Workers on Saturday began shutting down eastern Germany's last Soviet-designed nuclear power reactor, which was once on a list of nuclear installations prone to catastrophe.

The four-reactor power station near Greifswald on the Baltic Sea coast had supplied 10 percent of the electricity used by the 16 million people of the former East Germany.But its shutdown was planned as soon as West German experts examined it after the Berlin Wall fell a year ago.

The last of the four reactors had been working at low output for months only because it also provided hot-water heating for 45,000 people and scores of factories.

The gradual shutdown of the reactor began Saturday. Plant spokesman Peter Baier said the plant will be completely off by Tuesday. A hastily built oil-fired plant is being put into operation to supply hot-water heat.

"It was a deep worry that it went on so long," said Klaus Schlueter, an environmental official and former member of the interim non-Communist East German Cabinet.

"The problem is the metal is brittle, and there were serious safety concerns. This is the main problem with all the old reactors in this region," Schlueter said in a telephone interview from Schwerin in northern Germany.

Greifswald, the only nuclear power station in former East Germany, is not the only old Soviet reactor creating worries in Eastern Europe.

Among other cases, Austria wants Czechoslovakia to close a two-reactor power plant at Bohunice, 75 miles northeast of Vienna. Austrian Chancellor Franz Vranitzky said his country would supply electricity at its own expense.

Czechoslovakia, lacking alternative power sources, refuses to shut the Bohunice plant immediately but has promised a reassessment by a new government commission by Dec. 31.

An international commission spent four months examining the Bohunice plant and concluded that "a serious, uncontrollable accident must be expected at any time."