Radio-ecological state pines forests borons

Pathways of radioactive clouds formed due to nuclear tests in 1949 – 1960

Tests performed at the Site resulted in radioactive contamination of not only the entire territory of the Site, but far outside its peri-meter. Control performed by military specialists after each explo-sion or set of explosions was limited to determination of characte-ristics for each radioactive trace and, first of all, to determination of external exposure dose rates on population in vicinity of the Site. The main source of radiological contamination outside the Site limits is represented by traces of radioactive fallouts from atmospheric nuclear tests. Largest contamination was formed by ground tests when the high-temperature fireball touched the ground lifting up huge amounts of soil particles. Transfer of these particles by air flows and their gradual precipitation formed traces of radioactive fallouts over large distances. So, the first nuclear test formed narrow radioactive trace in the north-eastern direction. The spot of contamination lasts as a gradually widening band to the distances of about 700 kilometers off the Site perimeter with the largest width of the trace spot of 130 km. Novopokrovskiy and Beskaragaiskiy districts of Sempalatinsk oblast and several districts of Altai territory were subjected to radioactive contamination.

Most severe radioactive impacts were registered after the ground fusion explosion of 400 kt performed on 12 th of August 1953. Calculations showed that radioactive contamination due to this explosion covered vast territories ranging from eastern Ka-zakhstan, south of Altai territory, parts of Novosibirsk and Keme-rovo oblasts. Traces from this explosion reached Baikal lake in Tuva Republic.