Papers by Carlos Paradela
Physical Review C, 2014
Total fission cross sections of 181 Ta induced by protons at different relativistic energies have... more Total fission cross sections of 181 Ta induced by protons at different relativistic energies have been measured at GSI Darmstadt using the inverse kinematic technique. These data contribute to solve inconsistencies in previously reported measurements, but also help to benchmark state-of-the-art reaction codes. The energy range covered with these measurements allowed us to investigate the onset and temperature dependence of dissipative and transient effects at small deformation.
Physical Review C, 2020
99 Tc has been the subject of several experimental programs at the JRC-Geel since the late 1990s.... more 99 Tc has been the subject of several experimental programs at the JRC-Geel since the late 1990s. This work presents new transmission data measured at the GELINA facility with the time-of-flight technique, whose simultaneous analysis with past transmission experiments provided a revised set of resonance parameters up to 5 keV. An iterative analysis between the resonance and "continuum" energy ranges leads to average resonance parameters [S 0 = 0.51(3), γ 0 = 137(7) meV, D 0 = 12.8(2) eV] and theoretical average capture cross sections consistent with those reported in the literature. At E = 30 keV, we obtain a capture cross section of 1076(45) mb and a Maxwellian-averaged cross section (MACS) of 1016(43) mb. The agreement with the recommended MACS value of 933(47) mb remains within the quoted uncertainties. This result demonstrates the performances of transmission experiments to provide reliable theoretical capture cross sections for long-lived fission products in the energy range of interest for s-process nucleosynthesis calculations.
Resonance parameters of Gd isotopes derived from capture measurements at GELINA
The European Physical Journal A, 2020
Neutron capture yields for $$^{{155}}\hbox {Gd}$$ 155 Gd , $$^{{156}}\hbox {Gd}$$ 156 Gd , $$^{{1... more Neutron capture yields for $$^{{155}}\hbox {Gd}$$ 155 Gd , $$^{{156}}\hbox {Gd}$$ 156 Gd , $$^{{157}}\hbox {Gd}$$ 157 Gd , $$^{{158}}\hbox {Gd}$$ 158 Gd , and $$^{{160}}\hbox {Gd}$$ 160 Gd were determined applying the total energy detection principle technique using four $$\hbox {C}_{{6}}\hbox {D}_{{6}}$$ C 6 D 6 liquid scintillators and a $$^{{10}}\hbox {B}$$ 10 B -loaded ionization chamber. Time-of-flight experiments were carried out at a 30 m flight path station of the GELINA facility using enriched samples. Parameters for resonances in the energy region between 5 and 500 eV were obtained from a resonance shape analysis with REFIT. Resonance integrals for $$^{{155}}\hbox {Gd}$$ 155 Gd and $$^{{157}}\hbox {Gd}$$ 157 Gd derived from the parameters are 1511 (25) b and 801 (19) b, respectively. Average level spacings, average radiation widths and neutron strength functions were derived. The results were compared with data that are reported in the literature and recommended in evaluated data libraries.
Journal of Radioanalytical and Nuclear Chemistry, 2019
A characterisation of cylindrical samples by Neutron Resonance Transmission Analysis (NRTA) at th... more A characterisation of cylindrical samples by Neutron Resonance Transmission Analysis (NRTA) at the GELINA facility of JRC Geel (Belgium) is presented. The samples were designed and produced for reactivity worth measurements in the MINERVE reactor of CEA Cadarache (France). NRTA was applied to determine the nuclide composition of UO 2 , Al 2 O 3 and liquid samples that were doped with silver. The volume number densities of 238 U, 107 Ag and 109 Ag obtained by NRTA are within 2 % fully consistent with the values that are quoted by the manufacturer. In addition, the NRTA data reveal a tungsten contamination which is not reported by the provider. It is shown that such a contamination contributes by up to 5.7 % to the reactivity worth.
EPJ Web of Conferences, 2017
To support the US Department of Energy Nuclear Criticality Safety Program, neutron-induced cross ... more To support the US Department of Energy Nuclear Criticality Safety Program, neutron-induced cross section experiments were performed at the Geel Electron Linear Accelerator of the Joint Research Center Site Geel, European Union. Neutron capture and transmission measurements were carried out using metallic natural cerium and vanadium samples. Together with existing data, the measured data will be used for a new evaluation and will be submitted with covariances to the ENDF/B nuclear data library.
EPJ Web of Conferences, 2017
For the purpose of nuclear security and safeguards, an active neutron interrogation non-destructi... more For the purpose of nuclear security and safeguards, an active neutron interrogation non-destructive assay technique, Delayed Gamma-ray Spectroscopy (DGS), is under development. The technique of DGS uses the detection of decay γ rays from fission products to determine ratios of fissile nuclides in a sample. A proper evaluation of such γ-ray spectra requires integration of nuclear data such as fission cross-sections, fission yields, half-lives, decay-chain patterns, and decay γ-ray yields. Preliminary DGS experiments with the Pulsed Neutron Interrogation Test Assembly, named PUNITA, of the European Commissions' Joint Research Center have been performed. Signals of delayed γ ray from nuclear materials were successfully observed.
EPJ Web of Conferences, 2017
Neutron-induced reactions can be used to study the properties of nuclear materials of interest in... more Neutron-induced reactions can be used to study the properties of nuclear materials of interest in the fields of nuclear safeguards and security. The elemental and isotopic composition of these materials can be determined by using the presence of resonance structures. This idea is the basis of two non-destructive analysis techniques which have been developed at the GELINA neutron time-of-flight facility at JRC-Geel: Neutron Resonance Capture Analysis (NRCA) and Neutron Resonance Transmission Analysis (NRTA). A combination of NRTA and NRCA has been proposed for the characterisation of particle-like debris of melted fuel formed in severe nuclear accidents. In this work, we present a quantitative validation of the NRTA technique which was used to determine the areal densities of Pu enriched reference samples used for safeguards applications. Less than 2% bias has been obtained for the fissile isotopes, with well-known total cross sections.
EPJ Web of Conferences, 2017
A great deal of effort has been dedicated to the revision of the standard values in connection wi... more A great deal of effort has been dedicated to the revision of the standard values in connection with the neutron interaction for some actinides. While standard data compilation are available for decades nuclear data evaluations included in existing nuclear data libraries (ENDF, JEFF, JENDL, etc.) do not follow the standard recommended values. Indeed, the majority of evaluations for major actinides do not conform to the standards whatsoever. In particular, for the n + 235 U interaction the only value in agreement with the standard is the thermal fission cross section. A resonance re-evaluation of the n + 235 U interaction has been performed to address the issues regarding standard values in the energy range from 10 −5 eV to 2250 eV. Recently, 235 U fission cross-section measurements have been performed at the CERN Neutron Time-of-Flight facility (TOF), known as n TOF, in the energy range from 0.7 eV to 10 keV. The data were normalized according to the recommended standard of the fission integral in the energy range 7.8 eV to 11 eV. As a result, the n TOF averaged fission cross sections above 100 eV are in good agreement with the standard recommended values. The n TOF data were included in the 235 U resonance analysis that was performed with the code SAMMY. In addition to the average standard values related to the fission cross section, standard thermal values for fission, capture, and elastic cross sections were also included in the evaluation. This paper presents the procedure used for re-evaluating the 235 U resonance parameters including the recommended standard values as well as new cross section measurements.
Characterization of melted fuel by neutron resonance spectroscopy
2015 4th International Conference on Advancements in Nuclear Instrumentation Measurement Methods and their Applications (ANIMMA), 2015
Neutrons can be used as a tool to study properties of materials and objects. An evolving activity... more Neutrons can be used as a tool to study properties of materials and objects. An evolving activity in this field focusses on neutron induced reaction cross sections. The probability that a neutron interacts with a nucleus strongly depends on the energy of the neutron. The cross sections reveal the presence of resonance structures, the energy and width of which are nuclide specific. As such, these resonance structures can be used as fingerprints to determine the elemental and isotopic composition of materials and objects. They are the basis of two analytical methods which have been developed at the Institute for Reference Materials and Measurements of the European Commission's Joint Research Centre (EC-JRC-IRMM): Neutron Resonance Capture Analysis (NRCA) and Neutron Resonance Transmission Analysis (NRTA). The first technique is based on the detection of gamma rays emitted during a neutron capture reaction in the sample being studied; the latter determines the fraction of neutrons transmitted through a sample positioned in a neutron beam. In the past both techniques have been applied to determine the composition of archaeological objects and to characterize nuclear reference materials. More recently a combination of NRTA and NRCA is being studied as a non-destructive method to determine the heavy metal content of particle-like debris of melted fuel that is formed in severe nuclear accidents such as the one which occurred at the Fukushima Daiichi nuclear power plant in Japan. This study is part of a collaboration between the Japan Atomic Energy Agency (JAEA) and EC-JRC-IRMM and is a spin-off from the core activity of IRMM, i.e. the production of nuclear data for nuclear technology applications. This contribution focusses on a newly developed NRTA measurement station that has been set up recently at one of the flight paths of the neutron time-of-flight facility GELINA at the EC-JRC-IRMM. The basic principles of NRTA and first results of measurements at the new set up will be discussed.
In this work we have investigated total fission cross section of 181 Ta+ 1 H at FRS (FRagment Sep... more In this work we have investigated total fission cross section of 181 Ta+ 1 H at FRS (FRagment Separator-GSI) at 1, 0.8, 0.5 and 0.3 GeV with an specific setup, providing high accuracy measurements of the cross section values. We compare the results obtained in this experiment, with several calculations performed with the intra-nuclear cascade model (INCL v4.1) coupled to de-excitation code (ABLAv3p), according to two different models describing fission process at high-excitation energies: statistical model of Bohr and Wheeler and the dynamical description of the fission process. The comparison with data of previous experiments is also discussed in order to address the existing discrepancies with this new results.
Physics Procedia, 2013
SOFIA (Study On FIssion with Aladin) is an innovative experimental programme on nuclear fission c... more SOFIA (Study On FIssion with Aladin) is an innovative experimental programme on nuclear fission carried out at GSI. In August 2012, we used relativistic secondary beams of neutron-deficient actinides and pre-actinides provided by the FRS and studied their fission, induced by electromagnetic interaction, in inverse kinematics. This experiment will provide for the first time complete isotopic yields (nuclear charge and mass) for both fragments over a broad range of fissioning nuclei from 238 Np down to 183 Hg. In this article, we discuss the experimental setup and present promising preliminary results.
Physical Review C, 2012
The yield of the neutron capture reaction 232 Th(n, γ) has been measured at the neutron time-of-f... more The yield of the neutron capture reaction 232 Th(n, γ) has been measured at the neutron time-of-flight facility n_TOF at CERN in the energy range from 1 eV to 1 MeV. The reduction of the acquired data to the capture yield for resolved resonances from 1 eV to 4 keV is described and compared to a recent evaluated data set. The resonance parameters were used to assign an orbital momentum to each resonance. A missing level estimator was used to extract the s-wave level spacing of D 0 = 17.2 ± 0.9 eV.
Journal of Nuclear Science and Technology, 2009
The neutron capture cross section of 237 Np has been measured for fast neutrons supplied at the c... more The neutron capture cross section of 237 Np has been measured for fast neutrons supplied at the center of the core in the Yayoi reactor. The activation method was used for the measurement, in which the amount of the product 238 Np was determined by-ray spectroscopy using a Ge detector. The neutron flux at the center of the core calculated by the Monte Carlo simulation code MCNP was renormalized by using the activity of a gold activation foil irradiated simultaneously. The new convention is proposed in this paper to make possible a definite comparison of the integral measurement by the activation method using fast reactor neutrons with differential measurements using accelerator-based neutrons. ''Representative neutron energy'' is defined in the convention at which the cross section deduced by the activation measurement has a high sensitivity. The capture cross section of 237 Np corresponding to the representative neutron energy was deduced as 0:80 AE 0:04 b at 214 AE 9 keV from the measured reaction rate and the energy dependence of the cross section in the nuclear data library ENDF/B-VII.0. The deduced cross section of 237 Np at the representative neutron energy agrees with the evaluated data of ENDF/B-VII.0, but is 15% higher than that of JENDL-3.3 and 13% higher than that of JENDL/AC-2008.
Design of iToF: A ToF-wall detector to identify relativistic ions in R3B-FAIR
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2012
Narrow gas-gap resistive-plate-chambers were proposed to be used for the construction of a time-o... more Narrow gas-gap resistive-plate-chambers were proposed to be used for the construction of a time-of-flight detector for relativistic heavy ions in the R3B experiment at FAIR. Updated simulations with GEANT4, using state-of-the-art reaction codes as event-generators, allow to realistically evaluate the requirements of the detector for ion measurements. In our studies of detector designs we included what we called self-supported RPCs as well as sandwich structures. We propose a design for a modular detector optimized for R3B at FAIR and other applications.
EPJ Web of Conferences
Self-Indication Neutron Resonance Densitometry (SINRD) is a passive non-destructive method that i... more Self-Indication Neutron Resonance Densitometry (SINRD) is a passive non-destructive method that is being investigated to quantify the 239 Pu content in a spent fuel assembly. The technique relies on the energy dependence of total cross sections for neutron induced reaction. The cross sections show resonance structures that can be used to quantify the presence of materials in objects, e.g. the total cross-section of 239 Pu shows a strong resonance close to 0.3 eV. This resonance will cause a reduction of the number of neutrons emitted from spent fuel when 239 Pu is present. Hence such a reduction can be used to quantify the amount of 239 Pu present in the fuel. A neutron detector with a high sensitivity to neutrons in this energy region is used to enhance the sensitivity to 239 Pu. This principle is similar to self-indication cross section measurements. An appropriate detector can be realized by surrounding a 239 Pu-loaded fission chamber with appropriate neutron absorbing material. In this contribution experiments performed at the GELINA time-of-flight facility of the JRC at Geel (Belgium) to validate the simulations are discussed. The results confirm that the strongest sensitivity to the target material was achieved with the self-indication technique, highlighting the importance of using a 239 Pu fission chamber for the SINRD measurements.
LaBr3 γ-ray spectrometer for detecting 10B in debris of melted nuclear fuel
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2016
Journal of Analytical Atomic Spectrometry
A non-destructive technique for the elemental and isotopic analysis.
Studies on fission with ALADIN
The European Physical Journal A, 2015
Performance of timing-RPC prototypes with relativistic heavy ions
Residues production in the $^{136}$Xe +p spallation reaction relevant for the incineration of nuclear waste
The perspective of incineration of nuclear wastes in subcritical reactors (ADS) have triggered a ... more The perspective of incineration of nuclear wastes in subcritical reactors (ADS) have triggered a dedicated long-range research program at GSI in order to reach a full comprehension of the protons and deuterons induced spallation reactions by measurements of evaporation and fission residues with the FRS spectrometer in inverse kinematics. One of the studied systems was 136Xe + p at different energies. Such system behavior remains similar to that of a lead system, found in ADS spallation target, while it can be studied at lower energies reached for the last. In this presentation, we will report on the results obtained on the spallation of 136Xe by protons at 500 A MeV and 200 A MeV, supplying experimental information in an energy range which contributes significantly to the spallation shower in a thick target geometry, and where the intra-nuclear cascade codes present more discrepancies with data. The main challenge of this experiment is related to the lower energy, because of the app...
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Papers by Carlos Paradela