Determining nuclear weapons yields from bomb debris | Chemical & Engineering News
Volume 94 Issue 28 | p. 9 | Concentrates
Issue Date: July 11, 2016

Determining nuclear weapons yields from bomb debris

Mass spec method enables a new estimate of the size of the 1945 Trinity test
Department: Science & Technology
News Channels: Analytical SCENE, Environmental SCENE
Keywords: nuclear weapons, Trinity test, physical chemistry, mass spectrometry
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A new analytical approach suggests that Trinity, the world’s first nuclear weapons test, produced a blast equivalent to 22,100 tons of TNT.
Credit: Jack Aeby/Manhattan Project
Color photo of the Trinity test blast.
 
A new analytical approach suggests that Trinity, the world’s first nuclear weapons test, produced a blast equivalent to 22,100 tons of TNT.
Credit: Jack Aeby/Manhattan Project

Whether for treaty monitoring or historical interest, sometimes it is necessary to evaluate the yield of a nuclear weapons test long after the fact. A new method that involves measuring stable molybdenum isotopes could get around the time sensitivity of current approaches, which include monitoring seismic signals and measuring short-lived radionuclides (Proc. Natl. Acad. Sci.USA 2016, DOI: 10.1073/pnas.1602792113). Researchers from Los Alamos National Laboratory used mass spectrometry to measure the amounts of different molybdenum isotopes in debris samples from the 1945 Trinity nuclear weapons test, the world’s first. 95Mo and 97Mo are stable radionuclide daughters in the decay chains from plutonium fission, therefore the test debris has elevated 95Mo/96Mo and 97Mo/96Mo levels compared with natural abundances. The team used the molybdenum ratios and the amount of plutonium in the debris to calculate that the yield of the Trinity test was equivalent to 22,100 metric tons of TNT; the official Department of Energy estimate is 21,000 metric tons of TNT. Although the paper implies that the approach could be used to evaluate modern-era tests, the researchers declined to answer whether it could be used to evaluate underground tests, such as those done as recently as January by North Korea.

 
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