Abstract
Prototype FBR plant 'Monju' experienced IVTM (In-Vessel Transfer Machine) drop trouble on August 26, 2010. The collision damage and the impact load due to IVTM drop were investigated by the numerical dynamic response analysis. From the analysis results, it was confirmed that the impact load was significantly reduced by the plastic deformation of the installation flange of IVTM and the installation mat of the sleeve structure on the fixed plug, where these two parts were directly contacted each other at collision, compared with the results by the hypothetical elastic analysis. And also it was confirmed that the plastic regions were limited to near collision surface of these two parts and almost other parts remained elastic. This means that the two parts which are contacted each other at collision should be replaced, but other parts are little damaged and are expected to be reused.
