The ENDF/B-VIII.0 Compendium Volume III: Radioactive Decay Plots
Plots of radioactive decay particles (energy vs. probability of emission) for 1,645 isotopes with discrete emissions are presented in Volume III.
07 ISOTOPE AND RADIATION SOURCES↗
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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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Wait for it: post-supernova winds driven by delayed radioactive decays
In most astrophysical situations, the radioactive decay of {sup 56}Ni to {sup 56}Co occurs via electron capture with a fixed half-life of 6.1 days. However, this decay rate is significantly slowed when the nuclei are fully ionized because K-shell electrons are unavailable for capture. In this paper, we explore the effect of these delayed decays on white dwarfs (WDs) that may survive Type Ia and Type Iax supernovae (SNe Ia and SNe Iax). The energy released by the delayed radioactive decays of {sup 56}Ni and {sup 56}Co drives a persistent wind from the surviving WD’s surface that contributes to the late-time appearance of these SNe after emission from the bulk of the SN ejecta has faded. We use the stellar evolution code MESA to calculate the hydrodynamic evolution and resulting light curves of these winds. Our post-SN Ia models conflict with late-time observations of SN 2011fe, but uncertainties in our initial conditions prevent us from ruling out the existence of surviving WD donors. Much better agreement with observations is achieved with our models of post-SN Iax bound remnants, providing evidence that these explosions are due to deflagrations in accreting WDs that fail to completely unbind the WDs. Future radiative transfer calculations and wind models utilizing simulations of explosions for more accurate initial conditions will extend our study of radioactively powered winds from post-SN surviving WDs and enable their use as powerful discriminants among the various SN Ia and SN Iax progenitor scenarios.
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Radioactive Decay Computation with a Graph Approach for Solving a Linear Dynamic System
ABSTRACT: This article gives two graph-based algorithms for radioactive decay computation. The first algorithm identifies the connected components of the graph induced from the given radioactive decay dynamics to reduce the size of the problem. The solutions are derived over the precalculated connected components, respectively and independently. The second algorithm utilizes acyclic structure of radioactive decay dynamics. The algorithm evaluates the reachable vertices of the induced system graph from the initially activated vertices and finds the minimal set of starting vertices populating the entire reachable vertices. Then, the decay calculations are performed over the reachable vertices from the identified minimal starting vertices, respectively, with the partitioned initial value over the reachable vertices. A formal argument is given to show that the proposed graph inspired divide and conquer calculation methods perform the intended radioactive decay calculation. Empirical efforts comparing the proposed radioactive decay calculation algorithms are presented.
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Incorporating radioactive decay into charging and coagulation of multicomponent radioactive aerosols
Compositional changes by the decay of radionuclides in radioactive aerosols can influence their charging state, coagulation frequency and size distribution throughout their atmospheric lifetime. The importance of such effects is unknown as they have not been considered in microphysical and global radioactivity transport studies to date. Here, we explore the effects of compositional changes on the charging efficiency and coagulation rates of aerosols using a set of kinetic equations that couple all relevant processes (decay, charging and coagulation) and their evolution over time. Compared to a coupled aggregation-tracer model for the prediction of the radioactive composition of particulates undergoing coagulation, our kinetic approach can provide similar results using much less central processing unit time. Altogether with other considerations, our approach is computational efficient enough to allow implementation in 3D atmospheric transport models. The decay of radionuclides and the production of decay products within radioactive aerosols may significantly affect the aerosol charging rates, and either hinder or promote the coagulation of multicomponent radioactive aerosols. Our results suggest that radiological phenomena occurring within radioactive aerosols, as well as subsequent effects on aerosol microphysics, should be considered in regional and global models to more accurately predict radioactivity transport in the atmosphere in case of a nuclear plant accident.
54 ENVIRONMENTAL SCIENCES↗
The ENDF/B-VIII.0 Compendium Volume IV: Radioactive Decay Rank-Order Analyses
Version 8 of the Evaluated Nuclear Data File (ENDF/B-VIII.0) contains a wealth of nuclear data representing the most recent collection of evaluated neutron cross section measurements, isotopic radioactive decay, and much more. This Compendium has been prepared as a easily-navigable reference of the contents of the ENDF/B-VIII.0 library, while making no statement regarding the accuracy of those contents. The Compendium is split into four volumes. In Volume IV, radioactive decay properties are presented in tabular form, sorted by isotope, energy, element-then- energy, and probability of emission.
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Boson Fermion Nucleus Explanation for Violation of Parity in the Radioactive Decay of Cobalt-60: Monograph #12
In 1957, Chien-Shuing Wu subjected cobalt-60 to supercooled temperatures and a strong magnetic field while measuring radioactive decay. This experiment showed violation of parity— a long-held, fundamental precept in physics stating that nuclear radioactive-decay emission flux will not vary in the solid angle about the nucleus. During Wu’s experiment, beta particles (electrons) exhibited asymmetry, preferentially exiting the cobalt-60 nuclei in the polar region opposite the applied magnetic field. Gamma-ray emissions were anisotropic, preferring to exit the nucleus around the equatorial region. The boson fermion nucleus (BFN) explains the origins of these observed phenomena, where the nuclear structure is pinned in the strong magnetic field with minimal motion in supercooled conditions, while beta particles and gamma rays are emitted from specific locations within the nuclear structure.
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Computational Errors in the Calculation of Long Radioactive Decay Chains
For safety security of objects utilizing atomic energy, the effect of numerical errors on the calculation of the activity and integrals of the activity in time when using Bateman’s formula and Siewers’ algorithm to calculate radioactive decay chains is investigated. The smallest errors obtain when using Siewers’ algorithm and Bateman’s formula together with long arithmetic. It is shown that the standard calculations of radioactive decay chains according to Bateman’s formula with double precision lead to significant errors. However, these errors have almost no effect on the dose characteristics of mixtures of radionuclides. The analysis is based on data contained in ICRP Publication No. 107.
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Multimessengers from the Radioactive Decay of r -process Nuclei
The radioactive β-decay of nuclei synthesized in the rapid neutron capture process (r-process) releases a variety of particles, including electrons, γ-rays, neutrinos, and neutrons. These particles provide a rich set of multimessenger signals that carry information about the astrophysical environments where neutron-rich nucleosynthesis occurs. In this work, we calculate from first principles the emission spectra resulting from the β-decay of r-process nuclei. Our approach incorporates detailed nuclear structure and decay data to model the energy distributions of each particle species. We couple the spectra with a nuclear reaction network simulation to obtain the temporal evolution of these distributions. We find that the emission distributions vary significantly in time and are nonthermal, with substantial average energies. We investigate these nuclear signals as a direct probe of heavy element formation and show that they are complementary observables to kilonova.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Normalizing Radionuclide Concentration Exposure Rate and Dose Rate Data for the Effects of Radioactive Decay and Weathering Processes
This report describes the procedure that will be implemented to normalize radiological data, collected at various times, to one point in time. Raw radiological data is adjusted for the effects of radioactive decay and weathering processes. Normalizing the radiological data to one point in time enables data that has been collected at various times to be directly compared and utilized in radiological assessment, statistical analysis, and atmospheric dispersion models. This report fulfills a deliverable requirement for the U.S. Department of Energy’s, NA-84 Technology Integration Program for the FY17 project, SNL17-CM-635, Normalizing Radiological Data for Analysis and Integration into Models.
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Late-time photometry of type IA supernova SN 2012cg reveals the radioactive decay of {sup 57}Co
Seitenzahl et al. have predicted that roughly three years after its explosion, the light we receive from a Type Ia supernova (SN Ia) will come mostly from reprocessing of electrons and X-rays emitted by the radioactive decay chain {sup 57}Co → {sup 57}Fe, instead of positrons from the decay chain {sup 56}Co → {sup 56}Fe that dominates the SN light at earlier times. Using the Hubble Space Telescope, we followed the light curve of the SN Ia SN 2012cg out to 1055 days after maximum light. Our measurements are consistent with the light curves predicted by the contribution of energy from the reprocessing of electrons and X-rays emitted by the decay of {sup 57}Co, offering evidence that {sup 57}Co is produced in SN Ia explosions. However, the data are also consistent with a light echo ∼14 mag fainter than SN 2012cg at peak. Assuming no light-echo contamination, the mass ratio of {sup 57}Ni and {sup 56}Ni produced by the explosion, a strong constraint on any SN Ia explosion models, is 0.043{sub −0.011}{sup +0.012}, roughly twice Solar. In the context of current explosion models, this value favors a progenitor white dwarf with a mass near the Chandrasekhar limit.
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Pulsational Pair-instability Model for Superluminous Supernova PTF12dam:Interaction and Radioactive Decay
Being a superluminous supernova, PTF12dam can be explained by a {sup 56}Ni-powered model, a magnetar-powered model, or an interaction model. We propose that PTF12dam is a pulsational pair-instability supernova, where the outer envelope of a progenitor is ejected during the pulsations. Thus, it is powered by a double energy source: radioactive decay of {sup 56}Ni and a radiative shock in a dense circumstellar medium. To describe multicolor light curves and spectra, we use radiation-hydrodynamics calculations of the STELLA code. We found that light curves are well described in the model with 40 M {sub ⊙} ejecta and 20–40 M {sub ⊙} circumstellar medium. The ejected {sup 56}Ni mass is about 6 M {sub ⊙}, which results from explosive nucleosynthesis with large explosion energy (2–3)×10{sup 52} erg. In comparison with alternative scenarios of pair-instability supernova and magnetar-powered supernova, in the interaction model, all the observed main photometric characteristics are well reproduced: multicolor light curves, color temperatures, and photospheric velocities.
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Solving Complex Radioactive Decay Chains for Future Assessment and Cleanup Decisions - 17046
In support of U.S. Environmental Protection Agency's on-line calculators for risk and dose assessment, a decay chain tool was developed to address the need to understand how radionuclide activity changes with time as the activity measured in the past will be different from current and future levels. When a radionuclide decays, its activity decreases exponentially as a function of time transforming into a different atom - a decay product. The atoms keep transforming to new decay products until they reach a stable state and are no longer radioactive. The series of decay products created to reach this balance is called the decay chain. For radionuclide chains, the daughter products can have significant implications in dosimetry and remediation. Thus, risk assessors evaluating sites with radioactive contamination need to plan for future progeny ingrowth, in addition to sampled radionuclides. These are important considerations for risk quantification during the characterization and cleanup plans, particularly when sampling may have occurred years before the remediation cleanup work begins. If a radionuclide half-life and current activity are known, then hand-calculating the future activity is straightforward. However, calculating the ingrowth of progeny quickly becomes cumbersome for longer chains such as the Thorium-232 decay series. For the more complex chains where many daughters are formed, possibly with multiple branches, this calculation involves solving a complex set of simultaneous differential equations known as the Bateman Equation. The Decay Chain Activity Projection Tool calculates the activity of radionuclides and their progeny as a function of time. This tool currently uses a combination of Perl, JavaScript, Plot.ly, and jQuery to automatically construct the radionuclide decay chains, solve the resulting Bateman Equation, and provide the user with tabular solution output and plots. Additional software may be used as development advances. The risk assessor can then use the data for exposure assessment and cleanup decisions without further costly sampling. The benefits of providing this calculator are to prevent overestimation of risk due to decay of the parent isotope and to avoid underestimation of risk due to ingrowth of progeny more toxic than the parent. Graphs are provided to show the simultaneous decay rates and ingrowth, as well as tabular output at time-point T and all the decay half-life intervals. (authors)
12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
Radioactive decay of $\mathrm {{}^{90}Sr}$ in cement: a non-equilibrium first-principles investigation
Cement is an inexpensive and relatively easily manageable material that is used as a last barrier for nuclear waste disposal. Under these conditions, the cement is in contact with low radiation doses, but there is a distinct possibility of being contaminated with radioactive products. Of particular concern is the medium lived half-life product 90 Sr (28.8 years) due to its ability to replace Ca. 90 Sr undergoes β-decay to 90 Y which, in turn, β-decays to stable 90 Zr. In this work, we discuss systematically the chain of non-equilibrium processes that result as a consequence of β-decay events in cement. We first use density functional-based methods to study the consequences of the sudden increase of the nuclear charge from Z to Z+1, a possible induced ionization and the perturbation of the surrounding electronic charge. Secondly, we use molecular dynamics simulations to study the recoil of the daughter nucleus. Finally, we discuss the damage caused by the ionization cascade produced during the propagation of the β-electron and the resulting chemical and structural perturbation.
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A Method for Understanding the Behaviour of Radioactive Decay Chains in Radiological Assessments - 19382
In many radiological groundwater pathway assessments, especially those where the assessment timescales of interest are relatively short (say a few thousand years or less), contributions to effective dose or radiological risk are dominated by radionuclides such as C-14, Cl-36 or I-129. Over longer timescales, additional radionuclides can also become key contributors to risk. In particular, members of the U-238 decay chain, notably Ra-226 and Pb-210, are likely to be key radionuclides. Other decay chains that can contribute significantly to dose or risk at times far into the future include Np-237 → U-233 → Th-229 and U-235 → Pa-231 → Ac-227. In this paper, a method is described for understanding decay chain behaviour in radiological assessments. The method uses a graphical approach in which the various modes of transport and decay in a system of connected compartments are represented as pathways between two nodes in a two-dimensional grid. Each pathway corresponds to a distinct transport and decay process. By so doing, the different transport and decay processes can be identified in a systematic way. The result is an algorithm for generating the contributions to effective dose or radiological risk without explicit solution of the transport equations. The method has been tested against numerical models and analytic solutions and found to give excellent agreement, while at the same time providing information about decay chain behaviour that would be difficult to obtain from a numerical assessment model. The power of the method is illustrated by applying it to some examples based on real repository concepts. (authors)
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Astromers in the Radioactive Decay of r-process Nuclei
Certain nuclear isomers are well known to affect nucleosynthesis with important observable consequences (e.g., 26 Al and 180 Ta). We study the impact of nuclear isomers in the context of rapid neutron capture process (r-process) nucleosynthesis. Here we demonstrate that nuclear isomers are dynamically populated in the r process and that some are populated far from thermal equilibrium; this makes them astrophysical isomers, or "astromers." We compute thermally mediated transition rates between long-lived isomers and the corresponding ground states in neutron-rich nuclei. We calculate the temperature-dependent β-decay feeding factors, which represent the fraction of material going to each of the isomer and ground state daughter species from the β-decay parent species. We simulate nucleosynthesis following the decay of a solar-like r-process composition and include as separate species nuclear excited states with measured terrestrial half-lives greater than 100 μs. We introduce a new metric to identify those astromers most likely to be influential and summarize them in a table. Notable entries include many second peak nuclei (e.g., the Te isotopic chain) and previously overlooked isomers in stable nuclei (e.g., 119 Sn, 131 Xe, and 195 Pt). Finally, we comment on the capacity of isomer production to alter radioactive heating in an r-process environment.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
File format for normalizing radiological concentration exposure rate and dose rate data for the effects of radioactive decay and weathering processes
This report specifies the electronic file format that was agreed upon to be used as the file format for normalized radiological data produced by the software tool developed under this TI project. The NA-84 Technology Integration (TI) Program project (SNL17-CM-635, Normalizing Radiological Data for Analysis and Integration into Models) investigators held a teleconference on December 7, 2017 to discuss the tasks to be completed under the TI program project. During this teleconference, the TI project investigators determined that the comma-separated values (CSV) file format is the most suitable file format for the normalized radiological data that will be outputted from the normalizing tool developed under this TI project. The CSV file format was selected because it provides the requisite flexibility to manage different types of radiological data (i.e., activity concentration, exposure rate, dose rate) from other sources [e.g., Radiological Assessment and Monitoring System (RAMS), Aerial Measuring System (AMS), Monitoring and Sampling). The CSV file format also is suitable for the file format of the normalized radiological data because this normalized data can then be ingested by other software [e.g., RAMS, Visual Sampling Plan (VSP)] used by the NA-84’s Consequence Management Program.
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Radioactive Decay Chain Truncation Rules for Emergency Response Radiological Assessments
A set of radionuclide - decay chain truncation rules have been developed for use in the Turbo FRMAC and Specialized Hazard Assessment Response Capability (SHARC) software programs used to support radiological emergency response activities . Following the proposed rules, the software will truncate a decay chain after it encounters a progeny radionuclide with a half - life greater than 5,000 years. An analysis of the projected dose from many parent and progeny radionuclides over a 50 - year time period yielded that a radionuclide half - life cutoff of 5,000 years will exclude a negligible dose. Implementing the truncation rules will reduce the time required for assessments and minimize computer hardware requ irements without having a significant detrimental effect on dose projections and emergency response decisions. It is noted that the truncation rules may not be suited for long - term ( greater than 50 year) environmental assessments.
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Isochronic Evolution and the Radioactive Decay of r-process Nuclei
Abstract We report on the creation and application of a novel decay network that uses the latest data from experiment and evaluation. We use the network to simulate the late-time phase of the rapid neutron capture ( r ) process. In this epoch, the bulk of nuclear reactions, such as radiative capture, have ceased, and nuclear decays are the dominant transmutation channels. We find that the decay from short-lived to long-lived species naturally leads to an isochronic evolution in which nuclei with similar half-lives are populated at the same time. We consider random perturbations along each isobaric chain to initial solar-like r -process compositions to demonstrate the isochronic nature of the late-time phase of the r -process. Our analysis shows that detailed knowledge of the final isotopic composition allows for the prediction of late-time evolution with a high degree of confidence despite uncertainties that exist in astrophysical conditions and the nuclear physics properties of the most neutron-rich nuclei. We provide the time-dependent nuclear composition in the Appendix as supplemental material.
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