Investigation of Xenon Oscillations at the Ringhals-3 PWR

Typ
Examensarbete för masterexamen
Master Thesis
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Publicerad
2011
Författare
Nylander, Rikard
Modellbyggare
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Sammanfattning
In this thesis, an investigation of observed deviations in xenon oscillations between measured data and calculations in SIMULATE-3 is presented. During the validation of the new GARDEL monitoring interface at Ringhals-2, 3 and 4 PWRs anomalies were found for transients with inserted control rods. When control rods were withdrawn, axial oscillations in the neutron flux were noticed. The period for both the measured and calculated oscillations was around 25 to 30 hours, which indicates xenon oscillations. Nevertheless, the calculations predicted xenon oscillations shifted by half a period compared to the measurements. The purpose for this thesis was to find out why these anomalies occurs and give guidelines to allow a proper modeling of this type of events in the future. Three different paths where chosen for this investigation. First, the same transient was evaluated in PARCS in order to see if this code could predict the correct behavior of the oscillations. CORE SIM was also used along with a calculation in MatLab in order to evaluate the stability of the given core. Finally a parametric study in SIMULATE- 3, based on the result from PARCS and the corresponding evaluation, was performed to find out the reason of the discrepancy between the calculations and measurements. The calculation in PARCS turned out to be unfeasible, and the evaluation of the core stability did not give any conclusive results i.e. the core was indeed found to be unstable with respect to xenon oscillations. In the parametric study though, the reason of the discrepancy could be tracked back to the power specified in the input file. The thermal power in the secondary side has been used, while the nuclear power is the one that should be used during a transient.
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Fysik, Physical Sciences
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