irradiation creep tests for Types M316, FV548, and PE-16.
Swelling and Tensile Property Changes in Neutron-Irradiated Type 316 Stainless Steel
Authors: Garr KR , Pard AG
Published: March 2009

Specimens of Type 316 stainless steel, given different thermomechanical treatments resulting in either a cold-worked or solution-annealed and aged structure, were irradiated in the Experimental Breeder Reactor-II (EBR-II) at 500 to 600 °C (932 to 1112°F) to a fluence of 7.4 × 1026 neutrons (n)/m2 (E > 0.1 MeV). Three specimen configurations were used: small sheet tension specimens, small right-circular cylinders for immersion density, and thin foils for transmission electron microscopy (TEM). TEM revealed voids in all specimens. Immersion density indicated swelling in cold-rolled specimens only after irradiation at temperatures near 600°C (1112°F). Considerable recovery and precipitation were observed in the cold-rolled specimens. Results of tension tests revealed an increase in strength and decrease in ductility for specimens originally in a solution-annealed and aged condition. Cold-rolled specimens exhibited a decrease in strength and a slight increase in total elongation. True stress-true plastic strain was best described by the Ludwigson equation, σ = K3εn3 ± exp (K4 + n4ε), in all cases. Irradiation causes a decrease in the work-hardening exponent, n3, and strength factor, K3. After irradiation, the values of n3 and K3 tended toward common values for both preirradiation treatments.
Effect of Fast Reactor Irradiation on the Tensile Properties of 20 Percent Cold-Worked Type 316 Stainless Steel
Authors: Fish RL , Watrous JD
Published: March 2009

Fast neutron irradiation effects on the tensile properties of 20 percent cold-worked Type 316 stainless steel are presented to fluences of 3.6 × 1022 neutrons (n)/cm2, E > 0.1 MeV (3.6 × 1026 n/m2, E > 16 fJ), at irradiation temperatures of 700 to 1125°F (644 to 880 K). The tests were performed over the range of room temperature to 1600°F (1144 K) employing strain rates of 1.82 × 10-3 to 1.82/min (3 × 10-5 to 3 × 10-2/s).

Irradiation defect hardening at irradiation temperatures below 900°F (755 K) resulted in strength increases. Thermal annealing of the original cold-work operated to reduce the strength of material irradiated near 1000 and 1100°F (811 and 866 K), in the fluence range investigated. Elongation values initially increased at most irradiation temperatures and then decreased with fluence beyond 1022 n/cm2 (1026 n/m2). Both strength and ductility decreased with increasing temperature at fluences beyond 1022 n/cm2 (1026 n/m2). The 450°F (505 K) unirradiated elongation level was maintained or improved for all irradiation conditions investigated, which suggests that low ductility will not present a problem during refueling operations.
Tensile Properties of Fast Reactor Irradiated Type 304 Stainless Steel
Authors: Fish RL , Hunter CW
Published: March 2009

Tension tests were performed on annealed Type 304 stainless steel specimens sectioned from Experimental Breeder Reactor-II (EBR-II) duct thimbles. The specimens had accumulated neutron fluences of up to 10.3 × 1022 neutrons (n)/cm2, E > 0.1 MeV (10.3 × 1026 n/m2, E ×16 fJ). Irradiation temperatures for the material tested ranged from 700 to 750°F (644 to 672 K). The tests were performed at temperatures of room temperature to 1400°F (1033 K), employing strain rates of 2 × 10-3 to 2/min (3.3 × 10-5 to 3.3 × 10-2/s).

At test temperatures below 800°F (700 K), the strength increased with fluence until about 7 × 1022 n/cm2 (7 × 1026 n/m2), beyond which no further increase was observed. The elongation decreased with fluence, reaching levels as low as 0.5 percent uniform and 1.3 percent total elongation at 700°F (644 K). High-fluence failures below 800°F (700 K) occurred by transgranular channel fracture.

At test temperatures above 1000°F (811 K), elongations were reduced to very low levels at high fluences (average total elongation (TE) = 0.03 percent). Extensive intergranular fracture at the high fluences produced the low ductility and resulted in failure of the specimens before reaching the strength characteristic of the true hardness of the material.
Effects of Neutron Irradiation on Microstructure and Mechanical Properties of Nimonic PE-16
Authors: Sklad PS , Clausing RE , Bloom EE
Published: March 2009

Specimens of Nimonic PE-16, a γ'-hardened austenitic alloy, were irradiated in the Experimental Breeder Reactor-II (EBR-II) in order to determine the effect of neutron irradiation on the microstructure and mechanical properties. Specimens with two different aging treatments were irradiated at temperatures ranging from 650 to 823 K and fluences ranging from 1.2 × 1026 neutrons (n)/m2 to 4.0 × 1026 n/m2. The aging treatments were: (A) 2h at 1313 K + 2 h at 1073 K + 16 h at 973 K; and (B) 4 h at 1313 K + 1 h at 1173 K + 8 h at 1023 K. Postirradiation transmission electron microscopy (TEM) revealed the presence of voids in all irradiated specimens. No difference in the fluence dependence of swelling at an irradiation temperature of 773 K was observed between the specimens with Preirradiation Treatment A and the specimens with Preirradiation Treatment B. In contrast, the temperature dependence of swelling appears to be sensitive to the particular preirradiation aging treatment used. TEM also shows that existing precipitates coarsen slightly during irradiation and that precipitation of γ'-precipitates occurs on irradiation-produced dislocation loops and voids.

Specimens irradiated at 773 K were tensile tested at 683, 773, 873, and 973 K. There is no significant difference in postirradiation mechanical properties between the two preirradition heat treatments. There is a large increase in yield strength after irradiation, which is consistent with the observed changes in microstructure. The ductility decreases as the test temperature increases. The low ductilities observed at the higher test temperatures are associated with a tendency for intergranular fracture. Auger spectroscopy of fracture surfaces on a specimen fractured at 823 to 873 K in the Auger chamber indicates that the concentrations of phosphorus and sulfur are a factor of two or three higher, and that the concentrations of iron and chromium are a factor of two lower, on surfaces of grain boundary fracture than on surfaces resulting from ductile fracture within the same specimen. There is also an enrichment of nickel at grain boundaries. In addition, helium release was observed at the time of fracture.
Tensile and Hardness Property Evaluations of Irradiated Zircaloy Cladding Under Off-Normal and Transient Conditions
Authors: Lowry LM , Perrin JS , Bauer AA
Published: March 2009

A program is being conducted to determine the mechanical behavior of irradiated Zircaloy-4 fuel rod cladding subjected to anneals under temperature and time conditions that simulate various off-normal and transient reactor operating conditions. This paper reports the initial phase of the program, which is a study of changes in hardness and tensile properties that accompany isothermal and transient anneals. A special transient annealing apparatus was built to subject specimens to the desired temperature/time conditions. Hardness and tensile strength decreased with increase in the maximum annealing temperature from 800°F (425°C) to 1300°F (705°C). Changes above 1100°F (595°C) were related to recrystallization and grain growth.
Swelling Simulation Studies of Type 316 Stainless Steel
Authors: Ellis JA , Appleby WK , Lauritzen T
Published: March 2009

The effects of some compositional and processing variations on the irradiation-induced swelling of 20 percent cold-worked Type 316 stainless steel have been investigated. Bombardment by 5-MeV nickel ions was used to simulate the fast neutron irradiation which occurs in breeder reactor core components. Swelling in cold-worked Type 316 was found to be lowered by additions of silicon and molybdenum. Swelling was also reduced by increasing the solution-annealing temperature prior to the final cold-working operation.
Void Growth Suppression by Dislocation Impurity Atmospheres
Authors: Weertman J , Green WV
Published: March 2009

A detailed calculation is given of the effect of an impurity atmosphere on void growth under irradiation damage conditions. Norris has proposed that such an atmosphere can suppress void growth. We have found the hydrostatic stress field of a dislocation that is surrounded by an impurity atmosphere and from it have calculated the change in the effective radius of a dislocation line as a sink for interstitials and vacancies. The calculation of the impurity concentration in a Cottrell cloud takes into account the change in hydrostatic pressure produced by the presence of the cloud itself. It is assumed that the hydrostatic pressure field of an impurity atom exists over a radial distance larger than the radius of the impurity atom. It is found that void growth is eliminated whenever dislocations are surrounded by a condensed atmosphere of either oversized substitutional impurity atoms or interstitial impurity atoms. A condensed atmosphere will form whenever the average impurity concentration is larger than a critical concentration.
Effects of Interstitial Solutes on the Microstructures of Self-Ion Irradiated Vanadium
Authors: Agarwal SC , Potter DI , Taylor A
Published: March 2009

Vanadium and vanadium containing 0.1 percent carbon, 0.4 percent carbon, 1.0 percent nitrogen, and 1.0 percent oxygen were irradiated with 3-MeV 51V+ ions in the temperature range 650 to 880°C (1202 to 1616°F) to a dose level of ∼20 dpa. The results show that nitrogen is most effective in controlling the void swelling. Carbon and oxygen also suppress the swelling considerably when compared with unalloyed vanadium. Except for vanadium-1.0 percent nitrogen, all compositions exhibit a fine platelet precipitate with {012} habit at 650°C (1202°F). In the case of vanadium-carbon alloys, this phase persisted even at higher temperatures. Vanadium and vanadium-1.0 percent oxygen showed fine precipitation on dislocations and void surfaces at 880°C (1616°F). Vanadium-0.1 percent carbon exhibited a metastable {013} carbide precipitate at 880°C (1616°F), whereas vanadium-0.4 percent carbon showed equilibrium V2C phase with some {012} precipitates. This {012} precipitation was irradiation induced and was dependent upon the carbon concentration. Vanadium-1.0 percent nitrogen did not show any evidence of precipitation over the entire temperature range.
Swelling and Gamma-Prime Particle Stability of Ion-Bombarded Iron-Chromium-Nickel Alloys
Authors: Bleiberg ML , Bajaj R , Baron IM , Chang A , Chickering RW , Diamond S
Published: March 2009

Nickel-ion bombardment studies were conducted on experimental alloys which were designed to provide basic information on the influence of composition, residual elements, and γ'-precipitates on swelling in the iron-chromium-nickel alloy system. Bombardments were conducted at temperatures ranging from 550 to 750°C (1022 to 1382°F) to maximum damage of 250 displacements per atom (dpa).

Comparison of identical alloys with and without γ'-precipitates showed that titanium and aluminum additions to the matrix compositions suppressed swelling. It is inferred that the aluminum increases the incubation dose while titanium reduces the swelling rate. The γ'-precipitates influence swelling only as they affect matrix chemistry.

Fine γ'-particles (8 to 18 nm) were precipitated under irradiation and approached an equilibrium size at high damage levels. A slight coarsening of 30-nm particles was observed, but there was only a slight increase in the volume fraction of the γ'-particles due to the irradiation. It was concluded that disorder dissolution was not an important mechanism in these alloys.
Nickel-Ion Damage in a Precipitation-Hardened Nickel-Aluminum
Authors: Kirchner LG , Smidt FA , Kulcinski GL , Sprague JA , Westmoreland JE
Published: March 2009

A precipitation-hardened nickel 14 atom percent aluminum alloy has been irradiated with 2.8 MeV 58Ni+ ions at a damage rate of 4.4 × 10-2 displacements per atom (dpa)/s, over a temperature range of 525 to 725 °C (977 to 1337 °F), to a damage level of 20 dpa, and at 625 °C (1157°F) over a dose range of 4 to 125 dpa. The experiment was designed to examine the stability of Ni3Al precipitates as a function of temperature and dose as well as their role in reducing swelling.

Prior to irradiation, the precipitates were cuboidal in shape with a mean edge length of 400 Å. Ion bombardment to 20 dpa at 725 °C (1337 °F) generated a higher precipitate density with a reduced and highly uniform size of 85 Å. At all other temperatures, the precipitate structures were less well defined and took on a ragged appearance with a wide spread in sizes as small precipitates formed between the original ones. A few scattered voids were formed at the two highest damage levels at 625 °C (1157 °F), but the swelling was negligible.