In rooms throughout his home, 90-year-old Masakazu Saito has dozens of old clocks indicating it is 8:15 a.m. — the time an atomic bomb flattened Hiroshima and nearly killed him seven decades ago.

“This keeps me remembering the event that should never happen again,” he says.

Although Saito, who was stationed in Hiroshima as an army lieutenant at the time, survived injuries from the bombing, he still suffers from the after-effects.

This spring, Saito will travel to New York to attend an international conference on the Nuclear Non-Proliferation Treaty (NPT) as a member of the delegation of the Japan Confederation of A- and H-Bomb Sufferers Organizations.

The confederation, which brings together survivors of the atomic bombings of Hiroshima and Nagasaki, works to realize a world free of nuclear arms.

“I will keep crying for the abolition of nuclear weapons until my death,” Saito said. He will be the oldest atomic-bomb survivor in the delegation.

Signatory countries of the NPT, which came into force in 1970, have held a review conference every five years to assess its performance. The next gathering is scheduled for April 27 to May 22 at the United Nations with participants from some 190 countries planning to attend. The Japanese confederation plans to send about 50 people.

When the atomic bomb was dropped on Hiroshima on the morning of Aug. 6, 1945, Saito, then 21, was in a barracks about 1.8 km from ground zero.

While talking with a senior officer, Saito said, he casually looked out the window and saw three U.S. warplanes flying overhead. One of them dropped something, and seconds later a blinding flash of light and a heat wave struck the building, instantly evaporating the water in a goldfish bowl in the room and causing the ceiling to collapse.

About 90 percent of the 400 soldiers in the camp were killed immediately.

Saito suffered severe burns to his back and arms.

As he struggled out of the barracks, he was confronted with hellish scenes, such as girls lying on the ground crying for help. He saw some with their eyeballs hanging out of their eye sockets, and intestines protruding from their bodies.

He tended to victims as best he could but then lost consciousness. When he came to, Saito said, he found he had been laid together with corpses in a large hole dug in a schoolyard ahead of a mass incineration. He shouted and was helped out of the hole just in time.

After the war, when Saito returned to his hometown in Iwate Prefecture, local people discriminated against him due to their fears of radiation. Because of this, he was driven to despair about his future and was obsessed with suicidal thoughts.

However, he regained a sense of optimism when he started communicating with other atomic bomb survivors. Later, he established a group of survivors in his hometown and organized activities to raise awareness about the horrors of nuclear weapons.

However, there was no sign that any of the nuclear-armed countries were ready to abandon their arsenals. Impatient with the lack of progress, Saito visited the U.S. during the previous NPT conference, in 2010.

“I’m wishing for the abolition of nuclear weapons so that we can leave a green Earth for future generations,” he said. “I’ll make my last appeal to the world’s leaders” at this year’s NPT meeting.