Radio-ecological conditions in inhabited localities
Nuclear explosions performed at SNTS resulted in prolifera-tion of radioactive fallouts outside the site perimeter. After the site was stopped, this stipulated the need to study more thoroughly the radiation conditions in inhabited localities adjacent to the site. Since 1990, many studies performed by researchers from Russia, the USA, Austria, France, Check Re-public, Slovenia, Germany, Japan, and Kazakhstan as well as by various international organizations such as IAEA, NATO and others were devoted to this topic. In order to evaluate the long-term consequences of these nuclear explosions, at the territory of over than 600 inhabited localities (including villages, wintering and summering sites) in East-Kazakhstan, Pavlodar and Karaganda oblasts were performed radiological studies of soil, vegetation, water and air basin. There were studied such parameters of radiological situation as exposi-tion (equivalent) dose rate for gamma radiation (EDR); con-tents of artificial radionuclides (caesium-137, strontium-90, plutonium-238, plutonium-239 and 240, polonium-210, am-ericium-241) in the environment and human bodies. Ob-tained results were verified by independent laboratories in Austria, France, Slovenia, USA and laboratories of IAEA.
The first, most comprehensive and focused study of the terri-tories adjacent to the Semipalatinsk Test Site was completed in 1990-1992 leaded by Khlopin Radium Institute (Leningrad, nowadays St.Peterburg), by researchers from Moscow Insti-tute for Physics and Technology and by Complex Airborne Survey Expedition of the State Company “Aerogeologia” em-ploying both land-based and aviation technologies. These studies included determination of exposition dose rates, pa-rameters of surface contamination of soil and vegetation with radionuclides, contents of 90Sr and 137Cs in water; samples of aerosols were taken in atmospheric air; radon concentrations in living premises were measured. Large scope of research was done at investigation of radiation situation in villages adjacent to the site (Dolon’, Kainar, SArjal, Karaul, Mostik, Maiskoye, Yegendybulak and Chagan). Airborne and ground-based methods were used to survey the total area of more than 30,000 square kilometers.
At that, particular attention was paid to investigations in five villages: Dolon’, Mostik, Kainar, Karaul and Sarjal located 100 – 200 km away from places of ground nuclear tests and suf-fered from radioactive precipitations more than other ones.
Among the main conclusion of these works are: “Radiological situation in vicinity of Semipalatinsk Nuclear Test Site is stipu-lated by both global fallouts and by atmospheric tests previ-ously performed at the Site. Based on current values of EDR and contamination rates one could hardly expect nowadays any additional on-going exposure for local population in vil-lages adjacent to the Site exceeding annual average value over 1 mSv or 0.1 BER.
In spite of the fact that in Dolon’ village the contamination rates for l37Cs and 90Sr are considerably below 1 Ci/km2, one should perform detailed surveying for plutonium in the vil-lage, its neighborhood and to outline the plutonium trace determining plutonium presence forms in soil. This all is nec-essary because the village lies on the trace path of radioac-tive fallouts in 1949 with contamination density for pluto-nium exceeding 0.1 Ci/km2 in the trace’s periphery and in the northern and north-western parts of the trace. It worth doing the radiochemical studies of food grown at those farms and private gardens.”
Second, more representative study of the villages outside SNTS was performed in 1993 – 1994 by two IAEA missions leaded by P. Stegner. Specialists from Kazakhstan, Russia, United States, France and Great Britain worked for the mis-sions. Objectives of the missions were:
• to assess radio-ecological situation in territories ad-jacent to the test site using available dosimetry in-formation
• to determine possible dose rates and exposure of people in Semipalatinsk oblast.
Main activities were performed in the inhabited localities Moldary, Dolon’, Sarjal, Kainar, Akjar, Sarapan.
Final report of the Second Mission included the following: “In most of the districts, exposition doses for gamma-radiation and contamination levels of the environment are very close to those corresponding to normal global fallouts. Some dis-tricts show slight increase which is still negligible in terms of exposure to local population. Village Dolon’ has got some higher level for plutonium compared to its neighbors, but annual dose still remains quite low of about 0.13 mSv/year.”
Third surveying, financially supported by NATO, was per-formed in 1995 – 1996 by 9 experts from France, Check Re-public, and Germany. Unlike previous studies, in this one ra-dionuclide contents in human bodies for inhabitants of SNTS-neighboring villages Mostik, Maiskoye, Dolon’ were deter-mined.
These investigations showed that “radioactive contamination of upper soil due to nuclear tests has almost stopped. The background in general corresponds to its non-disturbed natu-ral values. Remnants of long-living radionuclides in human bodies are negligible and generated in 1995 the additional radiation load due to 90Sr and 137Cs of just 1% of the natural background value. It is still open the question about radiation load on population due to intake of 239Pu.”
One should note that during the whole period of National Nuclear Center activities the issues related to modern radio-ecological situation in inhabited localities adjacent to SNTS are in charge of the Institute for Radiation Safety and Ecol-ogy. Unlike listed above studies, the Institute aimed its activi-ties not only at investigation of the situation in the villages, but at all territories adjacent to the Site as well. So, most comprehensive radio-ecological investigations were per-formed at territories of Maiskiy district in Pavlodar oblast, Abralinskiy and Beskaragaiskiy districts in East-Kazakhstan oblast. There were assessed not only external exposures, but the character and scopes of radionuclide intakes. Results ob-tained made it possible to assess more reliably the dose load on local population from artificial nuclides; present-day load lies within the range 0.03 – 0.6 mSv/year what is considerably below permissible levels.
Making general conclusion the following should be stated:
1. Among studied artificial nuclides, cesium-137 pro-vides the largest contribution to external radiation dose.
2. Highest values of radiological parameters were regis-tered in inhabited localities within traces from ra-dioactive fallouts formed due to ground tests (vil-lages Mostik, Dolon’, Sarjal, Kainar.
3. Residual long-living radionuclides in human bodies represent vanishingly small threat to people provid-ing additional radiation load due to strontium-90 and cesium-137 of only about 1 % to the load from natural background.
4. High costs of plutonium analyses prevented from undertaking of more detailed studies of this most hazardous radionuclide. Available data show that plutonium-239+240 in traces of radioactive fallouts outside SNTS contour exceed for several times that of global fallouts.
5. Radiological situation in studied inhabited localities varies representing at the same time no hazard to the population in terms of regulatory documents. External irradiation doses remain at levels of natural background. Obtained doses of internal irradiation did not reveal any exceeding over regulatory accept-able values; at that, such studies are to be continued aimed at both further investigation of the villages and individuals.
Arrangement of filter-ventilation intake equipment, sampling locations for soil and water during investigations performed by Khlopin Radium Institute in 1990 – 1992.