In nuclear power plants surveillance tests are required to detect failures in standby safety system components as a means of assuring their availability in case of an accident. However, the performance of surveillance tests at power may have adverse impact on safety as evidenced by the operating experience of the plants. The risk associated with a test includes two different aspects: (1) a positive aspect, i.e., risk contribution detected by the test, that results from the detection of failures which occur between tests and are detected by the test, and (2) a negative aspect, i.e., risk contribution caused by the test, that includes failures and degradations which are caused by the test or are related to the performance of the test. In terms of the two different risk contributions, the risk effectiveness of a test can be simply defined as follows: a test is risk effective if the risk contribution detected by the test is greater than the risk contribution caused by the test; otherwise it is risk ineffective. The methodology presentation will focus on two important kinds of negative test risk impacts, that is, the risk impacts of test-caused transients and equipment wear-out. The evaluation results of the risk …

The ATLAS Electromagnetic (EM) calorimeter (EMCAL) Front End Board (FEB) will be located in custom-designed enclosures solidly connected to the feedtroughs. It is a complex mixed signal board which includes the preamplifier, shaper, switched capacitor array analog memory unit (SCA), analog to digital conversion, serialization of the data and related control logic. It will be described in detail elsewhere in these proceedings. The electromagnetic interference (either pick-up from the on board digital activity, from power supply ripple or from external sources) which affects coherently large groups of channels (coherent noise) is of particular concern in calorimetry and it has been studied in detail.

The first phase of a high current, short bunch length electron beam research facility, the AWA, is near completion at Argonne. At the heart of the facility is a photocathode based electron gun and accelerating sections designed to deliver 20 MeV pulses with up to 100 nC per pulse and with pulse lengths of approximately 15 ps (fw). Using a technique similar to that originated at Argonne's AATF facility, a separate weak probe pulse can be generated and used to diagnose wake effects produced by the intense pulses. Initial planned experiments include studies of plasma wakefields and dielectric wakefield devices, and expect to demonstrate large, useful accelerating gradients (> 100 MeV/m). Later phases of the facility will increase the drive bunch energy to more than 100 MeV to enable acceleration experiments up to the GeV range. Specifications, design details, and commissioning progress are presented.

The purpose of this document is the quantitative definition of objectives, targets, and parameters of the Next-Step device to follow the present RFX experiment; this device is given the name RFXNS. Although developed over five years ago, much of the material distilled into the 1988 RFP tactical plan is useful in establishing the goals and parameters of RFXNS. This earlier plan established tentative parameters of an RFP next step based on: predictions of RFP ignition and commercial-reactor devices; and the assumed successful operation of highly complementary RFP experiments RFX and ZTH/CPRF. Programmatic changes and evolution that have occurred since 1988 strongly impact the role and characteristics of an RFXNS: the Los Alamos ZTH/CPRF project and fusion program was terminated in mid-construction for reasons of MFE cost savings and concept focusing; great progress has been made in launching ITER; and reactor projections for the tokamak have increased in detail and variety, but not in commercial promise and competitiveness. A brief status of and perspective from each of the above three points is necessary before the key issues and their implementation to form the basis of the RFXNS definition are given.

The reactions of forming (U,Zr)C solid solutions from their elemental components or similarly less stable reactants such as UC{sub 2} are strongly exothermic due to the high stability of these solid solutions. A simple approach of utilizing this heat of formation energy to assist the solid solution reaction process is to intimately mix the less stable reactant powders and then pressed them into a compact. The compact is then heated to the ignition temperature of the reaction. The feasibility of this reaction method to synthesize (U,Zr)C solid solutions has been demonstrated in this study. The preliminary results also show that both the initial composition and the heating rate have a significant effect on the nature of the reaction process. As expected the degree of powder mixing was also found to affect the completeness of the reaction.

The pulsed characteristics of gated, stripline configuration microchannel-plate (MCP) detectors used in X-ray framing cameras deployed on laser plasma experiments worldwide are examined in greater detail. The detectors are calibrated using short (20 ps) and long (500 ps) pulse X-ray irradiation and 3--60 ps, deep UV (202 and 213 nm), spatially-smoothed laser irradiation. Two-dimensional unsaturated gain profiles show < 5% percent long-range transverse variations but up to 3 dB/cm drop in gain parallel to the pulse propagation direction. Up to 50% gain enhancements due to voltage reflection from the bends of a meander stripline geometry and from the ends of conventional straight striplines are also observed. Reproducible gate profiles are obtained with either picosecond X-ray or UV bursts and FWHM extracted with 3 picosecond accuracy. A novel single-shot method for measuring local gate propagation speeds using a tilted MCP is also demonstrated. Detailed output versus input studies indicate a linear dynamic range of 300. At higher irradiances, the gradual transition from linear behavior to hard saturation is gathered over a range of 10{sup 5} in irradiation and fitted using a discrete dynode model. Finally, a pump-probe experiment quantifying for the first time long-suspected gain depletion by strong localized irradiation was …

One of the many mechanisms underlying complex behavior in physical systems is competition between different length or time scales, which may arise naturally in the considered system or may be imposed by external influences. The purpose of this paper is the following. By means of three examples the authors will illustrate how identification of relevant length scales can lead to a separation of the system behavior in two regimes. Far from the competition region, it can be described in very simple ways, usually involving a few degrees of freedom. On the contrary, when relevant scales are in conflict, the behavior of the system turns out to be complex, typically chaotic. Therefore, the success of this approach is that it goes straightforwardly to the deep reasons for complex behavior, making amenable to analytical studies all other regimes.

Work in our laboratory has focused on the influence of solvent motion on the rates and energetics of photochemical charge separation in glassy solids. The efficiencies of many nonadiabatic electron transfer reactions involving photochemical electron donors with relatively low excited state energies, such as porphyrins and chlorophylls, are poor in the solid state. Recent work has shown that placing a porphyrin-acceptor system in a glassy solid at low temperature significantly raises the energy of ks ion-pair state. This destabilization can be as much as 0.8 eV relative to the ion pair state energy in a polar liquid. This contrasts sharply with photosynthetic reaction centers, which maintain medium-independent electron transfer rates with relatively small free energies of charge separation. Using this information we have set out to design photochemical systems that produce long-lived radical ion pairs in glassy solids with high quantum efficiency. These systems maintain their efficiency when placed in other glassy matrices, such as polymers. An important consequence of this effort is the design of molecules that minimize the electronic interaction between the oxidized donor and reduced acceptor. This minimization can be attained by careful design of the spacer groups linking the donor and acceptor and by using more …

We discuss a high-density fusion reactor which utilizes a flow-through Z pinch magnetic confinement configuration. Assessment of this reactor system is motivated by simplicity and small unit size (few hundred MWe) and immunity to plasma contamination made possible at high density. The type reactor discussed here would employ a liquid Li vortex as the first wall/blanket to capture fusion neutrons with minimum induced radioactivity and to achieve high wall loading and a power density of 200 w/cm{sup 3}.

Anthropogenic emissions from industrial activity, fossil fuel combustion, and biomass burning are now known to be large enough (relative to natural sources) to perturb the chemistry of vast regions of the troposphere. A goal of the IGAC Global Emissions Inventory Activity (GEIA) is to provide authoritative and reliable emissions inventories on a 1{degree} {times} 1{degree} grid. When combined with atmospheric photochemical models, these high quality emissions inventories may be used to predict the concentrations of major photochemical products. Comparison of model results with measurements of pertinent species allows us to understand whether there are major shortcomings in our understanding of tropospheric photochemistry, the budgets and transport of trace species, and their effects in the atmosphere. Through this activity, we are building the capability to make confident predictions of the future consequences of anthropogenic emissions. This paper compares IGAC recommended emissions inventories for reactive nitrogen and sulfur dioxide to those that have been in use previously. We also present results from the three-dimensional LLNL atmospheric chemistry model that show how emissions of anthropogenic nitrogen oxides might potentially affect tropospheric ozone and OH concentrations and how emissions of anthropogenic sulfur increase sulfate aerosol loadings.

The theory for an elliptic mesh generator is developed for use in the advection step of a 3D ALE algorithm. This mesh generator is derived by a variational principle for an unstrutured 3D grid using finite elements. An arbitrary weight function is introduced which is based on the geometric properties of the existing mesh. These geometric weights should allow for a smooth grid that retains the general shape of the original mesh.

In nuclear power plants surveillance tests are required to detect failures in standby safety system components as a means of assuring their availability in case of an accident. However, the performance of surveillance tests at power may have adverse impact on safety as evidenced by the operating experience of the plants. The risk associated with a test includes two different aspects: (1) a positive aspect, i.e., risk contribution detected by the test, that results from the detection of failures which occur between tests and are detected by the test, and (2) a negative aspect, i.e., risk contribution caused by the test, that includes failures and degradations which are caused by the test or are related to the performance of the test. In terms of the two different risk contributions, the risk effectiveness of a test can be simply defined as follows: a test is risk effective if the risk contribution detected by the test is greater than the risk contribution caused by the test; otherwise it is risk ineffective. The methodology presentation will focus on two important kinds of negative test risk impacts, that is, the risk impacts of test-caused transients and equipment wear-out. The evaluation results of the risk …

The artificial pinning center (APC) approach to NbTi superconductor fabrication offers the potential benefits of higher current density and lower cost than the conventional process for NbTi. We have been evaluating several approaches for fabricating NbTi via the APC approach to determine whether these advantages can be realized in a practical conductor. The study began with the fabrication by several vendors of 10kg size samples which were evaluated as short samples. This was followed by the scale-up of one process to 150mm diameter billets. This material was evaluated first in a solenoid configuration and recently in a one-meter long dipole. We will report here on the results of these coil tests and other characterization results for this new material. We will also describe the plans to continue the scale-up to full size billets and we will discuss the potential cost savings of this approach compared with conventional NbTi fabrication.

In this paper, we introduced an alternative deep-submicrometer doping technology, Projection Gas Immersion Laser Doping (P-GILD). Representing the marriage of lithography and diffusion, P-GILD is a resistless, step-and-repeat doping process that utilizes excimer laser light patterned by a dielectric reticle to selectively heat and, thereby, dope regions of an integrated circuit. Results of physical and electrical characterization are presented for ultra-shallow p{sup +} {minus}n and n{sup +} {minus}p junctions produced by gas immersion laser doping (GILD), a phenomenologically identical technique that utilizes an aluminum contact mask rather than a dielectric reticle to pattern the beam. Junctions produced using GILD exhibit uniformly-doped, abrupt impurity profiles with no apparent defect formation in the silicon. Electrically, sheet and contact resistivities of the ultra-shallow junctions are less than 100{Omega}/sheet and 1 {times} 10{sup {minus}6} {Omega}{sm_bullet}cm{sup 2}, respectively, while n{sup +} {minus}p and p{sup +} {minus}n diodes exhibit nearly ideal forward bias behavior and reverse leakage current densities less than 5 nA/cm{sup 2} at {minus}5V. Uniformity of both diode characteristics and sheet resistance for junctions produced by the step-and-repeat process is also shown to be better than {plus_minus}5% across a 4-inch wafer.

Rare-earth (RE) doped ZrO{sub 2} prepared by a method of coprecipitation from aqueous solution shows many properties such as good thermal stability and large surface area ({approximately}80 m{sup 2}/g) that are suitable for use as catalyst supports and sorbents for a variety of molecules. The authors have measured the vibrational densities of states of surface hydroxyl groups as well as physisorbed water molecules in La{sub 0.1}Zr{sub 0.9}O{sub 1.95} and Nd{sub 0.1}Zr{sub 0.9}O{sub 1.95} by inelastic neutron scattering. The spectrum of dry RE-ZrO{sub 2} exhibits a peak at about 455 meV characteristic of the O-H stretch vibrations of surface hydroxyl groups. At a submonolayer coverage of H{sub 2}O this peak broadens and shifts to a slightly lower energy. At higher coverage three bands, corresponding to the O-H stretch ({approximately}430 meV), H-O-H bend ({approximately}200 meV) and librational motion ({approximately}80 meV), were observed. The decreasing energy and larger width of the OH stretch band with increasing H{sub 2}O coverage indicate the influence of hydrogen bonding on the motion of water molecules.

Recent changes in the Oak Ridge Y-12 Plant mission make possible the access by industry to a national resource with a history of manufacturing high precision components from conventional, exotic, and hazardous materials. Turning, milling, grinding, and many nontraditional machining techniques combined with high- accuracy dimensional inspection, nontraditional testing, and a broad range of surface treatments/coatings support national programs requiring the highest possible quality. The Centers for Manufacturing Technology (1-800-356-4USA) at the Oak Ridge Y-12 Plant site provide an impressive mix of resources and opportunities to American industry.

Beamlet is a full scale single beam prototype laser system, built to demonstrate the laser technology and performance of the 192 beam National Ignition Facility (NIF) fusion laser driver. Both laser systems apply multipass amplifier architectures. By passing the beam four times through the large aperture amplifier sections, the small signal gain during the first few passes is used efficiently to reduce expensive staged amplifier chains. The beamlet prototype laser integrates results of development programs for large aperture components: large aperture optical switch, polarizers, 2 x 2 multisegment amplifiers and new pulse generation and pre-amplification techniques. The authors report on performance test results of the recently completed 1 {omega}-laser section of Beamlet.

The differential cross sections for production of K{sub s}{sup 0}`s, {Lambda}`s and {pi}{sup {minus}}`s from Si and Pb targets using 14.6 {times} A GeV/c Si beams at the AGS are presented as a function of rapidity and transverse mass. These results are compared with model predictions and K{sub s}{sup 0} production is compared with {pi}{sup {minus}} production.

In this paper we consider the problem of interprocessor communication on a Completely Connected Optical Communication Parallel Computer (OCPC). The particular problem we study is that of realizing an h-relation. In this problem, each processor has at most h messages to send and at most h messages to receive. It is clear that any 1-relation can be realized in one communication step on an OCPC. However, the best known p-processor OCPC algorithm for realizing an arbitrary h-relation for h > 1 requires {Theta}(h + log p) expected communication steps. (This algorithm is due to Valiant and is based on earlier work of Anderson and Miller.) Valiant`s algorithm is optimal only for h = {Omega}(log p) and it is an open question of Gereb-Graus and Tsantilas whether there is a faster algorithm for h = o(log p). In this paper we answer this question in the affirmative by presenting a {Theta} (h + log log p) communication step algorithm that realizes an arbitrary h-relation on a p-processor OCPC. We show that if h {le} log p then the failure probability can be made as small as p{sup -{alpha}} for any positive constant {alpha}.

The current shortage of {sup 18}O has revived interest in using one step UV photodissociation of formaldehyde to enrich {sup 13}C, {sup 17}O and {sup 18}O. The frequency doubled output of the copper laser pumped dye laser system currently in operation at LLNL can be used to drive this dissociation. The authors use a simple kinetics model and their experience with Atomic Vapor Laser Isotope Separation (AVLIS) process design to examine the relative merits of different designs for a formaldehyde photodissociation process. Given values for the molecular photoabsorption cross section, partition function, spectroscopic selectivity, collisional exchange and quenching cross sections (all as parameters), they perform a partial optimization in the space of illuminated area, formaldehyde pressure in each stage, and formaldehyde residence time in each stage. They examine the effect of cascade design (heads and tails staging) on molecule and photon utilization for each of the three isotope separation missions, and look in one case at the system`s response to different ratios of laser to formaldehyde costs. Finally, they examine the relative cost of enrichment as a function of isotope and product assay. Emphasis is as much on the process design methodology, which is general, as on the specific application …

The US Department of Energy is sponsoring a research and demonstration program on the Nevada Test Site to develop and test an optimized cleanup system for large-area, surface plutonium contamination. The project addresses three principle areas: vegetation and soil removal, volume reduction of the displaced soil, and site restoration consisting of soil stabilization and revegetation. Soil stabilization and revegetation are critical in order to prevent erosion and reestablish wildlife habitat. A series of field and laboratory studies have been initiated to develop technologies to stabilize and restore sites disturbed by TSSM activities. Soil stabilization studies will test suitable techniques and materials to control wind and water erosion. Revegetation studies will focus on determining suitable plant species, proper techniques for establishing plants by direct seeding, procedures for transplanting native shrubs, soil fertility and irrigation requirements, and effects of herbivory on plant establishment. Additional studies will determine the extent of plutonium contamination on native vegetation, and the potential for removing plutonium from vegetation. Laboratory and greenhouse studies will determine effects of plutonium decontamination processes on soil microbial populations, and the effects of gravel mulches and soil texture on plant establishment. Following completion of these studies, the most promising technologies will be demonstrated …

The four-gap superconducting resonators which have been developed at Argonne for use in the low-beta positive ion-injector for ATLAS have potential applications for ions with velocities less than 0.007c and q/m less than 0.1. It was previously observed that at low velocities these structures can be focusing in both longitudinal and transverse phase spaces due to an inherent alternating-phase-focusing property. Studies are underway to determine the optimum combination of multi-gap structures and solenoids at low velocity and low q/m. In this paper the authors present the results of acceptance studies for the first three resonators at the front of the positive-ion injection linac, with and without the focusing solenoids. These studies include the effects of higher-order distortions in longitudinal and transverse phase spaces since minimizing such aberrations is very important for most nuclear physics applications of such accelerators.

Using diamond anvil cells, {sup 129}I Moessbauer spectroscopy (MS) and resistivity measurements were carried out in the layered antiferromagnet VI{sub 2} at 0-45 GPa and 4-300 K. MS to 15 GPa revealed an impressive increase in Neel temperature and a slight increase in transferred hyperfine field. Pressure behavior of R(P,T), in particular near the metal-insulator pressure P{sub c}=44 GPa, is described. Being the lightest transition metal (TM) in the isostructural (TM)I{sub 2} series, the V{sup 2+} (d{sup 3} configuration) represents a typical candidate for a pure Mott-Hubbard gap closure. Results are compared with the heavy TM diiodides such as NiI{sub 2} and CoI{sub 2}, where it is expected that the charge transfer regime prevails. 3 figs, 10 refs.

The first phase of a high current, short bunch length electron beam research facility, the AWA, is near completion at Argonne. At the heart of the facility is a photocathode based electron gun and accelerating sections designed to deliver 20 MeV pulses with up to 100 nC per pulse and with pulse lengths of approximately 15 ps (fw). Using a technique similar to that originated at Argonne`s AATF facility, a separate weak probe pulse can be generated and used to diagnose wake effects produced by the intense pulses. Initial planned experiments include studies of plasma wakefields and dielectric wakefield devices, and expect to demonstrate large, useful accelerating gradients (> 100 MeV/m). Later phases of the facility will increase the drive bunch energy to more than 100 MeV to enable acceleration experiments up to the GeV range. Specifications, design details, and commissioning progress are presented.