EMPIRE is a modular system of nuclear reaction codes, comprising various nuclear models, and designed for calculations over a broad range of energies and incident particles. A projectile can be a ...neutron, proton, any ion (including heavy-ions) or a photon. The energy range extends from the beginning of the unresolved resonance region for neutron-induced reactions (∽ keV) and goes up to several hundred MeV for heavy-ion induced reactions.
The code accounts for the major nuclear reaction mechanisms, including direct, pre-equilibrium and compound nucleus ones. Direct reactions are described by a generalized optical model (ECIS03) or by the simplified coupled-channels approach (CCFUS). The pre-equilibrium mechanism can be treated by a deformation dependent multi-step direct (ORION + TRISTAN) model, by a NVWY multi-step compound one or by either a pre-equilibrium exciton model with cluster emission (PCROSS) or by another with full angular momentum coupling (DEGAS). Finally, the compound nucleus decay is described by the full featured Hauser-Feshbach model with
γ-cascade and width-fluctuations. Advanced treatment of the fission channel takes into account transmission through a multiple-humped fission barrier with absorption in the wells. The fission probability is derived in the WKB approximation within the optical model of fission.
Several options for nuclear level densities include the EMPIRE-specific approach, which accounts for the effects of the dynamic deformation of a fast rotating nucleus, the classical Gilbert-Cameron approach and pre-calculated tables obtained with a microscopic model based on HFB single-particle level schemes with collective enhancement. A comprehensive library of input parameters covers nuclear masses, optical model parameters, ground state deformations, discrete levels and decay schemes, level densities, fission barriers, moments of inertia and
γ-ray strength functions.
The results can be converted into ENDF-6 formatted files using the accompanying code EMPEND and completed with neutron resonances extracted from the existing evaluations. The package contains the full EXFOR (CSISRS) library of experimental reaction data that are automatically retrieved during the calculations. Publication quality graphs can be obtained using the powerful and flexible plotting package ZVView. The graphic user interface, written in Tcl/Tk, provides for easy operation of the system.
This paper describes the capabilities of the code, outlines physical models and indicates parameter libraries used by EMPIRE to predict reaction cross sections and spectra, mainly for nucleon-induced reactions. Selected applications of EMPIRE are discussed, the most important being an extensive use of the code in evaluations of neutron reactions for the new US library ENDF/B-VII.0. Future extensions of the system are outlined, including neutron resonance module as well as capabilities of generating covariances, using both KALMAN and Monte-Carlo methods, that are still being advanced and refined.
A new evaluation of spectrum averaged cross sections (SACS) of 235U, 238U, and 239Pu measured in the 252Cf(sf) reference neutron field is presented and found to be consistent with the original ...Mannhart SACS evaluation in IRDF-2002. The comprehensive vetted experimental database that includes SACS ratio and absolute SACS measurements of major actinides is being used to update the SACS database employed as input of the new GMApy code to derive the Neutron Standards. An update of the current neutron standards based on Time Projection Chamber (TPC) shape data, a new comprehensive uncertainty quantification, and revised SACS experimental database is proposed which result in a 0.7% increase of the evaluated 239Pu(n,f)/235U(n,f) crosssection ratio in the 1–5 MeV energy region. The increase is due to a 0.3% reduction of the standard 235U(n,f) cross section and a 0.4% increase of the 239Pu(n,f) reference cross section in the 1–5 MeV energy region. Those changes are well within estimated USU fission cross-section uncertainties of 1.2%, but are relevant for the evaluated mean values.
The IAEA Nuclear Data Section has coordinated several actions to setup and improve a database for recommended cross sections and nuclear decay data for various charged-particle reactions that can be ...used for medical radionuclide production. Some of the earlier evaluations did not provide uncertainties for the recommended cross sections. Updated evaluations with uncertainty quantification for 25 reactions relevant for production of
67
Cu,
103
Pd,
102mg
Rh,
114m
In,
125
I,
169
Yb,
177g
Lu,
186
Re,
192
Ir and
210,211
At therapeutic radioisotopes are presented. Recommended cross-section data and their uncertainties for production of therapeutic radionuclides are available on the Web page of the IAEA Nuclear Data Section at
https://nds.iaea.org/radionuclides
and also at the IAEA medical portal
https://nds.iaea.org/medportal
.
An extensive series of evaluations have been performed as part of an IAEA coordinated research project to study a set of nuclear reactions that produce the diagnostic gamma-ray emitting radionuclides
...51
Cr,
99m
Tc,
111
In,
123
I and
201
Tl. Recommended cross-section data in the form of excitation functions have been derived, along with quantifications of their uncertainties. These evaluations involved the compilation of all previously published values and newly measured experimental data, followed by critical assessments and selection of those experimental datasets and accompanying uncertainties judged to be fully valid and statistically consistent for model-independent least-squares fitting by means of Padé approximations. Integral yields as a function of the energy were also calculated on the basis of the recommended cross sections deduced from these various fits. All evaluated numerical results and their corresponding uncertainties are available online at
www-nds.iaea.org/medical/gamma_emitters.html
and also on the medical portal of the International Atomic Energy Agency/Nuclear Data Section (IAEA-NDS)
www-nds.iaea.org/medportal/
.
One of the current major problems in nuclear data evaluation is the unreasonably small evaluated uncertainties often obtained. These small uncertainties are partly attributed to missing correlations ...of experimental uncertainties as well as to deficiencies of the model employed for the prior information. In this article, both uncertainty sources are included in an evaluation of 55Mn cross-sections for incident neutrons. Their impact on the evaluated output is studied using a prior obtained by the Full Bayesian Evaluation Technique and a prior obtained by the nuclear model program EMPIRE. It is shown analytically and by means of an evaluation that unreasonably small evaluated uncertainties can be obtained not only if correlated systematic uncertainties of the experiment are neglected but also if prior uncertainties are smaller or about the same magnitude as the experimental ones. Furthermore, it is shown that including model defect uncertainties in the evaluation of 55Mn leads to larger evaluated uncertainties for channels where the model is deficient. It is concluded that including correlated experimental uncertainties is equally important as model defect uncertainties, if the model calculations deviate significantly from the measurements.
•We study possible causes of unreasonably small evaluated nuclear data uncertainties.•Two different formulations of model defect uncertainties are presented and compared.•Smaller prior than experimental uncertainties cause too small evaluated ones.•Neglected correlations of experimental uncertainties cause too small evaluated ones.•Including model defect uncertainties in the prior improves the evaluated output.
Here, the energy spectrum of prompt neutron emitted in fission (PFNS) plays a very important role in nuclear science and technology. A Coordinated Research Project (CRP) "Evaluation of Prompt Fission ...Neutron Spectra of Actinides" was established by the IAEA Nuclear Data Section in 2009, with the major goal to produce new PFNS evaluations with uncertainties for actinide nuclei.
An IAEA coordinated research project that began in 2012 and ended in 2016 was primarily dedicated to the compilation, evaluation and recommendation of cross-section data for the production of medical ...radionuclides. One significant part of this work focused on diagnostic positron emitters. These particular studies consist of 69 reactions for direct and indirect or generator production of
44
Sc(
44
Ti),
52m
Mn(
52
Fe),
52g
Mn,
55
Co,
61
Cu,
62
Cu(
62
Zn),
66
Ga,
68
Ga(
68
Ge),
72
As(
72
Se),
73
Se,
76
Br,
82
Rb(
82
Sr),
82m
Rb,
86
Y,
89
Zr,
90
Nb,
94m
Tc,
110m
In(
110
Sn),
118
Sb(
118
Te),
120
I,
122
I(
122
Xe),
128
Cs(
128
Ba), and
140
Pr(
140
Nd) medical radionuclides. The resulting reference cross-section data were obtained from Padé fits to selected and corrected experimental data, and integral thick target yields were subsequently deduced. Uncertainties in the fitted results were estimated via a Padé least-squares method with the addition of a 4% assessed systematic uncertainty. Experimental data were also compared with theoretical predictions available from the TENDL-2015 and TENDL-2017 libraries. All of the numerical reference cross-section data with their corresponding uncertainties and deduced integral thick target yields are available on-line at the IAEA-NDS medical portal
www-nds.iaea.org/medicalportal
and also at the IAEA-NDS web page
www-nds.iaea.org/medical/positron_emitters.html
.
Abstract
Nucleon scattering on tungsten and neighboring nuclei are analyzed with a coupled-channels method based on a soft-rotator structure model. The multiple band couplings and nuclear stretching ...factors are built using nuclear wave functions of the soft-rotator model with the Hamiltonian parameters adjusted to reproduce the energy of low-lying collective levels of corresponding nuclei. A regional lane-consistent dispersive coupled-channels optical-model potential is derived to reproduce the neutron total cross sections, nucleon elastic and inelastic scattering angular distributions, and analyzing powers. Excellent agreement with measurements is obtained for neutron total cross sections of
182,183,184,186
W,
178
Hf, and
181
Ta targets in the whole energy range from 100 keV to 200 MeV; other scattering data are found to be in good agreement with measurements. A deformation-dependent nuclear radius correction arising from the volume conservation condition is introduced and allowed to remove phenomenological radii dependencies on nuclear mass from the potential geometry.
A new suite of evaluations for 54,56,57,58Fe has been developed in the framework of the CIELO international collaboration. New resolved resonance ranges were evaluated for 54Fe and 57Fe, while ...modifications were applied to resonances in 56Fe. The low energy part of the 56Fe file is almost totally based on measurements. At higher energies in 56Fe and in the whole fast neutron range for minor isotopes the evaluation consists of model predictions carefully adjusted to available experimental data. We also make use of the high quality and well experimentally-constrained dosimetry evaluations from the IRDFF library. Special attention was dedicated to the elastic angular distributions, which were found to affect results of the integral benchmarking. The new set of iron evaluations was developed in concert with other CIELO evaluations and they were tested together in the integral experiments before being adopted for the ENDF/B-VIII.0 library.
We use the zero-range post-form DWBA approximation to calculate deuteron elastic and nonelastic breakup cross sections and estimate the breakup-fusion cross section that could serve as a surrogate ...for a neutron-induced reaction cross section. We compare the angular momentum dependence of the breakup-fusion compound nucleus formation cross section with that of the corresponding neutron-induced cross section.
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