Cameron W. Barr, Staff writer of The Christian Science Monitor

NO radioactive material was released in a recent mishap at an experimental reactor in Japan, but the metaphorical fallout continues to spread.

Public concerns prompted by the Dec. 8 incident, which plant managers sloppily attempted to cover up, will further delay and may even extinguish government plans to develop a network of reactors that simultaneously burn and generate nuclear fuel.

Japan relies heavily on nuclear power, the source of a third of the nation's electricity, and its officials have imagined the problem-ridden "fast-breeder" technology as a source of renewable energy.

The debate is over nuclear power, but the incident has engendered new forms of political might as well. Officials from the area around the reactor have shown an unusual willingness to confront the central government.

While activists praise this rare behavior, they vow to prevent the state-funded Power Reactor and Nuclear Fuel Development Corp. (PNC) from restarting the reactor at the facility, known as Monju. They also say they will continue to oppose the Japanese government's long-range plans to broaden the use of plutonium in its nuclear energy industry.

"I think we can scrap Monju," says Jinzaburo Takagi, a physicist who is a prominent opponent of the government's plutonium plans. "And the Japanese plutonium program should be revised substantially and scaled down."

The ruling coalition government has said it will investigate Monju and may reexamine overall nuclear energy policy. Press reports this week say officials of Japan's Science and Technology Agency have also acknowledged the need to review plans for the use of plutonium.

Ryukichi Imai, a high-level adviser to the government on nuclear matters, says of the Monju mishap: "It is not a tragedy as far as the technology is concerned. It was a tragedy as a public relations event."

On Dec. 8, managers shut down Monju as an estimated two tons of sodium in one of the reactor's cooling systems began to leak, setting off fire alarms. PNC officials tried to play down the incident, and later scrutiny showed that they repeatedly lied to the news media about their handling of the leak and delayed in informing local authorities.

Mr. Imai observes, "The stupidity of the PNC is beyond anybody's imagining, so the PNC deserves to be criticized."

Officials of Fukui Prefecture, where Monju is located, released an interim report Dec. 25 criticizing Monju's design, warning systems, and operating procedures. The prefecture has reportedly said it will not allow the reactor to be restarted unless improvements are made.

Monju is a prototype fast-breeder reactor. Its plutonium core is clad in a uranium "blanket" that is partially converted to plutonium during the nuclear reaction. It thus breeds its own fuel and then some.

Although there were once fears of a global uranium shortage, which in part inspired Japan's research on fast-breeders, now most countries are satisfied that they will not run out. This status quo generates a lot of radioactive waste from uranium reactors, a problem not yet solved, but that may be the lesser of two evils.

Japan proposes to reprocess spent uranium into plutonium which can then be burned in fast-breeders and other types of reactors. Japanese officials argue that reprocessing is energy efficient and dramatically reduces the amount of waste that must then be disposed of.

Like many nice ideas, it has some down sides. One is having to produce, store, and transport plutonium, a deadly and unpopular substance that in a high-grade form is the starting point for nuclear weapons. US officials worry that widespread reprocessing will create many more opportunities for countries or terrorists to obtain the 20 pounds of plutonium or less needed to make an atomic bomb.

Another is that the fast-breeder technology is so problematic and costly that it has been abandoned by most countries that have experimented with it. Nonetheless, Japan has plowed ahead with Monju and with a related reprocessing facility. The government has spent billions of dollars on the project, despite numerous delays, and seems content to work out the technological problems.

THE government's major obstacle has been public concern about safety. Some nuclear-energy advocates have claimed Japan's excellence at maintaining quality control will keep the industry safe, but incidents such as the Monju sodium leak undermine those assertions.

Satomi Oba, a Hiroshima resident who runs an activist group called Plutonium Direct Action, says the Dec. 8 leak has made it easier to rally opposition to Monju and to plutonium use in general. Activists with an Osaka-based organization called Stop the Monju say they have collected 880,000 signatures on a petition opposing the experimental reactor.

There is also great sensitivity in Japan to stockpiling plutonium. Not only was the bomb that exploded over Nagasaki a plutonium device, but the frequency of earthquakes makes many people uncomfortable with idea of storing what some consider to be the world's most lethal substance.

Officials acknowledge that it will take two years before Monju can return to operation, and activists like Ms. Oba and Mr. Takagi insist that the reactor should never be restarted.

But Takagi notes that Monju's closure means that Japan will accumulate high-grade plutonium even more quickly. He estimates that Japan already has tons of excess plutonium. Officials say they have only enough for research and note that plans are under way to begin burning a combination of plutonium and uranium at some of Japan's 49 reactors.

Imai, the government adviser, concedes the Monju leak is a compelling reason to revamp the PNC, although he favors continued research into plutonium and sodium-cooled reactors. He notes that in relative terms, there is not much reason to worry about the safety of nuclear energy in Japan.

That is not so for China and Russia, he adds. China faces a stark choice between burning coal, which generates gases that warm the climate, and expanding its nuclear industry. Russia, whose nuclear industry was responsible for the disaster at Chernobyl, Ukraine, continues to pursue fast-breeder technology.