From a modest suite of offices four floors about downtown Washington, Sam Edlow, his wife and son carry on one of the largest nuclear shipment businesses in the world.

With mon-and-pop simplicity, the Edlows shipped an estimated half-billion dollars worth of radioactive materials between six continents last year and they say they expect to ship about as much again this year.

Their cargoes range from hundreds of tons of enriched uranium ore sent overseas for eventual use in nuclear power plants, to lethal spent fuel of Swedish and South African research reactors entering the harbor of Portsmouth, Va.

Only about half of Edlow's 17-person staff minds the nuclear store. The other half runs a travel agency out of the same suite of offices at 1100 17th Street NW. Brochures on moving uranium ore are stored beside those offering Caribbean cruises.

"We decided if we could move nuclear materials we could move people," said Sam Edlow, the 65-year-old patriarch of the family and board chairman. His wife, Frances, is treasurer and their son, Jack, 30, is president. A second son, Robert, 28, imports Oriental art.

After two years of studying to be a rabbi, and a stint as a junk-battery dealer removing lead from discarded batteries, Sam Edlow began supplying lead shielding to a small research reactor in Ohio 21 years ago. It was a time of few government regulations, and most large companies were not interested in competing for the small amount of nuclear materials that were being imported and exported.

"To G.E. it was peanuts. To the Edlows, it was very nice," Edlow said.

When the Atomic Energy Commission formulated its import-export rules, Edlow was one of those consulted. His name appeared on the list of licenses given to potential foreign customers by the commission.

"Sam Edlow has been around since Day One of the nuclear industry. He's a pioneer in the field," said Carl Goldstein, assistant vice-president of the Atomic Industrial Forum.

With the exception of a few multi-national corporations that have their own shipping divisions, Edlow International has only one major rival, according to the Nuclear Regulatory Commission, the agency that succeeded the AEC. That rival is Transnuclear Inc., a White Plains, N.Y., firm owned largely by German and French interests.

Edlow's staff comes from a variety of backgrounds. Operations manager Norman Ravenscroft moved nothing more hazardous than furniture before joining Edlow a year and a half ago. Company Vice-president Diane Harmon, 32, joined the firm with a liberal arts degree and a couple of years with a travel agency.

Edlow says there's no reason for his staff to be nuclear experts. They are, he says, primarily "paper-pushers," putting uranium buyers and sellers together, and getting shipping approvals from the Nuclear Regulatory Commission, the Department of State, the Department of Energy, the Department of Commerce, the Department of Defense, and the Arms Control and Disarmament Agency.

In addition, Edlow arranges for shipments, contracts with the carriers -- ships, planes, trains, and trucks -- and ultimately supervises the shipments.

In his offices are clocks showing the time in Stockholm, Sydney, Tokyo, London, and Washington; maps of the world; and chalk boards charting shipments of radioactive material to ports around the world.

Edlow's shipments of highly radioactive spent fuel place Edlow International in the midst of controversy because of the continuing opposition of antinuclear activists and some local governments to such shipments.

Last July, Edlow International shipped two casks of highly radioactive spent fuel from a Swedish reactor that was brought by freighter to Portsmouth, Va., and later taken to a fuel-reprocessing plant in Aiken, S.C.

The seven pounds of spent fuel were divided, packed in steel and lead compartments, and loaded into two 15-ton lead-filled casks that were in turn fitted into steel frames and strapped to the ship.

Because spent fuel can be deadly if released, Fred Miller of the antinuclear Potomac Alliance and others want to ban the importation of spent fuel into the country.

That antinuclear sentiment has produced what Edlow calls the "creeping paralysis" that has closed off every major port south of Portsmouth to his shipments of spent fuel.

In the emotional fallout of the Three Mile Island, Edlow faces what he says is a general slowdown of the nuclear industry and a profusion of new regulations requiring him to provide security guards to accompany shipments of five kilograms or more of highly enriched uranium.

"It's very distasteful business. We don't like the job of being gun-toters and a quasi-military operation. Should Edlow be responsible for the common defense and welfare of the United States? I don't think so," Edlow said.

To avoid having to hire guards, Edlow divides his shipments so that they fall below the five-kilogram mark. "We go strictly by the letter of the law," Edlow Vice-President Harmon said.

Industry spokesmen and the NRC say Edlow's safety record is excellent, but Edlow says a minor nuclear accident is just a matter of time.

"I called my staff in and said, 'There's going to be an accident some day. Let's be confident and not get hysterical about it,'" Edlow said."I sleep very well at night.

Edlow International has already had several accidents. Two years ago, for example, a package of uranium hexafluoride, the feed material for the enrichment process, rolled off a railroad car in Georgia and caused the train to derail.

Enrichment is the process of converting natural uranium ore to fuel-quality material, increasing both its fissionable quality and its radioactivity.

Earlier this year, a truck loaded with unenriched uranium ore tipped over on a Wichita, Kan. freeway.

"It was cleaned up and everyone lived happily ever after. There was no scare stuff. Walter Cronkite didn't beat his breasts," Edlow said.

In addition to shipping, Edlow also provides "discreet" services to buyers and sellers of uranium on the international market.

"I like to use the word 'discreet' rather than 'confidential' because the word 'confidential' sounds like it's on the edge of legality. Let's just say the names of the buyers and sellers remain a secret," Edlow said, lowering his voice.