KYIV (AP) — A U.N. nuclear watchdog team has set off on an urgent mission to safeguard the endangered Russian-occupied Zaporizhzhia atomic power plant which has been at the heart of fighting in Ukraine. The world hopes this long-awaited trip will help avoid a nuclear catastrophe. The trip is to a country where the world’s worst nuclear accident, at Chernobyl in 1986, sent radiation across the region, shocked the world and intensified a global push away from nuclear energy. The stakes of the U.N. mission are high because of fighting at and near the plant, and because the plant is occupied by the Russian military. Elsewhere, new fighting was reported in southern Ukraine, with Ukrainian forces attacking a Russian-occupied city and neighboring regions.