The energy dependence of fission-fragment characteristics for neutron-induced fission on Pu-239

This report is in response to a nuclear data request on the OECD-NEA high priority request list for new measurements of prompt neutron multiplicities from 239Pu(n,f) in the incident neutron energy range from thermal to 5 eV. There exists experimental evidence for strong fluctuations of the average neutron multiplicity from resonance to resonance in 239Pu(n,f). These fluctuations have been shown to impact nuclear reactor benchmarks by reducing the criticality. One explanation for the fluctuating neutron multiplicity may be the competition between direct fission and the (n,γf) process. However, there is also evidence for fluctuations of the fission fragment mass yields from resonance to resonance. The mass yield fluctuations may also contribute to fluctuations of the neutron multiplicity averaged over all fission fragment masses. In order to model the contribution to the neutron multiplicity fluctuations by the fission fragment mass yield fluctuations new data on the correlations between fission fragment properties and neutron multiplicities are in need. In this report we present an experiment carried out to determine prompt neutron multiplicity correlations with fission fragment masses and total kinetic energies. The experiment has been carried out at the GELINA facility at JRC-Geel. Correlations between average neutron multiplicities and fission fragment properties have been measured with improved resolution in both mass and TKE, compared to data from the literature. Results show that the dependence of average neutron multiplicity per fission and fission fragment mass split is weak.JRC.G.2-Standards for Nuclear Safety, Security and Safeguard

Development and test of the high-precision gamma-beam monitor at the ESFRI facility ELI-NP

This document describes the development of a fission chamber for gamma beam intensity monitoring at the high-energy gamma line at ELI-NP. The fission chamber foreseen for monitoring the gamma beam intensity on the high-energy beam line at ELI-NP is an ionization chamber with several 238U deposits of a thickness in the range from 100 to 150 μg/cm2 in a compact design. The innovative design of the chamber allows measuring for each individual micro pulse arriving at a time interval of 1.6x10^-8 s.JRC.G.2-Standards for Nuclear Safety, Security and Safeguard

Energy dependant neutron multiplicity in 235U(n,f)

Experimental activities at JRC-Geel on prompt-fission-neutron (PFN) emission in response to OECD/NEA nuclear data requests are presented in this report. Specifically, investigations of PFN emission from the reaction 235U(n,f) in the region of the resolved resonances are presented. The experiment employs a scintillation detector array for neutron detection, while fission fragment properties are determined via the double kinetic energy technique using a position sensitive twin ionization chamber. This setup allows us to study several correlations between properties of neutron and fission fragments simultaneously. Results on PFN correlations with fission fragment properties from the present study differ significantly from earlier studies on this reaction, induced by thermal neutrons.JRC.G.2-Standards for Nuclear Safety, Security and Safeguard

Prompt fission neutron emission: Problems and challenges

This paper presents some of the challenges ahead of us even after 75 years of the discovery of the fission process and large progress made since then. The focus is on application orientation, which requires improved measurements on fission cross-sections and neutron and γ-ray multiplicities. Experimental possibilities have vastly improved the past decade leading to developments of highly sophisticated detector systems and the use of digital data acquisition and signal processing. The development of innovative fast nuclear reactor technology needs improved respective nuclear data. Advancements in theoretical modelling also require better experimental data. Theory has made progress in calculating fission fragment distributions (i.e. GEF code) as well as prompt neutron and γ-ray emission to catch up with the improved experiments.JRC.D.4-Standards for Nuclear Safety, Security and Safeguard

Recent developments for an active UF6 gas target for photon-induced fission experiments

Recent developments for an active uranium-hexafluoride-loaded gas target as well as results on the detector gas properties are presented. The gas of choice is a mixture of argon with small amounts of UF6. This contribution presents the experimental setup and focusses on the electron drift velocity with increasing UF6 content. A time-dependent decrease in electron drift velocity is observed in our setup.JRC.D.4-Standards for Nuclear Safety, Security and Safeguard

EUFRAT, Open Access to the nuclear research infrastructure at JRC Geel

Open access activities to the nuclear research facilities operated at the Joint Research Centre (JRC) in Geel are reported. These activities are carried out by the unit Standards for Nuclear Safety, Security and Safeguards of the Directorate for Nuclear Safety and Security as part of its work programme. The open access activities at JRC Geel run since 2014 as an institutional programme under the EURATOM work programme. In 2017 the JRC decided to start a JRC-wide open access scheme to its research infrastructure co-ordinated by the Directorate for Strategy, Work Programme and Resources. The transition to a JRC-wide open access scheme is discussed and the results of the first two calls for proposals during 2017 and 2018 are summarised.JRC.G.2-Standards for Nuclear Safety, Security and Safeguard