Preliminary results on the study of 237Np(n,f) at n_TOF/EAR2 in energies related to nuclear waste transmutation

The accurate knowledge of neutron-induced fission cross sections of isotopes involved in the nuclear fuel cycle is essential for the optimum design and safe operation of next generation nuclear systems. Such experimental data can additionally provide constraints for the adjustment of nuclear model parameters used in the evaluation process, resulting in a further understanding of the nuclear fission process. In this respect measurements of the 237Np(n,f) cross section have been performed at the n_TOF facility at CERN in the horizontal 185 m flight-path (EAR1) which were discrepant by 7% in the MeV region. The neutron-induced fission cross section of 237Np(n,f) was recently restudied at the EAR2 19.5 m vertical beam-line at CERN’s n_TOF facility, over a wide range of neutron energies, from 100 keV up to 15 MeV, using the time-of-flight technique and a modern set-up based on Micromegas detectors. This study was performed in an attempt to resolve the aforementioned discrepancies and to provide accurate data of a reaction that is frequently used as reference in measurements related to feasibility and design studies of advanced nuclear systems. Preliminary results with a high statistical accuracy that resolve the discrepancies will be presented along with a brief discussion concerning the facility and the analysis.

Download Full-text

Study of the neutron-induced fission cross section of 237Np at CERN's n_TOF facility over a wide energy range

EPJ Web of Conferences ◽

10.1051/epjconf/202023905006 ◽

2020 ◽

Vol 239 ◽

pp. 05006

Author(s):

A. Stamatopoulos ◽

A. Tsinganis ◽

M. Diakaki ◽

N. Colonna ◽

M. Kokkoris ◽

...

Keyword(s):

Experimental Data ◽

Energy Range ◽

Cross Section ◽

Fuel Cycle ◽

Fission Cross Section ◽

Nuclear Model ◽

Wide Energy Range ◽

Model Parameters ◽

Wide Range ◽

Induced Fission

Neutron-induced fission cross sections of isotopes involved in the nuclear fuel cycle are vital for the design and safe operation of advanced nuclear systems. Such experimental data can also provide additional constraints for the adjustment of nuclear model parameters used in the evaluation process, resulting in the further development of fission models. In the present work, the 237Np(n,f) cross section was studied at the EAR2 vertical beam-line at CERN's n_TOF facility, over a wide range of neutron energies, from meV to MeV, using the time-of-flight technique and a set-up based on Micromegas detectors, in an attempt to provide accurate experimental data. Preliminary results in the 200 keV – 14 MeV neutron energy range as well as the experimental procedure, including a description of the facility and the data handling and analysis, will be presented.

Download Full-text

The 240Pu(n,f) cross section measurement at the new experimental area at CERN's n_TOF facility

HNPS Proceedings ◽

10.12681/hnps.1857 ◽

2019 ◽

Vol 24 ◽

pp. 139

Author(s):

A. Stamatopoulos ◽

For the NTOF Collaboration

Keyword(s):

Cross Section ◽

Cross Sections ◽

Fuel Cycle ◽

Evaluation Process ◽

Nuclear Fission ◽

Nuclear Model ◽

Model Parameters ◽

Experimental Area ◽

Wide Range ◽

Nuclear Systems

The accurate knowledge of the neutron-induced fission cross-sections of actinides and other isotopes involved in the nuclear fuel cycle are essential for the design of advanced nuclear systems. These experimental data can also provide feedback for the adjustment of nuclear model parameters used in the evaluation process, resulting in further developments of nuclear fission models. In the present work, the 240Pu(n,f) cross-section was measured at CERN's n_TOF facility over a wide range of neutron energies, from a few meV to several MeV, using the time-of-flight technique and a set-up based on MicroMegas detectors. This measurement was the first experiment to be performed in n_TOF's new experimental area (EAR-2), which offers a significantly higher neutron flux compared to the existing experimental area. Preliminary results as well as the experimental procedure, including a brief description of the facility, the sample mounting, the read-out process and the data handling and analysis, are presented.

Download Full-text

First results of the 230Th(n,f) cross section measurements at the CERN n_TOF facility

EPJ Web of Conferences ◽

10.1051/epjconf/202023905004 ◽

2020 ◽

Vol 239 ◽

pp. 05004

Author(s):

V. Michalopoulou ◽

A. Stamatopoulos ◽

R. Vlastou ◽

M. Kokkoris ◽

A. Tsinganis ◽

...

Keyword(s):

Energy Range ◽

Cross Section ◽

Cross Sections ◽

Fuel Cycle ◽

Fission Cross Section ◽

Reaction Cross ◽

Rare Isotope ◽

Fuel Cycles ◽

Broad Energy Range ◽

Nuclear Systems

The study of neutron-induced reactions on actinides is of considerable importance for the design of advanced nuclear systems and alternative fuel cycles. Specifically, 230Th is produced from the α-decay of 234U as a byproduct of the 232Th/233U fuel cycle, thus the accurate knowledge of its fission cross section is strongly required. However, few experimental datasets exist in literature with large deviations among them, covering the energy range between 0.2 to 25 MeV. In addition, the study of the 230Th(n,f) cross-section is of great interest in the research on the fission process related to the structure of the fission barriers. Previous measurements have revealed a large resonance at En=715 keV and additional fine structures, but with high discrepancies among the cross-section values of these measurements. This contribution presents preliminary results of the 230Th(n,f) cross-section measurements at the CERN n_TOF facility. The high purity targets of the natural, but very rare isotope 230Th, were produced at JRC-Geel in Belgium. The measurements were performed at both experimental areas (EAR-1 and EAR-2) of the n_TOF facility, covering a very broad energy range from thermal up to at least 100 MeV. The experimental setup was based on Micromegas detectors with the 235U(n,f) and 238U(n,f) reaction cross-sections used as reference.

Download Full-text

Neutron-induced fission cross-section measurement of 234U with monoenergetic beams in the keV and MeV range using MicroMegas detectors

HNPS Proceedings ◽

10.12681/hnps.1875 ◽

2019 ◽

Vol 24 ◽

pp. 250

Author(s):

A. Kanellakopoulos ◽

A. Stamatopoulos ◽

A. Tsinganis ◽

M. Kokkoris ◽

R. Vlastou ◽

...

Keyword(s):

Cross Section ◽

Neutron Beam ◽

Cross Sections ◽

Fission Cross Section ◽

Incident Neutron ◽

Tandem Accelerator ◽

Cross Section Measurement ◽

Preliminary Results ◽

Section Measurement ◽

Induced Fission

The fission cross-section of 234U was measured at incident neutron energies between 300 and 500 keV and 4 and 5 MeV with a setup based on “microbulk” MicroMegas detectors. The standard 235,238U fission cross-sections were used as reference. The neutron beams were produced via the 7Li(p,n) and the 2H(d,n) reactions at the neutron beam facility of the 5.5 MeV Tandem accelerator laboratory at NCSR “Demokritos”. The mass of the actinide content of the targets used and of their impurities was quantitatively determined via α – spectroscopy. The developed methodology and preliminary results are presented.

Download Full-text

Comprehensive stochastic sensitivities to resonance parameters

EPJ Web of Conferences ◽

10.1051/epjconf/202023913008 ◽

2020 ◽

Vol 239 ◽

pp. 13008

Author(s):

Pierre TAMAGNO ◽

Elias VANDERMEERSCH

Keyword(s):

Angular Distribution ◽

Cross Section ◽

Cross Sections ◽

Evaluation Process ◽

Nuclear Model ◽

Model Parameters ◽

Probability Method ◽

Matrix Formalism ◽

Resonance Parameters ◽

Critical Configurations

Integral experiments in reactors or critical configurations claim to have very small experimental and technological uncertainties. Therefore these latter can be considered valuable experimental information in nuclear data evaluation. Because in the evaluation process the information is carried by model parameters, to perform a rigorous feedback on a nuclear model parameters p - for instance using a measured reactivity ρ-sensitivities S =∂ρ/ρ⁄∂p/p are needed. In usual integral feedbacks, sensitivity to multi-group cross sections are first obtained with deterministic code using perturbation theory. Then these multi-group cross section sensitivities are “convoluted” with parameter sensitivities in order to provide the sensitivity on nuclear model parameter. Recently stochastic approaches have been elaborated in order to obtain continuous cross-section sensitivities thus avoiding the multi-group discretization. In the present work we used the recent Iterated Fission Probability method of the TRIPOLI4 code [1] in order to obtain directly the sensitivity to nuclear physics parameters. We focus here on the sensitivity on resonance parameters and exemplified the method on the computation of sensitivities for 239Pu and 16O resonance parameters one the ICSBEP benchmark PST001. The underlying nuclear model describing resonant cross sections are based in the R-matrix formalism [2] that provides not only the interaction cross sections but also the angular distribution of the scattered neutrons i.e. differential cross sections. The method has thus been updated in order to compute parameter sensitives that include both contributions: cross section and angular distributions. This extension of the method was tested with exact perturbation of angular distribution and fission spectrum.

Download Full-text