TVA Experience with Concrete Chimney Linings

The condition of the concrete lining for TVA's Bull Run chimney after 15 months of operation is described together with the effects of insulation, temperature change, drying out, and acid attack. Temperature gradients and thermal stresses for startup and shutdown cycles are computed and used to predict as well as explain the cracks found in the lining. The results of sonic tests and core analyses are given to show that drying out and acid attack have had little detrimental effect, and even with vertical cracks the lining is in no structural danger. Shrinkage stresses are shown to be much more critical for the transient temperature conditions than for the steady state. At Bull Run the condition was improved by controlling the draft in the annulus. At Paradise where a similar chimney was completed in 1968 changes in the design of the concrete lining were made to better control shrinkage cracks. Inspections and tests in both chimneys will be made periodically.