Overview of the history of neutronics computations

This paper provides some background and perspective on the history of neutronics computations. The author started his carerr at Bettis Atomic Power Laboratory (BAPL) in 1954. At that time, computers were primitive and unfamiliar to most of us. Bettis did own an IBM Card Programmed Computer, which, as its name suggested, had a punched-card memory, and some of the industry's first cross-section preparation codes (the early MUFTs) were written for this machine by Ben Mount. There was also at BAPL another digital machine, which spewed output everywhere on punched tape. But the laboratory's most powerful machine was an analog computer that solved two-group diffusion equations in two dimensions. An excellent physicist of that period argued that analog machines were the wave of the future because digital computers could never solve the diffusion equation in two dimensions. At the time, this seemed like a very reasonable prediction; yet it was not very long before Bettis was renting time on UNIVACs all over the country precisely to solve the two-dimensional diffusion equation. Since then, we have learned that it is always risky to predict future trends in the computer industry