A Computational Study on Instrumentation Guide Tube Failure During a Severe Accident in Boiling Water Reactors
NURETH-14 - 2011 September 25-30

Presented at:
2011 September 25-30
Toronto, Canada
Session Title:
E4-2 NPP Transients and Accidents Analysis

Walter Villanueva (Royal Institute of Technology)
Chi-Thanh Tran (Royal Institute of Technology)
Pavel Kudinov (Royal Institute of Technology)


This paper focuses on the nature and timing of Instrumentation Guide Tube (IGT) failure in case of severe core melt accident in a Nordic type Boiling Water Reactor (BWR). First, a 2D structural analysis of a RPV lower head is performed to determine global vessel deformation, timing and mode of failure. Next, a structural analysis is also performed on a 3D IGT section taking into account the influence of global vessel deformation and thermo-mechanical load from the melt pool. We have found that the IG tube was not clamped in the housing at the time when welding ring of the IGT nozzle has been melted and global failure of the vessel wall has not started yet. This suggests that IGT failure is the dominant failure mode in the considered case of a large (~200 tons) melt pool.

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