(Updates with details, background)
LJUBLJANA, Sept 30 (Reuters) - Slovenia will shut down its sole nuclear power plant Krsko (NEK) from overnight on Friday for regular maintenance that takes place every 18 months, NEK's spokeswoman Ida Novak Jerele told Reuters.
She said the plant, which is jointly owned by Slovenia and Croatia, is due to resume operations on around Nov. 1. The maintenance is not expected to have any environmental impact.
Jerele said work will include a security upgrade needed for a new hydro power plant on the river Sava about 8 km (5 miles) from NEK and due to start operating next year. NEK is located next to the Sava river.
NEK was built in cooperation with U.S. firm Westinghouse Electric Corporation and started operating in 1982. Earlier this year Slovenia and Croatia prolonged its lifespan by 20 years to 2043. (Reporting by Marja Novak; Editing by Susan Fenton)