Abstract
This paper shows how Total Monte Carlo (TMC) method and Perturbation Theory (PT) can be applied to quantify uncertainty due to nuclear data on reactor static calculations of integral parameters such as keff and βeff. This work focuses on thorium fueled reactors and it aims to rank different cross sections uncertainty regarding criticality calculations. The consistency of the two methods are first studied. The cross sections set used for the TMC method is computed to build adequate correlation matrices. Those matrices are then multiplied by the sensitivity coefficients obtained thanks to the PT to obtain global uncertainties that are compared to the ones calculated by the TMC method. Results in good agreement allow us to use correlation matrix from the state of the art nuclear data library (JEFF 3-3) that provide insight of uncertainty on keff and βeff for thorium fueled Pressurized Water Reactors. Finally, maximum uncertainties on cross sections are estimated to reach a target uncertainty on integral parameters. It is shown that a strong reduction of the current uncertainty is needed and consequently, new measurements and evaluations have to be performed.
Highlights
Studies of innovative nuclear systems rely on precise computational tools and reliable nuclear data
The Total Monte Carlo (TMC) method allows direct calculations of uncertainties, it is very costly in terms of computational power and the results may be difficult to discuss as all nuclear parameters are changing from an evaluation to another
The Perturbation Theory (PT) is based on sensitivity calculations that underline the parameters of prime importance in criticality calculations
Summary
Studies of innovative nuclear systems rely on precise computational tools and reliable nuclear data. For several years some efforts have been made to propagate nuclear data uncertainty on reactor’s calculations To this end, two main methods have been widely developed and used : the Total Monte Carlo (TMC) [1] method and the Perturbation Theory (PT) [2]. Two main methods have been widely developed and used : the Total Monte Carlo (TMC) [1] method and the Perturbation Theory (PT) [2] They have been applied to current and innovative reactors [3] to estimate integral parameters uncertainties, and to justify some new experimental programs for nuclear data measurements. Even if possible deployments of thorium fuel reactors is probably delayed to the second half of century, effort on nuclear data knowledge and specially new precise measurements with reliable uncertainties should be carried as in [4]. This paper aims to quantify the uncertainty limits on cross sections to reach a precision smaller than 0.5% for ke f f and 5% for βe f f as specified in [5]
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