nuclear-news

80 Years Ago: The First Atomic Explosion, 16 July 1945.

James B. Conant’s Eyewitness Account:
“The Whole Sky Suddenly Full of White Light Like the End of the World”

1,100 Square Miles in New Mexico Exposed to Radioactive Contamination

UCLA Report Suspected “Many Potential Long-Term Insidious Hazards” From Trinity Test Radiation

Washington, D.C., July 16, 2025 – Early in the morning of 16 July 1945, 80 years ago today, the U.S. Manhattan Project staged the first test of a nuclear weapon in the New Mexican desert. It was the first trial of a plutonium implosion weapon—the same weapon type that devastated Nagasaki a few weeks later. The explosion on the ground produced radioactive fallout contaminating over 1,100 square miles of the state, with some debris spreading as far north as Canada. Six weeks after the test, a “swath of fairly high radioactivity on the ground cover[ed] an area of about 100 miles long by 30 miles wide,” according to a Los Alamos Laboratory report published today for first time by the National Security Archive, while “gamma radiation was found in measurable but very low intensities in Santa Fe, Las Vegas, Raton and even in Trinidad, Colorado,” 260 miles from the point of detonation.

To mark the anniversary of this world-historic event, the National Security Archive today published a collection of essential declassified documents on the first atomic bomb test and the radioactive contamination that preoccupied government officials and medical experts during the years that followed. The new posting builds upon an Electronic Briefing Book of documents, photos, and period films published last year by the Archive, fortifying it with a number of significant new records, including:

• memoranda sent to Manhattan Project director Gen. Leslie R. Groves by his Scientific Advisor Richard C. Tolman on the so-called “100-ton test”—the Trinity “dress rehearsal”—and the reasons for holding a test of the implosion device at the Trinity site,
• Manhattan Project Director General Leslie Groves’ phoned-in message on the test minutes after it occurred, reporting that results were “probably … above expectations,”
• reports by Chief of British Mission Sir James Chadwick on the Test, who wrote, “Even now, a week later, I am filled with awe when I look back at this moment. It was a vision from the Book of Revelation,”
• and Harvard University President James B. Conant’s dramatic firsthand account of the test, observing that “the enormity of the light and its length quite stunned me.”

The Trinity Test planners prepared for possible adverse public health effects but did not know how far radioactive debris would spread, and the biological and public health impact of low-level radiation is still a contested issue. But during the years after Trinity, researchers with the Atomic Energy Project at the Medical School of the University of California, Los Angeles (UCLA) collected evidence to help determine whether the fallout produced a health hazard. While the studies drew no firm conclusions, a 1951 report by the Project found that there were “many potential long-term insidious hazards from the present low-level contamination which is the focal point of these studies.” The possibility that such hazards could eventually inspire legal action was concerning to medical experts who also wanted to learn more about the military implications of low levels of radiation contaminating “large land areas,” leading the Atomic Energy Commission to fund a research program at UCLA to determine the scope and impact of the contamination.

The Trinity test took place 80 years ago, but it is not entirely in the past. Researchers at the National Cancer Institute have determined that the test’s fallout contributed to excess numbers of thyroid cancers. To this his day, “down winders” in New Mexico seek federal compensation under the Radiation Exposure and Compensation Act (RECA), which so far has excluded that state, even though 33 of its counties, including tribal areas, experienced levels of radiation exposure that were higher than other U.S. counties covered by the Act.

July 18, 2025 - Posted by Christina Macpherson | history, weapons and war