When Jin Wook Chung, professor of nuclear engineering at the State University of New York, sold his home on Long Island and moved his family back to Seoul, his Korean wife cried for two weeks.

"The transition wasn't easy for her after all these years," he says. "And my son hates Korean food. All that he talks about are hamburgers."

But the decision by Chung, who had become a naturalized American, to return to Seoul and become vice president of the Korea Nuclear Fuel Development Institute was a major coup for this mother country.

One of the biggest problems facing developing nations with ambitious nuclear programs is a shortage of trained manpower. Most of these countries know all too well that persuading their nationals who have settled down in teaching and research posts in Europe and America to return home would go a long way toward filling that gap.

But reversing the brain drain is not easy.

"Many people come to us, mostly PhDs from America and Europe, and they expect to d something new." says Reza Khazanch, director of Iran's Isfahan Nuclear Technology Center.

"I have had many interviews with people like that, and the first thing I tell them is they have to make a choice.

"They can isolate themselves from Iran - from their country - and remain associated with development abroad. That's possible," says Khazaneh. "They can go to a university and become a professor. They can read the most up-to-date books. They can participate in international conferences, and work on projects that are, today, appreciated in Europe and America. That's one way.

"The second way. I tell them, is to come down to earth, to work with your hands-to fabricate something that's really necessary for the country-to work on the problems that face us, and forget about today's problems in America and Europe," Khazaneh says.

So many opt for the first alternative, however, that India generally does't even bother trying to lure home scientists who have spent more than a year in Britain or the United States.

"They imbibe that type of culture present in the advanced country, and they expect the same facilities here that are present there," says Homi Sethna, head of India's Department of Atomic Energy.

"Here, you cannot just turn around and pick up a telephone and say, 'Look I want this and this thing. Will you ship it out? Nothing of the kind," says Sethna. "Here, you jolly well have to do it with your hands. Go to the electronics people and say, 'Look, this is the type of instrumentation I want.' You've got to discuss it with them, sit with them, make it, put it in."

The problems inherent in this clash of cultures have a familiar ring to Khazanch.

"People who come back, they doubt," he sighs. "Sometimes, they tend toward the problems of Iran and how to solve the problems. But sometimes, they see that they are far away from what they have studied abroad-and it's very difficult to adjust."

Khazaneh, 44, who wrote his doctoral thesis at the University of California at Berkeley on a "computational problem of nonlinear space, time-dependence feedback," has clearly made his own choice.

"I, myself, have said goodbye to my doctoral thesis and what I have done in Berkeley," he says. "I am devoting myself to building the [WORD ILLEGIBLE] and looking into the problem [WORD ILLEGIBLE] really have in Iran- [WORD ILLEGIBLE] those problems."