KOZLODUY, BULGARIA -- No other nation depends more on a single nuclear power plant than does Bulgaria on the one here beside the Danube. This Soviet-designed plant represents more than 40 percent of Bulgaria's electrical generating capacity.

The price of that dependency became apparent last month when a generator accident at the Kozloduy Power Plant forced all of Bulgaria to go on a two-hour-on, two-hour-off electricity regimen. Workers here have protested that there are not enough experts to run the plant's seven reactors.

Last week, the German government permanently shut a nuclear plant in the former East Germany similar in design to Kozloduy, saying it could not meet modern safety standards.

The International Atomic Energy Agency has launched a comprehensive investigation of safety at Kozloduy. Under close scrutiny are four reactor blocks that lack concrete containment domes. Such domes seal in radiation in case of an accident and are considered essential safety features in the West.

"I think that safety must be the first consideration, not economics," said Kiril Nikolov, general manager at Kozloduy, which on cold winter mornings remains shrouded in the milky mists that billow from its cooling ponds. "If we prove in the investigation that the plant is not safe, we must make the decision to close it down."

That eventuality -- in a post-Communist country already jolted by oil shortages, food shortages, unpayable debts, severe industrial pollution and governmental paralysis -- raises the possibility that life in Bulgaria may soon get even darker.

"There would be a great economic disaster with unpredictable social" consequences, said Krasen Stanchev, chairman of the National Assembly's committee for the environment.

Bulgaria's energy predicament differs only in its severity from that facing much of Eastern Europe. Czechoslovakia depends on three nuclear power plants for a quarter of its electricity. Hungary's four reactors produce 48 percent of the electricity there.

Lacking oil and already too polluted to tolerate more coal-burning plants, these countries have been backed into an awkward and dangerous corner. They can close the plants and strap their economies at a vulnerable point in their transitions from socialism to capitalism, or they can stick with technology that does not meet modern safety standards.

This post-Communist quandary is one in which the rich countries of Western Europe, fearing a repeat of the 1986 Chernobyl nuclear disaster, take a keen interest.

Austrian Environment Minister Marilies Flemming has said the Kozloduy plant and ones like it constitute "the biggest threat to Central Europe."

Several Bulgarian nuclear specialists argue that Western Europe's concern about a possible accident should translate into financial help -- concessional loans or grants. Legislator Stanchev appealed to the European Community for urgent assistance in a letter two weeks ago.

It should be pointed out that Stanchev, an opposition assemblyman, is no friend of nuclear power. Indeed, he is a leader of the Eco-Glasnost movement, which forced the government this year to stop construction of a second nuclear power plant.

Stanchev argues that his country, as it developed under Communist rule, stupidly allowed itself to become simultaneously addicted to energy-wasting industry and to a nuclear power plant that kept it going.

But he acknowledges that it will take years, perhaps decades, before industry can be restructured to use less electricity and before alternative sources of power can be found.

Recent cuts here in the supply of oil from the Soviet Union and Iraq have heightened the country's nuclear dependence.

"In the short term, there is no alternative to Kozloduy," Stanchev said.

The Bulgarian government, which is down to less than $200 million in hard currency, needs an estimated $400 million to upgrade safety at Kozloduy and keep the plant operating until energy alternatives can be found.

Bulgaria's nuclear plant, like nearly all of the two dozen in Eastern Europe, was built with Soviet technology and financial assistance. However, political and economic turmoil in the Soviet Union limits its ability and willingness to help its former satellites.

"As you know, the relationship between Bulgaria and the Soviet Union is changing," said Kozloduy general manager Nikolov. "We have to pay in hard currency."

Since the overthrow last year of Todor Zhivkov, then the longest-serving Communist ruler, Bulgaria has joined the rest of the former East Bloc in opening its nuclear plant to Western inspection.

The Vienna-based International Atomic Energy Agency (IAEA) has been granted access to all records at Kozloduy and is doing a complete study of how operators here have responded to safety problems since the first reactor block opened in 1974.

Some West European naysayers, including senior EC officials, have dismissed all Soviet-designed nuclear plants as "accidents waiting to happen." However, the atomic agency said last month of its first visit: "The team was impressed by the qualifications and dedication of managers and staff."

With increased access to detailed operating records, some experts are concluding that reactors of Soviet design in Eastern Europe have better operating records than nuclear plants in the United States.

An analysis of data gathered by IAEA showed "that the performance of the {Soviet} design . . . is uniformly good throughout the region. This level of performance, whilst it does not place {Eastern Europe} at the top of the world league, is good by international standards," according to a November article in Nuclear Engineering International, an authoritative trade journal.

Here at Kozloduy, general manager Nikolov said that, for the time being, he can keep the plant operating safely while keeping the lights on in Bulgaria. He added, however, that there is only one way for his bankrupt country to afford the upgrades that would bring the plant up to modern safety standards. West European countries, he said, must come up with some money.