NEW YORK - Western experts on nuclear technology said the Soviet Union had the worst nuclear safety planning of any nation, even worse than that in developing countries and the rest of the Soviet bloc.

As a result, they suggested, the Russians have taken far more risks in their nuclear power program. That practice is probably linked directly to the nuclear plant disaster near Kiev in the last week, the experts said.

"In order of safety, one would put the Germans first, the Americans in the middle and the Russians at the bottom," said Dr. Bennett Ramberg, an expert in international reactor safety at the Center for International and Strategic Affairs at the University of California at Los Angeles.

Safety failures cited

Among the specific Soviet safety failures cited are these:

A design termed "hazardous" by American experts.

Reduced safety to save money.

Inadequate measures to contain radiation, cool nuclear fuel, use computers and provide backup safety needs.

Inadequate evacuation planning.

Failure to plan for worst-case accidents.

Placing nuclear reactors in populated zones.

Lack of public scrutiny of safety.

"Their plants would never be licensed in our country," said Dr. Richard T. Lahey, chairman of the department of nuclear engineering and science at the Rensselaer Polytechnic Institute in Troy, N.Y.

Safety compromises by the Soviet Union have been known for years in technical circles. They noted that after the 1979 nuclear accident at Three Mile Island in Pennsylvania, Soviet officials ridiculed the West for adding even more safety features.

They `take more chances'

"The Soviets take more chances than we do," said Philip R. Pryde, an expert on Soviet energy at San Diego State University.

Half of all Soviet reactors and most of the older ones are both graphite-moderated and water-cooled, an inexpensive design used virtually nowhere else commercially.

Instead of using water to slow down neutrons and control the nuclear reaction, the reactors use graphite. The graphite is relatively inexpensive and enables the use of less costly lower-enriched uranium requiring less processing, experts say.

Moreover, instead of the large, costly and complex pressure vessels common in Western reactors, the Soviet graphite units have smaller, relatively simple tubes of water surrounding fuel rods. The tubes go through the graphite. The water turns to steam to generate electricity, removing the heat of reaction in the process.

But there are potential safety problems. For one thing, at temperatures above 2,000 degrees Fahrenheit, graphite catches fire. To compensate, graphite reactors in the West use inert helium instead of water. The water operates at high pressures and in an accident breaks down into reactive hydrogen and oxygen, and propels more radiation into the air. "It's a rather hazardous system," Lahey said.

Beyond that, the Soviets have usually not built thick containment buildings of steel and reinforced concrete around their reactors. Such buildings cut down more than half of the radiation released from a major accident and allow perhaps two more days for people to escape, said Alan T. Crane, a nuclear expert at the Congressional Office of Technology Assessment.

"The Soviets thought containment domes were a waste of money," Ramberg said.

Lack of public debate

Another liability, experts said, is the lack of public safety debate, meaning far fewer minds are at work to foresee and solve problems.

And a professor of nuclear physics in Stockholm said that Soviet nuclear plants, unlike those in other industrialized countries, have "rather primitive" computer systems to monitor equipment, analyze data and sound alarms. He said the lack might well have contributed to the accident.

Underlying the entire Soviet nuclear safety activity is the philosophy that their reactors were so safe they did not need many expensive safety features, experts said. "It's technological optimism, and maybe even technological hubris," said Dr. Robert H. Randolph, assistant director of the National Council for Soviet and Eastern European Research in Washington.

But experts said that like Three Mile Island, the toxic leak at Bhopal , India, and the Challenger shuttle accident, the Soviet nuclear accident would probably have a significant impact on that philosophy.

"I should think this has to shake their confidence considerably," Crane said.