Abstract

The radiative capture cross section of a highly pure (99.999%), 6.125(2) grams and 9.56(5) 10-4 atoms/barn areal density 238-U sample has been measured with the Total Absorption Calorimeter (TAC) in the 185 m flight path at the CERN neutron time-of-flight facility n_TOF. This measurement is in response to the NEA High Priority Request list, which demands an accuracy in this cross section of less than 3% below 25 keV. These data have undergone careful background subtraction, with special care being given to the background originating from neutrons scattered by the 238-U sample. Pileup and dead-time effects have been corrected for. The measured cross section covers an energy range between 0.2 eV and 80 keV, with an accuracy that varies with neutron energy, being better than 4% below 25 keV and reaching at most 6% at higher energies.

Highlights

  • AND MOTIVATIONNuclear energy is an unavoidable component of future energy production, as outlined in the EU SET plan [1]

  • This paper focuses on the energy region from 0.2 eV–80 keV, spanning the resolved resonance region and part of the unresolved resonance region

  • The cross section is represented by a set of resonance parameters

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Summary

INTRODUCTION

Nuclear energy is an unavoidable component of future energy production, as outlined in the EU SET plan [1]. The latest evaluation in 2005 of the nuclear data available on 238U(n,γ ) by Derrien et al [6,7] aimed to address and quantify the situation and these results have been mostly adopted by the three main neutron cross-section libraries (ENDF/B, JEFF, and JENDL). These libraries have an uncertainty in the capture cross section of 2–3% in the energy region from 100 eV–5 keV,. By combining the new data sets, the evaluation should be able to reach the required accuracies for advanced nuclear systems

CURRENT DATA
EXPERIMENTAL SET UP
TAC detector
Samples
Data reduction
Background subtraction
Pileup and dead-time correction
Yield calculation
Residual background
Discussion on uncertainties
Resolved resonance region
Unresolved resonance region
CONCLUSIONS
Methods
Full Text
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