Abstract
A method of Covariance-Oriented Sample Transformation (COST) has been proposed in our previous work to provide the converged uncertainty analysis results with a minimal sample size. The transient calculation of nuclear reactor is a key part of the reactor-physics simulation, so the accuracy and confidence of the neutron kinetics results have attracted much attention. In this paper, the Uncertainty Quantification (UQ) function of the high fidelity neutronics code NECP-X has been developed based on our home-developed uncertainty analysis code UNICORN, building a platform for the UQ of the transient calculation. Furthermore, the well-known space-time heterogeneous neutron kinetics benchmark C5G7 and its uncertainty propagation from the nuclear data to the interested key parameters of the core have been investigated. To address the problem of “the curse of dimensionality” caused by the large number of input parameters, the COST method has been applied to generate multivariate normal-distribution samples in uncertainty analysis. As a result, the law of the assembly/pin normalized power and their uncertainty with respect to time after introducing an instantaneous perturbation has been obtained. From the numerical results, it can be observed that the maximum relative uncertainties for the assembly normalized power can up to be about 1.65% and the value for the pin-wise power distributions can be about 2.71%.
Highlights
With the great efforts made by OECD/NEA, a series of space-time neutron kinetics benchmark problems have been proposed [1]
The relative uncertainties of the assembly normalized power and pin-wise power distributions have been quantified during the transient process
The nuclear-data uncertainties have been propagated to the interested key parameters during the transient process for the C5G7 benchmark problem
Summary
With the great efforts made by OECD/NEA, a series of space-time neutron kinetics benchmark problems have been proposed [1]. Compared with the deterministic method, the statistical sampling method can provide the uncertainty analysis results without any low-order approximation and is universally applicable to all kinds of systems. It is regarded as the appropriate methodology to perform the uncertainty analysis for the transient modeling and simulations. The COST method has been proposed in our previous work to provide the converged UQ results with a minimal sample size [6] In this context, the uncertainty analysis has been implemented to the transient modeling and simulations of the C5G7 benchmark problem based on the COST method, quantifying the uncertainties of the interested key parameters during the transient process due to the nuclear-data uncertainties. The relative uncertainties of the assembly normalized power and pin-wise power distributions have been quantified during the transient process
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