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NKS Programme Area:NKS-R
Research Area:Severe accidents and Reactor Physics
Report Number:NKS-156
Report Title:Ex-Vessel Coolability and Energetics of Steam Explosions in Nordic Light Water Reactors
Activity Acronym:EXCoolSE
Authors:H. S. Park, T. N. Dinh
Abstract:The report summarizes activities conducted at the Division of Nuclear Power Safety, Royal Institute of Technology-Sweden (KTH-NPS) within the ExCoolSe project during the year 2005, which is a transition year for the KTH-NPS program. The ExCoolSe project supported by NKS contributes to the severe accident research at KTH-NPS concurrently supported by APRI, HSK and EU SARNET. The main objective in ExCoolSe project is to scrutinize research on risk-significant safety issues related to severe accident management (SAM) strategy adopted for Nordic BWR plants, namely the Ex-vessel Coolability and Energetic Steam explosion. The work aims to pave way toward building a tangible research framework to tackle these long-standing safety issues. Chapter 1 describes the project objectives and work description. Chapter 2 provides a critical assessment of research results obtained from several past programs at KTH. This includes review of key data, insights and implications from POMECO (Porous Media Coolability) program, COMECO (Corium Melt Coolability) program, SIMECO (Study of In-Vessel Melt Coolability) program, and MISTEE (Micro-Interactions in Steam Explosion Experiments) program. Chapter 3 discusses the rationale of the new research program focusing on the SAM issue resolution. The program emphasizes identification and qualification of physics-based limiting mechanisms for both in-vessel phenomena (melt progression and debris coolability in the lower head, vessel failure), and ex-vessel phenomena. Chapter 4 introduces research results from the newly established DEFOR (Debris Formation) program and the ongoing MISTEE program. The focus of DEFOR is fulfill an apparent gap in the contemporary knowledge of severe accidents, namely mechanisms which govern the debris bed formation and bed charatersitics. The later control the debris bed coolability. In the MISTEE program, methods for image synchronization and data processing were developed and tested, which enable processing of MISTEE data obtained with a high-speed Xray radiography and high-speed digital photography. Discussion of uncertainties and severe accident simulation code capability for prediction of the threats on containment integrity is given in Chapter 5.
Keywords:LWR; Severe Accidents; Accident Management; Ex-Vessel Melt; Debris Coolability; Steam Explosion; Experiments
Publication date:01 Apr 2007
ISBN:ISBN: 978-87-7893-220-4
Number of downloads:1666
Download:pdf NKS-156.pdf
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