The first thing they all say is how far they were from the hypocenter when the bomb went off.

Senji Yamaguchi was 14 years old, digging foxholes outside the Mitsubishi arms factory at Nagasaki on Aug. 9, 1945. He was wearing pants and a cap but no shirt. The white light struck the right side of his body.

"I was 1.2 kilometers from the flash," he said. He brushed back his hair to show the line above his right ear, where the cap was. He pulled up his shirt to show the line at his waist. Everything between was burned.

Yamaguchi spoke through a translator, as did the six other survivors of Hiroshima and Nagasaki who came to Washington yesterday. There are nearly 400,000 Hibakusha, or nuclear victims. In the rapid flow of Japanese one frequently heard the words "flash" and "mushroom," linguistic contributions from the United States.

They came to invite President Reagan to the 40th anniversary ceremonies in Hiroshima Aug. 6. They also will ask the Soviet Union's Mikhail Gorbachev and other world leaders.

Reagan declined to meet with the delegates here. So did Vice President Bush.

Yamaguchi found his way to a hospital before he collapsed. He spent eight months there. Three months later he found his liver was damaged and he had leukemia. He had 13 skin grafts. After graduating from high school he couldn't find a job because he was so badly disabled. People couldn't bear to look at him. Children would shout, "Here comes the Red Demon!" He cut his wrists but was rescued. Finally he decided to devote his life to the cause of the bomb survivors, and today he is the chairman of Nihon Hidankyo, a confederation of nuclear victims.

Two years ago he discovered he had skin cancer around his right eye.

The physical anguish of the Hibakusha never seems to end. Permanently weakened by abnormal blood conditions, they tire and sicken easily. On the job, they are accused of being lazy.

"It is hard to get married," said Shoji Sawada, a nuclear physicist at Nagoya. "When people hear you are a bomb victim they don't want to marry you. If you are married, there is the worry about children, if you should have children."

And there is the guilt. Sawada was 13 when the bomb destroyed his house in Hiroshima. His mother, crushed under a pile of burning beams, called to him as he tried desperately to free her before the fire overwhelmed them both. "Get away from here right now!" she shouted. So he left her there.

"When I thought about my mother under the smoke, I felt my heart was broken," he said. "Couldn't I really help her out? There must have been a way. Even now, 40 years after, I still hear my mother call my name."

Some of them still dream about it.

Satoru Konishi was a 16-year-old schoolboy in Hiroshima on that day, 4.5 kilometers from the hypocenter. He was sheltered by a low hill and saw the mushroom cloud towering above him, darkening the whole sky, but didn't realize what had happened. When he walked around the hill he found the city had disappeared.

"I heard a sound like boiling and I heard a voice, 'Give me water! Give me water!' and there was a man lying on the smoking, stinking earth. His face was boiled. It was white and soft as tofu. That was all I remember. I went around the city all that day but I can't remember anything except the man with the boiled face."

Six years later, a university student, Konishi began to have pains in the spine. He had trouble standing up. His mind couldn't focus on his studies and he was accused of being lazy. It was years before he could live a normal life. He is now a professor of German at Tokyo University.

The Hibakusha delegation was joined here by American veterans who were exposed to radiation at Hiroshima and Nagasaki. Victor F. Tolley, formerly of the 2nd Marine Division, was part of the occupation forces at Nagasaki. He and Jean Ralph, widow of another Marine, spoke at a press conference yesterday on the Hill. Ralph's husband entered Nagasaki Sept. 23, 1945, and stayed there nine months.

"In 1976," she said, "his bones began to break like balsa wood -- when he sneezed, when he grabbed a doorknob. He had multiple myeloma, a bone-marrow cancer caused by radiation, which has a latency of 30 to 35 years."

The disease is common today in Hiroshima and Nagasaki, she said. Harold Ralph died Aug. 18, 1978.

"We've been told the bomb was dropped to save lives," Jean Ralph said. "We don't know how many that might be, but we sure know how many have been lost."

Hibakusha delegations are also being sent to the United Nations, to China, France and Great Britain. Five nuclear victims will visit the Soviet Union late this month, seeking a meeting with Gorbachev.

"We are well aware that the atomic bombs were dropped by the United States in the war which was provoked by the militarism in Japan, and with which we ourselves did collaborate," their statement reads. "We are persistently demanding the Japanese government to admit its responsibilities in executing the war and to compensate the A-bomb victims for the affliction caused by the atomic bombing . . .

"There is no way out of this nightmare unless people all over the world realize through the testimonies of us victims that nuclear weapons cannot exist side by side with humanity, that they are by nature inhumane . . ."

Yesterday morning, accompanied by Sen. Mark Hatfield (R-Ore.), the group laid a wreath at the Tomb of the Unknown Soldier. The schedule was tight, for groups present flowers there every 15 minutes or so. Dozens of tourists, mostly children in shorts and T-shirts, stood on the steps watching the little ceremonies as they were repeated over and over.

The Hibakusha wore necklaces made of brightly colored origami flying cranes, an international peace symbol. They stood impassively on the white marble flagstones, dazzling in the hot sun. When the bugler played taps, they bowed low, in the classic Japanese gesture of greeting, humility, respect and farewell.

Then they went away unremarked by the children, who sat down to wait for the next ceremony.