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Transmission Nuclear Resonance Fluorescence Measurements of 238U in Thick Targets

Description: Transmission nuclear resonance fluorescence measurements were made on targets consisting of Pb and depleted U with total areal densities near 86 g/cm2. The 238U content n the targets varied from 0 to 8.5percent (atom fraction). The experiment demonstrates the capability of using transmission measurements as a non-destructive technique to identify and quantify the presence of an isotope in samples with thicknesses comparable to he average thickness of a nuclear fuel assembly. The experimental data also appear to demonstrate the process of notch refilling with a predictable intensity. Comparison of measured spectra to previous backscatter 238U measurements indicates general agreement in observed excited states. Two new 238U excited states and possibly a third state have also been observed.
Date: August 31, 2010
Creator: Quiter, Brian J.; Ludewigt, Bernhard A.; Mozin, Vladimir V.; Wilson, Cody & Korbly, Steve
Partner: UNT Libraries Government Documents Department

Nuclear Resonance Fluorescence to Measure Plutonium Mass in Spent Nuclear Fuel

Description: The Next Generation Safeguard Initiative (NGSI) of the U.S Department of Energy is supporting a multi-lab/university collaboration to quantify the plutonium (Pu) mass in spent nuclear fuel (SNF) assemblies and to detect the diversion of pins with non-destructive assay (NDA) methods. The following 14 NDA techniques are being studied: Delayed Neutrons, Differential Die-Away, Differential Die-Away Self-Interrogation, Lead Slowing Down Spectrometer, Neutron Multiplicity, Passive Neutron Albedo Reactivity, Total Neutron (Gross Neutron), X-Ray Fluorescence, {sup 252}Cf Interrogation with Prompt Neutron Detection, Delayed Gamma, Nuclear Resonance Fluorescence, Passive Prompt Gamma, Self-integration Neutron Resonance Densitometry, and Neutron Resonance Transmission Analysis. Understanding and maturity of the techniques vary greatly, ranging from decades old, well-understood methods to new approaches. Nuclear Resonance Fluorescence (NRF) is a technique that had not previously been studied for SNF assay or similar applications. Since NRF generates isotope-specific signals, the promise and appeal of the technique lies in its potential to directly measure the amount of a specific isotope in an SNF assay target. The objectives of this study were to design and model suitable NRF measurement methods, to quantify capabilities and corresponding instrumentation requirements, and to evaluate prospects and the potential of NRF for SNF assay. The main challenge of the technique is to achieve the sensitivity and precision, i.e., to accumulate sufficient counting statistics, required for quantifying the mass of Pu isotopes in SNF assemblies. Systematic errors, considered a lesser problem for a direct measurement and only briefly discussed in this report, need to be evaluated for specific instrument designs in the future. Also, since the technical capability of using NRF to measure Pu in SNF has not been established, this report does not directly address issues such as cost, size, development time, nor concerns related to the use of Pu in measurement systems. This report discusses basic NRF measurement ...
Date: January 14, 2011
Creator: Ludewigt, Bernhard A; Quiter, Brian J. & Ambers, Scott D.
Partner: UNT Libraries Government Documents Department

Nuclear Resonance Fluorescence for Materials Assay

Description: This paper discusses the use of nuclear resonance fluorescence (NRF) techniques for the isotopic and quantitative assaying of radioactive material. Potential applications include age-dating of an unknown radioactive source, pre- and post-detonation nuclear forensics, and safeguards for nuclear fuel cycles Examples of age-dating a strong radioactive source and assaying a spent fuel pin are discussed. The modeling work has ben performed with the Monte Carlo radiation transport computer code MCNPX, and the capability to simulate NRF has bee added to the code. Discussed are the limitations in MCNPX's photon transport physics for accurately describing photon scattering processes that are important contributions to the background and impact the applicability of the NRF assay technique.
Date: June 5, 2009
Creator: Quiter, Brian; Ludewigt, Bernhard; Mozin, Vladimir & Prussin, Stanley
Partner: UNT Libraries Government Documents Department

Potential National Security Applications of Nuclear Resonance Fluorescence Methods

Description: The objective of this report is to document the initial investigation into the possible research issues related to the development of NRF-based national security applications. The report discusses several potential applications ranging from measuring uranium enrichment in UF6 canisters to characterization of gas samples. While these applications are varied, there are only a few research issues that need to be addressed to understand the limitation of NRF in solving these problems. These research issues range from source and detector development to measuring small samples. The next effort is to determine how best to answer the research issues, followed by a prioritization of those questions to ensure that the most important are addressed. These issues will be addressed through either analytical calculations, computer simulations, analysis of previous data or collection of new measurements. It will also be beneficial to conduct a thorough examination of a couple of the more promising applications in order to develop concrete examples of how NRF may be applied in specific situations. The goals are to develop an understanding of whether the application of NRF is limited by technology or physics in addressing national security applications, to gain a motivation to explore those possible applications, and to develop a research roadmap so that those possibilities may be made reality.
Date: June 9, 2009
Creator: Warren, Glen A.; Peplowski, Patrick N. & Caggiano, Joseph A.
Partner: UNT Libraries Government Documents Department

Using Nuclear Resonance Fluorescence for Nondestructive Isotopic Analysis

Description: Nuclear resonance fluorescence (NRF) has been studied as one of the nondestructive analysis (NDA) techniques currently being investigated by a multi-laboratory collaboration for the determination of Pu mass in spent fuel. In NRF measurements specific isotopes are identified by their characteristic lines in recorded gamma spectra. The concentration of an isotope in a material can be determined from measured NRF signal intensities if NRF cross sections and assay geometries are known. The potential of NRF to quantify isotopic content and Pu mass in spent fuel has been studied. The addition of NRF data to MCNPX and an improved treatment of the elastic photon scattering at backward angles has enabled us to more accurately simulate NRF measurements on spent fuel assemblies. Using assembly models from the spent fuel assembly library generated at LANL, NRF measurements are simulated to find the best measurement configurations, and to determine measurement sensitivities and times, and photon source and gamma detector requirements. A first proof-of-principal measurement on a mock-up assembly with a bremsstrahlung photon source demonstrated isotopic sensitivity to approximately 1% limited by counting statistics. Data collection rates are likely a limiting factor of NRF-based measurements of fuel assemblies but new technological advances may lead to drastic improvements.
Date: July 14, 2010
Creator: Ludewigt, Bernhard A.; Mozin, Vladimir; Haefner, Andrew & Quiter, Brian
Partner: UNT Libraries Government Documents Department

Nondestructive Spent Fuel Assay Using Nuclear Resonance Fluorescence

Description: Quantifying the isotopic composition of spent fuel is an important challenge and essential for many nuclear safeguards applications, such as independent verification of the Pu content declared by a regulated facility, shipper/receiver measurements, and quantifying isotopic input masses at a reprocessing facility. As part of the Next Generation Safeguards Initiative, NA-241 has recently funded a multilab/university collaboration to investigate a variety of nondestructive methods for determining the elemental Pu mass in spent fuel assemblies. Nuclear resonance fluorescence (NRF) is one of the methods being investigated. First modeling studies have been performed to investigate the feasibility of assaying a single fuel pin using a bremsstrahlung photon source. MCNPX modeling results indicate that NRF signals are significantly more intense than the background due to scattered interrogation photons even for isotopes with concentrations below 1percent. However, the studies revealed that the dominant contribution to the background is elastic scattering, which is currently not simulated by MCNPX. Critical to this effort, we have added existing NRF data to the MCNPX photonuclear data files and are now able to incorporate NRF physics into MCNPX simulations. Addition of the non-resonant elastic scattering data to MCNPX is in progress. Assaying fuel assemblies with NRF poses additional challenges: photon penetration through the assembly is small and the spent fuel radioactive decay and neutron activity lead to significantly higher backgrounds. First modeling studies to evaluate the efficacy of NRF for assaying assemblies have been initiated using the spent fuel assembly library created at the Los Alamos National Laboratory (LANL).
Date: July 1, 2009
Creator: Quiter, Brian; Ludewigt, Bernhard; Mozin, Vladimir & Tobin, Steven
Partner: UNT Libraries Government Documents Department

Nuclear Resonance Fluorescence for Materials Assay

Description: This paper discusses the use of nuclear resonance fluorescence (NRF) techniques for the isotopic and quantitative assaying of radioactive material. Potential applications include age-dating of an unknown radioactive source, pre- and post-detonation nuclear forensics, and safeguards for nuclear fuel cycles Examples of age-dating a strong radioactive source and assaying a spent fuel pin are discussed. The modeling work has ben performed with the Monte Carlo radiation transport computer code MCNPX, and the capability to simulate NRF has bee added to the code. Discussed are the limitations in MCNPX?s photon transport physics for accurately describing photon scattering processes that are important contributions to the background and impact the applicability of the NRF assay technique.
Date: June 29, 2009
Creator: Quiter, Brian J.; Ludewigt, Bernhard; Mozin, Vladimir & Prussin, Stanley
Partner: UNT Libraries Government Documents Department

High Repetition Rate, LINAC-Based Nuclear Resonance Fluorescence FY 2008 Final Report

Description: This summarizes the first year of a multi-laboratory/university, multi-year effort focusing on high repetition rate, pulsed LINAC-based nuclear resonance fluorescence (NRF) measurements. Specifically, this FY2008 effort centered on experimentally assessing NRF measurements using pulsed linear electron accelerators, operated at various repetition rates, and identifying specific detection requirements to optimize such measurements. Traditionally, interest in NRF as a detection technology, which continues to receive funding from DHS and DOE/NA-22, has been driven by continuous-wave (CW), Van de Graff-based bremsstrahlung sources. However, in addition to the relatively sparse present-day use of Van de Graff sources, only limited NRF data from special nuclear materials has been presented; there is even less data available regarding shielding effects and photon source optimization for NRF measurements on selected nuclear materials.
Date: December 1, 2008
Creator: Watson, Scott M; Kinlaw, Mathew T; Jones, James L; Hunt, Alan W. & Warren, Glen A.
Partner: UNT Libraries Government Documents Department

Radiation Detection for Active Interrogation of HEU

Description: This report briefly describes the neutrons and gamma rays emitted by active interrogation of HEU, briefly discusses measurement methods, briefly discusses sources and detectors relevant to detection of shielded HEU in Sealand containers, and lists the measurement possibilities for the various sources. All but one of the measurement methods detect radiation emitted by induced fission in the HEU; the exception utilizes nuclear resonance fluorescence. The brief descriptions are supplemented by references. This report presents some active interrogation possibilities but the status of understanding is not advanced enough to select particular methods. Additional research is needed to evaluate these possibilities.
Date: December 9, 2004
Creator: Mihalczo, J.T.
Partner: UNT Libraries Government Documents Department

Applications of Photonuclear Physics for International Safeguards and Security

Description: Studies of nuclear resonance fluorescence based applications are presented. Important for these applications are data for isotopes such as {sup 239}Pu. Nuclear resonance fluorescence measurements of {sup 239}Pu were performed at the free electron laser facility at UC Santa Barbara using photons from a bremsstrahlung beam with an endpoint energies between 4.0 MeV and 5.5 MeV. Though no discrete states with significant confidence level were measured, we have excluded the region above 27(3) eV-barns, or 4-sigma, where we would expect only a small chance of false positives. Details of the measurements and the results are presented here.
Date: April 16, 2010
Creator: Johnson, M S; Hall, J M; McNabb, D P; McFarland, J; Norman, E; Bertozzi, W et al.
Partner: UNT Libraries Government Documents Department

Contraband Detection with Nuclear Resonance Fluorescence: Feasibility and Impact

Description: In this report they show that cargo interrogation systems developed to thwart trafficking of illicit nuclear materials could also be powerful tools in the larger fight against contraband smuggling. In particular, in addition to detecting special nuclear materials, cargo scanning systems that exploit nuclear resonance fluorescence to detect specific isotopes can be used to help find: chemical weapons; some drugs as well as some chemicals regulated under the controlled substances act; precious metals; materials regulated under export control laws; and commonly trafficked fluorocarbons.
Date: January 3, 2007
Creator: Pruet, J & Lange, D
Partner: UNT Libraries Government Documents Department

Techniques and use of a tunable, laser-based, MeV-Class Compton scattering light source

Description: A Compton scattering {gamma}-ray source, capable of producing photons with energies ranging from 0.1 MeV to 0.9 MeV has been commissioned and characterized, and then used to perform nuclear resonance fluorescence (NRF) experiments. The key source parameters are the size (0.01 mm{sup 2}), horizontal and vertical divergence (6 x 10 mrad{sup 2}), duration (10 ps), spectrum and intensity (10{sup 5} photons/shot). These parameters are summarized by the peak brightness, 1.5 x 10{sup 15} photons/mm{sup 2}/mrad{sup 2}/s/0.1%bandwidth, measured at 478 keV. Additional measurements of the flux as a function of the timing difference between the drive laser pulse and the relativistic photoelectron bunch, {gamma}-ray beam profile, and background evaluations are presented. These results are systematically compared to theoretical models and computer simulations. NRF measurements performed on {sup 7}Li in LiH demonstrate the potential of Compton scattering photon sources to accurately detect isotopes in situ.
Date: June 30, 2009
Creator: Albert, F; Anderson, S G; Gibson, D J; Hagmann, C A; Johnson, M S; Messerly, M et al.
Partner: UNT Libraries Government Documents Department

Absolute Photodissociation Quantum Yields for the NO3 Free Radical

Description: The nitrate free radical was photolyzed by a pulsed tunable dye laser between 470 and 685 nm, at 296 K, and in the presence of 10 torr N{sub 2}. The two product channels, NO + O{sub 2} and NO{sub 2} + O, were measured by resonance fluorescence of NO or of O. Absolute calibration of the method was achieved by in situ ultraviolet photolysis of NO{sub 2}, which yields both NO and O. With these data on photochemical yields, the photolysis coefficients for the two product channels at the surface of the earth with an overhead sun over wavelengths 470-700 nm are calculated to be j{sub 1}(NO + O{sub 2}) = 0.022 {+-} 0.007 s{sup -1} and j{sub 2}(NO{sub 2} + O) = 0.18 {+-} 0.06 s{sup -1}.
Date: January 1, 1980
Creator: Magnotta, Frank & Johnston, Harold S.
Partner: UNT Libraries Government Documents Department

RATE CONSTANT FOR THE REACTION NO2 + O->NO + O2

Description: By use of tunable laser flash photolysis and resonance fluorescence to detect primary products, the rate constant for the reaction 0({sup 3}P{sub J}) + NO{sub 2} {yields} O{sub 2} + NO has been measured. A value of k = 1.03 {+-} .01 x 10{sup -11} cm{sup 3} molecules{sup -1} sec{sup -1} was obtained at 296 K, which is a factor of 1.1 faster than the currently recommended value. The present work utilized in situ measurement of NO{sub 2} via laser induced fluorescence and generated oxygen atoms from five sources.
Date: January 1, 1980
Creator: Magnotta, Frank & Johnston, Harold S.
Partner: UNT Libraries Government Documents Department

Quantitative XRFA of carbon in a special matrix by the fundamental parameter method

Description: We report on results obtained from experiments using specially prepared carbon substrates and treatment of the data by means of recently introduced theory. Medium Z grids with known parameters have been coated on top of pyrolytic carbon substrates to achieve well defined absorption geometries. The various copper grids exhibit satisfactory performance in terms of mechanical stability, homogeneity and uniformity of the coating. A detailed study of the measurement results shows that there is a more rapid increase of the associated C-K{alpha} countrate from the coated samples compared to the pure elements and is attributed to the contribution of secondary enhancement effects, including those resulting from photoelectrons generated after the primary ionization. A variety of multilayer analyzers has also been evaluated during these experiments. Only a certain combination of muitilayer component materials have been found to be appropriate for use as dispersing elements due to the reflectivity and spatial resolution requirements of our long wavelength spectrometer. Another experimental factor is the low intensity of available tube photons which is due to the selection of the target material and absorption effects in the target as well as the tube window. 12 refs., 7 figs., 2 tabs.
Date: May 1, 1996
Creator: Weber, F.A.; Da Silva, L.B.; Barbee, T.W. Jr.; Ciarlo, D. & Mantler, M.
Partner: UNT Libraries Government Documents Department

Investigation of the Pressure Dependence of SO3 Formation

Description: The kinetics of the pressure dependent O + SO2 + Ar reaction have been investigated using laser photolysis resonance fluorescence at temperatures of 289 K, 399 K, 581 K, 699 K, 842 K and 1040 K and at pressures from 30-665 torr. Falloff was observed for the first time in the pressure dependence. Application of Lindemann theory yielded an Arrhenius expression of k(T) = 3.3 x 10-32exp(-992/T) cm6 molecule-1 s-1 for the low pressure limit and k(T) = 8.47 x 10-14exp(-468/T) cm3 molecule-1 s-1 for the high pressure limit at temperatures between 289 and 842 K. The reaction is unusual as it possesses a positive activation energy at low temperature, yet at higher temperatures the activation energy is negative, illustrating a reaction barrier.
Date: December 2003
Creator: Naidoo, Jacinth
Partner: UNT Libraries