Unit 6 was in the guaranteed shutdown state and Spring Location and Relocation (SLAR) tool was being used in the pressure tubes as part of the planned fuel channel maintenance. While performing SLAR operation in fuel channel G12, an electrical fault in the tool resulted in a discharge of electric energy that caused damage to both the pressure tube and the calandria tube. The tool was retracted and it was later determined that the Primary Heat Transport System (PHTS) coolant was leaking into the moderator. Inspection exhibited a through hole in the pressure tube approximately 3 mm in diameter and a through hole in the calandria tube of 6 mm in diameter. Operations personnel proceeded with stabilization of unit 6 by installing isolating shield plugs to stop the flow of PHTS coolant into the moderator. The pressure tube and calandria tube have been replaced and the unit returned to service.