Keywords:Fukushima Daiichi Nuclear Power Plants, Severe Accident, MCCI, SAMPSON
In current Japanese national project we have organized all the available information in order to clarify the known condition of the power plant. Based on such information a best estimate current condition of the plant has been proposed in which MCCI played a major role in the accident determining the large hydrogen generation for the explosion of Unit 3 and Unit 4. Uncertainties remain on the modality of lower head failure and debris discharge as well as on the possibility of water injection during the MCCI. The present paper shows results of sensitivity analysis on the above mentioned parameters.