Criticality Experiments with Fast 25 and 49 Metal and Hydride Systems During the Manhattan Project

TL;DR

This paper revisits historic criticality experiments from the Manhattan Project, providing detailed technical insights and modern analysis to highlight their importance in nuclear safety and computational validation.

Contribution

It offers detailed technical documentation of Manhattan Project criticality experiments and applies modern MCNP6 simulations to interpret these historic measurements.

Findings

Validated experimental results with modern computational methods

Enhanced understanding of early criticality safety lessons

Provided comprehensive technical details previously unavailable

Abstract

Criticality experiments with $^{235}$U (metal and hydride) and $^{239}$Pu (metal) were performed during the Manhattan Project. Results from these experiments provided necessary information for the success of the Manhattan Project. These experiments have been previously described in compilations made after the Manhattan Project, but those works are either lacking in technical details or are not publicly available. This work aims to provide detailed information while showcasing the enduring impact of these experiments 75 years after they were performed. Furthermore, we use modern computational methods embodied in the MCNP6 code and ENDF data to analyze and interpret these historic measurements. The world's first four criticality accidents are also discussed, as lessons learned from these helped shape the field of criticality experiments.