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Nuclear Energy Conference & Expo (NECX)
September 8–11, 2025
Atlanta, GA|Atlanta Marriott Marquis
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The Frisch-Peierls memorandum: A seminal document of nuclear history
The Manhattan Project is usually considered to have been initiated with Albert Einstein’s letter to President Franklin Roosevelt in October 1939. However, a lesser-known document that was just as impactful on wartime nuclear history was the so-called Frisch-Peierls memorandum. Prepared by two refugee physicists at the University of Birmingham in Britain in early 1940, this manuscript was the first technical description of nuclear weapons and their military, strategic, and ethical implications to reach high-level government officials on either side of the Atlantic. The memorandum triggered the initiation of the British wartime nuclear program, which later merged with the Manhattan Engineer District.
A. W. Gray
Nuclear Technology | Volume 12 | Number 4 | December 1971 | Pages 342-347
Technical Paper | Reactor | doi.org/10.13182/NT71-A30982
Articles are hosted by Taylor and Francis Online.
An analytical study has been completed to define minimum critical mass parameters for a spherical region containing a 235U-H2O mixture reflected by a natural uranium-water mixture. The study indicates that for an optimum natural-H2O reflector, the calculated minimum critical mass for the central sphere lies in the range of 75 to 200 g of 235U. The analytic study was divided into three phases. In the first phase homogeneous two-region systems were examined using diffusion theory programs. The results indicated a minimum critical mass of 451-g 285U for an optimal system. In the second phase a Monte Carlo program was utilized to compute keff for uranium metal rod-H2O moderated lattices for which experimental data are available. The purpose of the second phase was to establish the validity of the Monte Carlo program as an analytical tool. In the third phase the Monte Carlo program was used to calculate 235U + H2O spheres closely reflected by an optimum lattice of natural uranium rods. The Monte Carlo program indicates that the minimum critical mass in an H2O-moderated system reflected by a uranium metal lattice is 135 ± 65 g 235U.
