Abstract
In the present work, the measurement of the 236U(n,f) cross section was performed, with reference to the 238U(n,f) reaction. The measurements took place at the neutron beam facility of the National Centre for Scientific Research "Demokritos" (Greece) and the quasi-monoenergetic neutron beams were produced via the 2H(d,n)3He reaction in the energy range 4–10 MeV. Five actinide targets (two 236U, two 238U and one 235U) and the corresponding Micromegas detectors for the detection of the fission fragments were used. Detailed Monte Carlo simulations were performed, on one hand for the study of the neutron flux and energy distribution at the position of each target, and on the other hand for the study of the energy deposition of the fission fragments in the active volume of the detector. The mass and homogeneity of the actinide targets were experimentally determined via alpha spectroscopy and the Rutherford Backscattering Spectrometry, respectively. The experimental procedure, the analysis, the methodology implemented to correct for the presence of parasitic neutrons and the cross section results will be presented and discussed.
Highlights
The accurate knowledge of neutron-induced cross sections is of great importance for the study and design of new generation reactors
The detection system consisted of a stack of ionisation gas cells based on the Micromegas Microbulk technology [9, 10] for the detection of the fission fragments (FF), each one containing one actinide target, the backing of which served as the detector drift electrode
· σU8 where Y are the FF counts recorded by the detectors and corrected for i) the parasitic counts induced by neutrons of lower energies than the main neutron beam, generated from deuteron reactions at the structural materials of the gas cell and beam line ( f in/out) and from the other sources described in sec 2.1 ( f par) and ii) the amplitude cut introduced in the analysis ( f amp.cut)
Summary
The accurate knowledge of neutron-induced cross sections is of great importance for the study and design of new generation reactors. In the energy range 4 - 10 MeV few available data sets exist in literature, leading to discrepancies between the latest evaluations up to 9%. The rest of the measurements have been performed several decades ago with quasimonoenergetic neutron beams by Meadows [4] and White and Warner [5] and in a wide energy range by Rosler et al [6] and Henkel [7]. New measurements were performed in the energy range 4 - 10 MeV and are presented here. A first exploratory experiment was previously performed [8], in order to establish the analysis methodology and new measurements were performed in this energy range
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