In English

Validation of POLCA7 cross section model

Rashed Sarwar
Göteborg : Chalmers tekniska högskola, 2013. 100 s. CTH-NT - Chalmers University of Technology, Nuclear Engineering, ISSN 1653-4662; 282, 2013.
[Examensarbete på avancerad nivå]

POLCA7, developed by Westinghouse Electric Company, is a three-dimensional code for simulating the neutronic, thermal, and hydraulic behavior of a reactor core by solving the coupled two-group neutron diffusion - thermal hydraulic problem with state-of-the-art methods involving the Analytical Nodal Method. The performance of the macro-micro cross section model of POLCA7 is very crucial for providing appropriate nodal parameters required by the core simu- lator’s neutron flux solver in order to carry out desired core physics calculations. Therefore, the objective of this thesis is to validate the most important components of the cross section model such as the isotopic history model, the xenon feedback model, spectrum interaction models and the tabulation of microscopic cross section data as function of the fuel exposure, coolant density and coolant density history. For the purpose of quantifying the accuracy of these cross section model components, the thesis has been divided into three broad numerical studies, starting with a set of simplistic two-dimensional single-node test problems involving shutdown cooling that has been evaluated against reference solutions prepared by solving the neutron transport equation (i.e. PHOENIX4). Following this, similar comparison for a set of two-dimensional 2x2 mini-cores involving one shuffling was conducted while the final evaluation involved a set of three-dimensional 2x2 mini-cores. Based on the numerical results obtained from the three different phases, it is concluded that the current cross section model of POLCA7, in combination with the standard three-dimensional tabulation of microscopic cross section data performs well with an acceptable accuracy for the considered depletion history, i.e. for the most severe history cases the error in reactivity is below 200 pcm in single-node simulations. However, the performance of the spectrum interaction models did not perform as expected since they fail to account for the leakage induced spectrum changes resulting in an oscillation with a peak-to-peak amplitude of 400 pcm for the most severe history cases.

Publikationen registrerades 2013-09-18. Den ändrades senast 2013-09-18

CPL ID: 183573

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