Nuclear Database Research Articles

Possible origins and implications of the shoulder in reactor neutrino spectra

We analyze within a nuclear database framework the shoulder observed in the antineutrino spectra in current reactor experiments. We find that the ENDF/B-VII.1 database predicts that the antineutrino shoulder arises from an analogous shoulder in the aggregate fission beta spectra. In contrast, the JEFF-3.1.1 database does not predict a shoulder for two out of three of the modern reactor neutrino experiments, and the shoulder that is predicted by JEFF-3.1.1 arises from $^{238}$U. We consider several possible origins of the shoulder, and find possible explanations. For example, there could be a problem with the measured aggregate beta spectra, or the harder neutron spectrum at a light-water power reactor could affect the distribution of beta-decaying isotopes. In addition to the fissile actinides, we find that $^{238}$U could also play a significant role in distorting the total antineutrino spectrum. Distinguishing these and quantifying whether there is an anomaly associated with measured reactor neutrino signals will require new short-baseline experiments, both at thermal reactors and at reactors with a sizable epithermal neutron component.

Features of MCNP6

MCNP6 can be described as the merger of MCNP5 and MCNPX capabilities, but it is much more than the sum of these two computer codes. MCNP6 is the result of six years of effort by the MCNP5 and MCNPX code development teams. These groups of people, residing in Los Alamos National Laboratory’s X Computational Physics Division, Monte Carlo Codes Group (XCP-3) and Nuclear Engineering and Nonproliferation Division, Radiation Transport Modeling Team (NEN-5) respectively, have combined their code development efforts to produce the next evolution of MCNP. While maintenance and major bug fixes will continue for MCNP5 1.60 and MCNPX 2.7.0 for upcoming years, new code development capabilities only will be developed and released in MCNP6. In fact, the initial release of MCNP6 contains numerous new features not previously found in either code. These new features are summarized in this document. Packaged with MCNP6 is also the new production release of the ENDF/B-VII.1 nuclear data files usable by MCNP. The high quality of the overall merged code, usefulness of these new features, along with the desire in the user community to start using the merged code, have led us to make the first MCNP6 production release: MCNP6 version 1. High confidence in the MCNP6 code is based on its performance with the verification and validation test suites, comparisons to its predecessor codes, our automated nightly software debugger tests, the underlying high quality nuclear and atomic databases, and significant testing by many beta testers.

Influence of nuclear basic data on the calculation of production cross sections of superheavy nuclei

The center of the predicted island of stability of superheavy nuclei (SHN) has not yet been observed experimentally. Many theories are being developed to understand the synthesizing mechanism of superheavy nuclei. However, all of them have to use some basic nuclear data. Three data tables, FRDM1995 [P. M\oller et al., At. Data Nucl. Data Tables 59, 185 (1995)], KTUY2005 [H. Koura et al., Prog. Theor. Phys. 113, 305 (2005)], and WS2010 [Ning Wang et al., Phys. Rev. C 82, 044304 (2010)], are used to investigate the SHN production. Based on the dinuclear system concept, the evaporation residue cross sections of SHN for $Z$=112--118 are calculated for the $^{48}\mathrm{Ca}$-induced hot fusion reactions. It turns out that unlike the predictions made with the KTUY2005 and WS2010 data, the magic numbers $Z$=114 and $N$=184 predicted with the FRDM1995 data do not contradict the experimental data obtained so far.

Point model equations for neutron correlation counting: Extension of Böhnel׳s equations to any order

Various methods of autocorrelation neutron analysis may be used to extract information about a measurement item containing spontaneously fissioning material. The two predominant approaches being the time correlation analysis (that make use of a coincidence gate) methods of multiplicity shift register logic and Feynman sampling. The common feature is that the correlated nature of the pulse train can be described by a vector of reduced factorial multiplet rates. We call these singlets, doublets, triplets etc. Within the point reactor model the multiplet rates may be related to the properties of the item, the parameters of the detector, and basic nuclear data constants by a series of coupled algebraic equations – the so called point model equations. Solving, or inverting, the point model equations using experimental calibration model parameters is how assays of unknown items is performed. Currently only the first three multiplets are routinely used. In this work we develop the point model equations to higher order multiplets using the probability generating functions approach combined with the general derivative chain rule, the so called Faà di Bruno Formula. Explicit expression up to 5th order are provided, as well the general iterative formula to calculate any order. This work represents the first necessary step towards determining if higher order multiplets can add value to nondestructive measurement practice for nuclear materials control and accountancy.

SU‐E‐T‐673: Recent Developments and Comprehensive Validations of a GPU‐Based Proton Monte Carlo Simulation Package, GPMC

Purpose:A GPU‐based Monte Carlo (MC) simulation package gPMC has been previously developed and high computational efficiency was achieved. This abstract reports our recent improvements on this package in terms of accuracy, functionality, and code portability.Methods:In the latest version of gPMC, nuclear interaction cross section database was updated to include data from TOPAS/Geant4. Inelastic interaction model, particularly the proton scattering angle distribution, was updated to improve overall simulation accuracy. Calculation of dose averaged LET (LETd) was implemented. gPMC was ported onto an OpenCL environment to enable portability across different computing devices (GPUs from different vendors and CPUs). We also performed comprehensive tests of the code accuracy. Dose from electro‐magnetic (EM) interaction channel, primary and secondary proton doses and fluences were scored and compared with those computed by TOPAS.Results:In a homogeneous water phantom with 100 and 200 MeV beams, mean dose differences in EM channel computed by gPMC and by TOPAS were 0.28% and 0.65% of the corresponding maximum dose, respectively. With the Geant4 nuclear interaction cross section data, mean difference of primary proton dose was 0.84% for the 200 MeV case and 0.78% for the 100 MeV case. After updating inelastic interaction model, maximum difference of secondary proton fluence and dose were 0.08% and 0.5% for the 200 MeV beam, and 0.04% and 0.2% for the 100 MeV beam. In a test case with a 150MeV proton beam, the mean difference between LETd computed by gPMC and TOPAS was 0.96% within the proton range. With the OpenCL implementation, gPMC is executable on AMD and Nvidia GPUs, as well as on Intel CPU in single or multiple threads. Results on different platforms agreed within statistical uncertainty.Conclusion:Several improvements have been implemented in the latest version of gPMC, which enhanced its accuracy, functionality, and code portability.

Intriguing trends in nuclear physics authorship

The increase in authorship of nuclear physics publications has been investigated using the large statistical samples. Large collections of bibliographical metadata represent a very powerful tool for understanding of the past, present, and, perhaps, future research trends. This has been accomplished with nuclear data mining of nuclear science references and the experimental nuclear reaction databases. The data analysis shows a strong anticorrelation between authorship increase of experimental papers and overall reduction of measurements due to closures of many small nuclear physics facilities. These findings suggest that article authorship is a very complex phenomenon, and presently-observed increase or “inflation” in authorship could be explained by the adaptation to the changing research environment, in addition to the evolving authorship rules that progressed over the years from very strict to lenient. The results of this study and their implications are discussed and conclusions presented.

Evaluation of Westcott g(T n )-factors used in k 0-NAA for “non-1/v” (n,γ) reactions

The Westcott convention was introduced in the early 1990s in k 0-NAA to allow the analysis of nuclides whose thermal neutron capture cross-sections do not follow the “1/v”-law, so called “non-1/v” nuclides. Most affected nuclides are Lu-176, Eu-151 and Yb-169. Westcott introduced a neutron temperature dependent “g(T n )-factor” for the activation by thermal neutrons. Recently the extended Hogdahl convention was introduced in k 0-NAA for “non-1/v” nuclides using the same factor, emphasizing the interest in the analysis using these nuclides. This paper reviews most publications on “g(T n )-factors” for NAA and provides new factors based on the most recent evaluated nuclear database ENDF/B-VII.1.

Production cross–section calculations of medical 32P, 117Sn, 153Sm and 186,188Re radionuclides used in bone pain palliation treatment

Abstract In this study, production cross–section calculations of 32P, 117Sn, 153Sm and 186,188Re radionuclides used in bone pain palliation treatment produced by 30Si(d,γ)32P, 118Sn(γ,n)117Sn, 116Sn(n,γ)117Sn, 150Nd(α,n)153Sm, 154Sm(n,2n)153Sm, 152Sm(n,γ)153Sm, 186W(d,2n)186Re, 187Re(γ,n)186Re, 185Re(n,γ)186Re and 187Re(n,γ)188Re reactions have been investigated in the different incident energy range of 0.003–34 MeV. Two-component exciton and generalised superfluid models of the TALYS 1.6 and exciton and generalised superfluid models of the EMPIRE 3.1 computer codes have been used to pre-equilibrium (PEQ) reaction calculations. The calculated production cross–section results have been compared with available experimental results existing in the experimental nuclear reaction database (EXFOR). Except the 118Sn(γ,n)117Sn, 150Nd(α,n)153Sm and 185Re(n,γ)186Re reactions, the two-component exciton model calculations of TALYS 1.6 code exhibit generally good agreement with the experimental measurements for all reactions used in this present study.

Status of the Prediction of Reactor Anti-neutrino Spectra

New generation neutrino physics experiments at reactors have recently determined the value of the θ13 mixing angle. Even though their principle is to use multiple detectors allowing to minimize the influence of reactor and nuclear physics ingredients on their results, these ingredients cannot be totally eliminated. They include reactor simulations, but also new computations of reactor anti-neutrino energy spectra. Recently, after a new computation of the reactor anti-neutrino energy spectra, based on the conversion of integral data of the beta spectra from 235U, and 239;241Pu, a deficit of reactor anti-neutrinos measured by short baseline experiments was pointed out. This is called the reactor anomaly, a new puzzle in the neutrino physics area. Since then, numerous new experimental neutrino projects have emerged. In parallel, computations of the anti-neutrino spectra independent from the ILL data would be desirable. One possibility is the use of the summation method, summing all the contributions of the fission product beta decay branches that can be found in nuclear databases. Studies have shown that in order to obtain reliable summation anti-neutrino energy spectra, new nuclear physics measurements of selected fission product beta decay properties are required. Lately, the first integral measurement of the beta spectrum associated to fast fission of 238U has been performed. Even more recently, the question of the influence of forbidden decays in the determination of reactor anti-neutrino energy spectrum has been raised. At this conference, we will present the methods used to compute reactor anti-neutrino energy spectra, the recent published developments on the topic, remaining open questions and some experimental outlooks.

Challenge of PWR new core design simulation: A focus on uncertainties due to nuclear data and reflector modelling

This paper presents a reactor core uncertainty analysis in the framework of the OECD/NEA UAM Benchmark. Three types of uncertainties affecting the predictions of power distribution in the core of a nuclear reactor are discussed: the uncertainties of basic nuclear data, the uncertainties resulting from the use of different simulation tools and those due to approximations in reflector modelling. The contribution of nuclear data uncertainty on the power distribution of a UOX and a MOX core is assessed with the XSUSA tool. Overall, the results obtained with different tools in both institutions are in good agreement, showing that the power distribution uncertainty due to the use of different simulation tools is much lower than the one due to nuclear data, which is a large contributor. Lastly, the paper presents preliminary work showing the relevance of reflector modelling on the uncertainty of the power distribution at nominal conditions as well as on an asymmetrical case representative of accidental conditions.

Sequencing of the mitochondrial genome of the avocado lace bug Pseudacysta perseae (Heteroptera, Tingidae) using a genome skimming approach

Lace bugs (Tingidae) are a family of phytophagous heteropterans, some of which are important agricultural and forestry pests. They currently comprise around 2500 species distributed worldwide, for which only one mitochondrial genome has been described so far. We sequenced the complete mitochondrial genome and the nuclear ribosomal gene segment of the avocado lace bug Pseudacysta perseae using a genome skimming approach on an Illumina Hiseq 2000 platform. Fifty-four additional heteropteran mitogenomes, including the one of the sycamore lace bug Corythucha ciliata, were retrieved to allow for comparisons and phylogenetic analyses. P. perseae mitochondrial genome was determined to be 15,850bp long, and presented the typical organisation of insect mitogenomes. The phylogenetic analysis placed P. perseae as a sister to C. ciliata but did not confirm the monophyly of Miroidae including Tingidae. Our results contradicted widely accepted phylogenetic hypothesis, which highlights the limits of analyses based on mitochondrial data only. Shotgun sequencing approaches should provide substantial improvements in harmonizing mitochondrial and nuclear databases.

Mining the human complexome database identifies RBM14 as an XPO1-associated protein involved in HIV-1 Rev function.

By recruiting the host protein XPO1 (CRM1), the HIV-1 Rev protein mediates the nuclear export of incompletely spliced viral transcripts. We mined data from the recently described human nuclear complexome to identify a host protein, RBM14, which associates with XPO1 and Rev and is involved in Rev function. Using a Rev-dependent p24 reporter plasmid, we found that RBM14 depletion decreased Rev activity and Rev-mediated enhancement of the cytoplasmic levels of unspliced viral transcripts. RBM14 depletion also reduced p24 expression during viral infection, indicating that RBM14 is limiting for Rev function. RBM14 has previously been shown to localize to nuclear paraspeckles, a structure implicated in retaining unspliced HIV-1 transcripts for either Rev-mediated nuclear export or degradation. We found that depletion of NEAT1 RNA, a long noncoding RNA required for paraspeckle integrity, abolished the ability of overexpressed RBM14 to enhance Rev function, indicating the dependence of RBM14 function on paraspeckle integrity. Our study extends the known host cell interactome of Rev and XPO1 and further substantiates a critical role for paraspeckles in the mechanism of action of Rev. Our study also validates the nuclear complexome as a database from which viral cofactors can be mined. This study mined a database of nuclear protein complexes to identify a cellular protein named RBM14 that is associated with XPO1 (CRM1), a nuclear protein that binds to the HIV-1 Rev protein and mediates nuclear export of incompletely spliced viral RNAs. Functional assays demonstrated that RBM14, a protein found in paraspeckle structures in the nucleus, is involved in HIV-1 Rev function. This study validates the nuclear complexome database as a reference that can be mined to identify viral cofactors.

Exploring the Impact of Nuclear Data Uncertainties in Ultra-high Resolution Gamma Spectroscopy for Isotopic Analysis Using Approximate Bayesian Computation

High purity germanium (HPGe) currently provides the highest readily available resolution gamma detection for a broad range of radiation measurements, but microcalorimetry is a developing option that has considerably higher resolution even than HPGe. Superior microcalorimetry resolution offers the potential to better distinguish closely spaced X-rays and gamma-rays, a common challenge for the low energy spectral region near 100 keV from special nuclear materials, and the higher signal-to-background ratio also confers an advantage in detection limit. As microcalorimetry continues to develop, it is timely to assess the impact of uncertainties in detector and item response functions and in basic nuclear data, such as branching ratios and half-lives, used to interpret spectra in terms of the contributory radioactive isotopes. We illustrate that a new inference option known as approximate Bayesian computation (ABC) is effective and convenient both for isotopic inference and for uncertainty quantification for microcalorimetry. The ABC approach opens a pathway to new and more powerful implementations for practical applications than currently available.

ONRLDB--manually curated database of experimentally validated ligands for orphan nuclear receptors: insights into new drug discovery.

Orphan nuclear receptors are potential therapeutic targets. The Orphan Nuclear Receptor Ligand Binding Database (ONRLDB) is an interactive, comprehensive and manually curated database of small molecule ligands targeting orphan nuclear receptors. Currently, ONRLDB consists of ∼11 000 ligands, of which ∼6500 are unique. All entries include information for the ligand, such as EC50 and IC50, number of aromatic rings and rotatable bonds, XlogP, hydrogen donor and acceptor count, molecular weight (MW) and structure. ONRLDB is a cross-platform database, where either the cognate small molecule modulators of a receptor or the cognate receptors to a ligand can be searched. The database can be searched using three methods: text search, advanced search or similarity search. Substructure search, cataloguing tools, and clustering tools can be used to perform advanced analysis of the ligand based on chemical similarity fingerprints, hierarchical clustering, binning partition and multidimensional scaling. These tools, together with the Tree function provided, deliver an interactive platform and a comprehensive resource for identification of common and unique scaffolds. As demonstrated, ONRLDB is designed to allow selection of ligands based on various properties and for designing novel ligands or to improve the existing ones.Database URL: http://www.onrldb.org/

OBSERVABILITY-IN-DEPTH: AN ESSENTIAL COMPLEMENT TO THE DEFENSE-IN-DEPTH SAFETY STRATEGY IN THE NUCLEAR INDUSTRY1

Defense-in-depth is a fundamental safety principle for the design and operation of nuclear power plants. Despite its general appeal, defense-in-depth is not without its drawbacks, which include its potential for concealing the occurrence of hazardous states in a system, and more generally rendering the latter more opaque for its operators and managers, thus resulting in safety blind spots. This in turn translates into a shrinking of the time window available for operators to identify an unfolding hazardous condition or situation and intervene to abate it. To prevent this drawback from materializing, we propose in this work a novel safety principle termed “observability-in-depth”. We characterize it as the set of provisions technical, operational, and organizational designed to enable the monitoring and identification of emerging hazardous conditions and accident pathogens in real-time and over different time-scales. Observability-in-depth also requires the monitoring of conditions of all safety barriers that implement defense-in-depth; and in so doing it supports sensemaking of identified hazardous conditions, and the understanding of potential accident sequences that might follow (how they can propagate). Observability-in-depth is thus an information-centric principle, and its importance in accident prevention is in the value of the information it provides and actions or safety interventions it spurs. We examine several “event reports” from the U.S. Nuclear Regulatory Commission database, which illustrate specific instances of violation of the observability-in-depth safety principle and the consequences that followed (e.g., unmonitored releases and loss of containments). We also revisit the Three Mile Island accident in light of the proposed principle, and identify causes and consequences of the lack of observability-in-depth related to this accident sequence. We illustrate both the benefits of adopting the observability-in-depth safety principle and the adverse consequences when this principle is violated or not implemented. This work constitutes a first step in the development of the observability-in-depth safety principle, and we hope this effort invites other researchers and safety professionals to further explore and develop this principle and its implementation.

Excitation Function of 56Fe(n,α)53Cr Reaction from Threshold to 20 MeV for Fusion Applications

The current state of nuclear data evaluations requires improvement for fusion applications. In this context, the excitation function of the 56Fe(n,α)53Cr reaction from threshold to 20 MeV has been calculated using the Hauser-Feshbach statistical model with preequilibrium effects by the TALYS-1.4 code. Different types of nuclear level density models have been used in the calculation. The present calculations are compared with existing experimental data as well as with latest available evaluated nuclear data libraries ENDF/B-VII.1, JEFF-3.2, and JENDL-4.0. Good agreement between the calculated and the experimental data validates the nuclear model approaches with increased predictive power to supplement and extend the nuclear database. The present calculations have also been compared with the (n,α) reaction cross-section systematics at 14.5-MeV neutron energy.

Simulating γ–γ coincidences of β-delayed γ-rays from fission product nuclei

Analyzing radiation from material that has undergone neutron induced fission is important for fields such as nuclear forensics, reactor physics, and nonproliferation monitoring. The γ-ray spectroscopy of fission products is a major part of the characterization of a material׳s fissile inventory and the energy of incident neutrons inducing fission.Cumulative yields and γ-ray intensities from nuclear databases are inputs into a GEANT4 simulation to create expected γ-ray spectra from irradiated 235U. The simulations include not only isotropically emitted γ-rays but also γ–γ cascades from certain fission products, emitted with their appropriate angular correlations. Here γ singles spectra as well as γ–γ coincidence spectra are simulated in detectors at both 90° and 180° pairings.The ability of these GEANT4 Monte Carlo simulations to duplicate experimental data is explored in this work. These simulations demonstrate potential in exploiting angular correlations of γ–γ cascades in fission product decays to determine isotopic content. Analyzing experimental and simulated γ–γ coincidence spectra as opposed to singles spectra should improve the ability to identify fission product nuclei since such spectra are cleaner and contain more resolved peaks when compared to γ singles spectra.

Selection and evaluation of potential burnable absorbers incorporated into modified TRISO particles

The quadruple isotropic (QUADRISO) particle concept modifies tri-structural-isotropic (TRISO) particles to add a layer of burnable absorber next to the fuel kernel. Previous studies have evaluated QUADRISO fuel particle designs for the transmutation of neptunium and plutonium, as a modification to the plutonium–thorium fuel cycle, and for excess reactivity management. This study screens the available nuclear isotope database to identify potential burnable absorbers for incorporation into modified TRISO fuel particles in a representative Very High-Temperature Reactor (VHTR). Based on this screening, eleven potential burnable absorbers are tested as QUADRISO burnable absorber layers, in either oxide or carbide forms. The addition of a burnable absorber layer to the TRISO fuel resulted in an increase in reactor operational lifetime in all cases considered in the present work when compared to a reactor with the same excess reactivity without burnable absorbers. The B4C, CdO and Gd2O3 cases resulted in the greatest operational lifetime, for the same initial excess reactivity, and the addition of these burnable absorbers to TRISO fuel particles decreased the magnitude of the excess reactivity change over the reactor lifetime when compared to the unmodified TRISO case. Thermal cross-section effects in QUADRISO particles generally result in excess reactivity decreasing with increasing temperature.

Metrology for New Generation Nuclear Power Plants–MetroFission

Metrology for New Generation Nuclear Power Plants–MetroFission

Development of an Evaluated Nuclear Database for Modern Technologies

The main phases in the development of the constants required for neutron-physical calculations of fast reactors, ranging from systems of BNAB group constants to modern national libraries of the BROND and ROSFOND evaluated nuclear data files, are examined. Problems for subsequent conversion of the libraries into licensed sets of standard data for nuclear technological projects are formulated.