Pink ribbons signaling a decontamination operation being carried out are seen in Kawamata town, Fukushima prefecture, Japan, July 31, 2015. On March 11, 2011, a massive tsunami devastated the Fukushima Daiichi nuclear plant in northeast Japan, triggering meltdowns, spewing radiation and forcing tens of thousands of residents to flee their homes, making it the world's worst nuclear disaster since Chernobyl. REUTERS/Toru Hanai 

Yoshiteru Kohata, a 86-year-old Nagasaki atomic bombing survivor and retired school teacher, who returned to his home region of Fukushima after World War Two, looks around a seaside playground, damaged by the March 11, 2011 earthquake and tsunami, in his birthplace of Soma, Fukushima Prefecture, Japan, July 31, 2015. Survivors of the Hiroshima and Nagasaki attacks, 70 years ago this month, figure among a majority of Japanese opposing a plan to reboot reactors taken offline after the Fukushima nuclear disaster. REUTERS/Toru Hanai 

Yoshiteru Kohata, a 86-year-old Nagasaki atomic bombing survivor and retired school teacher, who returned to his home region of Fukushima after World War Two, prays at the Haranomachi Airfield Monument in Minamisoma, Fukushima Prefecture, Japan, July 31, 2015. Haranomachi Airfield Monument is a memorial for those who trained during the war at the airfield as pilots, including 'kamikaze' who flew on suicide missions, and for those from the Haranomachi area who died in the war. Kohata said he, too, might have flown to his death had not an army colonel told him not to quit school and train as a pilot. "There were many who died at the age of 16," he said. REUTERS/Toru Hanai 

A tear falls from the eye of Yoshiteru Kohata, a 86-year-old Nagasaki atomic bombing survivor and retired school teacher, who returned to his home region of Fukushima after World War Two, at his home in the town of Miharu, Fukushima Prefecture, Japan, July 31, 2015. REUTERS/Toru Hanai 

Yoshiteru Kohata, a 86-year-old Nagasaki atomic bombing survivor and retired school teacher, who returned to his home region of Fukushima after World War Two, poses with a portrait taken when he was in middle school, at his home in the town of Miharu, Fukushima Prefecture, Japan, July 31, 2015. REUTERS/Toru Hanai 

Yoshiteru Kohata (L), a 86-year-old Nagasaki atomic bombing survivor and retired school teacher, who returned to his home region of Fukushima after World War Two, looks at a Geiger counter to check the radiation level with an examiner in the garden at his home in the town of Miharu, Fukushima Prefecture, Japan, July 31, 2015. REUTERS/Toru Hanai 

Atsushi Hoshino, a 87-year-old Hiroshima atomic bombing survivor, former college professor and ex-president of Fukushima University, speaks next to a radiation monitoring post measuring a radiation level of 0.123 microsievert per hour, at a park near his home in Fukushima, Japan, July 30, 2015. Hoshino was a high school student deployed to a munitions factory when a U.S. bomber dropped an atomic bomb on Hiroshima. REUTERS/Toru Hanai 

Small statues of Jizo, a Buddhist deity, for victims of the March 11, 2011 earthquake and tsunami, are seen in Soma, Fukushima Prefecture, Japan, July 31, 2015. Survivors of the Hiroshima and Nagasaki attacks, 70 years ago this month, figure among a majority of Japanese opposing a plan to reboot reactors taken offline after the Fukushima nuclear disaster. REUTERS/Toru Hanai 

Atsushi Hoshino, a 87-year-old Hiroshima atomic bombing survivor, former college professor and ex-president of Fukushima University, shows a family photo taken in 1941 (he is standing in the centre) at his home in Fukushima, Japan, July 30, 2015. REUTERS/Toru Hanai 

Akira Yamada, a 89-year-old Hiroshima atomic bombing survivor, former college professor and ex-president of Fukushima University, speaks during an interview with Reuters at his home in Fukushima, Japan, July 30, 2015. REUTERS/Toru Hanai 

Akira Yamada, a 89-year-old Hiroshima atomic bombing survivor, former college professor and ex-president of Fukushima University, shows an undated photo of Atomic Bomb Dome on his album during an interview with Reuters at his home in Fukushima Japan, July 30, 2015. Yamada, chairman of Fukushima's atomic bomb survivors group, was at home 2.5 km from the centre of the explosion when the bomb fell on Hiroshima. REUTERS/Toru Hanai 

A tourist sits in front of a board containing messages of support from Maihama station in Chiba prefecture, at the Fukushima station in Fukushima, Japan, July 30, 2015. REUTERS/Toru Hanai