Donald Olander

• University of California, Berkeley

Three hydride mini-fuel rods were fabricated and irradiated at the MIT nuclear reactor with a maximum burnup of 0.31% FIMA or ∼5 MWd/kgU equivalent oxide fuel burnup. Fuel rods consisted of uranium-zirconium hydride (U (30wt%)ZrH1.6) pellets clad inside a LWR Zircaloy-2 tubing. The gap between the fuel and the cladding was filled with lead-bismuth...

A novel light water reactor fuel has been designed and fabricated at the University of California, Berkeley; irradiated at the Massachusetts Institute of Technology Reactor; and examined within the Radiochemical Processing Laboratory at the Pacific Northwest National Laboratory. This fuel consists of U0.17ZrH1.6 fuel pellets core-drilled from TRIGA...

The properties of the two-phase uranium-zirconium hydride U0.3ZrH1.6 pertaining to its performance as a nuclear fuel for uranium-zirconium light-water reactors (LWRs) are reviewed. Much of the available data come from the Space Nuclear Auxiliary Power (SNAP) program of four decades ago and from the more restricted database prepared for the Training...

During a severe accident such as a LOCA, fuel rods are exposed to steam. Rods are heated by fission-product decay and by steam oxidation of the cladding. The energy balance on the rod includes heat losses by convection to the surrounding steam and by thermal radiation to the surrounding fuel rods and to the ultimate heat sink, the reactor pressure...

The reaction of XeF2 with the Si(100) surface was studied by modulated (10–1000 Hz) molecular beam-mass spectrometry in the temperature range 300–1300K and equivalent XeF2 pressure of 5×10−6 to 10−4 Torr. Simultaneous bombardment of the reacting surface by Ar+ was used to determine the extent of ion-enhancement of the reaction. In the absence of th...

Reaction of Al0 3Ga0 7As with molecular chlorine was studied with and without simultaneous bombardment by energetic argon ions.The reaction products signals were measured as functions of surface temperature.For the purely thermal reactions, the main products below 600 K were AlCl3, AsCl3 and GaCl3.The etching rates were two orders of magnitude lowe...

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Monophase thorium–zirconium hydrides (ThZr2Hx) have been fabricated starting from a metallic alloy and the hydrogen stoichiometry determined by X-ray diffraction. Incoherent Quasielastic Neutron Scattering (IQNS) on the hydrides was conducted over the temperature range 650–750 K at the Backscattering Silicon Spectrometer (BASIS) at the Spallation N...

Three sets of independent experiments were conducted to determine the kinetics of hydrogen desorption from and adsorption on δ-zirconium hydrides. One method involved measurement of hydrogen gas pressure-buildup as a result of dehydriding in a closed vessel. The other two involved thermogravimetric experiments, measuring the rate of mass loss durin...

The dislocation-controlled migration process is qualitatively consistent with all experiments designed to test the hypothesis. It also explains the very large scatter of the measured velocities of small inclusions in crystals of high perfection. Larger inclusions in natural salt crystals, on the other hand, are not limited by the number of dislocat...

Four hydride mini-fuel rods are being fabricated to be irradiated in the MIT reactor under typical LWR conditions. The fuel pellets are fabricated from TRIGA fuel that consists of uranium-zirconium hydride (U 0.17ZrH 1.6). Each mini-fuel rod consists of five pellets clad in Zircaloy. The gap between the fuel and cladding is filled with helium gas f...

Attainable discharge burnups for oxide and hydride fuels in PWR cores were investigated using the TRANSURANUS fuel performance code. Allowable average linear heat rates and coolant mass fluxes for a set of fuel designs with different fuel rod diameters and pitch-to-diameter ratios were obtained by VIPRE and adopted in the fuel code as boundary cond...

This special issue of Nuclear Engineering and Design consists of a dozen papers that summarize the research accomplished in the DOE NERI Program sponsored project NERI 02-189 entitled “Use of Solid Hydride Fuel for Improved Long-Life LWR Core Designs”. The primary objective of this project was to assess the feasibility of improving the performance...

Properties of the two-phase hydride U0.3ZrH1.6 pertinent to performance as a nuclear fuel for LWRs are reviewed. Much of the available data come from the Space Nuclear Auxiliary Power (SNAP) program of 4 decades ago and from the more restricted data base prepared for the TRIGA research reactors some 3 decades back. Transport, mechanical, thermal an...

The transient response of a uranium zirconium hydride (U0.31ZrH1.6) fuel element to conditions typical of a light water reactor reactivity insertion accident has been studied. Hydrogen diffusion within the fuel is treated as a function of the time-dependent temperature profile. Temperature and hydrogen concentration dependence of thermal properties...

Two uranium–thorium–zirconium hydrides, (UTh4Zr10)H1.9 and (U4Th2Zr9)H1.5, have been fabricated and characterized. Fabrication involved arc melting of the constituent pure metals to form homogenous alloys, followed by hydriding at elevated temperatures in a hydrogen gas environment. The compounds were characterized by X-ray powder diffractometry as...

The important developments in nuclear fuels and their problems are reviewed and compared with the status of present light-water reactor fuels. The limitations of LWR fuels are reviewed with respect to important recent concerns, namely provision of outlet coolant temperatures high enough for use in H2 production, destruction of plutonium to eliminat...

Corrosion of uranium particles in dispersion fuel by the aluminum matrix produces interaction layers (an intermetallic-compound corrosion product) around the shrinking fuel spheres. The rate of this process was modeled as series resistances due to Al diffusion through the interaction layer and reaction of aluminum with uranium in the fuel particle...

Irradiation-induced diffusion in finite, two-phase systems is analyzed and applied to the geometry of dispersion fuels of the type used in research and test reactors. A fissioning sphere irradiates the surrounding medium in which fission also takes place. In place of the fission rate used in conventional irradiation-induced diffusion coefficient (D...

Molten mixtures of LiF, NaF, and BeF2 may be useful as a liquid first wall in a fusion-energy reactor. For design, it is necessary to know the thermodynamic properties of these mixtures, in particular, the total pressure as a function of temperature and composition. For successful application inside fusion chambers, the total pressure normally shou...

Theories of fission-fragment-driven re-solution of fission-gas atoms from intragranular bubbles in irradiated UO2 nuclear fuel are reviewed. Two mechanisms of re-solution are generally accepted: the heterogeneous process destroys entire bubbles in the path of fission fragments and returns the gas to the solid as individual atoms; the homogeneous pr...

The U–Zr hydride U0.31ZrH1.6 offers a number of advantages over oxide fuel for light-water reactors. Fission-gas release appears to be very small (release fraction ∼10−4) up to 600°C, which is close to the maximum fuel temperature. Initial irradiation-induced swelling can be as large as 5% for temperatures exceeding 650°C. Hydrogen redistributes du...

Knowledge of the vapor pressure of fluoride salts is necessary in order to assess the suitability of these salts as a liquid first wall for fusion energy schemes. A combination of Thermogravimetric Analysis (TGA) and Knudsen Cell Mass Spectrometry (KCMS) was used to characterize the vapor phase above mixtures of LiF, NaF, and BeF₂. The s...

The consistencies among the reported univariant hydrogen pressures in the three two-phase regions of the Zr-H system, aZr/δZrH2-xZr/βZr, and βRZr/δZrH2–x, are evaluated with the thermodynamic constraint derived by Speiser.16 Hydrogen dissolution in Zr is evaluated by checking the consistencies among the Sieverts’law constant, the terminal solubilit...

The thermodynamic constraint relating the standard free energy of formation of an oxide (MOc) to its oxygen potentials by ΔGf0(MOc) =½ƒocΔḠ(O2) dC′ has been used to develop the full spectrum of oxygen potentials of the U─O and Zr─O systems at high temperatures. Henry's law is applied to the metal region in the U─O system. Oxygen dissolution in liqu...

The solubility and release kinetics of hydrogen in single-crystal zirconia were investigated by the infusion–extraction method. Equilibration in hydrogen at pressures between 1.4 and 11 atm (0.14 and 1.1 MPa) and at temperatures from 1300° to 1600°C produced H/Zr ratios varying from 4 × 10−5 to 1.3 × 10−4. Dissolution was exothermic with an enthalp...

Hydriding kinetics of modified Zircaloy claddings was studied by the thermogravimetric method at 400°C and the tube-burst technique at 315°C. Some specimens were prefilmed with a thin oxide layer by air oxidation on both the inner and outer surfaces which were either pickled or blasted. In the thermogravimetric test, the hydriding rates of bare cla...

The pressures of the vapor species in equilibrium with Flibe at similar to600degreesC are determined from work by, Buchler and Stauffer and by Baes and coworkers. The former authors show that the principal vapor species are BeF2(g) and LiBeF3(g). The measurements and the theoretical model of Baes provide accurate values of the activity, coefficient...

High-pressure hydriding of Zircaloy (Zry) cladding was studied using the tube-burst technique. The aim was to demonstrate a practical laboratory test that reliably predicts the hydriding resistance of cladding. The test consists of pressurizing a section of tubing with hydrogen (wet or dry) and measuring the time to failure. Surviving specimens las...

It is generally believed that thermal fission gas release from LWR fuel occurs mainly via interconnected grain boundary bubbles. Grain boundary diffusion is not considered to be a significant mechanism. We investigated this supposition by two methods; first, by assessing the distance a gas atom can migrate in a grain boundary containing perfectly a...

The distinction between reversible and irreversible compression of an ideal gas in a cylinder with a frictionless piston is analyzed quantitatively. Reversible compression is achieved by moving small masses appropriately distributed vertically onto the piston as it descends and compresses the gas. In the past, this example has been used pedagogical...

As a means of improving the gap-thermal conductance, a liquid metal (LM) is proposed as the gap-filling material replacing helium gas in the conventional light water reactor fuel rod. The potential application of the concept includes power reactor fuel rods, special-purpose test-reactor experimental rods, and mixed-oxide fuel rods. Novel fabricatio...

The volatilization rates of urania in pure steam and in mixtures of steam and argon, steam and helium, and in steam/Ar/H2 were measured in a thermogravimetric apparatus at atmospheric pressure and temperatures from 1250°C to 1600°C. The objective was to clarify the kinetics and mechanism of the volatilization process and to assess the validity of e...

Recently a Peer Review Committee established by the US Nuclear Regulatory Commission issued its report on VICTORIA, a detailed mechanistic computer code that addresses the release of fission products from degraded reactor fuel and the ex-core behavior of the released material. The present paper summarizes the findings of the report relevant to the...

Oxidation of UO2 by pure steam at pressures of 7 and 70 atm and 500°C and 600°C was measured in a thermogravimetric apparatus. The kinetics are linear, vary as the square root of the steam pressure, and are consistent with initial rates extrapolated from higher-temperature experiments in 1-atm steam. At temperatures characteristic of normal operati...

In order to better understand the processes occurring in defective fuel rods in a nuclear reactor, radiolysis of saturated steam by Cm-244 alpha particles was investigated at temperatures between 250 and 300°C. Radiolysis took place in gold-plated steel chambers and the yields of H2 and of O2 were measured mass spectrometrically as functions of dos...

The thermochemistry of urania volatilization as UO3 obtained from several literature sources was reviewed. The predicted equilibrium pressures of UO3 over pure UO2+x in a gas of known oxygen potential and temperature fall into one of two groups that differ by one order of magnitude at 2000 K and two orders of magnitude at 1500 K. The recent theoret...

Recently a Peer Review Committee established by the US Nuclear Regulatory Commission issued its report on VICTORIA, a detailed mechanistic computer code that addresses the release of fission products from degraded reactor fuel and the ex-core behavior of the released material. The present paper summarizes the findings of the report relevant to the...

Fission-product release experiments were performed on trace-irradiated specimens of LWR fuel. The behavior of Te, I, Ru, Mo and Xe were followed in stoichiometric and pre-oxidized fuel. Maintenance of the desired O/U ratio was accomplished using an in situ microbalance during annealing. Fractional releases were determined from the intensities of ch...

The literature dealing with experiments and modeling of UO2 oxidation at temperatures > ∼ 600°C is reviewed and a detailed model is proposed. Mechanistic modeling is subjected to the principle of detailed balancing, which provides a framework for the elementary reactions contained in the reaction scheme. This principle interrelates the rate constan...

The results of several experimental studies aimed at improving understanding of the chemical processes that cause severe degradation of defective light-water reactor fuel cladding are reported. The competition between oxidation and hydriding of zirconium and zircaloy exposed to steam-hydrogen mixtures at 70 bar and 350–400°C was studied by thermogr...

Severe accident modeling requires knowledge of the heat effects accompanying simultaneous dissolution of UO2 and fusion of Zircaloy to form the UZrO melt. Estimation of the enthalpy changes must rely chiefly on data from the UO and ZrO binary systems. The partial molar enthalpies of oxygen in the pure liquid metals are determined by application...

Hydriding kinetics of thin sponge-Zr layers metallurgically bonded to a Zircaloy disk has been studied by thermogravimetry in the temperature range 350–400°C in 7 MPa hydrogen-steam mixtures. Some specimens were prefilmed with a thin oxide layer prior to exposure to the reactant gas; all were coated with a thin layer of gold to avoid premature reac...

A thermogravimetric apparatus for operation in 1 and 70 atm steam-hydrogen or steam-helium mixtures was used to investigate the oxidation kinetics of sponge-Zr containing 215 ppm Fe. Weight-gain rates, reflecting both oxygen and hydrogen uptake, were measured in the temperature range 350–400°C. The specimens consisted of thin sponge-Zr layers metal...

The chemical diffusion coefficient of oxygen in UO2−x has been measured using molten Zircaloy held in a UO2 crucible to establish the concentration driving force. The oxygen-to-uranium distribution set up by this method was determined by scanning electron microscopy/image analysis of the number density and area fraction of uranium metal precipitate...

The hydriding characteristics of Zircaloy-2(Zry), sponge zirconium (as a liner on Zry plate), and crystal-bar zirconium exposed to pure H2 at 0.1 MPa or 7 MPa and 400°C were determined in a thermogravimetric apparatus. The morphology of the hydrided specimens was also examined by optical microscopy. For all specimen types, the rate of hydriding in...

The rate of fuel dissolution by melting cladding during a severe fuel damage accident is shown to be controlled by the flow of fission product decay heat to the interaction zone, which supplies the endothermic enthalpy changes accompanying UO2 dissolution and αZr(O) melting. Diffusion in the growing U-Zr-O melt is rapid and the liquid-phase concent...

The pressure-composition-temperature (p-C-T) relationships of the systems U(L)-N, Zr(L)-O, and Th(L)-O are derived using thermodynamic constraints and a modified form of Sievert's law. The results are used to evaluate the thermodynamic functions of each system: The integral Gibbs enthalpy of formation of UN and the Gibbs energy of solution of nitro...

The available experimental data on dissolution of UO2 crucibles by a molten Zircaloy charge are compare to a two-stage kinetic model. During the initial stage, melt saturation by uranium and oxygen is approached by natural-convection mass transfer. In the following precipitation stage, no further UO2 dissolution occurs but oxygen enters the melt as...

Efficient room‐temperature vapor‐phase etching of SiC by the compound dioxygen difluoride (FOOF) has been demonstrated. FOOF was generated using a design based on thermal‐atomization technique which produced gram quantities of the compound per hour. On both poly‐ and epitype silicon carbide at room temperature, about 6% of the FOOF molecules striki...

Thermodynamic constraints are used to study the thermodynamic functions of the ZrN system over the temperature range from 1500 K to 3670 K. The results are presented as the nitrogen isobars superimposed on the revised phase diagram. The Gibbs energies of solution of nitrogen dissolution in solid and liquid Zr are also determined with the assumptio...

Enthalpy changes accompanying dissolution of Zr(O) and U02 in UZrO melts and precipitation of mixed uranium-zirconium oxides from these melts are determined. Data on the heats of solution of oxygen in the pure metals, standard enthalpies of formation of the pure oxides, and regular-solution interaction parameters in the UZr binary system are use...

Chemical thermodynamics and transport processes are inextricably linked in light- water reactor fuel rods. Two regimes can be identified, separated by their temperatures. During normal operation, the temperature at the center of the U02 pellet usually does not exceed lOOOOC, and most of the important chemistry takes place at the periphery, which is...

The dissociation of C60 to C58 has been observed on surfaces of silica and highly oriented pyrolytic graphite by modulated molecular beam reaction spectroscopy. At 1200 K on both surfaces approximately 5% of the incident C60 dissociates and desorbs as C58. The activation energy for C58 production from C60 on the surface (≈ 2.5 eV) is considerably s...

The reaction of polycrystalline β-SiC with thermal atomic hydrogen is investigated by modulated molecular beam mass spectrometry. The temperature and equivalent pressure on the surface are 300–1100 K and 6 × 10−6 –2 × 10−5 Torr, respectively. The reaction probability of atomic hydrogen is 9 × 10−5–5 × 10−4. Grain boundary effects are negligible and...

Several consequences of steam starvation of the gas filling the internals of the core of a light-water reactor in the fuel-uncovery phase of a severe accident up to cladding melting are analysed. Emphasis is placed on processes that occur in the H2-rich gas external to the fuel rod cladding; absorption of oxygen and hydrogen by the cladding; the co...

Langmuir vaporization mass spectrometry and inductively-coupled-plasma mass spectrometry were used to investigate the thermodynamic functions of the solid solution UyNd1−yO2±x. The major metal-bearing vapor species observed were UO2(g), UO3(g) and NdO(g). The system was treated as a pseudo-binary regular solution of urania and neodymia. The interac...

High temperature Zircaloy oxidation in the flowing steam—H2 environment of a severe fuel damage accident is analysed by integral diffusion theory. This approach provides details on the state of the cladding as a function of the time and elevation, with accuracy not attainable using conventional parabolic oxidation rate laws. The method is compatibl...

The kinetics of the reaction of molecular iodine with preoxidized Type 304 stainless steel was studied by mass spectrometric and gravimetric techniques. The temperature range was 438 to 803 K, and the iodine partial pressures in the 1-atm total pressure water vapor-hydrogen gas ranged from 1.33 to 133 Pa. Examination of the reacted surface by elect...

An experimental study of UO2 oxidation in pure steam and in H2O/Ar/H2 mixtures was conducted in a continuously recording thermogravimetric apparatus in the temperature range 1273–1623 K at one atmosphere system pressure. Two surface reaction models were utilized in the analysis of the data: the phenomenological model assumes the reaction rate to be...

Fission gas diffusion from a microstructure with a distribution of grain sizes undergoing grain growth is analyzed. Hillert's theory is used to describe the evolution in grain morphology, during which some grains enlarge while others shrink and may even disappear. Limiting cases of Booth release (when only diffusion occurs) and Malen release (when...

The interaction of a collisionless beam of thermal C60 nanoclusters with a silicon dioxide surface has been investigated with modulated molecular beam‐mass spectroscopic techniques. Analysis of the amplitude and phase lag of the desorbed C60 shows the interaction mechanism to involve the elementary steps of sticking, desorption, and long‐range surf...

The thermodynamic constraint for the oxygen potential of tetravalent metal oxides relates the standard free energy of formation to the relative partial molal energy by . This constraint and its variant have been utilized to construct the full spectrum of oxygen potentials of the U-O and Zr-O systems at high temperatures. Henry's law is assumed to a...

Among the proposed measures for reducing the damage rate to pressurized water reactor (PWR) pressure vessels are the following: 1. replacement of fuel rods in peripheral fuel assemblies with dummy rods-the [open quotes]fuel replacement[close quotes] (FR) approach; 2. insertion of neutron reflecting and attenuating materials between the core baffle...

Formation of neutral clusters in the vapor plume generated by laser‐pulse heating of YBa 2 Cu 3 O 7-x in vacuum was investigated. A Nd‐glass laser of 1060 nm wavelength and 1.75 ms pulse width was used to generate peak power densities in the range of 10⁴–10⁵ W/cm² over an area of 3–28 mm². Time‐of‐flight...

An approximate computational scheme that accounts for boundary movement during diffusion of a surface-deposited tracer into a polycrystalline solid is presented. The method is compared to exact solutions for stationary boundaries and for rapidly-moving boundaries and found to be acceptably accurate. The proposed method bridges the transition betwee...

The vapor pressures of the fullerenes C 60 and C 70 have been measured over the temperature range 400–600 °C by the Knudsen‐effusion thermogravimetric technique. For C 60 , a heat of sublimation of 38±1 kcal/mol is obtained, and the value for C 70 is 45±1 kcal/mol. The vapor pressure of C 60 ranges from 1.8×10^-5 and 1.4×10^-2 T...

A defect model for the thermochemistry of the mixed rare-earth uranium oxides has been developed. The parameters of the model were determined by fitting the theory to experimental oxygen potential data. The basic defects and associated equilibria found previously for pure urania were used in the mixed oxide defect model. In addition, the model proh...

The reaction of Cl2 with polycrystalline β-silicon carbide was studied by the modulated molecular beam-mass spectrometric detection method. The temperature range was 300–1000 K and beam intensities between 1016 and 1017/cm2 s were employed. The sole silicon-bearing gaseous product was SiCl4, which was produced with a maximum reaction probability of...

Formation of neutral clusters in the vapor plume generated by laser-pulse heating of YBaâCuâO{sub 7-{ital x}} in vacuum was investigated. A Nd-glass laser of 1060 nm wavelength and 1.75 ms pulse width was used to generate peak power densities in the range of 10⁴--10⁵ W/cm² over an area of 3--28 mm². Time-of-flight mass spectrometry was used t...

The reaction of molecular chlorine with polycrystalline molybdenum was studied by the modulated molecular beam mass spectrometry technique. Between 300 and 900 K, MoCl2 was produced with a reaction probability of about 10−3 on a chlorine-covered surface. At higher temperatures, the chlorine coverage decreased because of three direct reactions on th...

The oxidation of Zircaloy by steam and by steam-hydrogen mixtures was studied experimentally from 1100–1600°C using the continuously-recording gravimetric method. Parabolic kinetics based on oxygen diffusion in the solid were followed at low temperatures but steam starvation, nonisothermal behavior, and finite medium effects dominated at temperatur...

Cluster formation is traditionally observed by mass spectrometry, which has the disadvantage that the detection sensitivity often decreases with increasing mass. Alternatively, one may collect the clusters onto an atomically flat substrate and identify them by scanning tunneling microscopy (STM). Both techniques were used here. For the first techni...

The solubility of hydrogen in α- and β-Zircaloy was measured by the continuously-recording gravimetric method in the temperature range 950–1400 °C. Hydrogen partial pressures varied from 0.2 to 1 atm and the equilibrium H/Zr ratios ranged from 0.1 to 1. Oxygen contents of the metal up to 33 at % were investigated. Sievert's law was obeyed under all...

Thin films of β‐SiC were grown on Si substrates by excimer laser pulse ablation of bulk SiC. The films were examined by Auger electron, x‐ray, and photoelectron spectroscopies and laser ionization mass analysis techniques. The film was smooth as monitored by scanning electron microscopy. Scanning electron and scanning tunneling microscopy (STM) sho...

The crystalline-amorphous transformation of the intermetallic precipitates Zr[sub 2] (Fe,Ni) and Zr(Cr,Fe)[sub 2] in Zircaloy under irradiation is studied. Experiments show that the dose-to-amorphization increases exponentially with temperature and decreases with dose rate. A model for the transformation is proposed that accounts for these observat...

A chemical etching technique has been developed to measure concentration profiles of neutron-induced activities in specimens of UO2 fuel. Tests on material with an average grain diameter of about 20 μm indicate that the etchant removes planar layers with relatively minor selective attack at grain boundaries. The maximum deviation of peaks and troug...

Data on the leaching of U and Th from monazite are analyzed by a solid-state, movingboundary diffusion model with a surface reaction boundary condition. Nonstoichiometric leaching of the actinide elements with respect to each other and to the matrix is due to different transport properties of the former in the near-surface layers of the mineral and...

The solid-state diffusion model of actinide leaching developed in Part II of this series is applied to leaching of radiogenic daughters of the actinide decay chains. For an untreated natural monazite, the direct leaching component of 228Th release is larger than that for 232Th because of enhanced solid-state mobility for 228Th provided by 228Ra-rec...

Interaction of three natural monazite specimens with a bicarbonate-carbonate solution was investigated for times up to 6.8 years. Dissolution was observed to be incongruent with respect to 238 U and 232 Th as well as their radiogenic daughters 234 U, 230 Th, and 228 Th. Leaching was divided into a very rapid initial stage lasting a few hours and a...

The solubility of hydrogen in crystalline silicon from 1363–1473 K and from 1.7–9.2 atm has been measured using the method of high‐temperature, high‐pressure infusion followed by high‐temperature vacuum outgassing with mass‐spectrometric detection. The measured solubilities were in the range 1–5×10¹⁶ atoms/cm³ and exhibited a...

Thin films of (Beta) - SiC were grown on Si substrates by excimer laser pulse ablation of bulk SiC. The films were examined by Auger electron, x ray, and photoelectron spectroscopies. The film was smooth as monitored by scanning electron microscopy. Scanning electron and scanning tunneling microscopy showed inclusions in the deposited SiC film and...

The modulated molecular beam technique with in situ mass spectrometric phase sensitive detection was used to study the kinetics of atomic hydrogen reduction of hyperstoichiometric uranium dioxide. The atomic hydrogen portion of an incident mixed-collisionless H/H{sub 2} beam chemisorbed onto urania surface with a sticking probability of 0.7 {plus m...

Radioisotope measurements on ancient crystalline monazite, (Ce, Th)PO 4 , show that laboratory annealing of stored α-recoil damage caused a 10-fold decrease in the dissolution rate of structurally-incorporated 232 Th and greater reduction in the leachability of 228 Th accompanied by a profound reversal in the importance of four mechanisms responsib...

Laser ionization time-of-flight mass analysis (LIMA) used pulses (5ns) of a frequency- quadrupled Nd-YAG laser (266 nm) focused onto spots of 4–100 μm diameter to ablate material, and a reflectron time of flight tube to mass-analyze the plume. The observed mass spectra for Si, Pt, SiC, and UO 2 varied in the distribution of ablation products among...

Recent experimental and theoretical developments concerning the interaction of laser light with refractory solids are reviewed, with emphasis on long, low-power density pulses. Compared to short, high-power density irradiation, long pulses produce principally thermally-driven evaporation which can be related to the thermochemical properties of the...

The modulated molecular beam technique with in situ mass spectrometric phase sensitive detection was used to study the kinetics of atomic hydrogen reduction of hyperstoichiometric uranium dioxide. The atomic hydrogen portion of an incident mixed-collisionless H/Hâ beam chemisorbed onto urania surface with a sticking probability of 0.7 {plus minus}...

Description Temporarily out of stock; will ship by July 2011. This two-volume set is a collection of research results of radiation effects in structural materials and nuclear fuels. Complex topics are covered in detail with supporting evidence. Volume I — 50 papers on: microstructures; gas effects; radiation-induced segregation or phase changes; mi...

The quality of superconducting thin films evaporated from YBa2Cu3O7 targets was improved using a long pulse (ms) Nd-glass laser with 50 J pulse energy. The film produced on SrTiO3, held at 690 C, and post annealed at 880 C for about three hours began the transition to superconductivity at 85 K and had zero resistance at 79 K. The observed variation...

A technique was developed for measurement of the solubility and release kinetics of hydrogen in refractory nonmetals. Uranium dioxide specimens were saturated with hydrogen in a high-pressure furnace at pressures between 5 and 30 atm and temperatures from 1200 to 1600°C. Release was accomplished in a separate vacuum extraction apparatus in which th...

Deposition of superconducting thin films from YBa 2 Cu 3 O 7 targets using a long‐pulse (ms) Nd‐glass laser with 50 J/pulse energy has been demonstrated. The deposition rate was approximately 100 nm/pulse and the film stoichiometry was close to that of the target. Scanning electron microscopy revealed spherical inclusions in the film. Scanning tunn...

The kinetics of the gas-solid reaction of crystalline silicon, Si(111), and atomic hydrogen (thermally generated in a tungsten oven) have been studied by the modulated molecular beam mass spectrometric technique. Volatile silicon tetrahydride, SiH4, and recombined molecular hydrogen were the only reaction products detected from ambient temperature...

The nature of the vapor produced by pulse surface heating of UO 2 and several other materials was investigated using normal‐mode laser pulses with peak power densities between 10⁴ and 10⁶ W/cm². Maximum surface temperatures measured by optical pyrometry ranged from 1900 to 4200 K. At temperatures below ∼2400 K for U...