Browsing by Author "Ahtinen, Esa"

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Development and validation of a new noncondensable gas transport model for the APROS simulation software
(2008) Ahtinen, Esa
Helsinki University of Technology | Master's thesis
This Master's Thesis is a development and validation project of a new non- condensable gas transport model for the APROS simulation software. Earlier APROS versions were able to model non-condensable gas transport only in gas phase. After this thesis user can model convective non-condensable gas transport also in the liquid phase with absorption and release phenomena between phases. Non-condensable gases have several physical properties that make them important to take into account in certain types of nuclear safety analyses. Typical PWR has passive accumulators that contain borated water under pressurized nitrogen gas cushion. The accumulator water is gradually saturated with dissolved nitrogen. If this saturated water is injected into the primary circuit during pressure reduction, some of the dissolved nitrogen might be released from the primary coolant and form gas pockets. These gas pockets might terminate the natural circulation and hinder the heat transfer in the steam generators. In this thesis the new model is validated against old PACTEL and PKL experiments. After validation cases the new transport model is used to simulate primary to secondary circuit leak (PRISE) with one unisolated accumulator by using full-scale Loviisa APROS model. These simulations will give information about the local dissolved nitrogen concentrations against theoretical saturation concentrations.