Publications

Results 1751–1775 of 2,290

Search results

Jump to search filters

Dielectric Characterization of Mylar and The Effects of Doping Processes

Laros, James H.

Mylar® polymer is a bi-axially oriented polyethylene terephthalate (PET) polymer film used widely as a dielectric, specifically in capacitors. The dielectric characteristics of Mylar have been well studied and documented over the years; however, many of the mechanisms responsible for dielectric breakdown and failure are not understood for modified versions of the material. Previous studies on Mylar confirm that factors such as temperature, humidity, and voltage ramp rates can also have a significant effect on the dielectric properties and measurement of the dielectric properties. This study seeks to determine how dielectric properties, including permittivity, dielectric loss, and breakdown strength, are affected by doping of the polymer. To do this, two types of Mylar films, virgin film and film doped with a small-molecule electron-acceptor, are tested. Both types of materials are tested under a variety of environmental and experimental conditions, including testing at elevated temperatures, varying relative humidity, and varying ramp rates in dielectric breakdown testing. Analysis of permittivity, dielectric loss, and breakdown strength will be presented comparing virgin and doped Mylar to gain insight into the effects of doping with electron-acceptor molecules on dielectric properties under these varying environmental and test conditions.

More Details
TYPE Thesis or Dissertation YEAR 2016
OSTI

MELCOR/CONTAIN LMR Implementation Report - FY16 Progress

Laros, James H.; Humphries, Larry

This report describes the progress of the CONTAIN - LMR sodium physics and chemistry models to be implemented in MELCOR 2.1. In the past three years , the implementation included the addition of sodium equations of state and sodium properties from two different sources. The first source is based on the previous work done by Idaho National Laboratory by modifying MELCOR to include liquid lithium equation of state as a working fluid to model the nuclear fusion safety research. The second source uses properties generated for the SIMMER code. The implemented modeling has been tested and results are reported in this document. In addition, the CONTAIN - LMR code was derived from an early version of the CONTAIN code, and many physical models that were developed since this early version of CONTAIN are not available in this early code version. Therefore, CONTAIN 2 has been updated with the sodium models in CONTAIN - LMR as CONTAIN2 - LMR, which may be used to provide code-to-code comparison with CONTAIN - LMR and MELCOR when the sodium chemistry models from CONTAIN - LMR have been completed. Both the spray fire and pool fire chemistry routines from CONTAIN - LMR have been integrated into MELCOR 2.1, and debugging and testing are in progress. Because MELCOR only models the equation of state for liquid and gas phases of the coolant, a modeling gap still exists when dealing with experiments or accident conditions that take place when the ambient temperature is below the freezing point of sodium. An alternative method is under investigation to overcome this gap . We are no longer working on the separate branch from the main branch of MELCOR 2.1 since the major modeling of MELCOR 2.1 has been completed. At the current stage, the newly implemented sodium chemistry models will be a part of the main MELCOR release version (MELCOR 2.2). This report will discuss the accomplishments and issues relating to the implementation. Also, we will report on the planned completion of all remaining tasks in the upcoming FY2017, including the atmospheric chemistry model and sodium - concrete interaction model implementation .

More Details
TYPE SAND Report YEAR 2016
DOIOSTI

NSRD-11: Computational Capability to Substantiate DOE-HDBK-3010 Data

Laros, James H.; Brown, Alexander B.; Gelbard, Fred G.; Bignell, John B.; Pierce, Flint P.; Voskuilen, Tyler V.; Rodriguez, Salvador B.; Dingreville, Remi P.; Zepper, Ethan T.; Juan, Pierre-Alexandre J.; Le, San L.; Gilkey, Lindsay N.

Safety basis analysts throughout the U.S. Department of Energy (DOE) complex rely heavily on the information provided in the DOE Handbook, DOE - HDBK - 3010, Airborne Release Fractions/Rates and Respirable Fractions for Nonreactor Nuclear Facilities, to determine radionuclide source terms. In calculating source terms, analysts tend to use the DOE Handbook's bounding values on airborne release fractions (ARFs) and respirable fractions (RFs) for various categories of insults (representing potential accident release categories). This is typically due to both time constraints and the avoidance of regulatory critique. Unfortunately, these bounding ARFs/RFs represent extremely conservative values. Moreover, they were derived from very limited small-scale bench/laboratory experiments and/or from engineered judgment. Thus, the basis for the data may not be representative of the actual unique accident conditions and configurations being evaluated. The goal of this research is to develop a more accurate and defensible method to determine bounding values for the DOE Handbook using state-of-art multi-physics-based computer codes. This enables us to better understand the fundamental physics and phenomena associated with the types of accidents in the handbook. In this year, this research included improvements of the high-fidelity codes to model particle resuspension and multi-component evaporation for fire scenarios. We also began to model ceramic fragmentation experiments, and to reanalyze the liquid fire and powder release experiments that were done last year. The results show that the added physics better describes the fragmentation phenomena. Thus, this work provides a low-cost method to establish physics-justified safety bounds by taking into account specific geometries and conditions that may not have been previously measured and/or are too costly to perform.

More Details
TYPE SAND Report YEAR 2016
DOIOSTI
Results 1751–1775 of 2,290
Results 1751–1775 of 2,290