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All sourcesNASA NTRSDOE OSTI
DOE OSTI2010

Nuclear Data Sheets for A=182

Nuclear spectroscopic information for known nuclides of mass number 182 (Lu,Hf,Ta,W,Re,Os,Ir,Pt,Au,Hg, Tl,Pb) with Z=71 to 82 and N=111 to 100 have been evaluated and presented together with adopted energies and J{pi} of levels in these nuclei. No excited state data are yet available for {sup 182}Lu, while only limited structure information is available for {sup 182}Pb and {sup 182}Tl. Rotational band structures are known for {sup 182}Hg and {sup 182}Au but spin-parity assignments remain largely tentative. The decays of {sup 182}Lu, {sup 182}Hg, {sup 182}Au and {sup 182}Tl are not well established. The {sup 182}Hf isotope is of geophysical and astrophysical interest. This evaluation supersedes previous full evaluations of A=182 published by 1988Fi05 and 1975Sc13, and a selected (mainly high-spin) update of A=182 published by 1995Si04.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2010

First Observation Of New Neutron-Rich Magnesium, Aluminum, and Silicon Isotopes

The investigation of the limits of nuclear existence is fundamental to the understanding of nuclear forces and structure. The limits of binding for very neutron-rich nuclei and the location of the neutron dripline are established experimentally only for the lightest elements. We report on the discovery of the new neutron-rich isotopes {sup 40}Mg, {sup 42,43}Al, and {sup 44}Si. These rare isotopes were produced at the National Superconducting Cyclotron Laboratory by fragmentation of a 141 MeV/u {sup 48}Ca beam on a tungsten target. The combination of the A1900 fragment separator together with the analysis beam line of the S800 spectrograph provided a two-stage fragment separation with exceptional selectivity. The observation of the odd-odd nucleus {sup 42}Al, which was predicted to be unbound by FRDM [1] and HFB-8 [2] models, is the first indication that the neutron drip line may be located significantly further towards heavier isotopes in this mass region than it is currently believed.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2011

Measurement and simulation of the cross sections for nuclide production in {sup nat}W and {sup 181}Ta targets irradiated with 0.04- to 2.6-GeV protons

The cross sections for nuclide production in thin {sup nat}Wand {sup 181}Ta targets irradiated by 0.04-2.6-GeV protons have been measured by direct {gamma} spectrometry using two {gamma} spectrometers with the resolutions of 1.8 and 1.7 keV in the {sup 60}Co 1332-keV {gamma} line. As a result, 1895 yields of radioactive residual product nuclei have been obtained. The {sup 27}Al(p, x){sup 22}Na reaction has been used as a monitor reaction. The experimental data have been compared with the MCNPX (BERTINI, ISABEL), CEM03.02, INCL4.2, INCL4.5, PHITS, and CASCADE07 calculations.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2011

Measurement and simulation of the cross sections for the production of {sup 148}Gd in thin {sup nat}W and {sup 181}Ta targets irradiated with 0.4- to 2.6-GeV protons

The cross sections for the production of {sup 148}Gd in {sup nat}W and {sup 181}Ta targets irradiated by 0.4-, 0.6-, 0.8-, 1.2-, 1.6-, and 2.6-GeV protons at the ITEP accelerator complex have been measured by direct {alpha} spectrometry without chemical separation. The experimental data have been compared with the data obtained at other laboratories and with the theoretical simulations of the yields on the basis of the BERTINI, ISABEL, CEM03.02, INCL4.2, INCL4.5, CASCADE07, and PHITS codes.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2018

Motion of W and He atoms during formation of W fuzz

Measurements are conducted to identify the motion of tungsten and helium atoms during the formation of tungsten fuzz. In a first series of experiments the mobility of helium within the growing fuzz was measured by adding 3 He to the different stages of plasma exposure under conditions that promoted tungsten fuzz growth. Ion beam analysis was used to quantify the amount of 3 He remaining in the samples following the plasma exposure. The results indicate that the retention of helium in bubbles within tungsten is a dynamic process with direct implantation rather than diffusion into the bubbles, best describing the motion of the helium atoms. In the second experiment, an isotopically enriched layer of tungsten (~92.99% 182 W) is deposited on the surface of a bulk tungsten sample with the natural abundance of the isotopes. This sample is then exposed to helium plasma at the conditions necessary to support the formation of tungsten 'fuzz'. Depth profiles of the concentration of each of the tungsten isotopes are obtained using secondary ion mass spectrometry (SIMS) before and after the plasma exposure. The depth profiles clearly show mixing of tungsten atoms from the bulk sample toward the surface of the fuzz. Lastly, this supports a physical picture of the dynamic behavior of helium bubbles which, also, causes an enhanced mixing of tungsten atoms.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2011

Data evaluation methods and improvements to the neutron-capture {gamma}-ray spectrum

Improved neutron-capture {gamma}-ray spectra, not only of interest to the nuclear structure and reactions communities, are needed in a variety of applied and non-proliferation programs. This requires an evaluation of the existing experimental capture-{gamma} data. Elemental neutron-capture data taken from direct measurements at the Budapest Reactor have been used to collate the Evaluated Gamma-ray Activation File, a database of capture {gamma}-ray cross sections. These cross sections are then compared to Monte Carlo simulations of {gamma}-ray emission following the thermal neutron-capture process using the statistical-decay code DICEBOX. The aim of this procedure is to obtain the total radiative neutron-capture cross section and confidently increase the number of levels and {gamma} rays that can be assigned to a given isotope in the neutron data libraries. To achieve these goals and provide as complete information as possible in the neutron data libraries, it is also necessary to remain current with recent advances in nuclear structure physics and ensure that the latest data in the Evaluated Nuclear Structure Data File has been taken into consideration. This way an optimal level scheme can be derived by comparison with simulations and available experimental data. New information derived from this study can then be used to improve the nuclear structure and reactions databases with more-complete level schemes, and indeed, provide reliable and accurate input to a variety of applications which require this information. Recent results from neutron capture on the stable tungsten isotopes {sup 182,183,184,186}W are presented to illustrate the evaluation process.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2015

Evaluated 182,183,184,186 W Neutron Cross Sections and Covariances in the Resolved Resonance Region

Oak Ridge National Laboratory (ORNL) has recently completed the resonance parameter evaluation of four tungsten isotopes, i.e., 182,183,184,186 W, in the neutron energy range of thermal up to several keV. This nuclear data work was performed with support from the US Nuclear Criticality Safety Program (NCSP) in an effort to provide improved tungsten cross section and covariance data for criticality safety analyses. The evaluation methodology uses the Reich-Moore approximation of the R-matrix formalism of the code SAMMY to fit high-resolution measurements performed in 2010 and 2012 at the Geel linear accelerator facility (GELINA), as well as other experimental data sets on natural tungsten available in the EXFOR library. In the analyzed energy range, this work nearly doubles the resolved resonance region (RRR) present in the latest US nuclear data library ENDF/B-VII.1. In view of the interest in tungsten for distinct types of nuclear applications and the relatively homogeneous distribution of the isotopic tungsten—namely, 182 W(26.5%), 183 W(14.31%), 184 W(30.64%), and 186 W(28.43%) - the completion of these four evaluations represents a significant contribution to the improvement of the ENDF library. This paper presents an overview of the evaluated resonance parameters and related covariances for total and capture cross sections on the four tungsten isotopes.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2015

GRAPhEME: a setup to measure (n, xn γ) reaction cross sections

Most of nuclear reactor developments are using evaluated data base for numerical simulations. However, the considered databases present still large uncertainties and disagreements. To improve their level of precision, new measurements are needed, in particular for (n, xn) reactions, which are of great importance as they modify the neutron spectrum, the neutron population, and produce radioactive species. The IPHC group started an experimental program to measure (n, xn gamma) reaction cross sections using prompt gamma spectroscopy and neutron energy determination by time of flight. Measurements of (n, xn gamma) cross section have been performed for {sup 235,238}U, {sup 232}Th, {sup nat,182,183,184,186}W, {sup nat}Zr. The experimental setup is installed at the neutron beam at GELINA (Geel, Belgium). The setup has recently been upgraded with the addition of a highly segmented 36 pixels planar HPGe detector. Significant efforts have been made to reduce radiation background and electromagnetic perturbations. The setup is equipped with a high rate digital acquisition system. The analysis of the segmented detector data requires a specific procedure to account for cross signals between pixels. An overall attention is paid to the precision of the measurement. The setup characteristic and the analysis procedure will be presented along with the acquisition and analysis challenges. Examples of results and their impact on models will be discussed. (authors)

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2015

Evaluated {sup 182,183,184,186}W neutron cross sections and covariances in the resolved resonance region - 14617

Oak Ridge National Laboratory (ORNL) has recently completed the resonance parameter evaluation of four tungsten isotopes, i.e., {sup 182,183,184,186}W, in the neutron energy range of thermal up to several keV. This nuclear data work was performed with support from the US Nuclear Criticality Safety Program (NCSP) in an effort to provide improved tungsten cross section and covariance data for criticality safety analyses. The evaluation methodology uses the Reich-Moore approximation of the R-matrix formalism of the code SAMMY to fit high-resolution measurements performed in 2010 and 2012 at the Geel linear accelerator facility (GELINA), as well as other experimental data sets on natural tungsten available in the EXFOR library. In the analyzed energy range, this work nearly doubles the resolved resonance region (RRR) present in the latest US nuclear data library ENDF/B-VII.1. In view of the interest in tungsten for distinct types of nuclear applications and the relatively homogeneous distribution of the isotopic tungsten - namely, {sup 182}W(26.5%), {sup 183}W(14.31%), {sup 184}W(30.64%), and {sup 186}W(28.43%) - the completion of these four evaluations represents a significant contribution to the improvement of the ENDF library. This paper presents an overview of the evaluated resonance parameters and related covariances for total and capture cross sections on the four tungsten isotopes. (authors)

42 ENGINEERING↗
DOE OSTI2012

NUCLEOSYNTHETIC TUNGSTEN ISOTOPE ANOMALIES IN ACID LEACHATES OF THE MURCHISON CHONDRITE: IMPLICATIONS FOR HAFNIUM-TUNGSTEN CHRONOMETRY

Progressive dissolution of the Murchison carbonaceous chondrite with acids of increasing strengths reveals large internal W isotope variations that reflect a heterogeneous distribution of s- and r-process W isotopes among the components of primitive chondrites. At least two distinct carriers of nucleosynthetic W isotope anomalies must be present, which were produced in different nucleosynthetic environments. The co-variation of {sup 182}W/{sup 184}W and {sup 183}W/{sup 184}W in the leachates follows a linear trend that is consistent with a mixing line between terrestrial W and a presumed s-process-enriched component. The composition of the s-enriched component agrees reasonably well with that predicted by the stellar model of s-process nucleosynthesis. The co-variation of {sup 182}W/{sup 184}W and {sup 183}W/{sup 184}W in the leachates provides a means for correcting the measured {sup 182}W/{sup 184}W and {sup 182}W/{sup 183}W of Ca-Al-rich inclusions (CAI) for nucleosynthetic anomalies using the isotopic variations in {sup 183}W/{sup 184}W. This new correction procedure is different from that used previously, and results in a downward shift of the initial {epsilon}{sup 182}W of CAI to -3.51 {+-} 0.10 (where {epsilon}{sup 182}W is the variation in 0.01% of the {sup 182}W/{sup 183}W ratio relative to Earth's mantle). This revision leads to Hf-W model ages of core formation in iron meteorite parent bodies that are {approx}2 Myr younger than previously calculated. The revised Hf-W model ages are consistent with CAI being the oldest solids formed in the solar system, and indicate that core formation in some planetesimals occurred within {approx}2 Myr of the beginning of the solar system.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2012

TUNGSTEN ISOTOPIC COMPOSITIONS IN STARDUST SiC GRAINS FROM THE MURCHISON METEORITE: CONSTRAINTS ON THE s-PROCESS IN THE Hf-Ta-W-Re-Os REGION

We report the first tungsten isotopic measurements in stardust silicon carbide (SiC) grains recovered from the Murchison carbonaceous chondrite. The isotopes {sup 182,183,184,186}W and {sup 179,180}Hf were measured on both an aggregate (KJB fraction) and single stardust SiC grains (LS+LU fraction) believed to have condensed in the outflows of low-mass carbon-rich asymptotic giant branch (AGB) stars with close-to-solar metallicity. The SiC aggregate shows small deviations from terrestrial (= solar) composition in the {sup 182}W/{sup 184}W and {sup 183}W/{sup 184}W ratios, with deficits in {sup 182}W and {sup 183}W with respect to {sup 184}W. The {sup 186}W/{sup 184}W ratio, however, shows no apparent deviation from the solar value. Tungsten isotopic measurements in single mainstream stardust SiC grains revealed lower than solar {sup 182}W/{sup 184}W, {sup 183}W/{sup 184}W, and {sup 186}W/{sup 184}W ratios. We have compared the SiC data with theoretical predictions of the evolution of W isotopic ratios in the envelopes of AGB stars. These ratios are affected by the slow neutron-capture process and match the SiC data regarding their {sup 182}W/{sup 184}W, {sup 183}W/{sup 184}W, and {sup 179}Hf/{sup 180}Hf isotopic compositions, although a small adjustment in the s-process production of {sup 183}W is needed in order to have a better agreement between the SiC data and model predictions. The models cannot explain the {sup 186}W/{sup 184}W ratios observed in the SiC grains, even when the current {sup 185}W neutron-capture cross section is increased by a factor of two. Further study is required to better assess how model uncertainties (e.g., the formation of the {sup 13}C neutron source, the mass-loss law, the modeling of the third dredge-up, and the efficiency of the {sup 22}Ne neutron source) may affect current s-process predictions.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2015

Determination of the effective sample thickness via radiative capture

Our procedure for determining the effective thickness of non-uniform irregular-shaped samples via radiative capture is described. In this technique, partial γ-ray production cross sections of a compound nucleus produced in a neutron-capture reaction are measured using Prompt Gamma Activation Analysis and compared to their corresponding standardized absolute values. For the low-energy transitions, the measured cross sections are lower than their standard values due to significant photoelectric absorption of the γ rays within the bulk-sample volume itself. Using standard theoretical techniques, the amount of γ-ray self absorption and neutron self shielding can then be calculated by iteratively varying the sample thickness until the observed cross sections converge with the known standards. The overall attenuation provides a measure of the effective sample thickness illuminated by the neutron beam. This procedure is illustrated through radiative neutron capture using powdered oxide samples comprising enriched 186 W and 182 W from which their tungsten-equivalent effective thicknesses are deduced to be 0.077(3) mm and 0.042(8) mm, respectively.

(n, γ) radiative capture↗
DOE OSTI2019

Assessment of Mechanical Properties for Dissimilar Metal Welds: A Nondestructive Approach

Several engineering components are fabricated by joining similar or dissimilar materials. In the present investigation, welded joints between low alloy steel and austenitic stainless steel were considered. This assembly is one of the critical components in the heat transport system of water-cooled reactors of nuclear power plants. 309L austenitic stainless steel and IN 182 alloys were used for buttering low alloy steel during fabrication of joints. Weld metal was 308L austenitic stainless steel and IN 182, respectively, for the two assemblies. Buttering by 309L SS was performed by gas tungsten arc welding, and the same was done by shield metal arc welding at the time of applying IN 182. Joining of 304L SS and buttered assembly in both the cases was carried out by shield metal arc welding. Evaluation of Vickers micro-hardness was done across the weld centerline for both joints. Microstructure of different regions was examined for the joints. Apart from conventional destructive tests, ultrasonic evaluation of joints was also carried out to ensure weld integrity. In this respect, ultrasonic velocity in longitudinal and shear mode was measured along the transverse direction of the weld. Young’s modulus was determined using ultrasonic tests as well as from the average hardness of different regions. The obtained Young’s modulus by two different techniques revealed satisfactory co-relation. The Young’s modulus obtained from ultrasonic measurements was used to determine the yield strength of different regions across the welds. This technique proved to be useful in identifying the failure prone area across the welded joint.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Evaluation of Tungsten Neutron Cross Sections in the Resolved Resonance Regions

We generated a preliminary set of resonance parameters for 182-184,186W in the neutron energy range of thermal up to several keV. The evaluation methodology uses the Reich-Moore approximation to t, with the R-matrix code SAMMY, the high-resolution measurements performed in 2010 and 2012 at the GEel LINear Accelerator (GELINA) facility. Particularly for 183W, the transmission data and the capture cross sections calculated with the set of resonance parameters are compared with the experimental values, and some of the average properties of the resonance parameters are discussed. In the analyzed energy range, this work almost doubles the existing resolved resonance evaluations in the ENDF/B-VII.1 library. The analysis of the performance of the calculated cross sections based on criticality benchmarks is still in progress and it is only briefly discussed.

Pigni, Marco T↗
DOE OSTI2018

No 182 W excess in the Ontong Java Plateau source

We report that small-scale W isotope variations in ancient and modern terrestrial rocks provide insights into Earth's accretion and early differentiation history as well as the long-term evolution of the Earth's mantle. Tungsten isotope studies on such rocks have exploited advances in mass spectrometry, both NTIMS and MC-ICPMS, which now permit the determination of W isotope ratios at unprecedented precision. While W isotope studies performed in different labs by MC-ICPMS and NTIMS generally exhibit excellent agreement, obtaining accurate W isotope data at this level of precision remains analytically challenging. For example, a recent NTIMS study reported a relatively large, +24 ppm excess in 182 W/ 184 W for a Phanerozoic sample from the Ontong Java Plateau (OJP), but no such 182 W/ 184 W anomaly was found in another study by MC-ICPMS. The present study aims to resolve the discrepancy between these two previous studies, and more generally to evaluate the agreement between different recent W isotope studies by NTIMS and MC-ICPMS. To this end, we report new W isotope data for OJP drill core samples obtained by MC-ICPMS. Additionally, the OJP samples analyzed here exhibit no resolvable 182 W/ 184 W excess relative to the standards and most terrestrial rocks. Moreover, the OJP samples as well as the terrestrial rock standards analyzed here exhibit small but variable W isotope variations for ratios involving 183 W, producing coupled variations in both ‘radiogenic’ (i.e., 182 W/ 183 W) and ‘non-radiogenic’ (i.e., 183 W/ 184 W) ratios. These W isotope variations are analytical in origin, induced during sample preparation, and very likely caused by a nuclear field shift isotope fractionation affecting primarily the odd isotope ( 183 W). The recently reported 182 W excess for an OJP sample may result from this nuclear field shift effect, as the NTIMS analyses had to rely on a double normalization involving the 183 W/ 184 W ratio. More generally, these results demonstrate that using 183 W data from any MC-ICPMS or NTIMS study requires a careful quantification of any potential analytical 183 W effect. Nevertheless, once such effects are taken into account, then both 182 W/ 184 W and 183 W/ 184 W can accurately be determined to a very high level of precision.

07 ISOTOPE AND RADIATION SOURCES↗
DOE OSTI2011

New Improved Nuclear Data for Nuclear Criticality and Safety

The Geel Electron Linear Accelerator (GELINA) was used to measure neutron total and capture cross sections of 182,183,184,186 W and 63,65 Cu in the energy range from 100 eV to {approx}200 keV using the time-of-flight method. GELINA is the only high-power white neutron source with excellent timing resolution and ideally suited for these experiments. Concerns about the use of existing cross-section data in nuclear criticality calculations using Monte Carlo codes and benchmarks were a prime motivator for the new cross-section measurements. To support the Nuclear Criticality Safety Program, neutron cross-section measurements were initiated using GELINA at the EC-JRC-IRMM. Concerns about data deficiencies in some existing cross-section evaluations from libraries such as ENDF/B, JEFF, or JENDL for nuclear criticality calculations were the prime motivator for new cross-section measurements. Over the past years many troubles with existing nuclear data have emerged, such as problems related to proper normalization, neutron sensitivity backgrounds, poorly characterized samples, and use of improper pulse-height weighting functions. These deficiencies may occur in the resolved- and unresolved-resonance region and may lead to erroneous nuclear criticality calculations. An example is the use of the evaluated neutron cross-section data for tungsten in nuclear criticality safety calculations, which exhibit discrepancies in benchmark calculations and show the need for reliable covariance data. We measured the neutron total and capture cross sections of 182,183,184,186 W and 63,65 Cu in the neutron energy range from 100 eV to several hundred keV. This will help to improve the representation of the cross sections since most of the available evaluated data rely only on old measurements. Usually, these measurements were done with poor experimental resolution or only over a very limited energy range, which is insufficient for the current application.

43 PARTICLE ACCELERATORS↗
DOE OSTI2012

ORNL Neutron Cross-Section Measurements Activities

To support the Nuclear Criticality Safety Program, neutron cross-section measurements have been initiated using GELINA at the European Commission Joint Research Center IRMM. Concerns about data deficiencies in some existing cross-section evaluations from libraries such as ENDF/B, JEFF, or JENDL for nuclear criticality calculations have been the prime motivator for new cross section measurements. Over the past years, many problems with existing nuclear data have been emerging. An example is the use of the evaluated neutron cross-section data for tungsten in nuclear criticality safety calculations, which exhibit discrepancies in benchmark calculations and show the need for reliable covariance data. We recently measured the neutron total and capture cross sections of 182,183,184,186 W, 63,65 Cu, and natural calcium in the neutron energy range from 100 eV to several hundred keV. This will help to improve the representation of the cross sections since most of the available evaluated data rely only on old measurements. Besides, most of the evaluations in the nuclear data libraries are missing high-fidelity covariance data. New covariance data for the libraries can only be created by a reevaluation of the cross-section data; however, sometimes this impossible because the data used in the analysis and evaluations are no longer available. In such cases, this shortfall can be overcome only by new experimental data included in a new evaluation.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2011

Neutron Total and Capture Cross Section of Tungsten Isotope

A new set of measurements for the total and capture cross section determination of W isotopes was done using GELINA (GEel LINear Accelerator), a neutron Time-Of-Flight facility at the Institute for Reference Materials and Measurements (IRMM). Measuring stations at different flight path lengths were used in order to cover a broad neutron energy range with high resolution demands. Experimental techniques adopted for both transmission and capture measurements are well established using a (6)Li glass detector and C(6)D(6) scintillation arrays as detections systems respectively., As target samples highly enriched (182,183,184,186)W metallic discs were used.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗