At Pearl Harbor on Dec. 7, it became difficult for President Bush to suppress tears for those who died there 50 years ago. The occasion reminded me that no official tears were ever shed for two men who made the supreme sacrifice a few years after Pearl Harbor in a secret incident that was important in helping George Bush and hundreds of thousands of other Americans to survive World War II.

On Sept. 2, 1944, the same day Lt. (j.g.) Bush was downed during a bombing run over the Pacific Island of Chichi Jima, two men were killed in Philadelphia in the effort to make the atomic bomb. The two civilian engineers were Peter Newport Bragg Jr. of Fayetteville, Ark., and Douglas Paul Meigs, of Owings Mills, Md.

A week earlier, 10 enlisted men had been assembled to meet at Oak Ridge, Tenn., with Lt. Col. Mark C. Fox and James Conant, president of Harvard. Conant was a personal adviser to Maj. Gen. Leslie C. Groves, whom President Franklin D. Roosevelt had assigned to lead the Manhattan Project to build the atomic bomb. Conant told the soldiers very little about what he was asking them to do, and he cautioned them that the job would be very dangerous, testing a new and untried process. "But," he said, "you will be winning the war." Any soldier who did not wish to participate could leave the room without prejudice. All 10 volunteered and were dispatched to the Philadelphia Navy Yard.

The Navy Yard pilot plant was under the direction of Philip Abelson, a co-discoverer of a precursor isotope in plutonium production, important for the second bomb (the Nagasaki weapon). The Philadelphia plant was testing a uranium isotope separation process for a much larger plant under construction by Col. Fox at Oak Ridge. The purpose of that plant, coded "S-50," was to supply slightly enriched uranium feed to the calutrons (of recent notoriety in Saddam Hussein's nuclear program) to speed delivery of weapons-grade uranium for what became the Hiroshima bomb.

At 1:20 p.m. on Sept. 2, 1944, a cylinder of uranium hexafluoride process gas exploded in the pilot plant, fracturing pipes containing live steam. The steam reacted with the uranium compound to produce hydrofluoric acid, one of the most corrosive of chemicals. Immersed in the steam and acid bath, Bragg, Meigs and the third man in the transfer room, one of the soldiers, suffered severe chemical and steam burns over their entire bodies and inhaled substantial amounts of chemical forms of uranium.

One of the soldiers outside the transfer room, Pvt. John Hoffman, rushed into the blinding cloud to help bring the three men and others outside the transfer room to showers, cutting off their clothes. The vital signs of the three men from the transfer room were ebbing as their bodies lay on the concrete floor of the nearby power plant. Meigs died first, followed by Bragg. I was the third man.

Blinded, because my corneas had been etched by the acid, I heard a doctor say to the Navy chaplain, "Attend to the third man; he's next." The chaplain proceeded to administer last rites as he had done for the others, but I heard myself reject the rites, saying, "I'm not going to die. I refuse to die." (My sight returned in about a week.)

Washington was perplexed by the event. Perhaps a nuclear explosion had occurred, even though the physics of the situation had predicted one would not. In fact, a nuclear explosion had not occurred; what happened was perhaps then the largest release in history of radioactive materials.

Groves dispatched a security officer to Philadelphia to stem information to the press. The general's concern was not only that the atomic bomb project might be compromised but that if project workers learned of the hazards of working with uranium, they might balk. Groves directed a board of inquiry "that there should be only one question to settle" and that involved making it clear to all that "the injuries were sustained while the men were in the line of duty and were not under the influence of alcohol or narcotics."

Groves sent his chief physician, Col. Stafford Warren, to Philadelphia. Warren collected the internal organs of the deceased and brought them back to Oak Ridge for analysis. The organs had become classified materials, since, after all, they contained uranium. The deceased were buried without them.

Abelson later testified that the Navy Hospital did not initially have instructions for treatment because those instructions were classified. An accident was not contemplated, but if such did occur, "the man injured could take the document covering the treatment along with him {!}" The Philadelphia experience taught Gen. Groves's doctors that more expeditious treatment would be required for persons exposed to uranium compounds. There were no exposure fatalities at the S-50 plant. And, in part because of what was learned from the Philadelphia accident, there were no further major mishaps, which ensured little delay for the Hiroshima bomb.

At the time of the accident, Elizabeth Meigs was on a train from Washington to Philadelphia to entice her husband from work so they could spend the Labor Day weekend together. She was met at the station with the sad news. Elizabeth was to learn nothing of the circumstances of Donald's death, then or ever. Peter's brother, Braxton Bragg, learned only decades later that his brother had died in an accident related to the production of the atomic bomb. Not even the Philadelphia coroner was told how the men had died.

John Hoffman was awarded the Soldiers Medal, the Army's highest non-combat decoration and the only one given by the Manhattan Project. Hoffman's citation (secret until it was declassified in 1946) read: "His quick and courageous actions under chaotic conditions were indicative of heroism in the highest degree." Hoffman later distinguished himself, among other notable accomplishments, as director of materials research at the National Bureau of Standards.

Philip Abelson became a respected editor of Science magazine; he has remained reluctant to speak of the Philadelphia event. Three soldiers who were critically injured in the accident, including me, are still living.

The40th anniversary in 1984 of Lt. Bush's wartime experience prompted me to write to the vice president noting that it "was a fateful day you shared with two others who were striving for victory thousands of miles away," and asking, "Just as you are being honored today, would it not be appropriate, 40 years after the event ... to honor the memories and families of Peter N. Bragg and Douglas P. Meigs?"

Months later, I heard from an assistant secretary of the Navy, Chase Untermeyer, that "This Nation will be eternally grateful to the many unsung heros whose selfless actions during World War II advanced our knowledge in the atomic field. Although it is not always possible to recognize the contributions of specific individuals, we can never forget their devotion and sacrifices that ultimately benefited mankind." In fact, the nation never forgot because it never knew.

For years, the articulate Braxton Bragg sought recognition for his brother's sacrifice not only from George Bush but also from various senators and congressmen but received similar platitudes in return.

The president has made it clear there "should be no apology" for America's dropping the atomic bomb on Hiroshima. He said he was grateful for the availability of that war-ending weapon and that to imply its use was somehow wrong was to engage in "rank revisionism."

There is much more to be told about the Philadelphia story and the push for the Hiroshima bomb. It will not be "rank revisionism" but rather the final lifting of the curtain of secrecy. Arnold Kramish, who worked on the Manhattan Project and for the Atomic Energy Commission, is writing a book about the Philadelphia experience discussed in this article.