Babies born today in the Chernobyl area of Ukraine face as big a risk of contracting radiation-related illnesses as children who lived there during the deadly 1986 nuclear explosion, according to research released yesterday by Israeli scientists. Thyroid, liver, and other diseases were more prevalent among children in the area than among unexposed children, the researchers reported. They also found a 70 percent rise in breast cancer since the disaster. According to the U.N., 7 million people, including 3 million children, have been put at risk by the Chernobyl explosion. A report released by the U.N. in April predicted that the worst health effects from the disaster were yet to come and that radiation levels would remain high until the middle of this century.