"Block 2 of the Beznau nuclear power plant shut down automatically," the nuclear plant operator Axpo said in a statement.
"This was triggered by a defect in the non-nuclear part of the power plant. All systems functioned perfectly during the rapid shut-down," the operator added.
The company also noted that steam escaped from the non-nuclear part of the plant when the power generating station was shut down.
The reactor which closed down automatically is expected to be recommissioned after the defect had been located and fixed.
Axpo Power, a wholly-owned subsidiary of Axpo Holding, is involved in generation, transmission, distribution, utilisation and marketing of electrical and other energy services.
