The director of the Clinch River breeder reactor project blamed most of its 450 percent cost overrun on the "national political debate" over the breeder yesterday as he answered charges that it has become a management fiasco and a financial disaster.

The estimated cost of the project has soared from $699 million in 1972 to $3.2 billion, but 80 percent of that $2.5 billion overrun is "the result of causes external to the project over which the project had no authority to manage," Lochlin Caffee testified at a hearing of a House Commerce and Energy subcommittee.

Caffee, a Department of Energy employe, said that more than a billion dollars of the overrun was caused directly by the "national policy debate" over whether to proceed with the reactor. Fund cutbacks and attempts to close down the project altogether during the Carter administration resulted in years of extra costs in salaries and inflation, he said.

If that debate had not taken place, he said the reactor would be running in 1983 for a cost of $1.95 billion. It is scheduled to begin operation in 1990 for $3.2 billion, 11 years late.

A. Ernest Fitzgerald, the Air Force cost watchdog who was lent to the subcommittee to investigate the breeder, disagreed with Caffey, saying that even now the project could run far beyond $3.2 billion. "The full extent of the overruns is not yet evident . . . according to the DOE, their contracts are adjusted rountinely," he said in his testimony.

A chief cause of the continually rising cost, he suggested, is the fact, that "the principal prime contracts have been written without binding provisions for cost, schedule, or specific technical performance."

Another cause, he said, is technical problems that have plagued the project.

He quoted from a Department of Energy memorandum which stated that the technical problems plaguing the steam generators, a key element in the breeder plant, "might be severe enough to warrant termination" of the contract.

The Department of Energy countered that the Clinch River breeder is not a simple technology and that significant technical advances beyond the state of the art had to be made in building the generators.

Problems with steam generators, have plagued not only the Clinch River project, but virtually all other breeders in the world.

Breeder reactors operate at high temperatures and use low-grade uranium fuel while making another nuclear fuel, plutonium, as a by-produce. The promise of making more fuel than it burns has apparently been a powerful reason for the continuation of the project through multimplying overruns and political trouble.