[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. · 1.27 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). · 3.72 Impact Factor
[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.
IEEE Transactions on Nuclear Science 05/2011; · 1.22 Impact Factor
[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 01/2011; 269(10):1130-1139. · 1.27 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.
Journal of Applied Physics 03/2008; 103(6):064910-064910-8. · 2.21 Impact Factor
[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). · 2.21 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.
Physics of Atomic Nuclei 11/2006; 69(12):2083-2089. · 0.54 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We report the present results of the CUORICINO experiment, a cryogenic experiment on neutrinoless Double Beta Decay (DBD) of 130Te consisting of an array of crystals with a total active mass of . 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 in the Gran Sasso Underground Laboratory. After several improvements the live time of the experiment is near 75%.
Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 04/2006; 559(2):352-354. · 1.14 Impact Factor
[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). · 3.72 Impact Factor
[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.
Nuclear Physics B - Proceedings Supplements. 01/2005;
[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).
[Show abstract][Hide abstract] ABSTRACT: 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.
[Show abstract][Hide abstract] ABSTRACT: There are a variety of motivations for quantifying Pu in spent (used) fuel assemblies by means of nondestructive assay (NDA) including the following: strengthen the capabilities of the International Atomic Energy Agencies to safeguards nuclear facilities, quantifying shipper/receiver difference, determining the input accountability value at reprocessing facilities and providing quantitative input to burnup credit determination for repositories. For the purpose of determining the Pu mass in spent fuel assemblies, twelve NDA techniques were identified that provide information about the composition of an assembly. A key point motivating the present research path is the realization that none of these techniques, in isolation, is capable of both (1) quantifying the elemental Pu mass of an assembly and (2) detecting the diversion of a significant number of pins. As such, the focus of this work is determining how to best integrate 2 or 3 techniques into a system that can quantify elemental Pu and to assess how well this system can detect material diversion. Furthermore, it is important economically to down-select among the various techniques before advancing to the experimental phase. In order to achieve this dual goal of integration and down-selection, a Monte Carlo library of PWR assemblies was created and is described in another paper at Global 2009 (Fensin et al.). The research presented here emphasizes integration among techniques. An overview of a five year research plan starting in 2009 is given. Preliminary modeling results for the Monte Carlo assembly library are presented for 3 NDA techniques: Delayed Neutrons, Differential Die-Away, and Nuclear Resonance Fluorescence. As part of the focus on integration, the concept of"Pu isotopic correlation" is discussed and the role of cooling time determination.