9. NUCLEAR EXPLOSIONS

9.1 General

Nuclear weapons tests and nuclear devices explosions were carried out in the USSR over a period since August 1949 (the first nuclear test) till October 24, 1990(the last nuclear test). The total number of the USSR nuclear tests is 715, and the total number of exploded nuclear charges and nuclear explosive devices is 969.

In [9.1] the following classification of nuclear explosion purposes is given:

NWR - nuclear weapons related tests (weapon development or modification);

SAM - studies of accidental models and emergencies;

WIE - weapons effects tests (studies of injurious effects of a nuclear explosion on military and civilian systems and equipment);

FMS - fundamental and methodical studies of the phenomena of a nuclear explosion;

ME - military exercise with a real nuclear detonation;

IE - industrial underground peaceful nuclear explosions and testing of peaceful nuclear explosion (PNE) technologies;

TIC - testing of industrial nuclear charges for use in peaceful activities.

The following classification is adopted for the types of Soviet nuclear tests (explosions):

• a surface explosion is a nuclear test on the earth’s surface or from a tower. In terms of physical criteria relating to the radiation environmental effects, the category of surface explosions includes all nuclear tests with the scaled height of burst (HOB) of no more than 35 m/kt^1/3;
• an air explosion is a nuclear test in the atmosphere with the scaled HOB of no less than 100 m/kt^1/3 (under these conditions the expanding fireball does not touch the ground surface). Within this category high-altitude explosions, for which the fireball size is comparable with the characteristic size of the atmosphere inhomogeneity (~ 7 km) should be distinguished; this category also includes space explosions;
• an underwater explosion is a nuclear test where the explosive device was under the water’s surface;
• an underground explosion is a nuclear test where the explosive device was under the ground surface.

For nuclear weapons testing in the USSR two test sites were organized: in 1948 - the Semipalatinsk Test Site (STS), where the first nuclear device was tested on August 29, 1949, and in 1954, according to the decree of the Government of the USSR from 31.07.54, - the Northern Test Site Novaya Zemlya (NTSNZ). The first nuclear test at the NTSNZ was held on September 21, 1955.

Outside the territory of the two test sites military nuclear tests were conducted:

• at the Missile Testing Range (MTR), from which the missile with nuclear and thermonuclear warheads to be tested in upper layers of the atmosphere and in outer space were launched;
• on September 14, 1954 near Totsk (Orenburg Region, Russian Federation) at the Firing Ground of the USSR Ministry of Defense in the course of the Army exercises with application of air nuclear explosion with energy release of 40 kt;
• on February 2, 1956 near Aral’sk (Kazakh SSR), where a surface explosion with energy release of 0,3 kt was held.

Besides the nuclear weapons tests, since January 15, 1965 in the USSR underground peaceful nuclear explosions were conducted. During the program’s realization 156 nuclear explosions were conducted, and the total number of exploded nuclear charges and devices was 173. In total 119 nuclear tests and peaceful nuclear explosions were conducted outside the territory of the nuclear test sites.

9.2. The summary of statistical data on location, type, date, purpose and energy release of nuclear weapon tests and peaceful nuclear explosions, conducted in the USSR in 1949-1990

All the data presented below are taken from the mentioned above official edition [9.1].

The contents of the Tables 9.1 - 9.6 is quite clear from their titles, so no commentary is needed.

Table 9.1

Table 9.2

Soviet Nuclear Weapons Tests and Peaceful Nuclear Explosions by Location

Table 9.3

Soviet Nuclear weapons Tests and Peaceful Nuclear Explosions by Type

Table 9.4

Soviet Nuclear Tests and Exploded Nuclear Devices by Purpose

Table 9.5

Total energy release of the USSR nuclear tests over time periods and regions of their conduct, kt (rounded values within 10 kt)

Table 9.6

Energy release of the USSR nuclear tests over the years and regions of their conduct, kt (rounded values within 10 kt)

9.3. The characterisation of accumulated radionuclides at the territory of ex-USSR as of 01.01.96

9.3.1. The radionuclide composition of radioactive fallout at the territory of ex-USSR as of 01.01.96

All radionuclides, the potential products of nuclear explosions with half-lives more than 4 years, may be divided into three groups [9.2]:

1. nuclear fission products (FP);
2. radionuclides induced by explosion neutrons (IR);
3. transuranium radionuclides (TR) - to that category both some components of nuclear explosives (for instance, plutonium-239) and heavy nuclei, formed as a result of nuclear reactions in the course of the explosion, may be attributed.

Considering the long-lived FP group, including 20 radionuclides with half-lives from 4.96 years (Eu-155) to 1,3x10¹¹ years (Sm-147), leads to a conclusion, that in the explosions’ products it is quite realistic to expect measurable contents of Sr-90, Cs-137, Sm-151 and Eu-155 and, possibly, Se-79, Nb-93m, Sn-121m, Sn-126, Eu-152, Eu-154.

As far as the IR group is concerned, it should be taken into account, that there are two ways of the radionuclides’ formation: (a) as a result of explosion neutrons interaction with construction elements of the explosion device and (b) as a result of explosion neutrons interaction with soil matter (in surface and low-attitude explosions). The (b) case also includes interaction of the explosion neutrons with construction components of a tower, barge, concrete platform and other structures, used for mounting or suspending nuclear devices before the explosion. The only principal difference between (a) and (b) categories is that in the (a) case more hard neutron spectrum "works", and, besides the (n, g) reaction, the threshold reactions of (n, 2n), (n, a), etc. types are quite possible (and they occur in fact). In the (b) case the (n, g) reaction "works" mainly.

22 radionuclides with half-lives from 5.24 to 1.5x10⁷ years may be attributed to the IR category. Having considered the list, we may conclude , that really Co-60 (the half-life is 5.24 years), Eu-152 (13.5 years), Eu-154 (8.59 years) can be recorded, and probably - Ni-63 (100 years), Nb-93m (16,1 years), Sn-121m (55years), Sm-151 (90 years), Eu-150 (36 years) , Hf-178m (31 years), Ir-192m (240 years), Pt-193 (60 years).

Whether one or another of the listed radionuclides is recorded, in significant extent depends on the choice of materials of construction elements used for a concrete nuclear explosion device manufacturing. Alloyed steels often include such components as nickel, titanium, cobalt and various rare earth elements. That is why IR sets in samples of soil, taken after explosion, ought to differ one from another.

Let’s consider europium isotopes in more detail. Despite statements in many published sources, europium isotopes Eu-152, Eu-154 and Eu-155 are at the same time fission fragments and neutron reactions products. According to calculation data for a contact 1 kt nuclear explosion with energy release completely due to the fission reaction, 4,87x10¹⁷ nuclei of Eu-152, 1,72x10¹⁹ nuclei of Eu-154, 8,7x10²¹ nuclei of Eu-155 are formed as a result of nuclear fission, and at the same time 3,7x10¹⁹ nuclei of Eu-152, 1,1x10¹⁹ nuclei of Eu-154, 7,6x10¹⁶ nuclei of Eu-155 are formed as a result of neutron capture reactions. It can be seen from this estimate, that Eu-155 is to be considered mainly as FP radionuclide and Eu-152 - as IR. As to Eu-154, its content depends on explosion type and conditions of its conduct (one should remember, that the estimate given above was made for a device, based only on fission reaction and detonated on the ground surface).

The third group, the transuranium radionuclides, contributes primarily to the environmental contamination. Firstly, when Pu-239 is used as a nuclear explosive (and this is not a rare case) in the course of explosion the next chain of reactions occurs: Pu-239 (n, g) Pu-240 (n, g) Pu-241 and Pu-239 (n, 2n) Pu-238. As far as the relative effectiveness of the three reactions essentially depends on the exploded device design and the share of thermonuclear reactions in the total energy release, all the mentioned plutonium isotopes are almost always found in various correlations, that is extremely useful for the traces’ separating in a case of their superposition. As far as rather long time has already passed after conducting the explosions, besides the four plutonium isotopes, in the mixture of the explosion’s radioactive products, the share of Am-241 (433 years) radionuclide formed as a result of Pu-241 (14,35 years) beta-decay would be essential.

Thus, it is obvious that isotopes of plutonium-238, 239, 240, 241 and americium-241 are the most significant and detectable quantitively transuranium radionuclides. Attention is also to be paid to plutonium-242, 243 and americium-243 [9.2].

Both theoretical and experimental estimations of radionuclide composition of the long-lived explosion products are presented in the report [9.2]. For that purpose large particles, deposited in the range of 105 km from the craters of explosions on 29.08.49 (the first nuclear test in the USSR) and on 12.08.53 (the first thermonuclear test in the USSR), were analyzed. The data on radionuclide composition of the both explosions’ products are presented in Tables 9.7 and 9.8.

Table 9.7

The radionuclides’ activities to Eu-152 activity ratios in large particles picked out at the nearby trace of the thermonuclear explosion of 12.08.53 (as of July 1995)

Table 9.8

9.3.2. Radionuclide contamination of the STS and adjoining regions

According to requirements formulated in 1948 [9.3], the nuclear weapon test site should be located in a desert area 200 km in diameter, adjacent to a railway station and an airfield. A site in 160 km from Semipalatinsk, limited by Shagan River (a tributary of Irtysh), Degelen and Kapyastan Mountains (being 100 km away one from another) turned out to meet the requirements. The test site’s initial area was about 5200 sq.km, its coordinates: 49.7 - 60.125 degrees of the North latitude and 77.7 - 79.1 degrees of the East longitude. Later on its limits were somewhat widened. The test site today’s schematic map is presented in Fig.9.1.

The geographical position together with preferentially Eastern (to the East, South-East and North-East) - direction of aerial mass motion (in frames of the general atmospheric circulation) predetermine the following regions as the most probable contamination areas at the USSR territory. (now Russian Federation and Republic of Kazakhstan): the Altay Land, the Republic of Altay (Russian Federation), the Semipalatinsk, East-Kazakhstan and Karaganda Regions (the Republic of Kazakhstan).

Numerous measurements of gamma-radiation fields at STS and adjoining areas, carried out by many institutions in the 1991-1993 time period and compared with formerly conducted aero-gamma-radiometric and aero-gamma-spectrometric measurements (1963-1975), show that the probability was realized, and the most significant traces, mainly from surface and low-altitude explosions, were recorded (outside the STS territory) just at the areas of the above mentioned regions.

Aero-gamma-spectrometric survey, carried out in 1991 by the State Scientific and Industrial Enterprise "Aerogeologiya" at STS and adjoining territories, showed the presence of recorded radioactive traces with cesium-137 levels beyond (1.11-1.85)x10¹⁰ Bq/km² from nuclear explosions of 29.08.49 (to 12-18 km along the straight line from the epicenter of explosion), 24.09.51 (to 55-65 km), 12.08.53 (to 80-95 km) and 15.01.65 ("Chagan" - to 13-18 km). Beginning with the distances the traces are not controured by a single isoline and are indistinguishable against the background of at first regional and then global contamination [9.5].

In the time period from 1949 till 1962 at STS 30 surface nuclear tests, i.e. such tests, when the explosion fireball is in contact with the day surface (including 5 cases, when the nuclear device failed to work) were carried out [9.4]. In consequence of such a contact huge amounts of soil are drawn into the explosion cloud, activated in it, and, as a result of that, well radiometrically recorded trace of radioactive fallout is formed - towards the winds’ preferential direction. First days, weeks and even months it is not difficult to observe such a trace by means of simple radiometric instruments at distances of hundreds kilometers from the considered explosion center (epicenter).

In [9.4] an estimate is given of significance and potential effect of each of 25 realized surface explosions and some air explosions, conducted at the STS, on all the territories, adjacent to the test site. As it can be seen from the work, in 5 cases of 30 surface nuclear tests, conducted at the STS, nuclear charge failed, and in 11 cases energy release was less than 0,5 kt, and the significant radioactive trace did not go out of the limits of the test site. The data on the tests are presented in the Table 9.9. The Table also included data on eight air explosions and an underground cratering explosion. It is convenient to examine the Table together with Fig. 9.1 (both taken from [9.4]).

Table 9.9

Dates and characteristics of some nuclear tests, conducted at Semipalatinsk Test Site

⁴ The failure of nuclear charge.

To evaluate relative significance of the traces on the basis of availaable primary data, gamma-radiation exposure field was integrated in the trace part, limited by 0,1 R isoline for each surface test and the underground cratering explosion. As may be concluded from that evaluation, the surface explosions of 29.08.49, 24.09.51, 12.08..53 and 24.08.56 might be qualified as nuclear explosions causing "very high" radioactive contamination (according to the authors’ technology). The surface explosions of 05.10.54, 21.09.55, 16.03.56 and 07.08.62 are to be attributed to the "high" contamination category, and the surface explosions of 02.08.55, 05.08.55, 25.03..56 and 25.09.62 - to that of "low" contamination, as well as the surface explosion of 29.07.55 (as it follows at least from the Fig. 9.1). Four air explosions are also presented in the Table 9.9, as their radioactive traces are shown in Fig. 9.1. Besides, four powerful air explosions (17.11.56, 10.04.57, 16.04.57 and 22.08.57) are included into the Table 9.9, as far as, in the opinion of the authors of [9.4], the tests were capable of producing "high" radioactive contamination in the remote zone. At the same time trajectories of speading of the air masses, carrying radioactive products of the explosions in the atmosphere, are not yet well known. And, at last, in the Table 9.9 data on the underground cratering nuclear explosion, conducted on 15.01.65 in the 1004 shaft ("Chagan") are presented. The explosion was carried out in order to form a large crater and fill it subsequently with water during the spring high-flood. The height of the upper edge of the formed cloud turned out to be 4800 m.. In the course of wind drift of the cloud it was "torn". Its lower part, containing the main part of radionuclides, moved across the Altay Land territory, and Barnaul city was caught in its train. It can be seen from Fig. 9.1, and, according to estimates of the authors of [9.4], the explosion may be attributed to "high" contamination category.

The main biologically significant nuclides at the territory, contaminated by radioactive fallout as a result of the air nuclear tests, are Sr-90, Cs-137 and plutonium. The total activity of the radionuclides after the tests at the STS, as of 01.01.96, is as follows:

• Cs-137 (gamma-activity) - ~ 1.48x10¹⁵ Bq (4x10⁴ Ci) (taking into account the activity lowering due to the radionuclide’s decay);
• Sr-90 (beta-activity) - ~ 10¹⁵ Bq (2,7x10⁴ Ci) (taking into account the activity lowering due to the radionuclide’s decay);
• plutonium (alpha-activity) - ~ 1.45x10¹⁴ Bq (6,5x10³ Ci).

Results of estimation of some effects of consequences of nuclear tests at STS on the population of 9 regions of Russia are presented in Table 9.10 [9.6].

Table 9.10

The tentative data on external exposure doses of the population (till the complete decay of radionuclides) in the area influenced by nuclear tests at the STS

9.3.3. Radionuclide contamination of the NTSNZ and adjoining regions

Nuclear tests at the NTSNZ were conducted at three technological grounds (Fig. 9.2) [9.7].

Zone A (the area of Chernaya and Bashmachnaya inlets).

Three underwater and two above-water tests (1955-62), a surface nuclear explosion (NE) of 07.09.57 and six underground NE in shafts (1972-75) were conducted at the ground. In Fig.9.2 the radioactive contamination spots are marked.

1 - the trace of 1957 NE. In a crater formed at the coast of Chernaya inlet, gamma-radiation dose rate does not exceed 400 mR/h, in the rest of the trace area (well 10 m from the crater) it is 80 mR/h and sharply decreases with the distance from the crater’s center. The crater’s place together with the adjacent contaminated lands has the status of sanitary-protective zone. As on 01.01.96, its area does not exceed 0.5 sq. km.

2 - a spot, formed as a result of 1955 underwater NE at Kushny Penninsula. Now its area is less than 0,2 sq. km, gamma radiation dose rate is less than 25 mR/h. The trace stretches to the South from the bay into the sea.

3 - a spot of an air NE of 1961-62 test series in 14 km to the North-West from the Potych cape. Its area is less than 0,2 sq. km, gamma-radiation dose rate now is less than 25 m R/h.

4 - the trace of a former outlet of steam and gas radioactive products of a 1973 underground NE. Now its area is less than 0,3 sq. km, gamma-radiation dose rate is less than 20 mR/h. The trace is narrow and spotty.

5 - a trace in the form of a broken spot resulted from a 1961 above-water NE, stretches from the bay to the North-East. Its area is less than 0,4 sq. km, gamma-radiation dose rate is less than 25 mR/h.

The natural background level, outside the noted places of higher radiation dose rate, is 7-11 mR/h.

Zone B (an area in the Western part of the Matochkin Shar strait).

It is the ground of conducting 36 NE in tunnels. At the territory, in some places of radioactive noble gases directly outflowed onto the earth surface after underground NE detonations. There are local plots with higher gamma-radiation level (by 1.5-2 times beyond the background level). There is a separate spot (tunnel A-37A), less than 0,3 sq. km, with maximum gamma-radiation level less than 500 mR/h, just at the point of former outlet of radioactive gases. A sanitary-protective zone is preserved till now in the A-37A tunnel area. At the rest of zone B territory, as well as at the settlement, gamma-radiation dose rate is 7-12 mR/h.

In the course of conducting underground NE in zone B two abnormal radiation situations took place [9.8]. The first case happened on 14.10.69 in A9 tunnel. In about 60 minutes after detonation a sudden break of steam and gas mixture occured along a tectonic crack in epicentral zone. At the technological ground the dose rate reached several hundreds R/h. On the third day slow transfer of radioactive products began from the test site territory to the North, North-West into the Barents Sea aquatory, where their detection at distances up to 500 km was possible. There was no radioactive fallout.

The second abnormal situation took place on 02.08.87 in A-37 tunnel. In about 1,5 minutes after detonation a break of steam and gas mixture suddenly occured along a natural rupture of an undermelted glacier at the mountain’s slope along the tunnel’s axis. Besides the radionuclides of noble gases, radionuclides of barium, iodine, cesium, strontium, antimonium,

tellurium, etc. got into the atmosphere. For 6 days the radioactive products were in the technological ground area. As a result of that, the dose rate in check point exceeded 500 R/h. There was no radioactive fallout outside the test site, with the exception of trace amounts of radioiodine.

Zone C (the area of Sukhoy Nos Penninsula).

It is the place of conducting air NE till 1962 (4 spots).

1 - the Western spot in 3 km to the East from the Fedorov Mountain (12 km from the Gagachiy Island). Its area is about 0,5 sq. km, the exposure rate by 2 times exceeds the background level.

2 - the central spot, located in the penninsula’s center (in 1,5 km to the North of two lakes).

Its area is about 0,3 sq. km, the exposure rate by 2 times exceeds the background level.

3 - the Northern spot, located in 10 km from the Tsivol’ki cape, along the azimuth of 150 degrees. Its area is about 0,3 sq. km, the exposure rate by 2 times exceeds the background level.

4 - the Eastern spot, located in 12 km to the North-East from the Klochkovskii Penninsula (between the 257 and 249 heights). Its area is about o,4 sq. km, the exposure rate by 2 times exceeds the background level.

The density of the test site territory (excluding sanitary-protective zones) contamination by cesium-137 is 1,5-6,7 GBq/km² (3,3 GBq/km² in average), by strontium-90 - 1,5-2,2 GBq/km², exposure rate is 7-12 mR/h, i.e.. the values almost do not differ from contamination density and radiation background level in the middle latitudes of the Northern Hemisphere. The highest density of contamination is observed at a limited plot (about 1 sq. km) around a surface NE (1957) crater on the Chernaya inlet seashore. There the value of Cs-137 contamination density varies from 0,4 kBq/m² to 0,4 MBq/m².

In the Chernaya inlet 3 underwater and 2 above-water NE were conducted. In 1993 data of joint studies of specialists of the Murmansk Institute for Biology of Northern Seas and Lublin University (Poland), devoted, in particular, to analysis of samples of bottom sediments from the Chernaya inlet, became available. According to the data of gamma-spectrometric analysis, Cs-137 activity in the bottom sediments is 1444.2 Bq/kg, and Am-241 activity - 2662.0 Bq/kg.

An estimate of some effects of consequences of nuclear tests at NTSNZ on the population of 21 regions of Russia is presented in Table 9.11 [9.6].

Table 9.11

The tentative data on external exposure dose of the population (till the complete decay of radionuclides) of various regions of Russia in the area influenced by nuclear tests at the NTSNZ

9.3.4. Nuclear explosions at the MTR

The missiles with nuclear and thermonuclear warheads to be tested in outer space were launched from the Missile Testing Range (MTR). The MTR launchers were located near Kapustin Yar, Astrakhan’ Region, Russian Federation. All the explosions, which took place over the MTR, are presented in Table 9.12.

Table 9.12

Nuclear explosions, conducted in the atmosphere and in space by using missiles, launched from MTR [9.1]

All the NE, listed in the Table 9.12, have not led to any contamination of the MTR territory and adjacent regions, as all the detonations were conducted at high altitudes.

Besides the explosions, mentioned in the Table 9.12, one more test is to be noted: a missile with nuclear warhead was launched from MTR on 2.02.56. The charge detonated near Aral’sk, Kazakhstan (NE No. 25 in the list [9.1]). So far any unclassified information, concerning radioactive contamination of that place is not available.

9.3.5. Area of Totsk 1954 Army exercises

The explosion of a nuclear bomb with energy release of 40 kt was conducted at the height of 350 m, the scaled height of burst was 102 m/kt^1/3 [9.9]. The fireball did not touch underlying surface , and fission products as well as residual plutonium dropped out on the remote trace. As a result of absorption of neutrons by the soil layer induced activity of various radionuclides (including Co-60, Eu-152 and Eu-154) formed in the epicenter of the explosion. A dust column, containing the induced radionuclides, which dropped out on the near trace to the extent of 210 km, raised from the epicentral zone. The maximum cumulative dose about 1 rem has been got on the trace up to 70 km from the epicenter.

On July 28-29, 1994, in the frames of works for preparing joint exercises of peace-making forces at the Totsk Firing Ground, a radiological examination of the place in the area of coming exercises was carried out. The examination was conducted by a team of specialists in the field of radiation safety, radiation protection and health physics, including 4 representatives of Russian party and 4 representatives of American party.

At the first stage of the works, 80 measurements of gamma-radiation dose rate were carried out, 38 samples of soil were taken by the Russian specialists to conduct further investigations in laboratories. The samples were taken in different points, including those along azimuth 79 degrees at 200, 300 and 650 m from the epicenter and along azimuth 259 degrees at 30 and 100 m from epicenter. The results of gamma-spectrometric analysis of a sample (azimuth 259 degrees, 100 m from the epicenter) are as follows: Eu-152 - 217 Bq/kg, Eu-154 - 8.9 Bk/kg, Co-60 - 8.5 Bq/kg, Cs-137 - 58 Bq/kg, Cs-134 - 1.5 Bq/kg, K-40 - 338 Bq/kg. The first three radionuclides are the Totsk 1954 explosion products ( Cs-134 is of Chernobyl origin, Cs-137 originated from the global fallout and partly - from Chernobyl).

An estimate of the Totsk explosion effect on the population of adjacent regions of Russia is presented in Table 9.13.

Table 9.13

The tentative data on external exposure dose of the population (till the complete decay of radiiunuclides) in the area, influenced by the nuclear explosion at 1954 Totsk Army exercises [9.6]

9.3.6. Peaceful nuclear explosions (PNE) in the USSR

Since 1965 the USSR had realized an extensive programme of underground nuclear explosions for use in peaceful activities. 124 peaceful nuclear explosions (135 exploded nuclear charges) were conducted and 32 tests (38 exploded nuclear devices) were carried out in order to work out the PNE technologies [9.1]. The programme was started up with a cratering explosion in 1004 shaft at STS on 15.01. 65, and it was stopped after the last in the programme NE "Rubin", held on 06.09.88 in the RN-1 shaft in Arkhangel’sk Region of RF [9.1].

The programme of peaceful nuclear explosions included the following main directions [9.1]:

1. Deep seismic probing of the earth’s crust in order to search promising structures for mineral resources prospecting.
2. Pilot experimental works on the oil extraction intensification and increase of oil recovery factor.
3. Experimental works for gas extraction intensification.
4. Pilot experimental studies for elaboration of technology for cavity production in rock salt.
5. Pilot experimental works on creating underground reservoirs.
6. Scientific research and experimental works for testing peaceful nuclear explosion technology.
7. Pilot experimental works on gas spouter shaft closure.
8. Experimental works on trench-pit creating in alluvial soils.
9. Experimental works on dam-tailing dump creating by ripping of rocks.
10. Pilot experimental works on burial of biologically hazardous petrochemical industrial waste-waters into deep geological structures.
11. Pilot experimental works on preventing sudden coal dust and methane outbursts.
12. Ore fragmentation technology testing.

Data on PNE location, energy release, depth of charge burial and the number of exploded charges are presented in Tables 9.14 and 9.15. More detailed information can be found in the official edition [9.1] and in [9.10].

Table 9.14

Soviet Underground Nuclear Explosions Conducted in the Interests of National Economy in 1965-1988, by Energy Release

Table 9.15

Soviet Underground Nuclear Explosions Conducted in the Interests of National Economy in 1965-1988, by Depth of Charge Burial

While carrying out the PNE program, 5 cratering explosions were conducted, 4 of them - at the STS, and one ("Taiga") - at the border of Perm’ Region and Komi Republic, 6 km to the North from Chusovskoye Lake. That experimental salvo nuclear explosion was conducted on March 23, 1971 to estimate a possibility of construction of "Pechora-Kolva" canal as a part of the project of transfer of Northern rivers’ waters to the drainage-basin of Volga River. At a distance of 200 - 300 km from the crater’s edge the gamma-radiation exposure rate begins to rise in the direction towards the epicenter. Maximum values of measured exposure rate were 2500 and 840 mR/h. The points are located in the limits of zones with exposure rate level higher than 500 mR/h in close vicinity to the crater [9.11].

Besides the above mentioned cratering explosions, where the release of a part of activity into the atmosphere was foreseen, in some cases the release of radioactive products to the earth’s surface also took place [9.12].

In particular, as a result of NE "Kristall" (02.10.74) and "Kraton-3" (24.08.78) in Yakutia a part of radionuclides released into the atmosphere, that caused radioactive contamination of some lands along the direction of spreading of the radioactive masses. Some release of gaseous products into the atmosphere was supposed at that object, in accordance with project conditions of charge burial to make an earth-fill dam. The process of the NE gaseous products filtration through the width of loosen rocks was under control and it did not go out of the frames of rated predictive models. Radiation safety of the works was ensured by corresponding technical measures, choice of favorable meteorological conditions and by continuous radiation monitoring. At "Kraton-3" object an unforeseen release of radionuclides into the atmosphere occurred due to non-proper grouting of holes (i.e. it was a NE with abnormal radiation situation). In that case the radioactive current of gases was recorded at a distance up to 150 km in the uninhabited forest and tundra area.

Short characterization of radiation situation at these objects is presented below.

Object "Kristall". In epicentral zone there is a hill (piled on) in the form of a truncated cone about 160 m in diameter and up to 8 m in height, covered with tundra vegetation. According to data of airborn gamma survey, made by the Central search and survey expedition of Production and Geological Association "Yakutskgeologiya" in 1990, at a plot 0,4 x 0,9 sq. km near the underground NE epicenter gamma-radiation exposure rates were mainly in the range from 15 to 30 mR/h; the maximum value was 110 mR/h. In the pile soil layer cobalt-60 and cesium-137 were detected and identified in trace amounts (less than 50 Bq/kg). In water samples, taken on the pile, no radionuclides were detected (the detection methods’ sensitivity being less than 0,1 Bq/l for cesium-137 and less than 100 Bq/l for tritium). As far as the object is situated in the area of strongly propagated permafrost, the migration of radionuclides with underground waters is very complicated.

The object is practically not hazardous either to the population or to the environment. Complications may arise only in a case of uncontrolled digging or drilling the pile. That is why any earthwork and drilling on the pile and within the range of 100 m are prohibited. In addition to that, according to recommendations of specialists of the All-Russia Research and Design Institute for Industrial Technology (VNIIPIPT) of the Minatom of RF, filling of some sections of the pile with clean soil layer up to 1.5 thick was carried out, that led to decreasing of the radiation level on the surface. Covering of the pile with clean soil also prevents the direct contact of people with radionuclides. It was also recommended to keep provisionally the sanitary-protective zone regime in the pile area with periodical monitoring of environmental objects.

Object "Kraton-3". According to data of measurements made in 1990, a radioactive trace was recorded up to 5 km from the NE epicenter. The trace’s width was from 0,5 to 2,5 km, the maximum level of gamma-radiation was up to 200 mR/h along its axis and up to 730 mR/h in the epicenter (the shaft collar). At present in the limits of remediated area the level of gamma-radiation exposure rate is 30 ¸ 50 mR/h on the average. As far as at the "Kraton-3" object contamination of the soil-vegetation cover with beta-emitting radionuclides along the trace up to 2 km long is an additional radiation factor, it was recommended to keep the sanitary-protective zone regime in the area with periodical radiation monitoring and restriction of economical activities.

Abnormal radiation situations took place also while conducting three more PNE: "Globus-1" (19.09.71) in Ivanovo Region, in 40 km to East-North-East from Kineshma; "A-1" (22.04.66) and "A-8" (17.01.79) in Kazakhstan, in 180 km to the North from Astrakhan’, In those cases the exposure rate outside the technological grounds was at the global background level, and directly in the work shafts zone it was from 15 to 60 mR/h.

9.3.7. Global radioactive fallout

Undoubtedly, Sr-90 and Cs-137 as well as tritium (to a degree) are the most significant isotopes in the global fallout due to their long life-time and, consequently, potential hazard.

The observed distribution of Sr-90 and Cs-137 global contamination levels on the Earth is determined by a number of factors. The most essential of them are as follows:

• nuclear weapon test characteristics (energy release, type, purpose, etc.);
• conducting of nuclear explosions mainly in the Northern hemisphere;
• general regularities of atmospheric circulation;
• meteorological and climatic peculiarities of particular regions.

According to data of the UNO Scientific Committee on Atomic Radiation Effects, since the first nuclear weapon tests till 1963 0.71x10¹⁸ Bq of Cs-137 was formed and released into the atmosphere. The contribution of following tests was lesser. In a case of uniform distribution of this amount of the radionuclides over the Earth’s surface in 1970 the following levels of contamination would be observed: 1.15x10⁹ Bq/km² for Sr-90 and 1.96x10⁹ Bq/km² for Cs-137. The actual contamination levels result from action of all the above mentioned factors, and in some places they differ greatly from the mean values.

Sr-90 distribution in soils was studied systematically. Till 1963 the amount of Sr-90 in soils grew rapidly. By 1964 significant part of the airborn Sr-90 (about 3.7x10¹⁷ Bq) dropped out onto the Earth’s surface. Later on, after cessation of air nuclear explosions in the USA and in the USSR the rate of Sr-90 fallout was largely compensated by its radioactive decay and removing to seas and oceans with rivers’ water streams. This may be illustrated by the following data on mean values of Sr-90 contamination of the former USSR territory:

The results were received for about 40 points located in different climatic zones of the country.

Detailed information, concerning Cs-137 global fallout distribution in 60-s, is available only for those areas of the former USSR, where the minute gamma-survey was conducted, using technique described in [9.13, 9.14].

The distances between flight strips were 50 km, as a rule. In some cases they reached 100 km. The mean concentration of radionuclides along the flight line was usually determined for sections of about 10 km in extent. The flight attitude was 25-50 m, so the resulting data specify a strip 100-200 wide on the ground (its area is about 1 km²). The reproducibility of Cs-137 content determination, taking into account the bridging accuracy, was no worse than 10 %. The accuracy of Cs-137 content determination was about 20 % at the contamination level about 0.37x10¹⁰ Bq/km².

In Figs. 9.3 - 9.4 maps are presented of the former USSR territory contamination (by the end of 60-s) due to nuclear explosions’ global fallout. The contamination levels are mainly in the range from (0.185 - 0.648)x10¹⁰ Bq/km², the mean Cs-137 content is 0.33x10¹⁰ Bq/km²[9.15].

Particular attention is paid to the extremely complicated pattern of contamination of the territory with Cs-137 and presence of numerous local areas with contamination levels quite different from those of surrounding territories. Somewhat similar spotty pattern can be also observed in the map of fallout. But in detail the maps do not completely coincide.

9.4. Existing databases

In the Ministry of Defense of RF information is available on all conducted nuclear tests on Novaya Zemlya, including data on the nuclear explosions types, radiation situation while conducting tests and radiation consequences of each test, and the dynamics of radioecological situation on Novaya Zemlya during 30 years.

A part of data is still classified, including data on parameters of tested charges and devices, some data on testing conditions, and an insignificant part of data, concerning radiation situation after the test. The rest, main part of the data, is completely unclassified.

In some data files blanks may take place in tables, concerning particular tests, as at that time it might be impossible to make some measurements by any technical reasons.

The following databases are available:

• the tests chronology;
• estimates of total amount of airborn radionuclides and amounts of separate radionuclides (calculated and measured data);
• parameters of radiation situation while conducting nuclear tests;
• the testing conditions;
• exposures formed at the test site and along the route of radioactive masses spreading;
• dynamics of accumulating some radionuclides in environmental objects at the test site (vegetation, fauna, water reservoirs, soil, etc.);
• radiation situation (background) before each test;
• dynamics of radioecological situation change at the test site, etc.

Besides the Ministry of Defense, the data are partly available in other departments, which took part in conducting the tests.

On the basis of instrumental studies, the following estimates are made:

• total amount of airborn radionuclides formed as a result of all tests;
• basic exposures in the regions for all years;
• environmental objects’ contamination;
• other estimates of radiation consequences;
• estimates of cavities in mining workings, that might be used for radioactive wastes storage or adapted for their disposal;
• radioecological capacity of a test site.

REFERENCES

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2. E.D.Stukin, Feasibility study of retrospective reconstruction of traces of nuclear explosions, conducted at the Semipalatinsk Test Site, contributing into contamination of investigated Altay Land territory, - IGKE Report, Moscow, 1995.

3. A.K.Kruglov, How the nuclear industry was created in the USSR,- Moscow, TsNIIAtominform, 1994, 380 pp. (In Russian).

4. Yu.V.Dubasov, G.A.Krasilov, A.M.Matushchenko et. al, "The chronology of air nuclear explosions at the Semipalatinsk Test Site and their radiation characterization", - Bulletin of the Public Information Center on Atomic Energy, TsNIIAtominform, 1996, No. 6, p. 39-46.

5. Yu.A.Izrael, E.D.Stukin et.al, "Reconstruction of the actual pattern of ground radioactive contamination as a result of nuclear tests and accidents", Meteorologiya and Gidrologiya, 1994, No. 8, p. 5-18.

6. V.A.Logachev, "Estimation and comparison of radiation exposure of the population of Russian Federation as a result of conducting air nuclear explosions at the test sites of ex-USSR and of the Chernobyl accident". - Report, presented to the International Conference "One Decade After Chernobyl: Summing up the Consequences of the Accident". - Austria center Vienna, Austria, April 8-12, 1996.

7. "Radioecological situation at the Central Test Site of Russian Federation". – In the collection: "Novaya Zemlya. Natural and cultural legacy. The history of discoveries". Moscow, Russian Research Institute for Cultural and Natural Legacy, The Foundation of Polar Studies, 1996, p. 156-157.

8. Nuclear Explosions in the USSR. Issue No. 1. The Northern Test Site. Reference data, Moscow 1992, 194 pp.

9. V.I.D’yachenko, V.V.Kazantsev, Yu.P.Martakov, S.V.Semenovykh, "Radiation situation in the area of nuclear explosion, conducted at the Totsk Firing Ground on September 14, 1954", Bulletin of the Public Information Center on Atomic Energy, TsNIIAtominform, 1995, No. 5-6, p. 44-47.

10. Yu.V.Dubasov, A.M.Matushchenko et al, "Underground explosions of nuclear devices at the territory of the USSR in 1965-1988: the chronology and radiation consequences", Bulletin of the Public Information Center on Atomic Energy, TsNIIAtominform, 1996, No. 6, p. 39-46. (in Russian).

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13. L.I.Boltneva, Yu.A.Izrael, I.M.Nazarov et.al, "Cs-137 and Sr-90 global contamination and external exposures at the territory of the USSR", Atom. Energ., 1977, V. 42, p. 355.

14. R.M.Kogan, I.M.Nazarov, Sh.D.Fridman, The fundamentals of gamma-spectrometry of natural environment,- Moscow, Atomizdat, 1969. (In Russian).

15. Yu.A.Izrael, The radioactive fallout after nuclear explosions and accidents, St.Petersburg. "Progress - Pogoda", 1996, 355 pp. (In Russian).