[Show abstract][Hide abstract] ABSTRACT: Near-monoenergetic photon sources at MeV energies offer improved sensitivity at greatly reduced dose for active interrogation, and new capabilities in treaty verification, nondestructive assay of spent nuclear fuel and emergency response. Thomson (also referred to as Compton) scattering sources are an established method to produce appropriate photon beams. Applications are however restricted by the size of the required high-energy electron linac, scattering (photon production) system, and shielding for disposal of the high energy electron beam. Laser-plasma accelerators (LPAs) produce GeV electron beams in centimeters, using the plasma wave driven by the radiation pressure of an intense laser. Recent LPA experiments are presented which have greatly improved beam quality and efficiency, rendering them appropriate for compact high-quality photon sources based on Thomson scattering. Designs for MeV photon sources utilizing the unique properties of LPAs are presented. It is shown that control of the scattering laser, including plasma guiding, can increase photon production efficiency. This reduces scattering laser size and/or electron beam current requirements to scale compatible with the LPA. Lastly, the plasma structure can decelerate the electron beam after photon production, reducing the size of shielding required for beam disposal. Together, these techniques provide a path to a compact photon source system.
Nuclear Instruments and Methods in Physics Research Section B Beam Interactions with Materials and Atoms 01/2015; 350. DOI:10.1016/j.nimb.2015.01.013 · 1.12 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Non-destructive assay (NDA) of 239Pu in spent nuclear fuel is possible using the isotope-specific nuclear resonance fluorescence (NRF) integral resonance transmission (IRT) method. The IRT method measures the absorption of photons from a quasi-monoenergetic γ-ray beam due to all resonances in the energy width of the beam. According to calculations the IRT method could greatly improve assay times for 239Pu in nuclear fuel. To demonstrate and verify the IRT method, the IRT signature was first measured in 181Ta, whose nuclear resonant properties are similar to those of 239Pu, and then measured in 239Pu. These measurements were done using the quasi-monoenergetic beam at the High Intensity γ-ray Source (HIγS) in Durham, NC, USA. The IRT signature was observed as a decrease in scattering strength when the same isotope material was placed upstream of the scattering target. The results confirm the validity of the IRT method in both 181Ta and 239Pu.
[Show abstract][Hide abstract] ABSTRACT: We have measured a large number of proton-induced radionuclide production cross sections from tellurium targets of natural isotopic composition at incident energies of 0.80, 1.4, and 23 GeV. The results of these measurements are compared to semi-empirical calculations and the contribution of this cosmo-genic activity to the background of the CUORE experiment, presently being realized, is evaluated.
Nuclear Instruments and Methods in Physics Research Section B Beam Interactions with Materials and Atoms 11/2012; 295:16-21. DOI:10.1016/j.nimb.2012.10.008 · 1.12 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Nuclear resonance fluorescence (NRF), a process by which a nucleus is excited by absorption of a specific quantum of energy and then deexcites via the emission of one or more γ rays, may be applied to nondestructively measure the isotopic composition of a sample. NRF excitations in 240Pu were identified in the energy range of 2.1 to 2.8 MeV using a 3-MeV bremsstrahlung source. Utilizing high-purity germanium detectors at backward angles, nine resonances in 240Pu were identified in this energy range. The measured integrated cross sections range from 29 to 104 eV b. These resonances are of interest to nuclear structure physics and provide unique signatures for the assay of 240Pu content for nuclear forensics, nuclear safeguards, and counterterrorism applications.
Physical Review C 09/2012; 86(3). DOI:10.1103/PhysRevC.86.034307 · 3.73 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Ever since there has been spent fuel (SF), researchers have made nondestructive assay (NDA) measurements of that fuel to learn about its content. In general these measurements have focused on the simplest signatures (passive photon and total neutron emission) and the analysis has often focused on diversion detection and on determining properties such as burnup (BU) and cooling time (CT). Because of shortcomings in current analysis methods, inspectorates and policy makers are interested in improving the state-of-the-art in SF NDA. For this reason the U.S. Department of Energy, through the Next Generation Safeguards Initiative (NGSI), targeted the determination of elemental Pu mass in SF as a technical goal. As part of this research effort, fourteen nondestructive assay techniques were studied. This wide range of techniques was selected to allow flexibility for the various needs of the safeguards inspectorates and to prepare for the likely integration of one or more techniques having complementary features. In the course of researching this broad range of NDA techniques, several cross-cutting issues were identified. This paper will describe some common issues and insights. In particular we will describe the following: (1) induced and non-induced fission-based techniques, (2) the role of neutron absorbers with emphasis on how these absorbers vary in SF as a function of initial enrichment, BU, and CT, as well as how some NDA techniques are more or less sensitive to neutron absorbers; and (3) the need to partition the measured signal among different isotopic sources and why this partitioning indicates which NDA techniques best integrate; (4) the importance of the "first generation" concept in the context of both diversion detection and in the context of determining Pu mass because the first generation indicates both the spatial and isotopic origins of the detected signal; and (5) the unique role played by 238U and why in most cases it primarily acts as an amplifier of the signal generated by 235U, 239Pu, and 241Pu.
[Show abstract][Hide abstract] ABSTRACT: In nuclear resonance fluorescence (NRF) measurements, resonances are excited by an external photon beam leading to the emission of gamma rays with specific energies that are characteristic of the emitting isotope. NRF promises the unique capability of directly quantifying a specific isotope without the need for unfolding the combined responses of several fissile isotopes as is required in other measurement techniques. We have analyzed the potential of NRF as a non-destructive analysis technique for quantitative measurements of Pu isotopes in spent nuclear fuel (SNF). Given the low concentrations of 239Pu in SNF and its small integrated NRF cross sections, the main challenge in achieving precise and accurate measurements lies in accruing sufficient counting statistics in a reasonable measurement time. Using analytical modeling, and simulations with the radiation transport code MCNPX that has been experimentally tested recently, the backscatter and transmission methods were quantitatively studied for differing photon sources and radiation detector types. Resonant photon count rates and measurement times were estimated for a range of photon source and detection parameters, which were used to determine photon source and gamma-ray detector requirements. The results indicate that systems based on a bremsstrahlung source and present detector technology are not practical for high-precision measurements of 239Pu in SNF. Measurements that achieve the desired uncertainties within hour-long measurements will either require stronger resonances, which may be expressed by other Pu isotopes, or require quasi-monoenergetic photon sources with intensities that are approximately two orders of magnitude higher than those currently being designed or proposed.This work is part of a larger effort sponsored by the Next Generation Safeguards Initiative to develop an integrated instrument, comprised of individual NDA techniques with complementary features, that is fully capable of determining Pu mass in spent fuel assemblies.
[Show abstract][Hide abstract] ABSTRACT: 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.
[Show abstract][Hide abstract] ABSTRACT: Transmission nuclear resonance fluorescence measurements were made on targets consisting of Pb and depleted U with total areal densities near 86g/cm2. The 238U content in the targets varied from 0% to 8.5% (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 the 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. Evidence of two new 238U excited states and possibly a third state have also been observed.
Nuclear Instruments and Methods in Physics Research Section B Beam Interactions with Materials and Atoms 05/2011; 269(10):1130-1139. DOI:10.1016/j.nimb.2011.02.081 · 1.12 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: There are a variety of motivations for quantifying plutonium in used (spent) fuel assemblies by means of nondestructive assay including the following: shipper/receiver difference, input accountability at reprocessing facilities and burnup credit at repositories or fuel storage facilities. Twelve NDA techniques were identified for providing fuel assembly composition information. 1 Unfortunately, none of these techniques, in isolation, is capable of determining the Pu mass in an assembly. However, it is expected that the Pu mass can be quantified by combining a few of the techniques. Determining which techniques to combine and estimating the expected performance of such a system is the purpose of a research effort recently begun. The research presented here is a complimentarily experimental effort. This paper will focus on experimental results of one of the twelve non-destructive assay techniques -passive neutron albedo reactivity. The passive neutron albedo reactivity techniques works by changing the multiplication that the pin experiences between two separate measurements. Since a single spent fuel pin has very little multiplication, this is a challenging measurement situation for the technique. Singles and Doubles neutron count rate were measured at Oak Ridge National Laboratory for three different burnup pins to test the capability of the passive neutron albedo reactivity technique.
[Show abstract][Hide abstract] ABSTRACT: Minimization of radioactive backgrounds is critical for experiments attempting to measure neutrinoless double beta decay (0nubetabeta). To estimate cosmic ray-induced radionuclide production in 0nubetabeta experiments, we have irradiated targets composed of natural isotopic composition molybdenum and germanium with 800 MeV protons at the Los Alamos Neutron Science Center (LANSCE). The targets were counted with high-purity germanium detectors at Lawrence Berkeley National Laboratory intermittently from 2 weeks to 1 year after irradiation to determine the cumulative cross sections for radionuclide production. In total, 30 radioactive products were observed in the Mo target and 20 in the Ge target. Our experimental results are compared with the predictions from the semi-empirical Silberberg and Tsao code as well as previously reported Mo experimental data.
[Show abstract][Hide abstract] ABSTRACT: The sensitivity for identification of high-Z objects in elemental form in the massive cargos of intermodal containers with continuous bremsstrahlung radiation depends critically on discriminating the weak signal from uncollided photons from the very intense flux of scattered radiations that penetrate the cargo. We propose that this might be accomplished by rejection of detected events with E ⩽ 2–3 MeV that contain the majority of multiply scattered photons along with a correction for single-scattered photons at higher energies. Monte Carlo simulations of radiographs with a 9 MeV bremsstrahlung spectrum demonstrate that rejection of detected events with E ⩽ 3 MeV removes the majority of signals from scattered photons emerging through cargos with Z ⩽ 30 and areal densities of at least 145 g cm−2. With analytical estimates of the single-scattered intensity at higher energies, accurate estimates of linear attenuation coefficients for shielded and unshielded uranium spheres with masses as small as 0.08 kg are found. The estimated maximum dose is generally so low that reasonable order tomography of interesting portions of a container should be possible.
[Show abstract][Hide abstract] ABSTRACT: The sensitivity for identification of high-Z objects in elemental form in the massive cargo of intermodal containers with continuous bremsstrahlung radiation depends critically on discriminating the weak signal from uncollided photons from the very intense flux of scattered radiations that penetrate the cargo. We propose that this might be accomplished by rejection of detected events with E 2-3 MeV that contain the majority of multiply-scattered photons along with a correction for single-scattered photons at higher energies. Monte Carlo simulations of radiographs with a 9-MeV bremsstrahlung spectrum demonstrate that rejection of detected events with E 3 MeV removes the majority of signals from scattered photons emerging through cargo with Z 30 and areal densities of at least 145 g cm². With analytical estimates of the single-scattered intensity at higher energies, accurate estimates of linear attenuation coefficients for shielded and unshielded uranium spheres with masses as small as 0.08 kg are found. The estimated maximum dose is generally so low that reasonable order tomography of interesting portions of a container should be possible.
Journal of Applied Physics 01/2007; 103(6). · 2.18 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: CUORICINO is an array of 62 TeO2 bolometers with a total mass of 40.7 kg (11.2 kg of 130Te), operated at about 10 mK to search for ββ(0ν) of 130Te. The detectors are organized as a 14-story tower and intended as a slightly modified version of one of the 19 towers of
the CUORE project, a proposed tightly packed array of 988 TeO2 bolometers (741 kg of total mass of TeO2) for ultralow-background searches on neutrinoless double-beta decay, cold dark matter, solar axions, and rare nuclear decays.
Started in April 2003 at the Laboratori Nazionali del Gran Sasso (LNGS), CUORICINO data taking was stopped in November 2003
to repair the readout wiring system of the 62 bolometers. Restarted in spring 2004, CUORICINO is presently the most sensitive
running experiment on neutrinoless double-beta decay. No evidence for ββ(0ν) decay has been found so far and a new lower limit, T
≥ 1.8 × 1024 yr (90% C.L.), is set, corresponding to 〈m
ν〉 ≤ 0.2–1.1 eV, depending on the theoretical nuclear matrix elements used in the analysis. Detector performance, operational
procedures, and background analysis results are reviewed. The expected performance and sensitivity of CUORE is also discussed.
[Show abstract][Hide abstract] ABSTRACT: We report the present results of the CUORICINO experiment, a cryogenic experiment on neutrinoless Double Beta Decay (DBD) of Te-130 consisting of an array of 62TeO(2) crystals with a total active mass of 40.7kg. The array is framed inside a dilution refrigerator, heavily shielded against environmental radioactivity and high-energy neutrons, and it is operated at a temperature of 8 mK in the Gran Sasso Underground Laboratory. After several improvements the live time of the experiment is near 75%. (c) 2005 Elsevier B.V. All rights reserved.
Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 04/2006; 559(2):352-354. DOI:10.1016/j.nima.2005.12.007 · 1.22 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In the last 10 years bolometers have become extremely powerful detectors in the search for rare events, due to their very good resolution. Cuoricino, a 62 bolometer array, in the first months of activity reached a resolution (average in all detectors) in the energy region of interest (2528 keV) of 7 keV and a limit on the t(1/2) of the process of 7.5(.)10(23) y. Cuoricino's 62 detectors constitute the biggest number of macrobolometers (790 g each) ever cooled and demonstrate the feasibility of large arrays of bolometers. Following the indication of Cuoricino in CUORE R&D a new detector has been developed trying to improve the reproducibility of the detector's performance, to increase the single detector
[Show abstract][Hide abstract] ABSTRACT: CUORE is a proposed experiment, already partially funded, to search for 0ν-DBD of 130Te using 988 TeO2 bolometers. It aims at reaching a sensitivity on the effective neutrino mass of the order of few tens of meV. The crucial parameter on which this expectation is based is background. Different strategies are under development to reduce as much as possible its value, among which the comprehension of CUORICINO background, a single CUORE tower running since 2003, plays an important role. Present results already achieved and studies that are underway are here presented and discussed.
[Show abstract][Hide abstract] ABSTRACT: We have measured cross sections for the 63Cu(alpha,gamma)67Ga reaction in the 5.9-8.7 MeV energy range using an activation technique. Natural Cu foils were bombarded with alpha beams from the 88 Cyclotron at Lawrence Berkeley National Laboratory (LBNL). Activated foils were counted using gamma spectrometry system at LBNL's Low Background Facility. The 63Cu(alpha,gamma)67Ga cross-sections were determined and compared with the latest NON-SMOKER theoretical values. Experimental cross sections were found to be in agreement with theoretical values.
[Show abstract][Hide abstract] ABSTRACT: We have measured cross sections for the 63Cu(α,γ)67Ga reaction in the 5.9- to 8.7-MeV energy range using an activation technique. Natural Cu foils were bombarded with α beams from the 88'' Cyclotron at Lawrence Berkeley National Laboratory (LBNL). Activated foils were counted using a γ-spectrometry system at LBNL's Low Background Facility. The 63Cu(α,γ)67Ga cross sections were determined and compared with the latest NON-SMOKER theoretical values. Experimental cross sections were found to be in agreement with theoretical values.
Physical Review C 03/2005; 71(3). DOI:10.1103/PhysRevC.71.035801 · 3.73 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: 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).