Development of an experimental set-up for the measurement of neutron-induced fission and capture cross sections of radioactive fissile nuclei

I Companis,I Tsekhanovich,J Matarranz,Q Ducasse,G Barreau,B Jurado,F Gunsing,J Heyse ,G Kessedjian ,A Plompen ,L Mathieu ,P Schillebeeckx ,S Czájkowski ,M Aïche

doi:10.1051/epjconf/20136205007

Abstract

A new experimental set-up for a simultaneous measurement of neutron induced capture and fission cross sections was designed, assembled and optimized. The measurements will be performed at GEel LINear Accelerator (GELINA) neutron time- of-flight facility in Belgium, where neutron cross sections can be measured over a wide energy range with high energy resolution. The fission events detector consists of a dedicated multi-plate high efficiency fission ionization chamber (IC). The -rays produced in capture reaction are detected by an efficient array of C6D6 scintillators. Fission -rays events are distinguished from capture events by the anticoincidence signals from the IC and the C6D6 detectors. For the undetected fission events a correction has to be applied with respect to the efficiency of the IC that should be high and known with a high precision. Another important issue is the good separation between fission-fragment (FF) and the high alpha pile-up. The performances of the IC during test experiments are presented, focusing in particular on the detection efficiency.

Highlights

The measurements will be performed at GEel LINear Accelerator (GELINA) neutron timeof-flight facility in Belgium, where neutron cross sections can be measured over a wide energy range with high energy resolution
The criticality analysis and design calculation for thorium-based reactors require an accurate knowledge of the neutron induced cross sections of 233U/239Pu, since this isotope plays the same role as 235U in standard nuclear power plants
On the contrary the C6D6 no3, placed in front of the ionization chamber (IC), will detect more probably the neutrons from the FF emitted on the forward direction which loose much less energy in the target

Summary

Introduction

New and accurate measurements for (n,f) and (n, ) of 233U are planned on different facilities Recent measurements for these reactions have been performed by the n-TOF collaboration at CERN and preliminary results were published [7]. They concluded that the capture cross section data of Weston [5] are overestimated by up to 20% in the RRR region. These results can than be considered to be poorly known and new measurements are needed. The ACEN group of CENBG decided to focus its interest on these reactions together with IRMM Geel (Belgium) [8] where the final experiment will be carried out on the neutron time-of-flight GELINA facility

Methods

Results

Conclusion