Myths of Nuclear Graphite in World War II, with Original Translations

TL;DR

This paper re-evaluates the historical narrative of Germany's abandonment of graphite in WWII nuclear reactors, revealing errors in wartime data and emphasizing material availability and strategic decisions over experimental mistakes.

Contribution

It uncovers inaccuracies in wartime nuclear data and highlights the role of material constraints and strategic choices in Germany's decision to avoid graphite as a moderator.

Findings

Incorrect carbon scattering cross section used in wartime data

Availability of pure petroleum coke enabled US production of nuclear-grade graphite

German decision was based on material constraints, not experimental errors

Abstract

We re-examine a common narrative that experimental errors by Walther Bothe in 1941 led Germany to abandon graphite as a reactor moderator during World War II. Using document-based nuclear archaeology, we first show that both American and German scientists used an incorrect carbon scattering cross section, thereby undermining the accuracy of all wartime data, including their conclusions on carbon's absorption. Moreover, we argue that the availability of exceptionally pure petroleum coke in the United States, rather than any academic breakthrough, decisively enabled their production of nuclear-grade graphite. In contrast, Bothe's Siemens electrographite had more boron contamination than any graphites considered in Fermi's experiments, rendering it genuinely impractical as a moderator. By reframing the decision to eschew graphite as a deliberate decision rather than a mere experimental oversight, we believe the German decision was a rational consequence of a complex interplay between material constraints and wartime priorities.