Two groups of Long Island high school students were in Kiev when the Soviet nuclear power-plant disaster was occurring about 60 miles away, and the group has assured family members that everyone is safe and that the trip will continue.

Domincik DiFranco's daughter, Linda, 17, is among eight Massapequa High School students and 18 adults visiting the Soviet Union. DiFranco said parents had been informed by the airline Finnair, which organized the trip, that everyone was all right.

He said his family discussed international terrorism in deciding whether Linda should make the trip "but we thought the Soviet Union would be safe. We never expected she'd be flying over a nuke plant when it blows."

He said he has heard that the group may have decided to leave Kiev today, a day earlier than scheduled, for Leningrad. But he added, "I was just watching the news, and they show the nuclear cloud hanging over Leningrad. I don't know what to think."

Loretta Stelter's daughter, Linda, 17, also was in Kiev with the group. Stelter said she has not heard directly from her daughter but from a Finnair tour guide.

"We talked to the tour guide through the U.S. Embassy in Moscow, and he said things are fine. They're continuing their tour of Kiev today and going on to Leningrad tomorrow," she said.

Another tour group included 19 students and 12 chaperones from Garden City and Roslyn high schools.

James Tarrou, a social studies teacher at Garden City High School, who was on the trip, talked by phone from Kiev to a Finnair representative in Moscow, according to his wife, Patricia.

She said she has been in touch with parents, all of whom heard from tour operators but not their children. "They're still concerned because they don't know what sort of radiation may be present in Kiev," she said.