GUIDE TO CALCULATING TRANSPORT EFFICIENCY OF AEROSOLS IN OCCUPATIONAL AIR SAMPLING SYSTEMS (open access)

GUIDE TO CALCULATING TRANSPORT EFFICIENCY OF AEROSOLS IN OCCUPATIONAL AIR SAMPLING SYSTEMS

This report will present hand calculations for transport efficiency based on aspiration efficiency and particle deposition losses. Because the hand calculations become long and tedious, especially for lognormal distributions of aerosols, an R script (R 2011) will be provided for each element examined. Calculations are provided for the most common elements in a remote air sampling system, including a thin-walled probe in ambient air, straight tubing, bends and a sample housing. One popular alternative approach would be to put such calculations in a spreadsheet, a thorough version of which is shared by Paul Baron via the Aerocalc spreadsheet (Baron 2012). To provide greater transparency and to avoid common spreadsheet vulnerabilities to errors (Burns 2012), this report uses R. The particle size is based on the concept of activity median aerodynamic diameter (AMAD). The AMAD is a particle size in an aerosol where fifty percent of the activity in the aerosol is associated with particles of aerodynamic diameter greater than the AMAD. This concept allows for the simplification of transport efficiency calculations where all particles are treated as spheres with the density of water (1 g�cm-3). In reality, particle densities depend on the actual material involved. Particle geometries can be very …
Date: November 12, 2013
Creator: Hogue, M.; Hadlock, D.; Thompson, M. & Farfan, E.
Object Type: Report
System: The UNT Digital Library
Compound Refractive Lenses for Thermal Neutron Applications (open access)

Compound Refractive Lenses for Thermal Neutron Applications

This project designed and built compound refractive lenses (CRLs) that are able to focus, collimate and image using thermal neutrons. Neutrons are difficult to manipulate compared to visible light or even x rays; however, CRLs can provide a powerful tool for focusing, collimating and imaging neutrons. Previous neutron CRLs were limited to long focal lengths, small fields of view and poor resolution due to the materials available and manufacturing techniques. By demonstrating a fabrication method that can produce accurate, small features, we have already dramatically improved the focal length of thermal neutron CRLs, and the manufacture of Fresnel lens CRLs that greatly increases the collection area, and thus efficiency, of neutron CRLs. Unlike a single lens, a compound lens is a row of N lenslets that combine to produce an N-fold increase in the refraction of neutrons. While CRLs can be made from a variety of materials, we have chosen to mold Teflon lenses. Teflon has excellent neutron refraction, yet can be molded into nearly arbitrary shapes. We designed, fabricated and tested Teflon CRLs for neutrons. We demonstrated imaging at wavelengths as short as 1.26 ? with large fields of view and achieved resolution finer than 250 μm which is …
Date: November 12, 2013
Creator: Gary, Charles K.
Object Type: Report
System: The UNT Digital Library
Evolution of Long-Term Stewardship at Hanford - 14189 (open access)

Evolution of Long-Term Stewardship at Hanford - 14189

Hanford�s Long-Term Stewardship (LTS) Program has evolved from a small, informal process, with minimal support, to a robust program that provides comprehensive transitions from cleanup contractors to long-term stewardship for post-cleanup requirements specified in the associated cleanup decision documents. The LTS Program has the responsibility for almost 100,000 acres of land, along with over 200 waste sites and will soon have six cocooned reactors. Close to 2,600 documents have been identified and tagged for storage in the LTS document library. The program has successfully completed six consecutive transitions over the last two years in support of the U.S. DOE Richland Operations Office�s (DOE-RL) near-term cleanup objectives of significantly reducing the footprint of active cleanup operations for the River Corridor. The program has evolved from one that was initially responsible for defining and measuring Institutional Controls for the Hanford Site, to a comprehensive, post remediation surveillance and maintenance program that begins early in the transition process. In 2013, the first reactor area―the cocooned 105-F Reactor and its surrounding 1,100 acres, called the F Area was transitioned. In another �first,� the program is expected to transition the five remaining cocooned reactors into the program through using a Transition and Turnover Package (TTP). …
Date: November 12, 2013
Creator: Moren, Richard J. & Grindstaff, Keith D.
Object Type: Article
System: The UNT Digital Library
Benchmarking Exercises To Validate The Updated ELLWF GoldSim Slit Trench Model (open access)

Benchmarking Exercises To Validate The Updated ELLWF GoldSim Slit Trench Model

The Savannah River National Laboratory (SRNL) results of the 2008 Performance Assessment (PA) (WSRC, 2008) sensitivity/uncertainty analyses conducted for the trenches located in the EArea LowLevel Waste Facility (ELLWF) were subject to review by the United States Department of Energy (U.S. DOE) Low-Level Waste Disposal Facility Federal Review Group (LFRG) (LFRG, 2008). LFRG comments were generally approving of the use of probabilistic modeling in GoldSim to support the quantitative sensitivity analysis. A recommendation was made, however, that the probabilistic models be revised and updated to bolster their defensibility. SRS committed to addressing those comments and, in response, contracted with Neptune and Company to rewrite the three GoldSim models. The initial portion of this work, development of Slit Trench (ST), Engineered Trench (ET) and Components-in-Grout (CIG) trench GoldSim models, has been completed. The work described in this report utilizes these revised models to test and evaluate the results against the 2008 PORFLOW model results. This was accomplished by first performing a rigorous code-to-code comparison of the PORFLOW and GoldSim codes and then performing a deterministic comparison of the two-dimensional (2D) unsaturated zone and three-dimensional (3D) saturated zone PORFLOW Slit Trench models against results from the one-dimensional (1D) GoldSim Slit Trench model. …
Date: November 12, 2013
Creator: Taylor, G. A. & Hiergesell, R. A.
Object Type: Report
System: The UNT Digital Library