Sensitivity and Uncertainty Analysis of the Keff Due to ENDF/B-VII.0 Cross Sections Uncertainties of the Major Isotopes in Nuclear Reactors

M Kaddour,O Allaoui,S El Ouahdani,B El Bakkari,Y Boulaich,T El Bardouni,H Boukhal,C El Younoussi,E Chakir,M Azahra

doi:10.13189/aep.2013.010103

Abstract

The main objective of this study is to estimate nuclear data uncertainties on the effective multiplication factor (Keff) related to elastic, inelastic, capture and fission cross sections and the correlations between them. Different rapid and thermal cases of the different IHECSBE benchmarks have been studied by using nuclear data evaluation ENDF/B-VII.0 to calculate the sensitivity vectors for 1 H, 16 O, 235 U and 238 U isotopes and four cases used to validate our sensitivity vectors. These sensitivity vectors are calculated by using the adjoint-weighted perturbation method based on the Kpert card of the Monte Carlo code MCNP6. Thus, the uncertainties induced by nuclear data have been calculated by combining the sensitivity vectors with the covariance matrices that are generated by the ERRORJ module of the recently updated of the nuclear data processing system NJOY99. In this study, we found several cross sections and covariance matrices lack the adjustment: the four cross sections (elastic, inelastic, capture and fission) of the 235 U and their covariance matrices Lack the adjustement especially in the rapid energies; the elastic cross section of the 16 O, the elastic and capture cross sections of the 1 H and their covariance matrices lack the adjustement especially in the thermal energies.

Highlights

Since the beginning of the century, the nuclear data evaluation communities are putting more and more attention to the assessment of uncertainties
We have studied the impact of the cross sections uncertainties for 1H, 16O, 235U, and 238U isotopes on the effective multiplication factor uncertainty in each selected case
The uncertainties on the Keff produced by elastic, inelastic scattering, capture and fission cross sections and the effect of the correlation between them are represented by adjoint-weighted technique and by pcm (1pcm = 10-5)

Summary

Introduction

Since the beginning of the century, the nuclear data evaluation communities are putting more and more attention to the assessment of uncertainties This increased interest concerns both basic data (cross section, emission spectrum ...) and calculated quantities for large systems. Such as neutron multiplication factor Keff, reactivity, reaction rate and others. Several probabilistic and deterministic codes are made for the analysis of the sensitivity and the uncertainties of the nuclear data on the integral nuclear parameters (SCALE, MCNP, KENO, DRAGON...). Most of these codes used the multigroup adjoint-weighted technique. The sensitivity profiles and covariance matrices are combined in order to obtain final uncertainties [9]

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Conclusion