THE CLINCH RIVER breeder reactor is turning into a peculiarly omnious symbol. If its construction is canceled, no scientific knowledge or technology will be lost. Its only purpose is to demonstrate on a commercial scale the breeder process now in operation at a smaller test facility at Handford, Wash. But if the Clinch River project is built, the main damage will be the signal that it sends to the rest of the world. It would be announced that Congress was overriding President Carter and committing the United States to the commercial exploitation of plutonium fuel. That would just about knock the bottom out of the President's attempts to restrain the proliferation of plutonium - and the weapons made out of it - throughout the world.

At this moment, the Clinch River reactor is only an item in next year's federal budget. Mr. Carter said in his energy message two months ago that he decided to drop it. But in Congress there is now a powerful campaign under way to hold the money in the budget and to force construction of the project. Some of its advocates evidently fear that cancellation would mean lost jobs. But beyond the actual construction contracts, there are not many jobs at stake. A curious psychology seems to be operating here. Throughout the nuclear industry - in both the federal installations and the private companies-there is a desperate anxiety to maintain what it sees as the momentum of the breeder idea. Cancellation of the Clinch River reactor might mean future federal research policy that no longer gave an absolute priority to the plutonium breeder. But a shift in focus there is long overdue.

Some of the Clinch River reacot's supporters have now offered the President a compromise: full funding but a year's delay in construction. Some compromise. The construction dates are irrelevant. What the world wants to see is whether Congress can make the President build the thing after he tried to dump it. There are a lot of people in Europe who darkly suspect that the Carter position on non-proliferation may degenerate into a mere ploy to derail the development of a competitive European breeder technology. If the Clinch River appropriation goes through, Mr. Carter will retain very little influence on other countries' efforts to build and export this dangerous equipment.

The case for the breeder is the possibility that this country might run into uranium shortages in the next century and need to recycles its fuel. The Carter budget provides half a billion dollars to push breeder research forward. But the country doesn't need to build a commercial breeder this year - or next. The budget authorization for Clinch River comes to a vote in the Senate Energy Committee today. The House is to vote on its next week. President Carter is trying to discourage the commercial traffic in plutonium here and around the world. He deserves congressional support.