A Study on Fabrication Technology of Ceramic Overpack - A Conceptual Design and Fabrication of a Full-Scale Ceramic Overpack -

Abstract

The conceptual design and fabrication test of a full-scale ceramic overpack were performed from the viewpoint of structural barriers as a part of program to evaluate their potential use as overpack under conditions of deep geological disposal.Materials investigated were porcelain (used for insulators) and A1 2 0 3 with high purity of 99.7 %. The selected design consisted of a cylindrical body with hemispherical heads at each end. The design thickness of overpack is the sum of the structural thickness and corrosion allowance. The thickness required to resist the lithostatic pressure was estimated by the basic cylinder buckling formulas and finite element stress analyses in both case of uniform and non-unifom external pressure conditions. These analyses showed that structural thickness of 119 mm was necessary for overpack of porcelain and 40 -for A1 2 03 under the predicted maximum uniform pressure. In addition, fracture probability of delayed failure, one of significant degradation mode, was estimated for overpack of porcelain.A full-scale overpack of porcelain, of dimensions 800 mm outer diameter x 2200 mm length x 150mm wall thickness, was fabricated under the ordinary level of fabrication technology.