The 1952 National Research eXperimental (NRX) reactor accident is generally regarded as the world’s first serious “reactor accident”. Wikipedia, however, does not give it the distinction of being the world’s first “nuclear accident”. That designation is given to the “Leipzig L-IV accident”.
The Leipzig accident first came to our attention during a recent gathering of AECL retirees for our regular Wednesday coffee-chat. Larry Hunt reported on a short article in a book “Secret Weapons of World War II”, by W.B. Breuer, that he had picked up at a W.B. Lewis Library book sale.
The book describes an event in June 1942, at a lab in Leipzig headed by the famous German physicist Werner Heisenberg. Details in the article were scarce and so the internet was searched for further details.
The web search revealed that the experimental group in Leipzig, under the leadership of Robert Doepel, had been experimenting with uranium and heavy water in various geometries. They had succeeded in demonstrating neutron multiplication but had not yet achieved a sustained nuclear chain reaction.
Various geometries and materials were used in a series of experiments conducted at Leipzig. Fine uranium and sometimes uranium oxide powder were used; both ordinary and heavy water, when the latter became available, were used as moderators.
The setup for the Leipzig L-IV experiment consisted of two concentric, double-walled, aluminum, spherical shells each encasing fine uranium powder. Heavy water was held both within the inner sphere cavity as well as in the inter-sphere gap. The outer shell measured about 1.6 m in diameter. This assembly was then immersed in a larger tank of water.
During an examination of the assembly, air and water inadvertently came in contact with the fine uranium power. The resulting chemical reaction led to a spontaneous ignition of the pyrophoric uranium powder and generated a large amount of hydrogen. The hydrogen and the burning uranium produced flames up to 6 m in height and the building housing the experiment was destroyed. This conflagration ended the experiments at Leipzig.
The Allied Alsos mission captured most of the German nuclear scientists and their equipment late in the war and revealed that the German nuclear program was nowhere near as advanced as the program in Canada (Montreal Laboratory/Petawawa Works) let alone the enormous Manhattan Project in the United States.
A YouTube video (https://www.youtube.com/watch?v=4Rp4c2PVP1Y ) describes the experiment setup in some details as well as the events leading to the accident, although there are some errors in the presentation.
The Canadian Nuclear Heritage Museum continues to collect nuclear-related artifacts and documents/anecdotes associated with the Canadian and international nuclear programs. Readers are encouraged to contact us at info@nuclearheritage.com to donate any materials they may have.
