The US Nuclear Regulatory Commission has started a Special Inspection to review the circumstances surrounding the blockage of a portion of the fire protection sprinkler system located outside of the reactor building, in an intake structure that houses some safety-related equipment.
Located 35 miles northwest of Minneapolis, the plant is operated by Northern States Power Company-Minnesota. On September 2, the company reported to the NRC that while performing testing of the intake structure fire suppression sprinkler system, workers identified blockage in a portion of the system. This piping supplies water from the Mississippi River to the sprinkler system in case of a fire in the building.
Although there is no immediate concern for safety, the NRC has decided to send a three-member team to inspect the plant and evaluate the condition of the fire suppression system in the intake building, the plant’s compensatory measures and the root cause investigation; determine if other sprinkler systems in the plant have similar blockage; look into existence of previous occurrences of this issue and review previous corrective actions; and determine if there are generic implications for other plants.
The company instituted a continuous compensatory fire watch and stationed backup fire suppression equipment in the intake building to make sure the plant could respond to a fire in this location.