Leonid Kuchma, Ukraine's president, said yesterday he would consider a new German plan to replace the aging Chernobyl nuclear power station, site of the world's worst nuclear disaster in 1986 , with coal and gas-fired electricity. He made his concession after a day of top-level talks with a German government delegation, led by Gerhard Schroder, chancellor, and Jurgen Trittin, anti-nuclear environment minister.