Publications

A semiconductor laser coupled to an external cavity is investigated using a composite-cavity mode approach. Strong frequency hopping for small cavity length changes is obtained, indicating instability of the laser operation against cavity lengths fluctuations.

Results have been obtained on hydrogen dose, dose rate and substrate temperature dependence for hydrogen-assisted thermal donor formation in Czochralski Si. The study combined ion implantation and hydrogen plasma exposure to inject hydrogen, and infrared absorption and spreading resistance probe measurements to detect the donors. Near surface donor concentrations increase with dose and temperature between 350 and 400°C. The penetration depth for thermal donor formation exhibits a $\sqrt{t}$ dependence, and a thermal activation energy of 1.5 ± 0.2 eV.

Adhesion between diamond films synthesized by a CVD method and tungsten has been investigated by a scratch and pull testing methods. Diamond films have been deposited at temperatures from 1173 to 1323 K with a growth rate ranging from 0.2 to 0.45 μm/hour. The films are highly crystalline and are dominated by (100) faces at low temperatures, changing to (111) at higher temperatures. Grain size and residual stress in the films increases with increasing deposition temperature. X-ray diffraction shows the expected diamond diffraction peaks plus peaks attributed to WC and W₂C. Raman spectroscopy shows a sharp diamond band for all of the films, with a small broad peak, attributed to amorphous carbon. There is no distinct correlation between diamond/amorphous carbon intensity with deposition temperature. Scratch adhesion testing shows the expected failure mode for brittle coatings, but can not be quantified because of severe degradation of the diamond stylus tip. Sebastion pull testing shows that the failure mode of the films correlates with deposition temperature, but specific adhesion strength values do not. Efforts are continuing to correlate adhesion strength with deposition and structural parameters of the diamond films.

Rational interpolation is frequently useful for generating functions which have an extended range over an abbreviated domain of definition. A simple technique for continued fraction interpolating function evaluation can easily be modified to obtain the function's derivative. This is a useful technique for developing numerical solutions for certain stiff partial differential equations. 9 refs., 2 figs.

Accomodation of lattice mismatch is investigated for the case of large (ε{lunate}>0.02) mismatch. In particular, the regime where the separation D between misfit dislocations is much less than the strained layer thickness h is considered here. The conventional Matthews-Blakeslee mechanism for creation of misfit dislocations is found to be inadequate for the case of large lattice relaxation owing to interactions amongst the misfit dislocations at the interface. According to St. Venant's principle, the stress fields of the dislocation network are screened beyond a distance D from the dislocation cores. This observation has several consequences, including large densities of threading dislocations and the "melting" of moderately relaxed heterointerfaces at conventional semiconductor growth temperatures. A number of experimental observations may be explained via these models. © 1991.

This 1990 report contains monitoring data from routine radiological and nonradiological environmental surveillance activities. Summaries of significant environmental compliance programs in progress such as National Environmental Policy Act (NEPA) documentation, environmental permits, environmental restoration, and various waste management programs for Sandia National Laboratories in Albuquerque (SNL, Albuquerque) are included. The maximum offsite dose impact was calculated to be 2.0 {times} 10{sup {minus}3} mrem. The total 50-mile population received a collective dose of 0.82 person-rem during 1990 from SNL, Albuquerque, operations. As in the previous year, the 1990 SNL operations had no adverse impact on the general public or on the environment. This report is prepared for the US Department of Energy in compliance with DOE Order 5400.1. 97 refs., 30 figs., 137 tabs.

There is no routine radioactive emission from Sandia National Laboratories, Tonopah Test Range (SNL, TTR). However, based on the types of test activities such as air drops, gun firings, ground- launched rockets, air-launched rockets, and other explosive tests, possibilities exist that small amounts of depleted uranium (DU) (as part of weapon components) may be released to the air or to the ground because of unusual circumstances (failures) during testing. Four major monitoring programs were used in 1990 to assess radiological impact on the public. The EPA Air Surveillance Network (ASN) found that the only gamma ({gamma}) emitting radionuclide on the prefilters was beryllium-7 ({sup 7}Be), a naturally-occurring spallation product formed by the interaction of cosmic radiation with atmospheric oxygen and nitrogen. The weighted average results were consistent with the area background concentrations. The EPA Thermoluminescent Dosimetry (TLD) Network and Pressurized Ion Chamber (PIC) reported normal results. In the EPA Long-Term Hydrological Monitoring Program (LTHMP), analytical results for tritium ({sup 3}H) in well water were reported and were well below DOE-derived concentration guides (DCGs). In the Reynolds Electrical and Engineering Company (REECo) Drinking Water Sampling Program, analytical results for {sup 3}H, gross alpha ({alpha}), beta ({beta}), and {gamma} scan, strontium-90 ({sup 90}Sr) and plutonium-239 ({sup 239}Pu) were within the EPA's primary drinking water standards. 29 refs., 5 figs., 15 tabs.

PC-1D is a software package for personal computers that uses finite-element analysis to solve the fully-coupled two-carrier semiconductor transport equations in one dimension. This program is particularly useful for analyzing the performance of optoelectronic devices such as solar cells, but can be applied to any bipolar device whose carrier flows are primarily one-dimensional. This User's Guide provides the information necessary to install PC-1D, define a problem for solution, solve the problem, and examine the results. Example problems are presented which illustrate these steps. The physical models and numerical methods utilized are presented in detail. This document supports version 3.1 of PC-1D, which incorporates faster numerical algorithms with better convergence properties than previous versions of the program. 51 refs., 17 figs., 5 tabs.

The disappearance of isocyanate groups in 20 lb/ft{sup 3} rigid polyurethane encapsulating foam (44402-20) was monitored by FTIR spectroscopy leading to an activation energy of 4 kcal/mole. The disappearance of isocyanates can be due to either crosslinking reactions or gas production. Attempting to separate these two reaction paths, we measured the gel time and volume change during cure leading to activation energies of 5 and 6 kcal/mole for the crosslinking and foaming mechanisms respectively. 3 refs., 16 figs.

This study examined the feasibility of the Safety Engineering Reactor for Accident Phenomenology (SERAPH), a research reactor with the capability to perform a wide array of safety experiments important in the design of commercial nuclear reactors. The study proceeded in two phases. In Phase 1, the experimental needs were examined and a wide-ranging survey of many fuel/coolant options for the SERAPH driver reactor was done. In Phase 2, the most promising candidates identified in Phase 1 were studied in more detail. A reactor with heavy-water coolant, BeO-PuO{sub 2} fuel matrix, and a standard pin geometry was found to have the required experiment capabilities while using relatively current technology. A reactor with helium coolant, BeO-PuO{sub 2} fuel matrix, and a unique geometrical configuration was found to have significantly higher capabilities but with greater technical risk. 5 refs., 34 figs., 36 tabs.

This report describes the results of high temperature steam testing and submergence testing of 12 different cable products that are representative of typical cables used inside containments of US light water reactors. Both tests were performed after the cables were exposed to simultaneous thermal and radiation aging, followed by exposure to loss-of-coolant accident simulations. The results of the high temperature steam test indicate the approximate thermal failure thresholds for each cable type. The results of submergence test indicate that a number of cable types can withstand submergence at elevated temperature, even after exposure to a loss-of-coolant accident simulation. 4 refs., 6 figs., 9 tabs.

This work documents a comparison of sensitivity and uncertainty analysis techniques that are likely to be used in support of repository performance assessments to determine compliance with the Nuclear Regulatory Commission (NRC) and the Environmental Protection Agency (EPA) regulations for high-level radioactive waste (HLW) repositories. A variety of parameter estimation and sensitivity analysis techniques were applied to a model of the Avra Valley aquifer, Arizona. Two approaches to sensitivity analyses were used, statistical and deterministic; these were applied to evaluate the sensitivity of the ground water travel time to changes in transmissivity. The effect of different boundary conditions on the calculated sensitivity derivatives was also evaluated. Parameter estimates and estimation errors were obtained via geostatistical and inverse techniques. The throughput'' of the kriging techniques suggests that the mean estimates derived from these techniques are frequently off the mark'' or inconsistent with the conceptual model. With no screening of the input parameter estimates for realism, non- conservative travel time estimates were obtained. The differential analysis sensitivity technique is shown to be dependent on the choice of design point, providing only a local measure of the sensitivity. The statistical approach to sensitivity identifies parameters which are both sensitive and uncertain, i.e., it shows when the uncertainty in a model parameter is important. Sensitivity estimates are also shown to be dependent on the choice of boundary conditions used. 92 refs., 55 figs., 13 tabs.

This report describes an architecture for compiling and representing electronic documents in a framework which accommodates knowledge about how the documents are composed, organized, and correlated. A general concept of referenceability is employed. While the concept is relevant to a wide range of application areas, it is described in familiar terms of an electronic document comprised of related textual information and graphics. The concept is applicable to all classes of objects which, together with their references, constitute the electronic document. The documents may themselves contain references to other documents, as well as to constituent object classes such as textual components, figures, footnotes, subject indexes, and the like. The objects and references can be dynamically combined according to a total logical structure representable within a window environment. The framework supports automatic resolution of references and display of related document objects through intercommunicating windows which constitute a relevant user view of a document. 6 refs., 9 figs.

This document describes the NEFTRAN-S computer code and is intended to provide the reader with enough information to use the code. NEFTRAN-S was developed for the United States Environmental Protection Agency for the assessment of ground-water flow and radionuclide transport from radioactive waste disposal in geologic formations. NEFTRAN-S is a successor to the NEFTRAN code. The code was developed in conjunction with NEFTRAN-2, which was developed recently for the United States Nuclear Regulatory Commission. As a result, some of the features contained in NEFTRAN-2 have been included in NEFTRAN-S. In particular, NEFTRAN-S includes an exponential-leach-rate source, decoupled time steps for source and transport, and an option for inputting pore-water velocities. Features unique to NEFTRAN-S include a user-friendly format for use on personal computers and coupling with statistical sampling and analysis using the SUNS software shell. This document was written to provide a comprehensive discussion of the NEFTRAN-S code including its history, the theory, its use and examples of possible applications. Minimal reference to previous documents is intended. 25 refs., 132 figs., 30 tabs.

The default format for the storage of x,y data for use with the UFO code is described. The format assumes that the data stored in a file is a matrix of values; two columns of this matrix are selected to define a function of the form y = f(x). This format is specifically designed to allow for easy importation of data obtained from other sources, or easy entry of data using a text editor, with a minimum of reformatting. This format is flexible and extensible through the use of inline directives stored in the optional header of the file. A special extension of the format implements encoded data which significantly reduces the storage required as compared wth the unencoded form. UFO supports several extensions to the file specification that implement execute-time operations, such as, transformation of the x and/or y values, selection of specific columns of the matrix for association with the x and y values, input of data directly from other formats (e.g., DAMP and PFF), and a simple type of library-structured file format. Several examples of the use of the format are given.

This report documents the findings of an experimental investigation of the effects of thermal aging on the fire damageability of electric cables. Two popular types of nuclear qualified cables were evaluated. For each cable type, both unaged (i.e., new off the reel) and thermally aged samples were exposed to steady-state elevated temperature environments until conductor-to-conductor electrical shorting was observed. Plots of the time to electrical failure versus the exposure temperature were developed and thermal damage thresholds were determined. For one cable type, the thermally aged cables were less vulnerable to thermal damage than were the unaged samples as demonstrated by an increase in the thermal damage threshold for the aged samples, and an extended survival time at exposure temperatures above the damage threshold for aged samples compared to unaged samples. For the second cable, the threshold of thermal damage was lowered somewhat by the aging process, an indication of an increased vulnerability to thermal damage due to aging. However, for the higher temperature exposures, no statistical difference between the damage times for aged and unaged cable samples was noted. For both cable types, the changes in the thermal damage threshold observed were not considered significant in terms of fire risk. 4 refs., 9 figs., 8 tabs.

The thrust of this progress report deals with the significant advances we have made in the past few months toward optimal radiating efficiency and optimal directionality from antenna arrays that fit inside a 5.5 in.-OD tool. The reasons spawning this development effort on antennas are the many uses for underground radar systems that can be built around such high-performance antennas. Targets of interest include large man-made voids, natural voids in strata, fractures zones in hard rock, edges and internal faults in salts domes and glaciers, etc. Recent progress includes observation of the radiation patterns of several dipole arrays which we designed to fit within a 5.5-inch OD borehole tool and to radiate efficiently at wavelengths in the band from 0.4 meter to 2 meters with optimal directionality. Front-to-back ratios of 15 dB are consistently observed in the horizontal plane of these arrays. These antennas are observed to radiate with high efficiencies, less than 1 dB loss, into air at 1.3 meter wavelength. 18 figs.

This report describes the finite difference computer code ZEPHYR3D, which is designed to solve three-dimensional, transient incompressible flow problems. ZEPHYR3D includes an energy equation that allows coupled thermal/fluid problems to be solved with the limits of the Boussinesq approximation. It also includes an implementation of the Smagorinsky subgrid scale turbulence model, which allows ZEPHYR3D to perform large eddy simulation of turbulent flows. This report includes the mathematical and numerical basis for ZEPHYR3D, a user's guide, and several example/benchmark problems. These problems include flow over a backward-facing step, free convection in an enclosure, and the collapse of a mixed region in a stratified environment. 22 refs., 32 figs., 2 tabs.

Early in 1990, J. A. Wilder, Supervisor of Sandia National Laboratories (SNLA), Division 2565 requested that a meeting of the scientists and engineers responsible for developing and producing switch tubes be set up to discuss in a semi-formal way the science and technology of switch tubes. Programmatic and administrative issues were specifically exempted from the discussions. L. Beavis, Division 7471, SNL and A. Shuman, EG G, Salem were made responsible for organizing a program including the materials and processes of switch tubes. The purpose of the Switch Tube Advanced Technology meeting was to allow personnel from Allied Signal Kansas City Division (AS/KCD); EG G, Salem and Sandia National Laboratories (SNL) to discuss a variety of issues involved in the development and production of switch tubes. It was intended that the formal and informal discussions would allow a better understanding of the production problems by material and process engineers and of the materials and processes by production engineers. This program consisted of formal presentations on May 23 and informal discussions on May 24. The topics chosen for formal presentation were suggested by the people of AS/KCD, EG G, Salem, and SNL involved with the design, development and production of switch tubes. The topics selected were generic. They were not directed to any specific switch tube but rather to all switch tubes in production and development. This document includes summaries of the material presented at the formal presentation on May 23.

The diffraction patterns produced by passing a laser beam through two different types of flowing gases are calculated. The first type of flow consists of periodic lines of gas flowing transverse to the beam's propagation. The second flow is turbulent. The measurable parameters in the diffraction patterns are derived and related to the gas temperature, pressure, velocity, and (in the case of the turbulent flow) to the flow's structure constant. A discussion on using the photorefractive effect to study turbulent flows is also given. In the latter case a method that relates the flow's structure constant to the decay time of the photorefractive crystal is given. 24 refs., 11 figs.

NEFTRAN-S was developed by Sandia National Laboratories for the United States Environmental Protection Agency as part of a program providing technical support for re-promulgation of the standard 40 CFR 191. The code is intended to provide realistic estimates of releases to the environment that could result from disposal of radioactive waste in geologic subsurfaces. One of the geologic environments that will be considered by the EPA in their analyses is unsaturated tuff. The information given in this report is intended to provide a conceptual model for the NEFTRAN-S code for calculations involving a generic site in unsaturated tuff. Information about the phenomena expected to dominate transport and methods for modeling transport in an unsaturated medium are presented. NEFTRAN-S calculations using this conceptual model are compared to TOSPAC calculations for three possible infiltration rates. TOSPAC is the code currently used in performance assessment for an unsaturated tuff site at Yucca Mountain in Nevada. 14 refs., 21 figs., 22 tabs.

The prediction of the chemical alteration of cementitious sealing materials and other cementitious components such as liners in the tuffaceous environment of Yucca Mountain is an essential element in understanding the longevity of these materials. This study uses a chemical equilibrium model to obtain information about the chemical reaction of ground water with concretes. Because concretes, cements, and grouts are metastable assemblages, it is expected that these materials will dissolve, cause secondary precipitations and react with the environment. These reactions will alter the porosity and hydraulic conductivity of the concretes. While the importance of these chemical and conductivity changes has not been completely assessed, this study provides insight into the importance of this chemical alteration.

Large-scale numerical simulations of turbulent flow past bare and appended submarine hulls have been completed with FIDAP versions 4.5 and 5.0. A standard k-ε turbulence model was employed to resolve the near-body flow field for all numerical calculations. Results from these simulations (profile plots and wake surveys of velocity, pressure and turbulent kinetic energy -- hull pressures and shear stresses -- total drag) are compared with data from dynamically similar experiments. The Reynolds number, based upon model length, for both simulation and experiment was 1.2 x 10⁷. Agreement between untuned numerical predictions and experimental data is remarkably close for several model geometries. In other cases, quantitative differences are attributed to the choice of turbulence model and the numerical implementation of boundary conditions.

Radiation measurement have been used for many years to aid in the characterization, handling, and processing of spent nuclear fuel. Applications have included radiation protection, international safeguards, fissile content estimation for reprocessing, and verification of records and calculations. The application of radiation measurements to support the identification of spent fuel assemblies for loading into burnup credit'' transport casks is of interest in the cask development program. A possible alternative to measurements is to use the administrative controls and operational procedures that have been used at reactor sites that make use of burnup credit for spent fuel storage. Experience at such sites needs to be carefully analyzed for its applicability to the misloading and misidentification probabilities. Since there are over 40,000 spent fuel assemblies stored at more than one hundred locations in the US, it is important to determine carefully the necessity for and applicability of any measurement requirement. It is imperative that any measurement system selected be as simple, inexpensive, quick, and non-intrusive as possible. In this report we will consider the information available from measurements of spent fuel that has cooled for more than ten years and examine the possible application of existing instrumentation to verifying the loading of burnup credit casks.

Sandia National Laboratories is conducting long-term aging research on representative samples of nuclear power plant Class 1E cables to determine the suitability of these cables for extended life (beyond the 40-year design basis) and to assess various cable condition monitoring techniques for predicting remaining cable life. This paper provides some results of mechanical measurements that were performed on cross-linked polyolefin (XLPO) cables and cable materials aged at relatively mild, simultaneous thermal and radiation exposure conditions for period of up to nine months. The mechanical measurements discussed in this paper include tensile strength, ultimate elongation, hardness, and compressive modulus. The modulus measurements were performed using an indenter developed at Franklin Research Center under EPRI sponsorship.