Experts say the challenge is no longer about whether to favor nuclear power or renewables. Nuclear power put to the testSeveral European nuclear power plants have faced shutdowns or output cuts this summer amid extreme heat, drought and cooling-water concerns. Experts say Korea’s coastal nuclear plants may be less vulnerable to the specific problems affecting some river-cooled plants in Europe. But the rapid growth of solar generation is creating a different challenge for the operation of Korea’s nuclear plants. At around noon on Aug. 7, solar power accounted for 26.6 percent of total electricity demand, exceeding nuclear power’s share.