Not until her first child was born eight years ago did Sylvia Blanchet seriously explore her concerns about nuclear catastrophe. No doubt, living on a farm next door to the Central Intelligence Agency headquarters in Langley agitated her Ground Zero Zeitgeist. But what gnawed most at the new mother was what would become of the children.

For her own peace of mind, Blanchet joined workshops exploring life in the Nuclear Age. But like most parents, she and husband Thomas Fricke wanted to protect their two kids from nuclear anxiety as long as possible. Still, they didn't want to ignore nuclear reality. So they set out to create a home environment that encouraged their children to ask questions about nuclear issues, that assured the children someone would listen to their worst fears.

"Kids aren't stupid -- they see what's happening in the newspapers and on TV," says Blanchet, 35, who two years ago moved with her family to Vermont. "If their parents deny it, that's a clear message that the parents feel they can't do anything about it. That expression of powerlessness ... makes kids feel hopeless."

Yet, according to evidence in recent studies, most American parents turn their backs on their children's fear of nuclear disaster -- a silence that can compound the worry children rightfully experience with fatalist despair.

Joanna Macy finds it ironic that parents and teachers who would usually rush to a child's side to dispel his fears so often are paralyzed when the monster in the closet is a nuclear warhead. But, then, the author of Despair and Personal Power in the Nuclear Age (New Society Publishers, $10.95), points out that obliteration of the human race isn't your run-of-the-mill bogeyman.

"They can't say it's just a nightmare and it'll go away -- because it won't," says Macy, the San Francisco mother of three. "Adults in a child's life today know they don't have the means to make this child safe. They can't dispel the fear."

Macy and other experts, who only in recent years turned attention to psychological fallout in children from the nuclear peril, say that besides feeling powerless, most parents give nuclear issues the silent treatment because of collective embarrassment.

"How do you look a child in the eyes when we've let things go to such a point that we are preparing to annihilate ourselves?" asks Macy. Prevailing thought prior to the late 1970s was that young children knew little about the nuclear threat and could care less. But nobody bothered to ask the children. Since then, behavioral scientists have discovered an unexpected turnabout in the childish mind: From about ages 6 to 13, youngsters typically grasp a far more realistic image of nuclear holocaust and its horrifying consequences than many adults.

From the findings of several surveys:

Pollsters for Global Education Associates, a New Jersey research group, avoided mentioning nuclear disaster when they asked fifth graders to talk about the future. Yet 90 percent of the children said they expected a nuclear war that they would not survive.

In a California survey two years ago of more than 900 students, grade 7 to 12, 51 percent said they first heard of nuclear weapons before between ages 5 and 10; more than half thought nuclear war between the United States and the Soviet Union would take place in their lifetime; 64 percent believed they and their family would not survive.

From the American Psychiatric Association's (APA) 1982 Task Force Report on "Psychological Aspects of Nuclear Developments": Of 328 high school students, a majority felt nuclear war was likely; 70 percent said the United States could not survive it. Half of a sample, grades 5 through 12, said the nuclear threat affected their thoughts about marriage and plans for the future.

Another California study found that more than 72 percent of the children polled "hardly ever" talked about the nuclear threat with their parents, although 42 percent thought about nuclear war "quite a bit" and 55.7 percent said they are afraid nuclear war might happen.

More eye-opening than such stats were representative comments by the children polled: typically the word "nuclear" provoked images of "the world as nothing, completely wiped out ... bombs exploding, people dying, buildings ruined, society demolished ... " When asked how that affected their daily thinking: "I am constantly aware that at any second the world might blow up in my face ... It's terrifying to think that the world may not be here in a half-hour."

In her book, The Strangelove Legacy (Harper & Row, $15.95), Phyllis La Farge, a contributing editor to Parents magazine, recounts a theater script called Changing the Silence that a high school junior performed as her outcry against nuclear war. The sentiments from the mouths of babes: "What's the use of going to college? What's the use of making money? What's the use of preparing for a future when I have none? ... I feel as though I'm dead right now. My grave was dug before I was even born." Reports La Farge: "For many adults {that} is crude, ungainly, embarrassing, the kind of outcry that makes them uncomfortable ... adults want to distance themselves by saying kids will outgrow feeling this way."

Unrelated research in Finland, Holland, Australia, the United States and Canada recently confirmed that young people most acutely express their anguish for the world and their fear of nuclear war around age 13. In the years following, expressions in indifference seem more prevalent.

"They're learning the adult way of coping, which is to shut down," says Macy. "Adults sanitize and whitewash the grim reality. Adults make it abstract. But kids, particularly those under 13, think of it like of an animal run over on the road -- a squashed, wrecked and dead body ... of multitudes of people. Maybe adults are afraid of talking about this with their kids because that would allow that child inside themselves to start to scream."

Last March, University of Massachusetts psychologist Susan Fiske reported in the journal "American Psychologist" signs of higher concern about the nuclear threat among children while most people visualize nuclear destruction in "abstract" terms of material rather than human loss. "The typical adult apparently worries seldom or relatively little about the possibility," Fiske found. "Given that people's beliefs about nuclear war include a low likelihood of personal survival and at least minimal worry, one might expect them to be more active."

Social analyst Robert Lifton coined the term "psychic numbing" in his research of the Hiroshima aftermath to mean "the turning off of feelings" aroused by possible nuclear destruction as too unpleasant to endure. Everyone threatened by nuclear horrors too great to contemplate, Lifton concluded in Death in Life, his hallmark chronicle of the aftermath of the nuclear attack on Hiroshima, is a victim of The Bomb.

At 40, Wendy Forman recalls the "Ban the Bomb" rallies from her childhood. She wonders what happened to that public attitude, that openly articulated dread of the apocalypse. But even for the Philadelphia family therapist and her husband, psychologist David Greenwald, it took the nuclear accident at Three Mile Island seven years ago to stir up their "visceral terror" and motivate them to "do something."

Since then, the couple has been researching the impact of the nuclear threat on children -- mostly by interviewing children. "It's such a downer," says Forman. "But it's like talking to your kids about AIDS ... or about child molesting. It is very difficult but as a good parent you have to do it ... The difference is with those other things, you can give them pointers. But most parents believe there is nothing they can do about stopping nuclear war -- so they don't talk to their children about it at all."

But the videotaped interviews, conducted by Forman and Greenwald in Philadelphia, and in Boston by psychologist Steven Zeitlin, indicate that giving kids pointers isn't the point. "Frequently the children in these interviews were able to express themselves clearly and seriously about a topic many adults believe does not affect children," write Greenwald and Zeitlin in No Reason to Talk About It: Families Confront the Nuclear Taboo (Norton & Co., $22.95), the book that grew out of the interviews. "Most of the children, however, were eager to talk ... so that they could see how the adult world would respond to these hidden concerns."

By the end of the interviews, reports Greenwald, most of the children "opened up," even those who were initially reluctant. "Perhaps they needed to sense the level of trust," he says. "Perhaps they needed to see that these adults were capable of hearing them before they fully expressed themselves."

A major finding of the study: "Kids tend to be matter-a-fact," says Greenwald. "They're aware, they're frightened, they're angry and concerned. But parents had a harder time dealing with their children's discomfort. That compounds the problem of families not discussing it. Parents don't want to talk about it so kids also don't talk about it, partly because they feel or sense that there really is no place to bring this concern."

Participants in Macy's "despair and empowerment in the Nuclear Age" workshops who learn to confront their nuclear angst often rationalize their silence. "Parents again and again tell me, 'I want them to be happy in the time they have left because I have no assurance my kids will grow up,' or 'children are too innocent to know about that,' or 'I don't want to spoil their childhood by bringing up fears they can do nothing about.' The main focus of my work is to persuade people that the opposite is true.

"What is hard for children is the silence of our society and of the adults in their lives about this. They interpret silence to mean indifference. They interpret it to mean you don't care. When young people can talk with adults about what they're feeling about our world, they feel a release of anxiety and sense of validation.

"But we have persuaded ourselves that to feel grief, fear and rage about this is a sign of personal pathology. In fact, not to is the true pathology. To pretend that we can go on with business as usual is a pathological response."

Two years ago, Toronto child psychologist Susan Goldberg surveyed children to discover the effects of the nuclear threat on their mental health. Hiding the intent of the questions, the Canadian researchers surveyed more than 2,000 students, grades 7 through 12. As expected, a majority listed nuclear war as among their top three greatest worries, ranking it second only to the fear of their parents' death.

But of most interest to experts were indications that the youngsters who reported feeling anxious often about nuclear war were also the ones most able to consider other future problems and take action. Concerns about nuclear disaster had not led them to "foreclose their futures" but rather just the opposite. Those who had blotted out their nuclear fears and succumbed to psychic numbing proved less able to plan their futures in other areas such as careers, marriage, children.

"People might assume that if a kid experiences anxiety about nuclear war, that's bad," says Forman. "But there is an optimal level of anxiety before you can do anything about it. People feel better when they take action. Despair and depression immobilize you."

Says Macy who calls herself a profound optimist: "All through history, every generation assumes that another generation will follow. It is the loss of certainty that life will go on that is in every heart. From now on out, we have got to live with the possibility of collective suicide through nuclear war. I am convinced that we can live healthy, productive, authentic lives without the certainty of a future -- but only if we face it.

"People are much stronger than they're given credit for -- and that includes the children."