American Electric Power Co. Inc., Columbus, Ohio, said it was forced to shut down its 1,090 Mw Cook Unit 2 nuclear plant in Bridgman, Mich., Thursday after silt from Lake Michigan infiltrated the power unit’s cooling water system.
Unit 1 was already off line to replace a circulating water pump discharge valve. AEP said the silt intrusion affected the cooling water systems for both units. The silt was drawn in by plant water intake pipes and degraded cooling water systems required for plant safety equipment and back-up power sources.
Three 16-ft-diameter pipes bring water from one-half mile out in Lake Michigan into the plant. Various cooling system pumps use this water for cooling.
Unit 2 was reducing power Thursday and expected to be taken off the grid later in the day. AEP said the plants will be returned to service after an investigation.
Observers said loss of 2,100 Mw of power in the Midwest was not expected to threaten the reliability of the grid. Electricity demand was expected to decline Friday with the beginning of the long Labor Day weekend.
Weather forecasts also pointed to relatively mild temperatures, reducing demand for air conditioning.
The Cook plant returned to service in 2000 after a 2 _ year shutdown for various safety issues.