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1.
R. A. Dewberry S. R. Salaymeh V. R. Casella F. S. Moore 《Journal of Radioanalytical and Nuclear Chemistry》2006,267(3):515-531
Summary This paper contains a summary of the holdup and material control and accountability (MC&A) assays conducted for the determination
of highly enriched uranium (HEU) in the deactivation and decommissioning (D&D) of the Reactor Fuel Fabrication Facility at
the Savannah River Site (SRS). The facility was used to fabricate HEU fuel assemblies, lithium-aluminum target tubes, neptunium
assemblies, and miscellaneous components for the SRS production reactors. The facility operated for more than 35 years. During
this time thousands of uranium-aluminum alloy (U-Al) production reactor fuel tubes were produced. After the facility ceased
operations in 1995, all of the easily accessible U-Al was removed from the building, and only residual amounts remained. The
bulk of this residue was located in the equipment that generated and handled small U-Al particles and in the exhaust systems
for this equipment (e.g., chip compactor, casting furnaces, log saw, lathes A & B, cyclone separator, Freon?cart, riser crusher,
…, etc). The D&D project is likely to represent an important example for D&D activities across SRS and across the Department
of Energy weapons complex. The Savannah River National Laboratory was tasked to conduct holdup assays to quantify the amount
of HEU on all components removed from the facility prior to placing in solid waste containers. The 235U holdup in any single component of process equipment must not exceed 50 g in order to meet the container limit. This limit
was imposed to meet criticality requirements of the low level solid waste storage vaults. Thus, the holdup measurements were
used as guidance to determine if further decontamination of equipment was needed to ensure that the quantity of 235U did not exceed the 50 g limit and to ensure that the waste met the Waste Acceptance Criteria (WAC) of the solid waste storage
vaults. Since HEU is an accountable nuclear material, the holdupassays and assays of recovered residue were also important
for material control and accountability purposes. In summary, the results of the holdup assays were essential for determining
compliance with the Waste Acceptance Criteria, Material Control & Accountability, and to ensure that administrative criticality
safety controls were not exceeded. This paper discusses theg-ray assay measurements conducted and the modeling of the acquired
data to obtain measured holdup in process equipment, exhaust components, and fixed geometry scrap cans. It also presents development
work required to model new acquisition configurations and to adapt available instrumentation to perform the assays. 相似文献
2.
Juliana S Luz Celso RR Ramos Márcia CT Santos Patricia P Coltri Fernando L Palhano Debora Foguel Nilson IT Zanchin Carla C Oliveira 《BMC biochemistry》2010,11(1):22
Background
The archaeal exosome is formed by a hexameric RNase PH ring and three RNA binding subunits and has been shown to bind and degrade RNA in vitro. Despite extensive studies on the eukaryotic exosome and on the proteins interacting with this complex, little information is yet available on the identification and function of archaeal exosome regulatory factors. 相似文献3.
4.
R. A. Dewberry 《Journal of Radioanalytical and Nuclear Chemistry》2005,262(3):783-787
The Analytical Development Section of Savannah River Technology Center (SRTC) was requested by the Facilities Disposition Projects (FDP) to determine the holdup of enriched uranium in the 321-M facility as part of an overall deactivation project of the facility. The 321-M facility was used to fabricate enriched uranium fuel assemblies, lithium-aluminum target tubes, neptunium assemblies, and miscellaneous components for the production reactors. The results of the holdup assays are essential for determining compliance with the Waste Acceptance Criteria, Material Control & Accountability, and to meet criticality safety controls. This report covers calibration of the detectors in order to support holdup measurements in the C and D out-gassing ovens. These ovens were used to remove gas entrained in billet assembly material prior to the billets being extruded into rods by the extrusion press. A portable high purity germanium detection system was used to determine highly enriched uranium (HEU) holdup and to determine holdup of 235U, 237Np, and 241Am that were observed in these components. The detector system was run by an EG&G Dart system that contains the high voltage power supply and signal processing electronics. A personal computer with Gamma-Vision software was used to control the Dart MCA and provide space to store and manipulate multiple 4096-channel -ray spectra. The measured 237Np and 241Am contents were especially important in these components because their presence is unusual and unexpected in 321-M. It was important to obtain a measured value of these two components to disposition the out-gassing ovens and to determine whether a separate waste stream was necessary for release of these contaminated components to the E-Area Solid Waste Vault. This report presents determination of the calibration constants from first principles for determination of 241Am and 237Np using this detection system and compares the values obtained for 237Np with the calibration factors obtained with a subsequent measurement using a point source of radioactive equilibrium 237Np/233Pa. 相似文献
5.
Dewberry CT Etchison KC Grubbs Ii GS Powoski RA Serafin MM Peebles SA Cooke SA 《Physical chemistry chemical physics : PCCP》2007,9(44):5897-5901
Hyperfine structures arising from the couplings of the nuclear spin angular momentum of (17)O (I = 5/2) with the end over end rotation of several metal-containing diatomic monoxides have been observed using a Fourier transform microwave spectrometer. The molecules have been produced by reacting (17)O(2) with laser ablated metal atoms. The oxygen-17 nuclear quadrupole coupling constants have been determined for the title molecules and are interpreted in terms of a simple Townes-Dailey model. Also, the oxygen-17 nuclear spin-rotation constants have been determined and used to calculate the oxygen-17 shieldings for each molecule. 相似文献
6.
MF Miller IA Franchi AS Sexton CT Pillinger 《Rapid communications in mass spectrometry : RCM》1999,13(13):1211-1217
The use of infrared laser-assisted fluorination to release oxygen from milligram quantities of silicates or other oxide mineral grains is a well-established technique. However, relatively few studies have reported the optimisation of this procedure for oxygen-17 isotope measurements. We describe here details of an analytical system using infrared (10 μm) laser-assisted fluorination, in conjunction with a dual inlet mass spectrometer of high resolving power ( approximately 250) to provide (17)O and (18)O oxygen isotope measurements from 0.5-2 mg of silicates or other oxide mineral grains. Respective precisions (1) of typically 0.08 and 0.04 per thousand are obtained for the complete analytical procedure. Departures from the mass-dependent oxygen isotope fractionation line are quantified by Delta(17)O; our precision (1) of such measurements on individual samples is shown to be +/-0.024 per thousand. In turn, this permits the offset between parallel, mass-dependent fractionation lines to be characterised to substantially greater precision than has been possible hitherto. Application of this system to investigate the (17)O versus (18)O relationship for numerous terrestrial whole-rock and mineral samples, of diverse geological origins and age, indicates that the complete data set may be described by a single, mass-dependent fractionation line of slope 0.5244+/- 0.00038 (standard error). Copyright 1999 John Wiley & Sons, Ltd. 相似文献
7.
8.
R. A. Dewberry R. A. Sigg S. R. Salaymeh 《Journal of Radioanalytical and Nuclear Chemistry》2010,283(1):163-169
The Savannah River Site (SRS) Burial Ground had a container labeled as Box 33 for which they had no reliable solid waste stream designation. The container consisted of an outer box of dimensions 48″ × 46″×66″
and an inner box that contained high density and high radiation dose material. From the outer box Radiation Control measured
an extremity dose rate of 22 mrem/h. With the lid removed from the outer box, the maximum dose rate measured from the inner
box was 100 mrem/h extremity and 80 mrem/h whole body. From the outer box the material was sufficiently high in density that
the Solid Waste Management operators were unable to obtain a Co-60 radiograph of the contents. Solid Waste Management requested
that the Analytical Development Section of Savannah River National Laboratory perform a γ-ray assay of the item to evaluate
the radioactive content and possibly to designate a solid waste stream. This paper contains the results of three models used
to analyze the measured γ-ray data acquired in an unusual configuration. 相似文献
9.
Wenbin Liu KBS Institute of Mathematics Statistics The University of Kent Canterbury CT NF Engl Wei Gong Ningning Yan LSEC 《计算数学(英文版)》2009,(1):97-114
In this paper, we study numerical methods for an optimal control problem with pointwise state constraints. The traditional approaches often need to deal with the deltasingularity in the dual equation, which causes many difficulties in its theoretical analysis and numerical approximation. In our new approach we reformulate the state-constrained optimal control as a constrained minimization problems only involving the state, whose optimality condition is characterized by a fourth order elliptic variational inequality. Then direct numerical algorithms (nonconforming finite element approximation) are proposed for the inequality, and error estimates of the finite element approximation are derived. Numerical experiments illustrate the effectiveness of the new approach. 相似文献
10.
Using pulsed jet chirped-pulse, and cavity-based Fourier transform microwave spectroscopies over 900 transitions have been recorded for the title molecule in the 1–4 GHz and 8–18 GHz regions. The C1,C2 and C3 carbon-13 species have been observed in natural abundance allowing a substitution structure for the CCC backbone to be determined. Nearly all the transitions observed were either a-type R branches or b-type Q branches. No c-type transitions were observed consistent with only the trans conformer being present under our experimental conditions. The χaa,χbb,χcc and χab components of the iodine nuclear quadrupole coupling tensor have been determined. Of note, several forbidden, ΔJ±2 transitions, and one ΔJ±3 transition were observed with quite reasonable intensity. These observations have been rationalized through considerations of near degeneracies between energy levels connected via a large χab value (≈1 GHz). 相似文献