The Soviet Union's PNE program was comprised of Program No. 6 and Program No. 7 of the Nuclear Explosions for the National Economy project. It was similar to the American Operation Plowshare, except that many of the tests were actual applications of nuclear technology and not simply tests. Under the Nuclear Explosions for the National Economy program, 239 nuclear tests were conducted, compared to the 28 tests conducted by the US.
The most famous of these tests was the Chagan underground nuclear test. The site chosen was a dry bed of the Chagan River at the edge of the Semipalatinsk Test Site in northeast Kazakhstan. The lip of the crater to be created would dam the river during its high spring flow.
The explosive yield was 140 kilotons, creating a crater 408 meters across and 100 meters deep. A major lake soon formed, now known as Lake Chagan or Lake Balapan.
Radioactivity from the Chagan test was detected in Japan, which violated the terms of the 1963 Partial Test Ban Treaty. The US complained to the Soviet Union, but the issue was eventually dropped.
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