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Conference Spotlight
Nuclear Energy Conference & Expo (NECX)
September 8–11, 2025
Atlanta, GA|Atlanta Marriott Marquis
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The Standards Committee is responsible for the development and maintenance of voluntary consensus standards that address the design, analysis, and operation of components, systems, and facilities related to the application of nuclear science and technology. Find out What’s New, check out the Standards Store, or Get Involved today!
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Trinity Test at 80: American Nuclear Society CEO Craig Piercy reflects on the Manhattan Project
By Craig H. Piercy, CEO and Executive Director of the American Nuclear Society
Eighty years ago today, at exactly 5:29:45 a.m. local time* on July 16, 1945, the United States Army detonated the world’s first nuclear bomb in the Jornada del Muerto desert of southern New Mexico. The searing flash and thunderous shockwave marked the culmination of the Manhattan Project, a secret, three-year national effort to harness nuclear fission and hasten the end of the Second World War.
The Trinity test, overseen by Manhattan Project director Major General Leslie Groves and Los Alamos Laboratory director Dr. J. Robert Oppenheimer, was the final act of that race to build the atomic bomb. Hoisted atop a 100-foot steel tower, the plutonium implosion device, known as the Gadget, unleashed a blast equal to 21,000 tons of TNT and temperatures hotter than the center of the Sun.
From ten miles away, observers wearing darkened welder goggles, looked on in stunned silence. “We knew the world would not be the same,” recalled Oppenheimer.
Masayoshi Sugimoto, Alan B. Smith, Peter T. Guenther
Nuclear Science and Engineering | Volume 97 | Number 3 | November 1987 | Pages 235-238
Technical Note | doi.org/10.13182/NSE87-A23505
Articles are hosted by Taylor and Francis Online.
The prompt fission neutron spectrum resulting from 239Pu fission induced by ∼0.55-MeV incident neutrons is measured from 1.0 to 10.0 MeV relative to that of 235U fission induced by the same incident energy neutrons. The measurements employ the time-of-flight technique. Energy-dependent ratios of the two spectra are deduced from the measured values. The experimentally derived ratio results are compared with those calculated from ENDF/B-V (revision 2) and with results of recent microscopic measurements. Using the ENDF/B-V 235U Watt parameters for the 235U spectrum, the experimental measurements imply a ratio of average fission spectrum energies of 239Pu/235U = 1.045 ± 0.003, compared to the value 1.046 calculated from ENDF/B-V (revision 2).
