RESIDUES FROM NUCLEAR TESTING AT THE TEST SITE AZGIR XA9953138

A. KIM Atomic Energy Committee of the Republic of , , Kazakhstan

Abstract

The Azgir test site is situated in the western part of the Republic of Kazakhstan, about 180 km north of the . The Azgir test site was used for conducting peaceful nuclear explosions from 1966 to 1979. 17 underground tests were carried out in 10 wells which created 9 special cavities in the salt with depths from 160 to 1500 m. The total volume of these cavities is about 1,000,000 cubic meter. Resulting from this activity, there is an environmental contamination that may have affected population living in the adjacent areas. The results of investigations of radiological conditions that were performed after the closing of the Azgir test site, and current activities of international and Kazakhstan's institutions for studying residues from nuclear tests are also discussed in this report.

Introduction

The former test site called Azgir (or Halit) is situated in the utmost west of the Republic of Kazakhstan, nearly 180 km north of the Caspian Sea, near the border to the Russian Federation. It's named after the nearby settlement of Azgir. The distance to the Russian border is less than 10 km to the south. Azgir belongs to the district of Kurmangazinsk, which itself is part of the . The site includes the settlement of Azgir, several technological buildings and altogether 11 individual test places were used for the nuclear explosions.

Quite near the settlement of Azgir, in the "West-Azgir" salt-dome, the altitude is 15.4 m above sea level. In comparison the area of the depression near the northern shore of the Caspian Sea is up to 28 m below sea level. At the surface of this area, sands, clays and solonitschak soils vary. These are all characteristics of a semidesert. The area is also characterized by numerous, small to medium sized lakes, which periodically dried out and are caused by the peculiar relief forms and the climate. Near Azgir, lakes are found that are fed by a karst phenomena and are continuously filled with water. The surface water shows a high content of different minerals.

The Azgir area has a typical arid climate. This is characterized by extremely low and large temperature fluctuations, which reach from - 42°C in the winter up to +45 °C in the summer. The average temperature in January for Azgir is nearly - 11°C; the average temperature in July is +25°C. Annual total precipitation is 200 mm and monthly peak values are reached in the summer. The evaporation during summer is much higher than precipitation for this time period. In winter an average snowcover of 0.2 m thickness exists for about three month.

The present level of infrastructure in the whole area north-west of the city of Atyrau, up to the Russian border, is not high. Connecting routes between the settlements are a few unpaved roads. The test places are also connected with the city by these unpaved roads. In summer the roads are occasionally blocked by sand dunes and in winter snow storms present driving problems. The nearest paved roads run to the south and north of Azgir, each at a distance of nearly 130 km. The nearest railway runs along the northern shore of the Caspian Sea, from Atyrau to the Russian city of Astrachan and from there further to the north towards the city of Saratov. The nearest railway stations are in Akkol and to the northwest in Shungaj at a distance of nearly 130 km and 100 km, respectively. The nearest railway station on Russian territory is in Charabali (Astrachan region) at a distance of nearly 75 km. The nearest Kazakhstan airport is in Atyrau (about 300 km).

All settlements are supplied with electricity network. The test places were powered in the past by there own electrical power generators. The drinking water for the settlements come from local wells.

Nuclear Activity at Azgir Test Site

At 1962 the Azgir site was suggested for conducting underground nuclear explosions in the salt. Between 1966 and 1979, at 10 different boreholes in salt, 17 nuclear explosions were conducted. The depth of the tests were from 160 to 1500 m. The purpose of these experiments was for research and direct economical applications. They assisted in the development and further improvement of technologies for creating underground cavities and seismic investigation of the earth's crust. The cavities were planned to be used for the storage of oil and natural gas from deposits in the Caspian Region.

The 11 separate places for the tests are marked A-I to A-XII (A-VI does not exist). The nuclear explosions took place only at 10 of these sites. Although site A-XII was developed, no nuclear explosion took place there. The test places A-I and A-II are located within the western summit of the rock salt structure called the "Great Azgir" salt dome. The other nuclear explosions took place in the eastern summit. 9 separate places are situated 17-20 km northeast of Azgir. The place A-I is located at approximately 2.5 km southeast and the place A-II is about 8 km north of Azgir. An overview of all nuclear explosions carried out in the Great Azgir, including important parameters, are listed in the table 2.1.

Radioactive inert gases were released from all of the explosions even if the explosion took place at the optimal mentioned depth. The time periods of this release were quite different for the various places. The time duration was from a few hours to few days. Above the A-I, A-II and A-VIII cavities there is contamination on the surface. Short lived radionuclides were detected as far as 8 km from the explosion epicenters. Settlements are not located within this distance except for site A-l. The distribution of the fallout was very much depending on the meteorological conditions during the explosions.

In the 1980s and 1990s the test sites were subject to partial clean-up activities. Radioactive contaminated soil and equipment were removed and disposed of in two of the cavities which resulted from the nuclear explosions. Monitoring of the radiological situation in the area of the test places were conducted directly following the explosions as well as in the recent past. These programmes monitored the radionuclides concentrations in soil, water and plants and any possible radioactive contamination in the neighboring settlements.

10 TABLE 2.1. UNDERGROUND NUCLEAR EXPLOSIONS ON THE GREAT AZGIR SALT- DOME DURING 1966-1979

No. Test place Date Depth, m Power, kt Ot-activity, Volume, TBq 103m3

1 A-I 22.04.66 160 ?1.1 3.92 * 2 A-II 01,07068 600 ?25 45.50 * 3 25.04.75 . 0.01-0.5 - - 4 14.10.77 0.01-0.5 _ 5 30.07.77 0.01-0.5 6 19.09.78 0.01-0.5 - 7 30.11.78 - 0.01-0.5 - - 8 10.01.79 - 0.01-0.5 - - 9 A-HI 22.12.71 986 <70 14.84 * 10 29.03.76 - < 10 - - 11 A-IV 29.07.76 1000 <60 45.50 * 12 A-V 30.09.77 1500 < 10 4.81 * 13 A-VII 17.10.78 970 <60 19.24 250 14 A-VIII 17.01.79 995 <60 19.24 235 15 A-IX 18.12.78 900 < 100 9.99 ** 16 A-X 24.10.79 980 <30 13.69 120 17 A-XI 14.07.79 980 < 15 22.25 70

* - cavities with brine ** - cavity was not created

Present Radiological Situation at the Test Site Azgir

Since 1991, after getting its sovereignty, Kazakhstan started developing its own regulatory system in the field of atomic energy use. In accordance with the Decrees of the President, appropriate structures in Kazakhstan were created. They are: the Atomic Energy Agency that serves as the main supervising governmental body and the National Nuclear Centre that combines all nuclear related scientific institutes, including the Nuclear Physics Institute who is responsible for the former Azgir test site. During this period the different scientific institution conducted both direct investigation and theoretical simulation.

Table 3.1. shown the total activity in the cavities and the surrounding salt rock for 1990 and the calculated values for 2000 (data of University of St. Petersburg). The total activity of alpha emitters for 1990 in the cavities and the surrounding salt rock is 226 TBq. The corresponding value for gamma emmitters is 9250 TBq. Aside from the surrounding salt rock, the brine in the cavities is also contaminated with a total activity of 423 TBq.

The radionuclides in the cavities and the surrounding salt rocks must be categorized into three groups - radionuclides from the explosive charge, fission products, and radionuclides generated through radiation (artificial radioactivity). According to the current knowledge, radionuclides caused by the nuclear explosion are concentrated at the bottom of the cavities. Fission products with a high level of radioactivity that were formed shortly after the explosion are accumulated in the lower part of the cavities. They are covered with a lens-like crust made out of glass, which actually is the melted salt rock, now in a solid state. The walls of the cavity are also covered with this type of crust. Less amounts of radionuclides are found in the salt rock surrounding the cavity, in particular Cs-137 and Sr-90.

11 TABLE 3.1. TOTAL ACTIVITY IN THE CAVITIES AND THE SURROUNDING SALT ROCK

Total activity, TBq Place 1990 2000 a-emitter fission products a -emitter fission products A-I 2,9 16,6 2,9 12,5 A-II 55,5 481 55,5 352 A-III 15,5 814 15,5 629 A-IV 55,5 481 55,5 370 A-V 4,8 166 4,8 122 A-VII 19,2 1258 19,3 925 A-VIII 19,2 1332 19,0 962 A-IX 10,0 1850 10,0 1369 A-X 13,7 703 14,3 518 A-XI 27,8 555 27,7 370 Total 226,1 7657 226,0 5296

During later investigations (by means of drilling into the concrete plugs or drilling new check boreholes into the cavities) it was found that radioactive inert gases escaped to the atmosphere with a total activity of 370000 TBq. Although this release occurred, contamination of soil, instruments and other equipment should have been controlled.

In the very close vicinity of the explosion and technological boreholes, a dose rate of up to 3 mSv/h was determined. The contaminated equipment had a surface activity of up to 16 kBq/cm2 for gamma-radiation and 160 Bq/cm2 for alpha-radiation. Results of earlier investigations are scarce and do not show a systematic behavior with regard to sampling location. The most recent data is from 1989, 1990 and 1991 and includes data from all sampling locations. This makes it possible to at least compare data from the various sampling locations. The analysis of results show that the groundwater is affected in the area of all investigated test regions. This is evidenced both by the analytical results of the waters and by the solid remains samples. The test places A-I and A- V especially show increased activity values for Cs-137 and Sr-90. These values are somewhat higher than the activity caused by the global fallout in surface waters. In the area around test places A-II, A-III, A-IV and A-V, the values do lie below the acceptable levels for the named radionuclides in drinking water. These measured results were the basis for the following near- surface clearing and decontamination of the individual areas. According to the available information, a total area of approximately 100,000 m2 was cleared.

The materials and substances deemed to be radioactively contaminated were stored in two of the existing cavities. The radioactive contaminated excavated soil was brought to cavity A-X. Cavity A-III was used to store radioactive contaminated equipment parts, that were cut into small pieces before disposal.

12 The Radium Institute estimates the volume of stored radioactively contaminated materials to be a total of 24,000 m\ The total added activity is given as 1.85 TBq. The total of the metallic waste amounts to approximately 200 m3 with a the total activity of 18.5 Gbq. A comparison of this value with the total activity of almost 10,000 TBq resulting in the rock salt from the nuclear tests shows that this post-induced amount makes up only about 0.02 % of the existing total activity.

The results of a 1995 joint expedition by the institutions of the National Nuclear Center and the Kazakhstan State Committee of Hydrometeorology can serve to characterize the current radiological situation in the area of the individual test places. Within the scope of these studies, mainly the local dose rate of the gamma radiation was measured, and on selected samples the specific activity for Cs-137 and several other radionuclides was determined. Table 3.2 shown the corresponding results.

TABLE 3.2: CURRENT LOCAL DOSE RATE AND SPECIFIC ACTIVITY IN THE AREA OF THE TEST SITE

Local dose rate of the Place gamma radiation, Specific activity, Bq/kg nSv/h Cs-137 Eu-155 Co-60 Am-241 A-I 90 6-132 6 3 - A-II 140 12-1907 4-13 1 - A-III 120 5 - 2696 4 1 21 A-IV 120 4-36 4 1 _ A-V 120 13-481 3 1 12 A-VII 120 4-29 4 1 - A-VIII 120 4-13 2-8 - 29 A-IX 100 15 - 1 - A-X 150 25- 562 5-11 2 - A-XI 100 5-19 6 - -

The specific activities for Cs-137 at all test places with the exception of site A-VIII lie significantly above the background level as it applies to Kazakhstan. As the range of obtained individual values shown in the table indicates, the Cs-137 contamination is distributed unevenly within an area. There are also in part significant variances between the areas themselves.

The highest values were measured at the test places A-II and A-III. In indicated settlements, however, the surface contamination of Cs-137 is within the global background value. Along with Cs-137, individual samples also showed the present of small amounts of other artificial radionuclides (Eu-155, Co-60, and Am-241). Evidence of Pu-239 and Pu-240 could also be found in samples from the test areas.

Conclusion

The results of investigations of the residues from nuclear testing at the Azgir test site conducted by different scientific institutions (Radium Institute, National Nuclear Center of Kazakhstan, State Committee of Hydrometeorology of Kazakhstan) are presented.

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