In 1946, the head of the KGB First Directorate, Boris Vannikov, sent Lavrentiy Beria an appeal from Soviet Academy of Science physicists to help them conduct airborne experiments that would allow them to collect radioactive particles near nuclear testing sites associated with the US ‘Operation Crossroads‘. The concept would have Beria instruct Commander in Chief of the Soviet Navy, Admiral Nikolai Kuznetsov, to direct a detachment of ships, already underway, to support the operation. The experiment would involve an unidentified “hydroplane-type aircraft” to fly within 500 kilometers of the center of the detonation of the second nuclear bomb test. The plane would fly through the radiation cloud, and samples of the particles captured through special filters would allow the Soviet scientists to determine type of bomb being tested by the Americans.
The following is a translation of Vannikov’s cover letter, and the detailed request from three physicists spelling out what the experiment would entail.
Top Secret
To Comrade L.P. BERIA
Academy Fellows Semenov, Kurchatov, and Alikhanov feel it necessary to dispatch an airplane to the atomic bomb test site at a distance of approximately 500 kilometers from the central testing location, which will make it possible to capture radioactive particles which can be used to identify the material from which the bomb is composed.
Since a Navy expedition has been authorized, Admiral Kuznetsov, upon receipt of your instruction, will be able to support this effort.
The necessary preparatory work has already been carried out by the Academy Fellow physicists.
B. Vannikov
Top Secret
Esteemed Lavrenty Pavlovich,
Several days ago, the concept was raised regarding the possibility of obtaining valuable information about the American bomb, specifically on determining the efficiency of the bomb and the material that it was made from (plutonium, uranium-233, or uranium-235. In order to carry this out, it is necessary for our hydroplane-type aircraft, equipped with air filters (for dust) on the day of the second detonation to be located at a distance of 500 kilometers from the center of the detonation. The aircraft must be equipped with gamma ray counters. Flying in from the leeward side at a distance of 300 kilometers from the detonation point and flying along, the aircraft should, with great probability, encounter a cloud of dust, flying with the wind, containing residue from the bomb shell material, undecomposed material from the main body of the bomb, and debris from the explosion. The gamma ray counter will make it possible for the aircraft to mark the moment of encounter with the radioactive cloud, and having activated the filter, fly into the cloud for half an hour. As the estimate indicates, during this time, the cotton in the filter will capture enough matter to subsequently analyze using radiometric methods in Moscow.
The aircraft must be deployed on a vessel sent by the Navy to an area located 500 kilometers from the detonation point. It would be significant if the vessel approached (should time allow) to the detonation downwind (that is, from the southwest). In this case, there is a chance that it too can be in the radioactive cloud and also take samples of the material using specially constructed filters installed in the vessel’s blower.
Should all go according to plan, with there being a significant chance for success, we draw your attention to the great interest in this experiment, since it provides significantly more important information than all other experiments drawn up by the expedition.
Regarding these experiments, there is an agreement with the Navy (Admiral Bogolepov). On Sunday, our colleagues (Doctor Zelmanov and associate Vetchinkin), fully instructed, flew to Vladivostok. However, in light of the too-small amount of time to organize the entire effort in Vladivostok, we feel it is completely necessary for your express instructions to be given to the Navy on the mandatory nature of these experiments, making them the central mission of the expedition.
Academic Fellow N. Semenov
Academic Fellow I. Kurchatov
Academic Fellow A. Alikhanov
Translation © 2025 by Michael Estes and TranslatingHistory.org
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