But Mr. Abe insisted that radioactive water had been contained at the Fukushima Daiichi plant and said that he would fend off “rumors” regarding Fukushima’s safety. He instructed the plant’s operator, the Tokyo Electric Power Company, to decommission the No. 5 and No. 6 reactors, which survived the March 2011 earthquake and tsunami that damaged the four other reactors. Mr. Abe said he stood by the reassurances about Tokyo’s safety that he gave to the International Olympic Committee this month before the city was awarded the right to host the 2020 Summer Olympic Games. But many Japanese believe that he is glossing over problems at the plant. Officials have acknowledged that radiation-contaminated groundwater has been seeping into the ocean since soon after meltdowns and explosions crippled the plant.