129 research outputs found
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Proceedings of the IAEA specialists` meeting on cracking in LWR RPV head penetrations
This report contains 17 papers that were presented in four sessions at the IAEA Specialists` meeting on Cracking in LWR RPV Head Penetrations held at ASTM Headquarters in Philadelphia on May 2-3, 1995. The papers are compiled here in the order that presentations were made in the sessions, and they relate to operational observations, inspection techniques, analytical modeling, and regulatory control. The goal of the meeting was to allow international experts to review experience in the field of ensuring adequate performance of reactor pressure vessel (RPV) heads and penetrations. The emphasis was to allow a better understanding of RPV material behavior, to provide guidance supporting reliability and adequate performance, and to assist in defining directions for further investigations. The international nature of the meeting is illustrated by the fact that papers were presented by researchers from 10 countries. There were technical experts present form other countries who participated in discussions of the results presented. This present document incorporates the final version of the papers as received from the authors. The final chapter includes conclusions and recommendations. Individual papers have been cataloged separately
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A parameterization of cloud droplet nucleation
Droplet nucleation is a fundamental cloud process. The number of aerosols activated to form cloud droplets influences not only the number of aerosols scavenged by clouds but also the size of the cloud droplets. Cloud droplet size influences the cloud albedo and the conversion of cloud water to precipitation. Global aerosol models are presently being developed with the intention of coupling with global atmospheric circulation models to evaluate the influence of aerosols and aerosol-cloud interactions on climate. If these and other coupled models are to address issues of aerosol-cloud interactions, the droplet nucleation process must be adequately represented. Here we introduce a droplet nucleation parametrization that offers certain advantages over the popular Twomey (1959) parameterization
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Solar wind channels for MeV particles
Plasma, magnetic field and charged particle data from the Ulysses spacecraft is used to demonstrate that MeV particles follow channels defined by solar wind flow regimes
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Probabilistic risk assessment for the Los Alamos Meson Physics Facility worst-case design-basis accident
This paper presents results from a Los Alamos National Laboratory Engineering and Safety Analysis Group assessment of the worse-case design-basis accident associated with the Clinton P. Anderson Meson Physics Facility (LAMPF)/Weapons Neutron Research (WNR) Facility. The primary goal of the analysis was to quantify the accident sequences that result in personnel radiation exposure in the WNR Experimental Hall following the worst-case design-basis accident, a complete spill of the LAMPF accelerator 1L beam. This study also provides information regarding the roles of hardware systems and operators in these sequences, and insights regarding the areas where improvements can increase facility-operation safety. Results also include confidence ranges to incorporate combined effects of uncertainties in probability estimates and importance measures to determine how variations in individual events affect the frequencies in accident sequences
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MORECA: A computer code for simulating modular high-temperature gas-cooled reactor core heatup accidents
The design features of the modular high-temperature gas-cooled reactor (MHTGR) have the potential to make it essentially invulnerable to damage from postulated core heatup accidents. This report describes the ORNL MORECA code, which was developed for analyzing postulated long-term core heatup scenarios for which active cooling systems used to remove afterheat following the accidents can be assumed to the unavailable. Simulations of long-term loss-of-forced-convection accidents, both with and without depressurization of the primary coolant, have shown that maximum core temperatures stay below the point at which any significant fuel failures and fission product releases are expected. Sensitivity studies also have been done to determine the effects of errors in the predictions due both to uncertainties in the modeling and to the assumptions about operational parameters. MORECA models the US Department of Energy reference design of a standard MHTGR
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Development of a fusion fuel cycle systems code
The tritium inventory in a D-T fusion experiment, like ITER, may be the major hazard onsite. This tritium is distributed throughout various systems and components. A major thrust of safety work has been aimed at reducing these tritium inventories, or at least at minimizing the amount of tritium that could be mobilized. I have developed models for a time-dependent fuel cycle systems code, which will aid in directing designers towards safer, lower inventory designs. The code will provide a self-consistent picture of system interactions and system interdependencies, and provide a better understanding of how tritium inventories are influenced. A systems'' approach is valuable in that a wide range of parameters can be studied, and more promising regions of parameter space can be identified. Ultimately, designers can use this information to specify a machine with minimum tritium inventory, given various constraints. Here, I discuss the models that describe tritium inventory in various components as a function of system parameters, and the unique capabilities of a code that will implement them. The models are time dependent and reflect a level of detail consistent with a systems type of analysis. The models support both a stand-alone Tritium Systems Code, and a module for the SUPERCODE, a time-dependent tokamak systems code. Through both versions, we should gain a better understanding of the interactions among the various components of the fuel cycle systems
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Calibration of scintillation detectors for MeV charged fusion products
The light output of ZnS scintillators used to detect escaping fusion products in the TFTR Tokamak is studied with 3.5 MeV alpha and 3 MeV proton beams. The emitted light first increases linearly with beam current and then saturates. In all cases investigated, the onset of the saturation corresponds to a power of about 1 mW absorbed within the ZnS powder. The scintillators have adequate time response up to 50--100 kHz
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