Slovenia's sole nuclear power plant Krsko shut down on Monday following problems in the steam system, the plant's authorities said in a statement, adding the incident caused no "negative effects".

The statement said: "On Monday, the nuclear power plant of Krsko automatically shut down due to disturbances on a steam line valve of the secondary system."

It added that all systems were functioning properly during the shut down.

It said that the incident "had no impact on the environment nor any other negative effects."

The Krsko nuclear plant situated about 90 kilometres (55 miles) east of capital Ljubljana was closed twice last year, once in April for a regular 42-day maintenance and another time in October owing to a steep increase in the flow of the river Sava used for cooling the plant.

The plant -- jointly built with Croatia in 1984 when they were both part of the former Yugoslavia -- accounts for about 40 percent of the EU country's electricity production.