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|NKS Programme Area:||NKS-R|
|Report Title:||Experimental and Analytical Investigations of Debris Bed Formation, Spreading, Coolability, and Steam Explosion in Nordic BWRs|
|Authors:||Pavel Kudinov, Alexander Konovalenko, Dmitry Grishchenko, Sergey Yakush, Simone Basso, Nazar Lubchenko, Aram Karbojian, |
|Abstract:||In case of severe accident in Nordic type BWRs core melt is fragmented in a deep water pool. There is uncertainty if formed bed if core debris will be coolable or if energetic steam explosion can threaten containment integrity. The goal of the project is to reduce uncertainties in debris coolability and steam explosion impact.
DECOSIM code has been developed for analysis of porous debris coolability and further validated against COOLOCE data. Debris bed cooling in post-dryout regime was addressed. Analytical models for prediction of the maximum temperature of the debris and relative size of the dry zone as a function of overheating parameter is proposed and validated against DECOSIM simulations. DECOSIM code was extended to in-vessel coolability analysis. The parameter ranges corresponding to coolable and non-coolable configurations were obtained for initially dry and quenched debris configuration.
Scaling approach and universal semi-empirical closure have been developed for prediction of particulate debris spreading using PDS-C tests. The approach has been validated against experimental data with different particle mixtures. The model for prediction of particulate debris spreading was implemented in the DECOSIM code.
An approach for analysis of steam explosion in Nordic BWR and sensitivity of steam explosion impulse to the uncertain modeling and scenario parameters has been proposed. TEXAS-V code is used for analysis. Obtained database of impulses TEXAS is used for development of a computationally efficient surrogate model that can be used in extensive uncertainty analysis.|
|Keywords:||Nordic BWR, severe accident, debris bed formation, coolability, steam explosion|
|Publication date:||29 Jun 2016|
|Number of downloads:||796|