Validation of POLCA7 cross section model
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Typ
Examensarbete för masterexamen
Master Thesis
Master Thesis
Program
Nuclear engineering, MSc
Publicerad
2013
Författare
Sarwar, Rashed
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
Utgivare
Sammanfattning
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.
Beskrivning
Ämne/nyckelord
Energi , Beräkningsfysik , Teknisk fysik , Energy , Computational physics , Engineering physics