TOKYO—Japan’s new prime minister on Sunday said the planned mass disposal of wastewater stored at the tsunami-wrecked Fukushima nuclear plant cannot be delayed, despite concerns from local residents. Speaking at his first visit to the facility since taking office, Fumio Kishida said his government would work to reassure residents nearby the plant about the technical safety of the wastewater disposal project. The Fukushima Daiichi plant suffered a triple meltdown in 2011 following a massive earthquake and tsunami. Kishida’s brief tour of the facility by its operator, Tokyo Electric Power Company Holdings, focused on the ongoing decommissioning of the plant, and the massive amount of treated but still radioactive water stored there. “I felt strongly that the water issue is a crucial one that should not be pushed back,” Kishida told reporters after the tour. The government and TEPCO announced plans in April to start releasing the water into the Pacific …