bluuebunny/crossref_metadata_2025 huggingface dataset:
Method for Determining Spray Penetration into Carpet
Authors: Byron DW , Robinson WH
Published: December 2008

Control of an indoor flea infestation involves two simultaneous steps: treatment of the animal to kill adult fleas and application of residual insecticides to the carpet (substrate) to kill immature stages.

Laboratory studies have shown that about 80% of the larvae in carpet remain at the base. The pesticide application method used in flea control must be capable of delivering pesticides to the target pest, flea larvae. The object of the research presented here was to investigate spray penetration into carpet using an 80015 flat-fan nozzle while varying the application pressure and spray height.

A solution containing a 0.24% water-soluble fluorescent dye (fluorescein sodium: C.I. 45350) and a 0.1% non-ionic wetting agent (Agral) in WHO standard water (CIPAC D) was applied to saxony pile (18 mm) carpet. The carpet samples were dried, then horizontally sectioned. The fluorescent dye was extracted and subjected to spectrofluorimetric analysis.

The results indicate that neither application pressure nor spray height within the ranges of 137.9, 206.9, 275.8, 344.8, 413.7, and 482.7 kPa (20, 30, 40, 50, 60, and 70 psi) at 35, 45, and 55 cm have a significant effect on the penetration potential into carpet. The application equipment used by pest control professionals for indoor flea control may not be adequate in view of its intended function or the importance of household flea infestations in the United States.
Unique Methods of Herbicide Application
Authors: Larsen TE
Published: December 2008

The last several years have witnessed the development of several unique and novel approaches to herbicide application. Since the widespread adoption of the use of herbicides in the 1940s the most widely used method of application has been hydraulic spray techniques. This method utilizes forcing a liquid containing the herbicide through various designs of orifices that meter and direct the solution onto the area to be treated. This method of application remained largely unchanged until the late 1970s.

With the commercial introduction of glyphosate (N-[phosphonomethyl]glycine) in the mid-1970s, changes began to take place in application technology. Glyphosate is formulated as the isopropylamine salt in the commercial product Roundup® herbicide. Glyphosate has some unique properties that prompted the search for new application techniques. It is a post-emergence, nonselective herbicide (at normal use rates) with broad-spectrum activity on both grass and broadleaf plants. It is translocated in plants, so that contact with the foliar portion of a plant results in the destruction of both the aboveground and the belowground portions of the plant. These features of glyphosate have prompted a wide range of unique application techniques to be developed or improved upon.

The principal motivation in the development of these new application techniques has been to utilize the activity of glyphosate in a selective manner. Another primary goal of some application techniques is the reduction in herbicide cost. Some techniques are able to reduce the amount of herbicide applied to a given area. Substantial cost savings can often be realized compared with conventional broadcast applications.

Within a short time after the introduction of glyphosate, several methods of selective application began to be developed. All utilized the same common principle. The herbicide is applied directly to the undesirable foliage while avoiding or minimizing contact with the foliage of the crop or desirable vegetation. By applying the herbicide in such a manner the weeds can be destroyed without damage to the crop.

Among the application methods developed were recirculating sprayers, rope-wick applicators, carpet wipers, roller applicators, and sponge wipers, as well as modifications to hooded and shielded applicators. Later unique concepts regarding broadcast applications were developed in an effort to improve the economics of pesticide application.

The characteristics of glyphosate are discussed. The advantages and disadvantages of various application techniques are summarized as are the precautions that should be exercised when applying glyphosate regardless of the application technique utilized.
Dry Application of Water-Dispersible Granules: A Three-Year Update
Authors: Gandrud DE , Skoglund JH
Published: December 2008

The trend in granular application of pesticides will be towards the use of small quantities of more concentrated granules. Three developments in recent years will hasten that trend:

1. Development and wide acceptance of dry flowable formulations. 2. Development and wide acceptance of pneumatic applicators for distributing conventional granular chemicals. These pneumatic applicators have lowered the broadcast rate which can be safely applied from 11 to 5.5 kg/ha. 3. Development of a new metering system to be used in conjunction with the pneumatic distribution system. The new combination has been calibrated to broadcast rates as low as 0.2 kg/ha.

Field tests were initiated in 1983 and repeated in 1984 and 1985 which showed that dry flowable herbicide formulations such as metribuzin can be applied to the soil dry at a rate of 0.6 kg/ha of formulated product and produce effective weed control.
A New Pediculicide Application System for Human Mass Delousing: Analysis of Operational Characteristics and Limitations
Authors: Darby WM , Boobar LR , Brown WM , Bunner BL , Nelson JH
Published: December 2008

A new pediculicide application system for human mass delousing has been developed by the U.S. Army Biomedical Research and Development Laboratory. This light-weight system is capable of operating either on its own air supply or any other available air supply greater than 4 scfm. Compliance with pediculicide label requirements is now possible through the use of newly designed guns.
Softening of Si and GaAs During Thermal Process
Authors: Suga H , Ichizawa M , Endo K , Tomizawa K
Published: December 2008

Semiconductor materials for highly integrated circuit devices need the resistance for the slippage during thermal process to prevent the defect induced degradation. Temperature dependence of strength of cz-Si and pcz-GaAs was investigated by micro-Vickers hardness tester. Hardness of cz-Si wafers lowers sharply with testing temperature and with precipitated oxygen content. Hardness of pcz-GaAs wafers starts to decrease at a temperature about 400°C lower than is the case for Si wafers. Dopant content dependence of hardness between 600 and 700°C was not observed in Si doped or Zn doped pcz-GaAs wafers.
Epitaxial Silicon Quality Improvement by Automatic Surface Inspection
Authors: Ruprecht DJ , Hellwig LG , Rossi JA
Published: December 2008

With increasing demands on epitaxial wafer surface quality, automated inspection is necessary. The results from automatic wafer inspection equipment are ambiguous without careful examination of the detected defects. To facilitate microscopic verification of automatically detected defects, we have designed a system for matching flaw counts to actual defects. Using this system, the epitaxial deposition process has been optimized to reduce surface defects.
Spreading Resistance Profiles in Gallium Arsenide
Authors: Mazur RG , Hillard RJ
Published: December 2008

The spreading resistance technique is widely used for profiling carrier concentration and resistivity in a variety of silicon structures. Several authors have reported some success in applying the spreading resistance technique to profiling doped GaAs samples. However, the use of spreading resistance measurements on GaAs is not widespread. The primary reasons for this are experimental problems with sample surface preparation and the very high values of contact resistance found in point contacts to GaAs. This paper details modifications to the spreading resistance technique to obtain reproducible and stable results on a variety of GaAs structures. It also discusses the current limits of such measurements.
High Dose Arsenic Implant for Bipolar Buried Layers
Authors: Ygartua CL , Swaroop R
Published: December 2008

The use of arsenic ion implant for a low sheet resistance and deep junction buried layer process was investigated. Appropriate ion doses and energy were found to obtain the desired buried layer profile using a pre-implant oxide. A low temperature (1050°C) oxidation was employed to remove the highly damaged surface region after diffusion/anneal of the arsenic implant. Damage was characterized after the buried layer process and epitaxial growth. The electrical performances and relative yield of the bipolar devices made from implanted and deposited (solid-source) arsenic buried layer were compared. The results indicated that implanted buried layer produced almost defect free epitaxial layer in the subsequent processing.
Accurate Junction-Depth Measurements Using Chemical Staining
Authors: Subrahmanyan R , Massoud HZ , Fair RB
Published: December 2008

The techniques of chemical staining, spreading resistance, and secondary-ion mass spectrometry (SIMS) have been used in the determination of the depth of diffused and ion-implanted junctions in an effort to estimate the accuracy of the staining method. Computer simulations were also used to study the behaviour of charge carriers in the semiconductor under illumination, and the accuracy of the junction depth obtained from raw spreading resistance data. It was observed that it is possible to measure junction depth reproducibly, to within 200 Å of the metallurgical junction depth, by carefully controlling the surface preparation of the sample and the lighting conditions under which the staining takes place.
Use of Polysilicon Deposition in a Cold-Wall LPCVD Reactor to Determine Wafer Temperature Uniformity
Authors: Starov V , Lane L
Published: December 2008

In the Varian 5101 LPCVD reactor operating in a Rapid Thermal Processing (RTP) mode the wafer is heated directly by a radiant heater. The wafer temperature in this case is measured by a pyrometer pointing at its center. To obtain a temperature map of the entire wafer, we have developed and characterized a polysilicon deposition process. Using the polysilicon thickness as a “chemical thermometer” [1], we have been able to improve the radiant heater design to obtain a temperature uniformity of 0.2% across a 100 mm wafer and 0.5% on wafers up to 150 mm. As an example of application of our study, the optimized design was used to deposit selective tungsten with thickness uniformity of 4% across 140 mm scan on 150 mm wafer.
NBS Submicron Particle Standards for Microcontamination Measurement
Authors: Lettieri TR
Published: December 2008

There is a recognized need for standard artifacts with which to calibrate the laser-scanning instruments which detect and monitor microcontamination on semiconductor wafers. Although commercial calibration wafers are available for this purpose, the present paper proposes the use of National Bureau of Standards (NBS) particle-sizing standard microspheres, deposited on polished silicon substrates, as an alternative working standard until such time as a true national calibration artifact is developed. To this end, several techniques for depositing the microspheres on semiconductor surfaces are presented in the paper. In addition, the techniques used to certify the NBS particle standards and the measurement results from each technique are summarized.
Particulate Cleanliness Testing of Filters and Equipment in Process Fluids
Authors: Goldsmith SH , Grundelman GP
Published: December 2008

Filters and equipment components used in critical semiconductor process lines must be accurately evaluated for particulate cleanliness. This requires accurate test methods, particle counting instruments, testing apparati, and careful analysis of data. This paper describes these criteria and how they can be applied.
Advanced VLSI Isolation Technologies
Authors: Kuo Y
Published: December 2008

Common issues in VLSI isolation technologies have been identified. Based on these issues, a critical review of conventional and novel isolation technologies such as oxide, trench, SEG, SOS, SIMOX, and ZMR is presented in this paper.
Modification of Control Charts for Use in an Integrated Circuit Fabrication Environment
Authors: Friedman DJ
Published: December 2008

For on-line statistical process control to be effective, it is necessary to correctly specify the distribution of the process generating the defects. Manufacturing and assembly operations have traditionally assumed measurement data to follow the normal distribution and defect data to follow the Poisson distribution. This paper will discuss the Integrated Circuit manufacturing industry, where the Poisson distribution assumption is known to be false. Suggestions will be made on how to modify existing control charts to allow for the clustering effects known to occur in IC manufacturing. By modifying control charts which assume the Poisson distribution, the same procedures and interpretations may be used in many cases: only the sample size or control limits would change. With other control charts however, significant clustering precludes their use.
Developments in Microencapsulation, High Concentration
Authors: Beestman GB , Deming JM
Published: December 2008

The earliest method of achieving microcapsules was the technique of coacervation. Polymers were used to disperse or suspend material to be microencapsulated. A polymer-rich phase was caused to develop in the suspension and envelop the suspended material. Further processing was required to harden the precipitated polymers to produce useful shell walls. Because coacervation was a dilute process and batch-to-batch variation was difficult to control, this technique did not gain wide practice in the microencapsulation of agricultural pesticides.

Microencapsulation by interfacial polymerization was a major step toward agricultural applications. Water-soluble monomers in the aqueous phase were reacted with oil-soluble monomers in the oil phase to produce microcapsule shell walls at the interface of suspended droplets. Although more concentrated suspensions of microcapsules could be produced by interfacial polymerization, agricultural formulations were limited to about two pounds of active ingredient per gallon. Recent break-throughs in interfacial polymerization have expanded this technology to concentrations of active ingredients typical of commercial agricultural products. Directly usable suspensions of microcapsules which can be diluted with formulating ingredients to contain four pounds of microencapsulated active ingredient per gallon have been made.
Microbial Formulations — Opportunities and Challenges
Authors: Devisetty BN
Published: December 2008

Microbial control of insect pests in agriculture, forestry, and vector (mosquitoes and black flies) markets is a commercial reality. Bacillus thuringiensis var. kurstaki (B.t.k.) is the predominant microbial pesticide for agriculture and forestry applications. Novel, effective, stable, potent, and economical formulations developed for corn borer control and forest pests have the potential of significantly replacing hazardous chemical treatments of food crops and forestry. Bacillus thuringiensis var. israelensis is the second most important microbial pesticide currently in large scale commercial use for control of mosquitoes and black flies. High potency, effective and economic granular and liquid formulations currently being field developed have the potential of enhancing its use both for mosquito control and black fly control. The limitations of current formulations of B.t.k. and B.t.i. and the challenges in the design of effective formulations are discussed in detail. The future for microbial pesticides is good considering advances being made in biotechnology, fermentation development and formulation technology.
Quality Control of Surfactants for Pesticide Formulations
Authors: Chasin DG , Vandegrift KP
Published: December 2008

Quality control of all components in pesticide formulations is becoming increasingly important because of such factors as (1) regulatory limitations on “inert” ingredients, (2) more chemically sensitive actives, (3) built-in adjuvant functionality, (4) the growth of pre-mix formulations, (5) inherently more sophisticated formulations, (6) difficulty in reworking certain types of formulations, and (7) overall emphasis on final formulation product quality.

Adequate quality control of POE-POP block copolymer nonionics, polymeric dispersants and surfactant blend products is especially important. Depending on surfactant chemistry and applications, a variety of wet chemical, chromatographic analyses and/or performance testing is needed to insure regulatory compliance, and reproducible quality and functionality. These Q.C. aspects are delineated in this paper.
A Technique for Dust Measurement
Authors: Goss GR , Reisch FJ
Published: December 2008

The presence of dust in either pesticide formulation ingredients or the finished product is a nuisance at best. Dust in the pesticide industry is commonly measured as minus 60 mesh (250 micrometers) material. Dust itself is much smaller airborne particulate matter. A device was constructed to measure airborne particles by weight and light absorption. A sample is introduced through a port into a 0.0566 m3 space. Dust generated during the fall is measured optically and gravimetrically. Absorbance is determined with a tungsten light source, a cadmium sulfide detector and a 0.305 m path length. Dust weight is determined by evacuation of the air above the sample and collection on filter paper. Instrument performance was determined with three types of absorbent minerals, a hormite, a montmorillonite and a diatomite. Light absorption and dust weight were linear with the amount of material introduced. Though materials were slightly different colors, a linear correlation was observed in dust weight vs. absorption plots. Particles in the dust ranged from 2 to over 200 microns, averages ranging from 20 to 65 microns.
Compacting and Granulating Systems for Agricultural Chemicals
Authors: Holley CA
Published: December 2008

Describes the need for compacting and granulating systems and the difference in the various types of equipment.
Spray Volume Effects on Deposition and Citrus Rust Mite Control
Authors: Salyani M , McCoy CW , Hedden SL
Published: December 2008

A field test was conducted to determine the deposition characteristics and biological efficacy of 4 different spray volumes applied at 2.4 km/h with an airblast sprayer for control of the citrus rust mite. Five acaricides and a copper tracer were applied at 4,700, 940, 470, and 235 L/ha. Copper deposition on leaves was determined by colorimetry. Mite population counts were made one week prior to application and at 2, 4, 6, 8, and 10 weeks after treatment to estimate residual effect. Spray volume had no significant effect on mean copper deposition and citrus rust mite control. Higher spray volumes showed more uniform coverage than the lower volumes. Acaricidal efficacy differed between compounds, yet all were superior to the untreated check.
Test Methods for Pest Control in the Telecommunications Industry
Authors: Appel AG , Woody LG
Published: December 2008

Pest control strategies and formulations were evaluated against cockroaches and honey bees, respectively. Insect tape, containing propoxur, repelled German cockroaches from pedestal closures significantly better when tape was placed at all points of entry. A knock down test to evaluate wasp spray formulations is presented as is a method for determining stress cracking in plastics treated with wasp sprays.
Anisotropy in Zircaloy
Authors: Picklesimer ML
Published: December 2008

The early days of the development of the study of the anisotropy in Zircaloy in the Zirconium Metallurgy Group, Metals and Ceramics Division, Oak Ridge National Laboratory are discussed. A program of research on developing zirconium base alloys for service in the Aqueous Homogeneous Reactor at Oak Ridge led to the long term study of anistropy of mechanical properties in Zircaloy and its relationship to the preferred orientation developed in the material by the fabrication procedures used. The history of the early research program is related, without review of the extensive technical data reported in the literature then and later. The study led to the development, ultimately, of a better understanding of the relationship between fabrication variables and the anisotropy of properties resulting, and an improvement in the commercial production of Zircaloy tubing. The tubing is the cladding for the uranium oxide fuel pellets used in light water reactors producing electrical power commercially throughout the world.
Effect of Irradiation at 588 K on Mechanical Properties and Deformation Behavior of Zirconium Alloy Strip
Authors: Morize P , Baicry J , Mardon JP
Published: December 2008

Irradiation tests conducted for the Advanced Fuel Assembly (AFA) grid development allowed the measurement of the mechanical characteristics, growth, and relaxation of the following materials: stress-relieved, α-annealed, and β-quenched Zircaloy-4, and α-annealed Zr-3Sn-1Mo. The mechanical characteristics of the zirconium alloys approached a limit value as early as 5 × 1024 n m−2, except for the β-quenched Zircaloy-4 for which the limit value was reached later at about 5 × 1025 n m−2. Uniform elongation at 588 K showed a minimum at about 5 × 1024 n m−2; beyond this fluence, stress-relieved Zircaloy-4 presented the most marked tendency to increase. Longitudinal direction growth of annealed Zircaloy-4 and longitudinal and transverse direction growth of stress-relieved Zircaloy-4 may be expressed by the formula ε = A(φt)n where n = 0.67 (stress-relieved Zircaloy-4) and n = 0.4 (annealed Zircaloy-4). It is doubtful that the growth is associated with a density change. The stress-relaxation of the zirconium base materials is nearly complete for 4 × 1025 n m−2, with the exception of Zr-1Nb which has an intermediate behavior between those of Zircaloy-4 and Inconel 718.

Tests on elementary grid cells, beyond 2 × 1025 n m−2, showed that the load exerted by the springs of Zircaloy-4 prototype cells is completely relaxed; for the AFA cells the residual load after irradiation at about 5 × 1025 n m−2 is comparable to that observed for an Inconel 718 manufactured cell.
Upper and Lower Bound Crystal Plastic Modelling of Creep Loci of Zircaloy
Authors: Murty KL , Mahmood ST , Adams BL
Published: December 2008

Biaxial creep of Zircaloy was examined in the cold-worked and recrystallized conditions in terms of creep loci at constant creep dissipation. Model predictions were made using the lower and upper bounding schemes along with the statistical averaging of crystallite behavior through the crystallite orientation distribution functions (CODF). Textural modifications following recrystallization treatment were found to have a negligible effect on the slip predictions based on easy slip on basal, prism, or pyramidal planes. The differences in the deformation behaviors of the cold-worked stress-relieved (CW-SR) and recrystallized materials were shown to arise from changes in the slip mode, basal slip being dominant in CW-SR and prism slip in recystallized materials. Deviations between the experimental results and model predictions brought out the importance of pyramidal slip in biaxial creep of Zircaloy materials. Dominance of basal slip in the CW-SR material is believed to be due to the hardening of the prismatic planes during fabrication.
Recycling Off-Grade Zircaloy Scrap Using a Molten-Salt Electro-Refining Process
Authors: Chintamani  , Saratchandran N , Pande P , Taneja AK , Sehra JC
Published: December 2008

Zircaloy hardwares meant for use in nuclear power reactors have to meet very stringent nuclear, metallurgical, and mechanical specifications. For this purpose, many complex chemical, metallurgical, and manufacturing processes have to be gone through. In view of these factors, the conversion yield from sponge to Zircaloy hardwares varies from 25 to 40%. The low recovery, low hafnium content in scrap, and the cost factor necessitate recycling of scrap to maximum extent.

A variety of processes have been developed for treating and recycling of scrap. A major portion of the remeltable stock is treated in an inert-gas plasma melting furance to make a consumable electrode which is further vacuum arc melted. The odd shape scrap is broken down by hydriding-dehydriding for mixing with sponge for further processing by vacuum arc melting.

The non-remeltable stock, where the degree of contamination with respect to interstitials is high, needs chemical processing. Two methods, chlorination and Kroll reduction and molten-salt electro-refining, have been attempted. In the first process, the scrap is converted into ZrCl4 which is subsequently reduced to sponge by the Kroll process. In the molten-salt electro-refining process, the scrap is converted into zirconium dendrites in NaCl-K2ZrF6 or NaCl-NaF-ZrCl4 bath. The product obtained by the electro-refining process meets reactor-grade specifications. This paper describes briefly the foregoing methods of recycling Zircaloy scrap at the Nuclear Fuel Complex, Hyderabad, India, with a critical review of the molten-salt electro-refining method.
Influence of Impurities and Temperature on the Microstructure of Zircaloy-2 and Zircaloy-4 after the Beta → Alpha Phase Transformation
Authors: Charquet D , Alheritiere E
Published: December 2008

The formation of the basketweave structure (BW) or the parallel plate (PP) structure after β quench is known to depend upon C, Si, and P content. Traces of other impurities, volatile at the melting point of zirconium but insoluble at lower temperatures, are the most efficient in changing the as-quenched microstructures. The effect of the β heat treatment temperature varies according to the nature of insoluble phases initiating the β → α phase transformation. When Si is the main impurity, cooling down from 1050°C leads to a parallel plate structure, whereas β heat treatments performed at higher temperatures promote a basketweave structure. This change of microstructure has been attributed to the variation of silicon solubility in the β phase with temperature. Volatile impurities with a low solubility result in different behavior under similar heat treatment; cooling down from 1050°C leads to the basketweave structure and fast cooling from 1200°C gives a parallel plate structure depending on impurity level.
Influence of Second-Phase Particles on Zircaloy Corrosion in BWR Environment
Authors: Rudling P , Vannesjö KL , Vesterlund G , Massih AR
Published: December 2008

The influence of morphology, chemical composition, and crystal structure of second-phase particles in Zircaloy-2 material upon its corrosion behavior is investigated. Five different thermochemically treated Zircaloy-2 cladding tubes with known boiling water reactor (BWR) corrosion properties are examined. The characterizations of second-phase particles are carried out by scanning transmission electron microscopy, where particles in the range of 50 to 5000 Å are analyzed. The morphology of larger particles is characterized by scanning electron microscopy. Chemical composition is evaluated by an energy dispersive X-ray system. Crystal structure of some of the particles is determined by the electron microdiffraction technique where the chromiumbearing particles are identified as a face center cubic (fcc) phase. It is found that the oxidation rate (oxide thickness) is an increasing function of particle size. It is also argued that the oxidation rate is an increasing function of the ratio of the number of particles with the hexagonal close packed (hcp) structure to the total number of chromium-bearing particles (with both hcp and fcc structures). The beta-quenched claddings with a high degree of supersaturation of low-soluble alloying elements indicates small oxide weight gains, while the nonquenched claddings with a low degree of supersaturation show large oxide weight gains.
Effect of Beta Quenching on the Microstructure and Corrosion of Zircaloys
Authors: Bangaru NV , Busch RA , Schemel JH
Published: December 2008

The effects of variations in the beta-quench parameters during the tube reduction process on the final microstructure and microchemistry of Zircaloy-2 and Zircaloy-4 cladding were studied by TEM/STEM and correlated with corrosion rates in 400 and 500°C steam autoclaves.

The Process A Zircaloy-2 specimens (recrystallization annealed) revealed primarily two types of ternary intermetallic compounds: tetragonal Zr2(Fe,Ni) and hexagonal Zr(Fe,Cr)2. The solutelean Zr2(Fe,Ni) particles were much coarser than the solute-rich Zr(Fe,Cr)2 particles. The Process A Zircaloy-4 specimens revealed only one type of ternary particles, Zr(Fe,Cr)2, but with much higher Fe/Cr ratios and mean particle size than those of the corresponding particles in Zircaloy-2. Also, both the cubic and hexagonal forms of Zr(Fe,Cr)2 were noted in this sample.

More aggressive beta quenching reduced the mean particle size and volume fraction of the intermetallic particles and increased their number density in both alloys; however, the changes were greater in Zircaloy-2. In both alloys, the degree of these changes was most pronounced when beta quenching was performed close to the final tube reduction step. In Zircaloy-2, the Zr-Fe-Cr type particles showed higher refinement than the Zr-Fe-Ni type particles.

The variations in Zircaloy microstructure with the timing and aggressiveness of beta quenching in the tube reduction process were attributed to differences in quench severity and thermal exposure after the quench. A critical discussion of the influence of alloy chemistry was also presented to reconcile the differences in beta-quenching response between Zircaloys 2 and 4. The 500°C steam autoclave corrosion data revealed significant improvement when beta quenching was performed close to the final tube dimensions.
Experimental and Theoretical Results of Cladding Oxidation Under Severe Fuel-Damage Conditions
Authors: Hofmann P , Neitzel HJ
Published: December 2008

Under severe fuel-damage (SFD) conditions a combined external and internal oxidation of the fuel-rod cladding occurs due to a reaction with steam or oxygen on the outside surface and the UO2 fuel on the inside surface. These reactions result in the formation of oxygenstabilized α-Zr(O) phases, ZrO2, and a (U,Zr) alloy. The reaction kinetics have been studied with isothermal and transient temperature experiments above 900°C. The tests were performed using short LWR fuel-rod sections in an (Ar + 25 vol% O2) environment. The numerical model PECLOX, which solves the Fick and Stefan equations, has been developed. It predicts the formation, growth, and disappearance of the various interaction layers and the corresponding oxygen profiles as functions of temperature and time.
Cumulative Fatigue and Creep-Fatigue Damage at 350°C on Recrystallized Zircaloy-4
Authors: Brun G , Pelchat J , Floz JC , Galimberti M
Published: December 2008

An experimental program undertaken by CEA, EDF, and FRAGEMA with the aim of characterizing the fatigue and creep-fatigue behavior of Zircaloy-4 following different annealing treatments (recrystallization, stress relief, etc.) is in progress. The results given in this paper concern only recrystallized material. Low-cycle fatigue curves and creep behavior laws under high stresses have been established. Sequential tests of pure fatigue and creep-fatigue were performed.

The cumulative life fractions at fracture depend on the sequence of loading, stress history, and number of cycles of prestressing. Miner's rule appears to be conservative with regard to a low-high loading sequence, whereas it is not for the reverse high-low loading sequences. Fatigue and creep damage are not interchangeable. Pre-creep improves the fatigue resistance. Pre-fatigue improves the creep strength so long as the beneficial effect of cyclic hardening overcomes the damaging effect of surface cracking. The introduction of a tension hold time into the fatigue cycle slightly increases cyclic hardening and reduces the number of cycles to failure. For hold times of less than 1 h, the sum of fatigue and creep life fractions is close to one.
Effect of Cold Reduction on Anisotropy of Zircaloy Tubing
Authors: Konishi T , Honji M , Kojima T , Abe H
Published: December 2008

The effect of cold-work parameters on the texture and the contractile strain ratio (CSR) was investigated using Zircaloy tubes fabricated by different reduction processes. The results were as follows:

1. For the as-rolled and stress-relieved tubes, the f-factors were strongly influenced by the reduction in area as well as the Q-value during final cold work. As the reduction in area increased under the same Q-value, the fr-factor decreased.

2. When these tubes were recrystallized, tubes with lower reduction had little change in texture and tubes with higher reduction showed greater change. Thus texture was independent of reduction in area in the case of recrystallized tubes.

3. The relation between reduction and CSR showed the same tendency as the above relation between reduction and fr-factor.

4. The tool design had a significant effect on the deformation texture. The experimental data for the f-factors correlated fairly well with that calculated on the basis of the theory that the texture is determined by the local strain ratio.
Introduction to Dust Explosions
Authors: Hertzberg M , Cashdollar KL
Published: December 2008

This Bureau of Mines paper is an introduction to the subject of dust explosions. The phenomena associated with the occurrence of dust explosions are described in general terms, with several specific examples of dusts that react so rapidly and exothermically with air that destructive pressures are generated when they are dispersed and ignited. The accompanying gas-dynamic phenomena are also considered in some detail in terms of rates of pressure rise, speed of flame propagation, confinement, turbulence, and propagation dynamics. The explosion probabilities in any given plant or facility can be quantified in terms of the state of dispersion of the dust, its lean limit concentration, and its ignitability characteristics (thermal, electrical, and chemical). Dust explosions are contrasted with gas explosions in terms of those factors. Other variables considered for the dusts include volatility, particle size, oxygen content of the dispersing “quo;air,”quo; initial temperature, initial pressure, the presence of added fuel gases, and inerting or extinguishing requirements. Data to be discussed include laboratory measurements and full-scale test results; phenomena to be considered include both the fundamental and the practical.
Thermal Autoignition Temperatures from the 1.2-L Furnace and Their Use in Evaluating the Explosion Potential of Dusts
Authors: Conti RS , Hertzberg M
Published: December 2008

The Bureau of Mines 1.2-L furnace for measuring the thermal autoignition temperatures (AITs) of dusts in air is described. The minimum AITs measured for a large number of dusts are presented, and the data are compared with those in the literature. The data reveal that the measured minimum AITs for the carbonaceous dusts correlate with their volatility yield and the temperature required for pyrolysis and devolatilization. Reaction kinetic factors play a role in determining the onset temperature for the pyrolysis-devolatilization process and in the exothermic oxidation reactions that lead to the autoignition of those volatiles.

The use of the minimum AIT data in estimating the explosion potential of a dust under a given set of operating conditions is also considered. The “ignition sensitivity” parameter and its use in an “explosibility index” are no longer recommended by the Bureau. Alternative means are discussed for evaluating the frequency or probability of explosions in terms of the measured minimum AIT and its relationship to operating conditions in a given facility and to other flammability properties of the dust.
Propagation of Coal Dust Explosions in Pipes
Authors: Pineau JP , Ronchail G
Published: December 2008

This paper discusses the possibilities of pulverized coal explosions in pneumatic conveying. To characterize the coal dust explosions, we measured, at different points on rectilinear pipes, possibly connected to a 1-m3 vessel, explosion overpressures, Pmax, and flame speeds.

Trials in an isolated, 250-mm-diameter, 20-m-long pipeline and ignition near a closed end showed the difficulty of the flame propagation that did not surpass 10 m with Pmax values at the maximum equal to 0.6 bar (60 kPa) for a one-end-open duct and 0.95 bar (95 kPa) for a closed duct. On the other hand, with the pipeline connected to a 1-m3 vessel, with ignition in the vessel, the Pmax values inside the pipe can reach 10 bar (1000 kPa) and flame speeds 1500 to 2000 m/s. When exchanging the 250-mm-diameter pipe for a 440-mm one, such a character is not obtained and flame speeds are 600 m/s at the maximum with overpressures around 2.5 bar (250 kPa). If the open end, 250-mm-diameter pipe connected to a 1-m3 vessel is only 10 m long, overpressures inside remain under that obtained in the vessel, that is, around 4 bar (400 kPa). With a 40-m-long pipe, the high speed flames seem unable to be sustained.

In the 1-m3 vessel and 150-mm-diameter open end pipe system, the overpressures in the pipe have similar values to that obtained in the vessel (Pmax: 5 bar [500 kPa]) and the flame propagates up to 20 m. When the pipe is 40 m long, Pmax values remain the same, but the flame stops generally after 20 m.

With closed end, 150- and 250-mm pipe connected to a 1-m3 vessel, flames cannot propagate the full length of the duct, but explosion overpressures may be 10 to 20 bar (1000 to 2000 kPa).

For low concentration it has been noticed, outside the duct, that the concentration is heterogeneous but shows periodical figures; when the flame appears the same periodicity is found again. This may be due to the geometry of the studied system.

All these trials demonstrate the difficulty of a pulverized coal explosion in a pipe with a diameter less than or equal to 250 mm and the influence of the dust cloud local concentration.
Secondary Dust Explosions
Authors: Srinath SR , Kauffman CW , Nicholls JA , Sichel M
Published: December 2008

Industrial dust explosions typically occur in a sequence—a primary explosion in a predispersed dust cloud followed by one or more secondary explosions. The convective flow induced by the primary explosion disperses the surrounding layered dust, resulting in a dust cloud into which the flame continues to propagate. Continual repetition of this process results in a secondary explosion—a rapidly accelerating flame accompanied by substantial overpressures, that causes most of the damage. Such secondary explosions have been studied in the laboratory in a flame acceleration tube (FAT), a 36.6-m-long tube with an internal diameter of 0.3 m. Tests have been conducted with flow-enhanced cornstarch, small size cornstarch, baghouse dust, floor sweepings, wheat dust, and navy bean dust. The development of the secondary explosions in these dusts is compared and discussed in terms of the observed pressures, fame velocities, gas velocities, gas temperatures, and dispersed dust concentrations. The presence of turbulence-generating grids in the flame path is found to result in flame acceleration, quite analogous to gaseous flames. This observation confirms the findings of numerical models. Experimental results from a study of dust entrainment using high-speed motion photography are presented.
Coal Dust and Gas Explosion Suppression by Barriers
Authors: Ng D , Sapko M , Furno A , Pro R
Published: December 2008

Explosion suppression barriers are devices that contain fire extinguishants that are activated to disperse at some critical point during the propagation of an explosion to suppress it. Suppression of coal dust explosions using barriers (both triggered and passive) has been investigated by the U.S. Bureau of Mines. The work reported in the present study is an update of the continuing study of passive barriers of both rigid and flexible construction. Suppressants tested were water and ABC powder (ammonium phosphate). The coal dust mixtures contained 60 to 65% total incombustible matter and were distributed in the Bureau's single entry experimental mine for a total distance of 111 m (365 ft). Dust explosions were initiated by a 7% methane-air gas zone at the face. The passive barriers were located at distances of 60 to 108 m (200 to 356 ft) from the face. At these distances, the magnitude of the explosion pressure pulse was about 0.70 to 1.14 bar (70 to 114 kPa) at the time the flame front arrived at the barrier. With the exception of the powders, the pressure pulse was sufficiently energetic to fracture the troughs and disperse the suppressants.

The powder (approximately 180 kg per test) was almost totally ineffective when used with the rigid barrier because it did not disperse. One to four troughs of water effectively suppressed explosions. It was found that the mounting arrangement for the flexible troughs was most important for successful operation and release of the suppressant.

Triggered barrier systems for protection against incipient gas explosions were tested in a simulated longwall panel. Results show that ABC powder was much more effective in suppressing the developing explosion than equal amounts of water released from the same pressurized reservoir. Although water was effective in stopping fully developed dust explosions, it had little effect against an explosion during its incipient stage.
Preventive and Design Measures for Protection Against Dust Explosions
Authors: Bartknecht W
Published: December 2008

There is an inherent danger of a dust explosion when combustible dusts are handled in industry. This is proven by the many explosions which have resulted in substantial losses and often in fatalities. To counteract danger it is important to know the safety characteristics of the dust deposits or dust cloud. Based on the test methods used, it can then be decided which of the available protective measures should be applied. A distinction has to be made between preventive and design measures for the explosion protection.

Preventive measures avert a dust explosion by:

• preventing the formation of an explosible dust/air mixture, • inerting or removing oxygen, and • eliminating effective ignition sources.

Design measures will not prevent a dust explosion, but they will limit consequences to an acceptable level.

They include:

• explosion-resistant design for the maximum explosion pressure, • explosion-resistant design for the reduced maximum explosion pressure in conjunction with explosion pressure venting or explosion suppression, and • means to divert the explosion from entering peripheral equipment.

A general overview is given of all protective measures and the necessary decision making criteria.
Ignition Probability of Hybrid Mixtures
Authors: Napier DH , Roopchand DR
Published: December 2008

The behavior of hybrid mixtures (combustible dusts and flammable gas in air) has been studied at concentrations near to the lower limit. The mixtures were comprised of polyethylene particles (5 to 50 μm and 30 to 44 μm) and either ethylene or methane. Experiments were undertaken in a modified Hartmann vertical tube apparatus with a resistive/capacitive spark discharge circuit. The measured variables in the system were: dust concentration, addition of flammable gas, total ignition energy, and rate of its delivery to the spark channel. Thereby, minimum ignition energies (MIE) given in terms of series resistances and lower flammable limits (LFL) were obtained. The results obtained were compared with values in the literature. This led to consideration and reporting of the significance and confidence of experimentally determined values of MIE and LFL. Extensive measurements on the ignition of hybrid mixtures demonstrated that simple additivity does not apply. Probability of ignition was increased by addition of flammable gases, the type of which proved to be of major importance.
Strategies for Long-Term Pollution Monitoring of the Coastal Oceans
Authors: Segar DA , Phillips DJH , Stamman E
Published: December 2008

Monitoring of long-term effects of marine pollution on regional marine ecosystems can be most useful to managers if based primarily on the use of bioindicators to monitor temporal changes in the mean background abundance of bioavailable contaminants in the region. Design of successful long-term, regional bioindicator monitoring programs requires that specific quantitative objectives be defined and expressed as null hypotheses. An optimum sampling and analysis plan designed to test these hypotheses must select the age, size range, and number of individuals per sample, the number of samples per site, the number of replicate analyses per sample, and other factors based on the known sources of variance in the environment, sampled population, and analysis procedure. Sampling sites must be systematically selected to be affected as little as possible by contaminant inputs which vary temporally on short time scales. Many suitable sites will require the transplantation of bioindicators, and the optimum program will probably require the exclusive use of transplanted populations.
Monitoring, Research, and Management: Integration for Decisionmaking in Coastal Marine Environments
Authors: O'Connor JS , Flemer DA
Published: December 2008

A rationale is presented for making research and monitoring interdependent to maximize the contributions of both activities to environmental management. Emphasis is placed upon better choices of temporal and spatial scales of marine assessments, thereby improving managerial guidance from monitoring and research. While appropriate scales are functions of particular environmental issues, the most useful scales “in the mean” appear to be long-term (including truly historical) and regional. The likelihood in the near-term of only limited incremental advances in understanding ecosystem processes, with marginal improvements in predictability, leads to an argument for more emphasis upon the use of managerially helpful, necessarily simple models. One such model is presented, to characterize the geographical prevalence of fin erosion in winter flounder (Pseudopleuronectes americanus), relative to the sources of plausible causes, from Canada to Delaware Bay. Changing emphasis from laboratory bioassays to field population-level effects is an important and essential step toward integrating ecosystem-level knowledge into the managerial and regulatory milieu.

It is now possible to quantify the geographic and, at least recent, temporal associations among man's waste sources and some of their biological effects. Further elaboration of source-fate-effects understanding with the help of simple models (for example, indices) is often more useful to managers than is detailed, piecemeal quantification of seemingly intractable ecosystem dynamics.
“Mussel Watch”—Measurements of Chemical Pollutants in Bivalves as One Indicator of Coastal Environmental Quality
Authors: Farrington JW , Davis AC , Tripp BW , Phelps DK , Galloway WB
Published: December 2008

The utility of the bivalve sentinel organism approach to monitoring for some chemicals of environmental concern in coastal and estuarine areas has been evaluated by regional and national programs and by smaller scale research efforts during the past 15 years. The extent and severity of coastal contamination by chemicals such as polychlorinated biphenyls, chlorinated pesticides, trace metals, and plutonium has been assessed in several bivalve sentinel organism programs. Advantages and limitations of this approach are presented and discussed briefly within the context of both national and international efforts.