The national Centers for Disease Control in Atlanta and the South Carolina health department have agreed to investigate 25 reported cases of a rare blood disease found within a 40-mile radius of a nuclear weapons fuel plant.

The Atlanta Constitution reported last week that doctors in seven South Carolina towns near the Savannah River plant, where weapons-grade plutonium and tritium are produced, have diagnosed more than 25 patients with the incurable blood disease polycythemia vera.

The normal prevalence of the disease, in which the body produces abnormally high numbers of blood cells, is not known, but doctors estimate from attempts to catalog recent cases that the disease strikes about one in 250,000 in this country. Under that estimate, no more than a few cases would be expected to pop up in the region of the nuclear materials plant. About 700,000 people live within 60 miles of the plant.

One confusing factor, however, is that there are a number of different varieties of polycythemia. The varieties appear similar on some tests but have quite different causes, and some are far more common than polycythemia vera. High altitude can cause the bones to make a larger than normal number of blood cells; smoking cigarettes can do the same.

Because of these other forms, the rare and most serious variety of the disease is hard to diagnose, Dr. Robert Winslow of the CDC said.

The cause of polycythemia vera is unknown. But its chief symptom is a greatly increased proportion of blood cells in the body, with veins becoming extremely congested with thick blood. The only treatment known to relieve the condition is periodic bleeding.

Though there is no proof that radiation causes the disease, Winslow told the Atlanta paper that it is at least conceivable in theory, because radiation can damage the DNA of bone marrow cells, possibly leading to diseased blood cells. Winslow added, however, that he could say nothing about the possibility of such an occurrence in the South Carolina case.

After hearing of one case from a man diagnosed as having the disease, reporters at the Constitution sought out reports of the disease from local doctors in the plant area, as part of an investigation of the health effects of nuclear plants.

In response to the Atlanta article, Rep. Butler Derrick (D-S.C.) requested a "thorough study . . . as soon as possible" by the CDC and the South Carolina Department of Health and Environmental Control.

Derrick, whose district includes the plant, said the state health department told him officials would begin contacting the seven doctors quoted in the story.

"I do not feel we should overreact to the report," Derrick said, "but I did feel the charges are serious enough to warrant a detailed, scientific study."

The Savannah River plant, which is run for the Energy Department by E.I. duPont de Nemours & Co., has been operating since December, 1953.