Fission cross section measurements for 240Pu, 242Pu

This report comprises the deliverable 1.5 of the ANDES project (EURATOM contract FP7-249671) of Task 3 "High accuracy measurements for fission" of Work Package 1 entitled "Measurements for advanced reactor systems". This deliverables provide evidence of a successful completion of the objectives of Task 3.JRC.D.4-Standards for Nuclear Safety, Security and Safeguard

Neutron induced fission cross section measurements of 240

Accurate neutron induced fission cross section of 240Pu and 242Pu are required in view of making nuclear technology safer and more efficient to meet the upcoming needs for the future generation of nuclear power plants (GEN-IV). The probability for a neutron to induce such reactions figures in the NEA Nuclear Data High Priority Request List [1]. A measurement campaign to determine neutron induced fission cross sections of 240Pu and 242Pu at 2.51 MeV and 14.83 MeV has been carried out at the 3.7 MV Van De Graaff linear accelerator at Physikalisch-Technische Bundesanstalt (PTB) in Braunschweig. Two identical Frisch Grid fission chambers, housing back to back a 238U and a APu target (A = 240 or A = 242), were employed to detect the total fission yield. The targets were molecular plated on 0.25 mm aluminium foils kept at ground potential and the employed gas was P10. The neutron fluence was measured with the proton recoil telescope (T1), which is the German primary standard for neutron fluence measurements. The two measurements were related using a De Pangher long counter and the charge as monitors. The experimental results have an average uncertainty of 3–4% at 2.51 MeV and for 6–8% at 14.81 MeV and have been compared to the data available in literature

Measurement of the 240Pu(n,f) cross-section at the CERN n-TOF facility : First results from experimental area II (EAR-2)

The accurate knowledge of the neutron-induced fission cross-sections of actinides and other isotopes involved in the nuclear fuel cycle is essential for the design of advanced nuclear systems, such as Generation-IV nuclear reactors. Such experimental data can also provide the necessary feedback for the adjustment of nuclear model parameters used in the evaluation process, resulting in the further development of nuclear fission models. In the present work, the 240Pu(n,f) cross-section was measured at CERN's n-TOF facility relative to the well-known 235U(n,f) cross section, over a wide range of neutron energies, from meV to almost MeV, using the time-of-flight technique and a set-up based on Micromegas detectors. This measurement was the first experiment to be performed at n-TOF's new experimental area (EAR-2), which offers a significantly higher neutron flux compared to the already existing experimental area (EAR-1). Preliminary results as well as the experimental procedure, including a description of the facility and the data handling and analysis, are presented

A compact fission detector for fission-tagging neutron capture experiments with radioactive fissile isotopes

© 2020 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).In the measurement of neutron capture cross-sections of fissile isotopes, the fission channel is a source of background which can be removed efficiently using the so-called fission-tagging or fission-veto technique. For this purpose a new compact and fast fission chamber has been developed. The design criteria and technical description of the chamber are given within the context of a measurement of the 233U(n, γ) cross-section at the n_TOF facility at CERN, where it was coupled to the n_TOF Total Absorption Calorimeter. For this measurement the fission detector was optimized for time resolution, minimization of material in the neutron beam and for alpha-fission discrimination. The performance of the fission chamber and its application as a fission tagging detector are discussed.Peer reviewe

Use of active scintillating targets in nuclear physics experiments - Measurement of spontaneous fission

A novel detector has been used, in order to perform measurements of spontaneous fission to α-decay ratios for 240Pu, 242Pu and 252Cf isotopes. The detectors are based on the well-known technique of liquid scintillating counting. The principle and advantages of the use of such detectors in nuclear physics is discussed. The application to the characterization of spontaneous fission is described and it is demonstrated that highly precise measurements are possible, and that the main limit is due to the isotopic content knowledge of the measured samples

High-precision spontaneous fission branching-ratio measurements for 240,242Pu^{240,242}\mathrm{Pu} and 252Cf^{252}\mathrm{Cf} isotopes

International audienceWe report here very precise measurements of the spontaneous fission branching ratio for the Pu240,242 and Cf252 isotopes, performed with a new kind of active scintillating target. It is shown that the method itself leads to unprecedentedly small uncertainties, and that these uncertainties are negligible compared to uncertainties on the isotopic content of the sample. Besides this capability we discuss the possibility to use this kind of detector for the systematic study of charged particle radioactivity, i.e., spontaneous fission, α decay, and heavy-ion radioactivity

Use of active scintillating targets in nuclear physics experiments - Measurement of spontaneous fission

A novel detector has been used, in order to perform measurements of spontaneous fission to α-decay ratios for 240Pu, 242Pu and 252Cf isotopes. The detectors are based on the well-known technique of liquid scintillating counting. The principle and advantages of the use of such detectors in nuclear physics is discussed. The application to the characterization of spontaneous fission is described and it is demonstrated that highly precise measurements are possible, and that the main limit is due to the isotopic content knowledge of the measured samples

High-precision spontaneous fission branching-ratio measurements for 240,242Pu and 252Cf isotopes

We report here very precise measurements of the spontaneous fission branching ratio for the 240,242Pu and 252Cf isotopes, performed with a new kind of active scintillating target. It is shown that the method itself leads to unprecedentedly small uncertainties, and that these uncertainties are negligible compared to uncertainties on the isotopic content of the sample. Besides this capability we discuss the possibility to use this kind of detector for the systematic study of charged particle radioactivity, i.e., spontaneous fission, α decay, and heavy-ion radioactivity.JRC.G.2-Standards for Nuclear Safety, Security and Safeguard