Evaluation of Postulated Spent Fuel Container Handling Accidents Using Numerical Simulations

Abstract

Ontario Power Generation (OPG) is transferring irradiated fuel from its CANDU nuclear generating stations in Ontario Canada, that has been cooled for a minimum of 10 years in the Irradiated Fuel Bay (IFB), into Dry Storage Containers (DSC). The Picketing Used Fuel Dry Storage Facility has been in operation for 6 years and over 200 DSC’s have been loaded to date. During the loading operation a DSC is lifted out of the IFB and craned over a wall into a decontamination pit (DP). This operation requires that the lid of the DSC be in place before the container is removed from the IFB. A lid clamp is used, which sits around the perimeter of the lid and maintains the boundary between the mating lid and container flange plates, to ensure that the lid is retained under normal and abnormal conditions. In the event of a crane failure, there is a potential for the DSC to impact the intermediate wall between the IFB and the DP. This may result in the DSC toppling over the wall and either falling into the DP or toppling back into the IFB. Both the IFB and the DP have floor impact pads to prevent structural damage. The lid clamp must demonstrate the ability to maintain the containment boundary under these postulated accident scenarios. A finite element model of the Dry Storage Container and the proposed lid clamp has been developed to assess the structural integrity of the lid clamp design. The postulated accident scenarios consider are a 9.9 meter drop in a centre of gravity over top edge orientation, in a top down flat end orientation and a near side drop orientation onto an impact pad representative of the IFB pad. Only the centre of gravity and near side orientations are presented in this paper. The simulations were carried out on a DEC ALPHA workstation using an in-house three dimensional non-linear multi-purpose finite element code entitled H3DMAP version 6.