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Uranium cubes reveal why the German nuclear project failed

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Based on a feed excerpt; full article content has not been acquired. Source evidence retrieved 05/11/2026, 14:13:24 UTC.

Briefings

A 2019 report by Timothy Koeth and Miriam Hiebert identified 14 mysterious uranium cubes from the German B8 reactor project, which failed to achieve criticality due to insufficient uranium and heavy water. Koeth received one cube in 2013, and the team tracked 10 others across the US, including one at the Smithsonian. The cubes were used by Heisenberg's team in the late 1940s, but the project lacked the necessary materials to build a bomb, as confirmed by a 2013 paper in the Proceedings of the National Academy of Sciences.

Key points

• 14 uranium cubes from the German B8 reactor project were identified by Timothy Koeth and Miriam Hiebert, with only 14 known to exist today.
• The project failed because the German team lacked sufficient uranium and heavy water to build a working nuclear bomb, despite Heisenberg's claims of proximity to criticality.

Context

The German nuclear project, led by Werner Heisenberg, aimed to build a reactor during World War II but ultimately failed to achieve criticality. Researchers identified 14 mysterious uranium cubes from this failed program, which were tracked by Timothy Koeth and Miriam Hiebert starting in 2013. The cubes were used by Heisenberg's team in the late 1940s, but the project lacked the necessary materials to build a bomb, as confirmed by a 2013 paper in the Proceedings of the National Academy of Sciences.

Limitations

Only 14 uranium cubes from the German B8 reactor project are known to exist today, and the specific design parameters of the failed reactor are not fully detailed in the available evidence.

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