Retrospective assessment of possible contamination outside the site

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. 

Main dose-forming traces of radioactive fallouts

Besides traces of local radioactive fallouts from ground tests, lands outside the Site were subjected to global contamination due to all high-altitude nuclear explosions in northern hemisphere.

After nuclear weapon tests were stopped, works aimed at evalua-tion of scope and rates of radioactive contamination as well as at evaluation of harm to local population due to activities at the Site were performed. These works revealed that present-day radioac-tive contamination of environment outside the Site perimeter are almost the same as global background values and impose no po-tential hazard to local population.
Besides traces of local radioactive fallouts from ground tests, lands outside the Site were subjected to global contamination due to all high-altitude nuclear explosions in northern hemisphere.
After nuclear weapon tests were stopped, works aimed at evalua-tion of scope and rates of radioactive contamination as well as at evaluation of harm to local population due to activities at the Site were performed. These works revealed that present-day radioac-tive contamination of environment outside the Site perimeter are almost the same as global background values and impose no po-tential hazard to local population.

Densities of radioactive fallouts due to nuclear tests: a – 05.10.54, b – 02.08.55 and c – 05.08.55.

So, for instance, investigations performed in villages Che-remushki, Mostik, Dolon’ and Bodene – these villages were subjected to multiple radioactive contamination – showed that even contamination revealed for 137Cs (20 Bq/kg) and 90Sr (9.8 Bq/kg) remains at the level of global fallout (9 Bq/kg and 15 Bq/kg, respectively). Contents of artificial long-living radionuclides in water, air and food does not exceed regulatory values accepted in Kazakhstan. Current radiological situation in investigated villages is normal and represents no hazard to local population.

External and internal effective irradiation doses to popula-tion due to introduced contamination in those villages does not exceed 1 mSv/year.