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At least 1,675 records · Page 93
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Deciphering spin-parity assignments of nuclear levels

Spin-parity assignments of nuclear levels are critical for understanding nuclear structure and reactions. However, inconsistent notation conventions and ambiguous reporting in research papers often lead to confusion and misinterpretations. Here, this paper examines the policies of the Evaluated Nuclear Structure Data File (ENSDF) and the evaluations by Endt and collaborators, highlighting key differences in their approaches to spin-parity notation. Sources of confusion are identified, including ambiguous use of strong and weak arguments and the conflation of new experimental results with prior constraints. Recommendations are provided to improve clarity and consistency in reporting spin-parity assignments, emphasizing the need for explicit notation conventions, clear differentiation of argument strengths, community education, and separate reporting of new findings. These steps aim to enhance the accuracy and utility of nuclear data for both researchers and evaluators.

Experimental Nuclear Physics↗
DOE OSTI2019

Determing the Radiative Heat Transfer out of the Fireball of an Atmospheric Nuclear Detonation using Experimental Data

When Edgerton, Germeshausen and Grier, Inc. (EG&G) conducted the atmospheric nuclear tests in the 1950s, they made several continuous records of the light output over time with special "streak cameras." Once processed, these "streak films" contained long bands of varying optical density on black-and-white 35mm film. The purpose for creating them was to determine the time-dependent rate of radiative heat transfer out of the fireball. Back then, EG&G's manual examination methods were not precise enough to make complete analysis worthwhile, so the data was never fully analyzed. With the advent of new computer software, recently developed analysis techniques have reduced uncertainty in the data to where re-analysis is providing results far more reliable than anything EG&G published. Previously inaccessible information can now be accurately gathered from the original films. The method described here allows the streak films to be analyzed so a radiative power curve for an atmospheric nuclear detonation can be constructed using only experimental data. It was applied to five streak films here, though it may be applicable to other types of films as well. The data was plotted and compared to solutions generated with the Hybrid Chemistry (HYCHEM) software. The results are explained, and uncertainty values are provided. If the results from more films show consistency and the sources of uncertainty are mitigated, enough data may be discovered to create a correction factor for HYCHEM or to make more accurate yield determinations using G.I. Taylor's equations. Several other conclusions and recommendations are also posed.

45 MILITARY TECHNOLOGY, WEAPONRY, AND NATIONAL DEF↗
DOE OSTI2020

Applying Compression-Based Metrics to Seismic Data in Support of Global Nuclear Explosion Monitoring

The analysis of seismic data for evidence of possible nuclear explosion testing is a critical global security mission that relies heavily on human expertise to identify and mark seismic signals embedded in background noise. To assist analysts in making these determinations, we adapted two compression distance metrics for use with seismic data. First, we demonstrated that the Normalized Compression Distance (NCD) metric can be adapted for use with waveform data and can identify the arrival times of seismic signals. Then we tested an approximation for the NCD called Sliding Information Distance (SLID), which can be computed much faster than NCD. We assessed the accuracy of the SLID output by comparing it to both the Akaike Information Criterion (AIC) and the judgments of expert seismic analysts. Our results indicate that SLID effectively identifies arrival times and provides analysts with useful information that can aid their analysis process.

45 MILITARY TECHNOLOGY, WEAPONRY, AND NATIONAL DEF↗
DOE OSTI2024

Correlation of As-read and As-run Dosimetry Data

The Nuclear Science Users Facilities (NSUF) is responsible for the coordination of experiments conducted in Advanced Test Reactor (ATR) by Universities and other outside organizations. Completion of the experiment and data reporting process is long and expensive. As such, it is expected that targets for temperature and neutron dosage are met. Simulations of expected reactor performance under specific conditions to meet these targets are critical for this process. However, it is not often that these reports are correlated with the data produced by monitors in ATR. This project aims to correlate simulation and read data from experiments in ATR to gauge uncertainty.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2023

COHERENT Collaboration data release from the measurements of CsI[Na] response to nuclear recoils

The data release from the measurements of the CsI[Na] response to low energy nuclear recoils by the COHERENT collaboration. The release corresponds to the results published in 'D. Akimov et al 2022 JINST 17 P10034.' We share the data in the form of raw ADC waveforms, provide benchmark subselections and event reconstruction scripts to enhance the transparency and reproducibility of our results.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2022

Natural Language Processing-Enhanced Nuclear Industry Operating Experience Data Analysis to Support Risk Model Parameter Estimations

This set of slides has been prepared for a talk at the INL AI/ML Symposium held on September 8, 2022. Presentation outline: Background - Nuclear power plant operating experience data sources • Research focus and motivation - Analyzing free-text operating experience data: present and future • Research method - Input - Methodological steps - Output • Conclusions and next steps

99 GENERAL AND MISCELLANEOUS↗
DOE OSTI2021

Results of time-of-flight transmission measurements for 142 Ce at a 50 m station of GELINA

Transmission measurements have been performed at the time-of-flight facility GELINA to provide data for a new evaluation of neutron resonance parameters for 142 Ce. The measurements were carried out at a 50 m transmission station using a Li-glass scintillator with the accelerator operating at 400 Hz. This report provides the experimental details required to deliver the data to the EXFOR data library, maintained by the International Network of Nuclear Reaction Data Centres (NRDC). The experimental conditions and data reduction procedures are described. In addition, the full covariance information based on the AGS concept is given such that resonance parameters together with their covariances can be derived in a least-squares adjustment to the data.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2021

Stochastically estimated covariance matrices for independent and cumulative fission yields in the ENDF/B-VIII.0 and JEFF-3.3 evaluations

A Monte-Carlo method for the generation of correlation and covariance matrices for independent and cumulative fission yields has been developed. The method uses a constrained Monte-Carlo resampling structure in order to vary evaluated fission yield libraries in a way that meets basic conservation principles. This results in the generation of correlation/covariance matrices with limited model bias and uncertainty; the matrices are primarily reflective of the evaluated fission yield uncertainties and correlations that arise from the evaluation process. This method has been applied to generate correlation and covariance matrices for all of the fissioning systems of the ENDF/B-VIII.0 and JEFF-3.3 evaluations, marking the first time such matrices have been generated for all of these systems. These covariance matrices have been published online for immediate public use. These correlation and covariance matrices can be used to improve uncertainty estimation in calculations of reactor antineutrino emission rates, decay heat problems, and nuclear forensics.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2021

Influence of nonstatistical properties in nuclear structure on emission of prompt fission neutrons

We report the Hauser-Feshbach fission-fragment decay (HF 3 D) model is extended to calculate the prompt fission neutron spectrum (PFNS) for the thermal-neutron-induced fission on 235 U, where the evaporated neutrons from all possible fission-fragment pairs are aggregated. By studying model parameter sensitivities on the calculated PFNS as well as nonstatistical behavior of low-lying discrete level spin distribution, we conclude that discrepancies between the aggregation calculation and the experimental PFNS seen at higher neutron emission energies can be attributed to both the primary fission-fragment yield distribution and the possible high spin states that are not predicted by the statistical theory of nuclear structure.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2019

Magnetic Microcalorimeter (MMC) Gamma Detectors with Ultra-High Energy Resolution

The goal of this LCP is to develop ultra-high resolution gamma-ray detectors based on magnetic microcalorimeters (MMCs) for accurate measurements of nuclear decay data and NDA of nuclear materials. For highest energy resolution, we are introducing erbium-doped silver (Ag:Er) as a novel sensor material and implement several geometry and design changes to improve the signal-to-noise ratio. The detector sensitivity will be increased by developing arrays of 32 Ag:Er pixels read out by 16 SQUID preamplifiers, and by developing a cryogenic Compton veto to reduce the spectral background. For highest energy resolution we will operate the MMC detector arrays in a dilution refrigerator with a base temperature <10 mK. The detector performance and utility will be demonstrated with radioactive sources of interest to the safeguards community. In FY16 and FY17, we had purchased a liquid-cryogen-free dilution refrigerator and installed 16 SQUID preamplifiers and writing for MMC detector operation at ~10 mK. We have also developed the process to fabricate the first Ag:Er-based MMCs, built prototype detector arrays and tested them with different radioactive sources. We have also shown that our MMC detectors can achieve the LCP goal of an energy resolution below 50 eV as needed to resolve most closelyspaced lines of interest for NDA. The goals for FY18 were then 1) to optimize the MMC design based on the measured detector characteristics and to increase the array size to 32-pixels for increased sensitivity, and 2) to demonstrate the utility of MMC gamma-ray detectors in applications relevant in nuclear safeguards.

42 ENGINEERING↗
DOE OSTI2022

Status of GNDS support in AMPX [Slides]

This presentation provides an overview of ENDF reading in AMPX, as well as information regarding low level access classes for GNDS used in AMPX and the use of these classes in AMPX and SAMMY.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2020

Updated ENDF-6 Format Approval Process [Slides]

The presentation begins by discussing the original ENDF/B-VIII.0 format proposal lifecycle and states that the GNDS Expert Group has developed a gitlab-friendly review process that addresses concerns raised by the format proposal lifecycle. As a result, a revised ENDF/B-VIII.0 format proposal lifecycle has been created. The presentation then discusses the necessary steps in the lifecycle that are as follows: create an issue in the issue tracker, make your changes directly to the manual, submit it for review and final approval. The presentation concludes by discussing two other things, including the transition CI/CD from buildbot system to built-in gitlab CI/CD and that the revised format review process document will follow, pending approval.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2022

Proposed Generalized Header File for TSLs [Slides]

This presentation discusses several recent issues have been raised over the past few years regarding inconsistent definitions for the number of scattering atoms between incoherent elastic and inelastic (MT2 and MT4 files, respectively) in the same MF7 file and isotopic distribution of primary scattering atom. It also discusses how processing codes handle these potential issues in different ways. Additionally, it discusses how the preferred solution would be automation in order to reduce possibility of user error and a proposed solution in the form of a MF7/MT1 file is examined with preliminary examples. The presentation concludes with a question-and-answer discussion.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2013

Benchmark analysis of high temperature engineering test reactor core using McCARD code

A benchmark calculation has been performed for a startup core physics test of Japan's High Temperature Engineering Test Reactor (HTTR). The calculation is carried out by the McCARD code, which adopts the Monte Carlo method. The cross section library is ENDF-B/VII.0. The fuel cell is modeled by the reactivity-equivalent physical transform (RPT) method. Effective multiplication factors with different numbers of fuel columns have been analyzed. The calculation shows that the HTTR becomes critical with 19 fuel columns with an excess reactivity of 0.84% Δk/k. The discrepancies between the measurements and Monte Carlo calculations are 2.2 and 1.4 % Δk/k for 24 and 30 columns, respectively. The reasons for the discrepancy are thought to be the current version of cross section library and the impurity in the graphite which is represented by the boron concentration. In the future, the depletion results will be proposed for further benchmark calculations. (authors)

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2016

Ab initio generation of thermal neutron scattering law for uranium dioxide

Neutronic analysis of moderated nuclear fission systems, e.g. nuclear reactors, relies upon an accurate prediction of the thermal neutron spectrum. Thermal neutrons have wavelengths on the order of the interatomic spacing between atoms in matter. Consequently, the scattering cross-sections of these neutrons are affected by the scattering law of the material (i.e. S(α,β), where α and β are dimensionless momentum and energy transfer variables), which describes the atomic structure and thermodynamic motion of the atomic nuclei. Uranium-dioxide (UO{sub 2}) is the primary fuel source for nuclear power reactors moderated by light water. In such systems (e.g. nuclear power reactors, spent fuel pools, etc.) the nuclear fuel comprises a large fraction of the system volume, approximately 1/3 in light-water reactors. Therefore, the scattering law of the fuel material may impact the thermal neutron spectrum and criticality of these systems. In this work previously established ab initio lattice dynamics (AILD) methods were utilized to calculate the phonon density of states (DOS), which acts as a fundamental input to the scattering law. Subsequently, the S(α,β) of UO{sub 2} was generated for publication as an ENDF thermal scattering library (TSL), which will be available for use in standard neutronics computer applications. (authors)

07 ISOTOPE AND RADIATION SOURCES↗
DOE OSTI2024

Nuclear Power Plant Colocation with Data Centers

This presentation is an overview of the nuclear siting and licensing process, including specific considerations and challenges for nuclear power plant colocation with data centers.

22 - GENERAL STUDIES OF NUCLEAR REACTORS↗