The Soviet Union has agreed to accept help for victims of the Chernobyl nuclear accident from an international bone marrow transplant organization, whose American chairman is expected to arrive in Moscow today.

The visit by Dr. Robert Gale would be among the first by an outsider offering medical assistance for victims of the nuclear reactor fire near Kiev.

Gale, chairman of the International Bone Marrow Transplant Registry's advisory committee, left Los Angeles last night and is to be met by Soviet health officials, according to Armand Hammer, chairman of Occidental Petroleum Corp., who helped arrange the visit.

Hammer, 87, is also chairman of President Reagan's cancer advisory panel and has had extensive business dealings for decades with the Soviet Union.

"This is a case in which humanitarian concerns transcend political boundaries," said Hammer by telephone from his home in Los Angeles last night. "Dr. Gale is the world's foremost authority on bone marrow transplantation, and this will make his wealth of knowledge available to the people of the Soviet Union."

Marrow transplantation is the only known effective treatment for severe radiation poisoning, which many experts believe could affect persons in the vicinity of the reactor.

Gale's trip was arranged so hastily that he did not have time to obtain a Soviet visa, Hammer said. During a one-hour stopover in Frankfurt today, he was to be met by a Soviet representative and given one, Hammer said.

Hammer said he offered to pay for Gale's trip but that Oleg Sokolov, charge d'affaires at the Soviet Embassy here, insisted that the Soviet Union pay for it. Whether Gale will visit the accident site is not clear, Hammer said.

"He hopes to go to the site so he can determine the extent of the needs so we can mobilize the donors if necessary," Hammer said. "Then we'll have to decide whether to send over other medical teams."

Gale's organization, which includes 128 medical centers that perform bone marrow transplants in 60 countries, is compiling a computerized registry of more than 50,000 potential marrow donors, listed by blood type, Gale said in an interview Wednesday.

About 40 percent of the Milwaukee-based registry's medical centers are in the United States and another 40 percent in Europe, he said.

Gale said he hopes that his organization, funded in part by the National Institutes of Health, can identify radiation victims and match them with potential marrow donors.

"We've been gearing up for this for the past several years, hoping we'd never have to use it," said Gale, an associate professor of medicine at the UCLA School of Medicine.

Hammer said he relayed Gale's offer of help Tuesday to "high Soviet officials" here and in Moscow. Hammer was in Washington this week for the opening of a major art exhibit from Soviet museums at the National Gallery of Art.

At a dinner there Wednesday night, he said, he negotiated directly with Soviet and State Department representatives to arrange Gale's visit.

Soviet authorities had rebuffed offers of help by other U.S. physicians groups, including a chapter of the International Physicians for the Prevention of Nuclear War, whose American and Soviet co-presidents shared the 1985 Nobel Peace Prize.

"There's no single country that could handle this kind of disaster," Gale said. "No center can do more than several transplants at a time."

If the Chernobyl accident spewed lethal radiation into the immediate vicinity, Gale said, the first wave of casualties might not be the worst.

Two to four weeks after the blast, he said, it could be followed by a much larger "second wave of death," caused by radiation damage to the marrow, the blood-producing tissue inside bones.

"That's exactly what we do in bone marrow transplantation," Gale said. "But we irradiate the patient intentionally" first to destroy diseased marrow. At Chernobyl, he noted, "they've been irradiated unintentionally. These are preventable deaths if we can identify the people at risk and match them with potential donors."

Marrow transplantation is a complex and high-risk operation first used in the late 1950s to treat leukemia, Gale said. More than 1,500 people worldwide, most of whom have leukemia or aplastic anemia, were treated that way last year.

The patient is first given a huge dose of total-body radiation to destroy damaged marrow cells. Then, in a procedure much like a blood transfusion, marrow is injected from a donor with the same blood type in the hope that it will reproduce.

Even between perfectly matched blood types, such transplants are extremely risky. If the recipient rejects the transplant, or the marrow rejects the patient, death is inevitable.

A person with damaged or inadequate marrow cannot produce enough blood cells to fight off infection and maintain health. In that sense, the effects of radiation poisoning are comparable to those of acquired immune deficiency syndrome (AIDS) and some leukemias.