Lower head integrity under steam explosion loads

Lower head integrity under steam explosion loads in an AP600-like reactor d esign is considered. The assessment is the second part of an evaluation of the in-vessel retention idea as a severe accident management concept, the f irst part (DOE/ID-10460) dealing with thermal loads. The assessment is cond ucted in terms of the risk oriented accident analysis methodology (ROAAM), and includes the comprehensive evaluation of all relevant severe accident s cenarios, melt conditions and timing of release from the core region, fully three-dimensional mixing and explosion wave dynamics, and lower head fragi lity under local, dynamic loading. All of these factors are brought togethe r in a ROAAM probabilistic framework to evaluate failure likelihood. The co nclusion is that failure is 'physically unreasonable'. (C) 1999 Elsevier Sc ience S.A. All rights reserved.