Bridge pins were used in the hanger assemblies for some multi-span steel bridges built prior to the 1980's, and are sometimes considered fracture critical elements of a bridge. During a test on a bridge conducted by the Federal Highway Administration (FHWA), ultrasonic field inspection results indicated that at least two pins contained cracks. Several pins were removed and selected for further examination. This provided an excellent opportunity to learn more about these pins and the application of x-ray systems at Lawrence Livermore National Laboratory (LLNL), as well as to learn more about the application of different detectors recently obtained by LLNL. Digital radiographs and computed tomography (CT) were used to characterize the bridge pins, using a LINAC x-ray source with a 9-MV bremsstrahlung spectrum. We will describe the performance of two different digital radiographic detectors. One is a detector system frequently used at LLNL consisting of a scintillator glass optically coupled to a CCD camera. The other detector is a new amorphous silicon detector recently acquired by LLNL.

Recently, the technique of using a nsec pulse to preform and ionize the plasma followed by a psec pulse to heat the plasma has enabled low-Z neon-like and nickel-like ions to laser driven by small lasers with only ten joules of energy. In this work we model recent experiments done using the COMET laser at LLNL to illuminate 1 cm long slab targets of Ti with a 4.8 J, 800 ps prepulse followed 1.6 nsec later by a 6 J, 1 psec drive pulse. The LASNEX code is used to calculate the hydrodynamic evolution of the plasma and provide the temperatures and densities to the XRASER code, which then does the kinetics calculations to determine the gain. The temporal and spatial evolution of the plasma is studied both with and without radiation transport included for the 3d and 3s {_} 2p Ne-like Ti resonance lines. Large regions with gains greater than 80 cm{sup {minus}1} are predicted for the 3p {sup 1}S{sub 0} {_} 3s {sup 1}P{sub 1} Ne-like Ti laser line at 326 {angstrom}. Given the large gain and large gradients in these plasmas, we do propagation calculations including refraction to understand which regions have the right combination of high …

Understanding physical processes accompanying ablation is necessary for optimal use of ultrashort laser pulse (USLP) material processing. We describe the implementation of self-consistent electromagnetic propagation -energy absorption in our numerical models and estimate effect on material removal of energy, pulselength and prepulses.

The Lawrence Livermore National Laboratory Flash X-ray (FXR) machine is being upgraded to produce two pulses. A very fast imaging system has been developed to characterize the electron beam diameter and shape. The system consists of a kapton target insertion mechanism and a framing camera. It has a fast gated imaging tube (500 ps) and CCD subsystem to capture and send the image to the control room. The beam diameter data provides insight on mechanisms that effect the x-ray spot size. These colorful beam measurements will be compared with our other diagnostics to form a more complete picture of beam behavior. A demonstration will be described where the image data was used to design a collimator to improve x-ray beam performance.

The recent development of miniature inductive adders has made it feasible to design programmable, high-repetition-rate pulsers with a substantially higher voltage than is possible using a conventional field-effect transistor architecture. Prototype pulsers using the new technology are being developed as part of a series of experiments at LLNL to test the concept of a recirculating induction accelerator. Preliminary numerical work is reported here to determine what effects the higher-voltage pulsers would have on the beam quality of the LLNL small recirculator.

The National Low Level Waste Management Program at the Idaho National Engineering and Environmental Laboratory has published a report containing key information about selected radionuclides that are most likely to contribute significantly to the radiation exposures estimated from a performance assessment of a low-level radioactive waste (LLW) disposal facility. The information includes physical and chemical characteristics, production means, waste forms, behavior of the radionuclide in soils, plants, groundwater, and air, and biological effects in animals and humans. The radionuclides included in this study comprise all of the nuclides specifically listed in 10CFR61.55, Tables 1 and 2, 3 H, 14 C, 59 Ni, 60 Co, 63 Ni, 90 Sr, 94 Nb, 99 Tc, 129 I, 137 Cs, 241 Pu, and 242 Cm. Other key radionuclides addressed in the report include 237 Np, 238 U, 239 Pu, and 241 Am. This paper summarizes key information contained within this report.

Mixed radioactive and hazardous wastes were buried at the Department of Energy's Idaho National Engineering and Environmental Laboratory (INEEL) Subsurface Disposal Area from 1952 to 1969. To begin the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) remediation process for the Subsurface Disposal Area, the Environmental Protection Agency (EPA) added the INEEL to its National Priorities List in 1989. DOE's Office of Environmental Restoration is planning several CERCLA treatability studies of remedial technologies that will be evaluated for potential remediation of the buried waste in the Subsurface Disposal Area. This paper discusses the in situ treatability studies that will be performed, including in situ vitrification, in situ grouting, and in situ thermal desorption. The in situ treatability studies will be conducted on simulated and actual buried wastes at the INEEL in 1999 and 2000. Results from the treatability studies will provide substantial information on the feasibility, implementability, and cost of applying these technologies to the INEEL Subsurface Disposal Area. In addition, much of the treatability study data will be applicable to buried waste site remediation efforts across the DOE complex.

There have been many recent developments in separation methods used for treating radioactive and non-radioactive metal bearing liquid wastes. These methods have included adsorption, ion exchange, solvent extraction and other chemical and physical techniques. To date very few, if any, of these processes can provide a low cost and environmentally benign solution. Recent research into the use of magnetite for wastewater treatment indicates the potential for magnetite both cost and environment drivers. A brief review of recent work in using magnetite as a sorbent is presented as well as recent work performed in our laboratory using supported magnetite in the presence of an external magnetic field. The application to groundwater and other aqueous waste streams is discussed. Recent research has focused on supporting magnetite in an economical (as compared to the magnetic polymine-epichlorohydrine resin) and inert (non-reactive, chemically or otherwise) environment that promotes both adsorption and satisfactory flow characteristics.

The internal space for a molecule, atom, or other n-body system can be conveniently parameterized by 3n - 9 kinematic angles and three hematic invariants. For a fixed set of kinematic invariants, the kinematic angles parameterize a subspace, called a kinematic orbit, of the n-body internal space. Building on an earlier analysis of the three- and four-body problems, we derive the form of these kinematic orbits (that is, their topology) for the general n-body problem. The case n = 5 is studied in detail, along with the previously studied cases n = 3,4.

The Department of Energy - Environmental Management (DOE-EM) National Spent Nuclear Fuel Program (NSNFP) is charged with the disposition of legacy spent nuclear fuel (SNF). While direct repository disposal of the SNF is the preferred disposition option, some DOE SNF may need treatment to meet acceptance criteria at various disposition sites. The treatments may range from electrometallurgical treatment (EMT) and chemical dissolution to engineering controls. As a planning basis, a need is assumed for a treatment process, either as a primary or backup technology, that is compatible with, and cost-effective for, this portion of the DOE-EM inventory. The current planning option for treating this SNF, pending completion of development work and National Environmental Policy Act (NEPA) analysis, is the EMT process under development by Argonne National Laboratory - West (ANL-W). A decision on the deployment of the EMT is pending completion of an engineering scale demonstration currently in progress at ANL-W. For this study, a set of questions was developed for the EMT process for fuels at several locations. The set of questions addresses all issues associated with design, construction, and operation of a production facility. A matrix table was developed to determine questions applicable to various fuel treatment options. …

A fast stripline beam kicker is used to dynamically switch a high current electron beam between two beamlines. The transverse dipole impedance of a stripline beam kicker has been previously determined from a simple transmission line model of the structure. This model did not include effects due to the long axial slots along the structure as well as the cavities and coaxial feed transition sections at the ends of the structure. 3-D time domain simulations show that the simple transmission line model underestimates the low frequency dipole beam coupling impedance by about 20% for our structure. In addition, the end cavities and transition sections can exhibit dipole impedances not included in the transmission line model. For high current beams, these additional dipole coupling terms can provide additional beam-induced steering effects not included in the transmission line model of the structure.

During the past fifteen years there has been a steady increase in the demand for radioisotopes in nuclear medicine and a corresponding decline in the number of reactors within the U.S. capable of producing them. The Advanced Test Reactor (ATR) is the largest operating test reactor in the U.S., but its isotope production capabilities have been limited by the lack of an installed isotope shuttle irradiation system. A concept for a simple "low cost" shuttle irradiation facility for ATR has been developed. Cost were reduced (in comparison to previous ATR designs) by using a shielded trough of water installed in an occupiable cubicle as a shielding and contamination control barrier for the send and receive station. This shielding concept also allows all control valves to be operated by hand and thus the need for an automatic control system was eliminated. It was determined that 4-5 ft of water would be adequate to shield the isotopes of interest while shuttles are transferred to a small carrier. An additional feature of the current design is a non-isolatable by-pass line, which provides a minimum coolant flow to the test region regardless of which control valves are opened or closed. This by-pass line allows …

The potential of a B-spline collocation method for numerically solving the equations of fluid dynamics is discussed. It is known that B-splines can resolve complex curves with drastically fewer data than can their standard shape function counterparts. This feature promises to allow much faster numerical simulations of fluid flow than standard finite volume/finite element methods without sacrificing accuracy. An example channel flow problem is solved using the method.

The privatization efforts at the U.S. Department of Energy's Hanford Nuclear Reservation have been very successful primarily due to a disciplined process for project selection and execution. Early in the development of Privatization at Hanford, the Department of Energy determined that a disciplined alternatives generation and analysis (AGA) process would furnish the candidate projects with the best probability for success. Many factors had to be considered in the selection of projects. Westinghouse Hanford Company was assigned to develop this process and facilitate the selection of the first round of candidate privatization projects. Team members for the AGA process were assembled from all concerned organizations and skill groups. Among the selection criteria were legal, financial and technical considerations which had to be weighed.

An important need while using robots or remotely operated equipment is the ability for the operator or an observer to easily and accurately perceive the operating environment. A classic problem in providing a complete representation of a work area is sensory overload or excessive complexity in the human�machine interface. In addition, remote operations often benefit from depth perception capability while viewing or manipulating objects. Thus, there is an on going effort within the robotic field to develop simplified telepresence interfaces. The Department of Energy�s Idaho National Engineering and Environmental Laboratory (INEEL) has been researching methods to generalize a human-machine interface for telepresence applications. Initial telepresence research conducted at the INEEL developed and implemented a concept called the VirtualwindoW. This system minimized the complexity of remote stereo viewing controls and provided the operator the �feel� of viewing the environment, including depth perception, in a natural setting. The VirtualwindoW has shown that the human-machine interface can be simplified while increasing operator performance. This paper deals with the continuing research and development of the VirtualwindoW to provide a generalized, reconfigurable system that easily utilizes commercially available components. The original system has now been expanded to include support for zoom lenses, camera blocks, wireless …

This paper presents our assessment of field experience related to pressurized water reactor (PWR) primary system leaks in terms of their number and rates, how aging affects frequency of leak events, the safety significance of such leaks, industry efforts to reduce leaks, and effectiveness of current leak detection systems. We have reviewed the licensee event reports to identify the events that took place during 1985 to the third quarter of 1996, and reviewed related technical literature and visited PWR plants to analyze these events. Our assessment shows that USNRC licensees have taken effective actions to reduce the number of leak events. One main reason for this decreasing trend was the elimination or reportable leakages from valve stem packing after 1991. Our review of leak events related to vibratory fatigue reveals a statistically significant decreasing trend with age (years of operation), but not in calendar time. Our assessment of worldwide data on leakage caused by thermal fatigue cracking is that the fatigue of aging piping is a safety significant issue. Our review of leak events has identified several susceptible sites in piping having high safety significance; but the inspection of some of these sites is not required by the ASME Code. …

Accelerated aging research on samples of composite material and candidate ultraviolet (UV) protective coatings is determining the effects of six environmental factors on material durability. Candidate fastener materials are being evaluated to determine corrosion rates and crevice corrosion effects at load-bearing joints. This work supports field testing of a 30-ft long, 18-ft wide polymer matrix composite (PMC) bridge at the Idaho National Engineering and Environmental Laboratory (INEEL). Durability results and sensor data from tests with live loads provide information required for determining the cost/benefit measures to use in life-cycle planning, determining a maintenance strategy, establishing applicable inspection techniques, and establishing guidelines, standards, and acceptance criteria for PMC bridges for use in the transportation infrastructure.

X-ray computed tomography (CT) imaging techniques in nondestructive evaluation (NDE) have seen increasing use in an array of industrial, environmental, military, and medical applications (Goebbels, et al., 1999). A brief overview and three diverse application studies of x-ray CT at the Lawrence Livermore National Laboratory (LLNL) will be discussed. (1) Bridge pins are fracture critical elements for some multi-span steel bridges. Recently, pins were removed from their hanger pin assemblies. These pins were selected for further examination by laboratory NDE techniques. High-energy x-ray radiography and CT were used to characterize these pins. (2) Cast light metals, aluminum and magnesium, are being used in an ever increasing number of applications to reduce automobile weight for improved gas mileage and lower emissions. After mechanical testing, the damage in notched Al-tensile test specimens was first determined using CT and subsequently by metallography analysis intended to benchmark the CT technique. (3) A computational approach to normal joint kinematics and prosthetic joint analysis offers an opportunity to evaluate and improve prosthetic joint replacements before they are manufactured or surgically implanted. Computed tomography data are combined with computational analysis to reveal regions where the joint design can be improved for better performance and longevity, prior to …

We present a new technique for the mechanical characterization of microactuators and apply it to shape memory alloy (SMA) thin films. A test instrument was designed which utilizes a spring-loaded transducer to measure displacements with resolution of 1.5 mm and forces with resolution of 0.2 mN. Employing an out- of-plane loading method for SMA thin films, strain resolution of 30 me and stress resolution of 2.5 MPa were achieved. Four mm long, 2 {micro}m thick NiTiCu ligaments suspended across open windows were bulk micromachined for use in the out-of-plane stress and strain measurements. Static analysis showed that 63% of the applied strain was recovered while ligaments were subjected to tensile stresses of 870 MPa. This corresponds to 280 mm of actual displacement against a load of 52 mN. Fatigue analysis of the ligaments showed 33% degradation in recoverable strain (from 0.3% to 0.2%) with 2 {+-} 10{sup 4} cycles for an initial strain of 2.8%.

We describe a method for computing linear observer statistics for maximum a posteriori (MAP) reconstructions of PET images. The method is based on a theoretical approximation for the mean and covariance of MAP reconstructions. In particular, we derive here a closed form for the channelized Hotelling observer (CHO) statistic applied to 2D MAP images. We show reasonably good correspondence between these theoretical results and Monte Carlo studies. The accuracy and low computational cost of the approximation allow us to analyze the observer performance over a wide range of operating conditions and parameter settings for the MAP reconstruction algorithm.

The authors report a study of the residual stresses and residual stress relaxation in Mo/Si and Mo{sub 2}C/Si EUV multilayers. The multilayers were fabricated by magnetron sputter deposition, and stress measured using the substrate curvature laser scanning technique. It was found that Mo{sub 2}C/Si multilayers exhibit higher compressive stress than Mo/Si of comparable period and layer thickness ratio. the multilayers sputtered at 0.5 mT Ar pressure have higher compressive stress than those sputtered at 2 mT Ar pressure. The data indicate that the residual stresses in the multilayers are primarily determined by the Si layers. Annealing of the multilayers at a heating rate of 5 C/minute as well as at a fixed temperature (isothermal) results in a reduction of the compressive stresses. Near zero stress is achieved after annealing at 300 C. The time dependence of the residual stress decrease during isothermal annealing was found to fit best to a bimolecular viscous flow model of defect annihilation in the amorphous Si layers. The relationships between the effects of annealing on the multilayer microstructure and the observed stress reduction are discussed.

This paper describes the program to stabilize nuclear materials, consistent with the Department of Energy Office of Environmental Management (EM) plan, Accelerating Cleanup: Paths to Closure. The program is managed by the Plutonium Stabilization and Disposition Focus Area, which defines and manages technology development programs to stabilize nuclear materials and assure their subsequent safe storage and final disposition. The scope of the Plutonium Stabilization and Disposition Focus Area (PFA) activities includes non-weapons plutonium materials, special isotopes, and other fissile materials. The PFA provides solutions to site-specific and complex wide technology issues associated with plutonium remediation, stabilization, and preparation for disposition. Our paper describes an important programmatic function of the Department of Energy nuclear materials stabilization program, including the tie-in of policy to research needs and funding for the nuclear materials disposition area. The PFA uses a rigorous systems engineering determination of technology needs and gaps, under the guidance of a Technical Advisory Panel, consisting of complex-wide experts. The Research and Development planning provides an example for other waste areas and should be of interest to Research and Development managers. The materials disposition maps developed by the PFA and described in this paper provide an evaluation of research needs, data gaps …

The thermal degradation of a commercial, stabilized, unfilled neoprene (chloroprene) rubber was investigated at temperatures up to 140 C. The degradation of this material is dominated by oxidation rather than dehydrochlorination. Important heterogeneous oxidation effects were observed at the various temperatures investigated using infrared micro-spectroscopy and modulus profiling. Intensive degradation-related spectral changes in the IR occurred in the conjugated carbonyl and hydroxyl regions. Quantitative analysis revealed some differences in the development of the IR oxidation profiles, particularly towards the sample surface. These chemical degradation profiles were compared with modulus profiles (mechanical properties). It is concluded that the profile development is fundamentally described by a diffusion-limited autoxidation mechanism. Oxygen consumption measurements showed that the oxidation rates display non-Arrhenius behavior (curvature) at low temperatures. The current results, when compared to those of a previously studied, clay-filled commercial neoprene formulation, indicate that the clay filler acts as an antioxidant, but only at low temperatures.

The use of electron beam accelerators in advanced X-ray radiography requires that the beam be focused to a very small spot size on a metallic bremsstrahlung converter target. The energy deposition of the beam into a small volume of target material rapidly converts the target into a high-density plasma. The space-charge density of the focused beam sets up a strong electric field at the surface of the grounded target, which then accelerates ions of target plasma and lighter contaminants into the beam. These backstreaming ions form a long channel which partially neutralizes the space charge of the beam, disrupting the beam focus and degrading the radiographic performance. One solution to this problem is to confine the backstreaming ions in a short channel with a self-biased inductive trap. Such a trap has been proposed for testing on the ETA-II accelerator. They present numerical simulations which show the effect of the high trapped-ion charge density on the beam spot size and emittance.