Safety aspects of Narora containment structure

Salient features of the containment of the Narora Atomic Power Project are described. The design internal pressure of 1.25 Kg/cm2 concurrent with a ground acceleration of 0.3 g has been adopted for the design of the inner containment and 0.07 kg/cm2 internal pressure for the outer containment. Certain modification to structural components to ensure leak tightness are mentioned. Taking into consideration the site seismicity and soil conditions at the site, allowable stresses adopted for safe shutdown earthwuake are 1.5 times normal stresses and 0.6 times yield stress for concrete and reinforcement respectively. A flat cellular slab of the containment separates heavy and light water atmospheres. 12 T 13 anchorage prestressing system is adopted. The system enables wider spacing of cables and higher diameter embedment and results into less deviation of cables from their original layout, making stress distribution more uniform. Acceptance tests carried out on prestressed structures and wobble and friction tests carried out on sheathing materials are mentioned. (M.G.B.)