New York Times, Aug 24, 1994 (emphasis added): U.S. Nuclear Accident in 1965 Was Staged, Documents Show — The Atomic Energy Commission staged a nuclear rocket accident in the Nevada desert in 1965 that sent a radioactive cloud more than 200 miles to Los Angeles, documents released today showed… [Details] were discovered in archival documents from the Energy Department, as part of a continuing inquiry into the Government’s secretive human radiation experiments… Jan. 12, 1965, in Jackass Flats, Nev., part of a rocket’s nuclear core was intentionally vaporized so that scientists could study the behavior of the reactor and the environmental effects of the radiation, the documents showed… [C]onsiderably more people were exposed than in other experiments because the cloud traveled so far, [Congressman Edward Markey] said. The cloud was tracked by aircraft, and increased radioactivity… was observed in Barstow, San Bernadino, Los Angeles and San Diego…
U.S. Dept. of Energy (pdf), 1995: Human Radiation Experiments… The Kiwi Transient Nuclear Test… involved a controlled nuclear excursion resulting in partial vaporization of the reactor core. This created a radioactive plume that, while low in radioactivity, was detectable far off-site… The U.S. Public Health Service monitored the cloud to beyond 200 miles downwind, which extended to Los Angeles and the Pacific Ocean.
Los Alamos National Laboratory of the University of California (pdf), 1968: Environmental Effects of the Kiwi-TNT Effluent — The Kiwi Transient Nuclear Test (Kiwi-TNT) was a controlled excursion… to vaporize a significant portion of the reactor core. The test studied… environmental effects of the radioactive materials released… The U.S. Public Health Service [USPHS] monitored the neighborhood and collected milk samples in southern… California to beyond 200 miles downwind. The course of the effluent cloud was tracked by aircraft… From 5 to 20% of the reactor core was vaporized with approximately 67% of the products from about 3 x 10^20 fissions released to the effluent cloud… USPHS provided offsite radiation surveillance by aerial tracking of the effluent cloud, monitoring radiation dosage of the off-site population, and collecting environmental samples in southern Nevada and California… Following the test… milk samples were collected… 14 locations in southern California. The milk sampling program continued for approximately a week. Vegetation samples were obtained… [Aircraft] tracked the effluent cloud from Death Valley over the Los Angeles area and terminated contact over the Pacific Ocean… The weather at the time of the test fulfilled the desired conditions… The winds were northeasterly [blowing to southwest] at all levels, ranging from 14 to 27 knots… The Kiwi-TNT reactor was “exploded” in the sense that it was a violent disruption and dispersion of an originally intact object. It blew up in an unusual fashion… Because the Kiwi-TNT was a unique, controlled simulation of a phenomenon frequently called a maximum credible reactor accident, there was great interest in the radiological characteristics and effects of the effluent many miles from the test point… The USPHS documented the effects of the long-range effluent cloud on the people and agriculture downwind. [Personnel] observed the radioactive cloud shortly after it reached California and again as it reached the Pacific Ocean… At 11 hours 20 minutes after the Kiwi-TNT event… aircraft again attempted to locate the effluent cloud… Positive signals were received over the ocean from Los Angeles to near Santa Barbara… [Several hours later] it returned to the previous search area and again detected weak, but positive signals… A few days after… officials observed increased radioactivity in routine air samples from the Barstow, San Bernardino. Los Angeles, and San Diego, California, areas…