MAAP5 Analyses on Intentional Depressurization of Reactor Coolant System During Station Blackout of Zion Nuclear Power Plant

Abstract

The purpose of this research is to evaluate the effectiveness of intentional depressurization as a mitigation action following a TMLB’s accident. There have been many studies to evaluate the pros and cons of such an action as a counter measurement against TMLB’s, yet in this research, the latest version of EPRI’s accident simulation computer code “MAAP 5.06” is used. For the intentional depressurization, the most effective depressurization timing and the depressurization rate were investigated through the sensitivity calculations. Furthermore, since the accident progression during the TMLB’ sequence is governed by the decay heat, that is, the release fraction from the fuel, various kind of fission product release models including newly proposed model (1/√P CORSOR-M) are applied and their impacts on the overall accident progress is studied.

At the start, the base case with no counter action is studied and different Fission Products release models are applied in each run. The effect of depressurization timing and rates are studied. Then the effect of the release is studied. Following that, Intentional depressurization rate and time with default MAAP setting for Fission Product release model are studied. Finally, the best approaches to delay the accident and mitigate the consequences are simulated using 1/√P CORSOR-M model. The effect and results are studied and summarized. A conclusion is drawn after running all these different simulations.

Date of Award	Dec 2022
Original language	American English
Supervisor	Akihide Hidaka (Supervisor)