Chancellor Angela Merkel told mediapersons after a meeting with the premiers of five states where the atomic power plants are located that seven reactors which went on stream before 1980 will be shut down until mid-July.
In addition, an eighth reactor, which began operating in the northern state of Schleswig Holstein in 1983, but was taken out of the power grid after a series of accidents, will remain closed indefinitely, Merkel said.
A government order on the temporary closure of the reactors has been issued on the basis of a provision in the country's new energy law, which empowers the federal and state governments to take necessary measures to deal with an emergency situation without amending the law. National security has utmost priority in taking this decision, she said.
Merkel on Monday announced a three-month moratorium on the governments controversial plans to extend the life span of all 17 reactors on an average by 12 years, which was agreed by her cabinet about six months ago and signed into law by German President Christian Wulff at the end of last year.
The seven reactors will remain closed during the moratorium and a planned review of reactor safety systems, which are scheduled to last till July 15.
The chancellor left it open whether any of the older reactors will be taken out permanently. A decision will be taken on the basis of the outcome of the safety review and in consultation with the state governments and operators of the power plants during the three-month period, she said.
Germany's Minister for Economic Affairs and Technology Rainer Bruederle, who was present at the meeting, said that even though only the nine new reactors will continue to generate electricity during the next three months, the country has sufficient electricity to meet its power needs without the share of the seven reactors.
At present, 23 per cent of the country's electricity supply comes from the atomic sector.
As Merkel met the state premiers in the chancellery, thousands of anti-nuclear activists and members of the opposition parties demonstrated outside demanding a permanent closing down of the older reactors and a reversal of the governments decision to extend the life span of the reactors.