Verification of the new implementations in SHARKX against TSUNAMI to perform pinpower UQ and representativity analysis

Abstract

SHARKX is a set of Perl-based tools built around the lattice code CASMO-5 which is used to perform sensitivity analysis and uncertainty quantification (UQ). SHARKX has been recently extended to perform UQ on pinpower and representativity analysis (RA). Its aim is to calculate uncertainties due to the nuclear data cross sections on the fission rate of selected pins and to provide a rigorous basis to assess the relevance of an experiment to a given application.The main objective of the work summarised in the present paper is to verify the proper implementation of the SHARKX UQ and RA methodologies. The verification is carried out by comparing the UQ and RA results of SHARKX to the ones of the TSUNAMI code, currently the reference in the field for this kind of calculations. The verification of the proper UQ and RA implementation in SHARKX is performed for a set of test cases relevant to the LWR-PROTEUS experimental campaign. Only nuclear data (cross sections) uncertainty is considered and propagated in the SHARKX and TSUNAMI codes.For various test problems, the comparison with TSUNAMI has shown that the new UQ and RA implementations in the SHARKX methodology are carried out successfully. However, it is found that discrepancies are introduced in sensitivity coefficient calculation of SHARKX by neglecting the perturbation of the resonance self-shielding treatment, the so called “implicit effect”. Such approximation can have significant impact on both UQ and RA especially for Gadolinium doped fuel.The effect of the input uncertainty in UQ and RA is also investigated by comparing the results obtained with the variance–covariance matrix (VCM) of ENDF/B-VII.1, JENDL4.0 and SCALE6. The choice of input VCM is the major source of result discrepancies for UQ on kinf and pinpower. However, for RA, it is found to be of the same order of magnitude than the method discrepancies, i.e. the differences between SHARKX and TSUNAMI coming from the “implicit effect”.