Non-conventional analysis and design of Calandria top hatch beams

In the 500 MWe PHWR building, the Calandria vault is required to be covered up from shielding consideration in order to limit the radiation level in the pump room floor within an acceptable value. The flooring is normally done with concrete. In view of the fact that this covering is to be done after the Calandria end shields are installed in the vault, the usual method is to place a number of precast R.C.C. beams side by side with filling material between the beams. As these beams can be removed in a certain eventuality, the covering is called Calandria vault top hatch. The top hatch beams are required also to support the reactor shutdown and control systems. For this purpose, a number of sleeves are embedded in the hatch beam concrete penetrating it. In the 500 MWe reactor, because of the numerous openings in the beams, the reinforcement changes its direction, and it necessitates the nonconventional approach. In this paper, the non conventional approach to the analysis and design of the top hatch beams is suggested. The sequence of construction of the beams, the FEM analysis, the loads for in-plane analysis and the three-dimensional analysis are reported. The increased thickness of the sleeves is required as shear connectors. (K.I.)