US. DEPARTMENT OF THE INTERIOR 

GEOLOGICAL SURVEY

OPEN FILE REPORT 01-312

The Containment of Soviet 

Underground Nuclear Explosions

VitalyV.Adushkin

Institute of Dynamics of Geospheres

Of the Russian Academy of Sciences

Moscow, Russia

William Leith 

U.S. Geological Survey 

Reston, Virginia 20192

This report is preliminary and has not been reviewed for conformity with

U.S. Geological Survey editorial standards or stratigraphic nomenclature.

Any use of bade, product, or firm names is for descriptive purposes only

and does not imply endorsement by the US. Government

SEPTEMBER 2001
USGS Open File Report 01-312: Containment of Soviet Underground Nuclear Explosions

TABLE OF CONTENTS

PREFACE................................................................................................................................................ 3

Chapter 1. THE NUCLEAR TESTING PROGRAM................................................................................ 5

1.1 Introduction.............................................................................................................................. 5

1.2 Definitions of Containment...................................................................................................... 5

1.3 Brief History of Nuclear Testing in the USSR.......................................................................... 6

1.4 Limits on Nuclear Testing........................................................................................................ 9

1.5 Types of Underground Nuclear Tests..................................................................................... 9

1.6 Locations Where Nuclear Tests were Conducted................................................................. 12

1.7 Underground Testing at the Semipalatinsk Test Site............................................................ 14

1.8 Announcement of Nuclear Tests........................................................................................... 16

1.9 Detonation Authority and Procedures................................................................................... 16

Chapter 2. CONTAINMENT OF UNDERGROUND NUCLEAR TESTS............................................... 19

2.1 What Happens During an Underground Nuclear Explosion.................................................. 19

2.3 How Nuclear Explosions Remain Contained ....................................................................... 22

2.4 Selecting Location Depth and Spacing................................................................................. 23

2.6 The Containment Evaluation Panel....................................................................................... 26

2.7 Containing Vertical Shaft Tests............................................................................................. 27

2.8 Containing Horizontal Tunnel Tests..................................................:................................... 28

2.9 Types of Radiation Releases ................................................................................................ 32

2.10 Record of Containment.......................................................................................................... 34

2.11 "Tired Mountain" Syndrome.................................................................................................. 35

2.12 Statistics on the Containment History of Soviet Tests.......................................................... 38

2.13 A Few Examples....................................................................................................................43

Chapter 3. MONITORING ACCIDENTAL RADIATION RELEASES.................................................... 46

3.1 Criteria for Conducting a Test............................................................................................... 46

3.2 Examples of Containment Failures....................................................................................... 47

3.3 Groundwater Contamination.................................................................................................47

3.4 How Safe is Safe Enough? ................................................................................................... 50

Acknowledgements 50 

Bibliography 51

On the Cover: Section of a "line of sight" pipe, extending 

from one of the three tunnels at Degelen mountain test site 

no. 169/2. This pipe, which is about 2 meters in diameter, 

was evacuated during the nuclear test at this site, on the 

4th of October, 1989.
USGS Open Fiie Report 01-312: Containment of Soviet Underground Nuclear Explosions

PREFACE

This report was prepared in 2000-2001 under a contract between the U.S. Geological Survey and 

the Institute of Dynamics of Geospheres of the Russian Academy of Sciences (Contract no. 

OOHQSA0727. This goal of the project was to produce, for Soviet underground nuclear testing, a 

report mirroring Dr. Gregory van der Vink's report, "Containment of Underground Nuclear 

Explosions", published in 1989 by the U.S. Congress' Office of Technology Assessment. That 

report reviewed in detail the containment of U.S. nuclear tests at the Nevada Test site, with 

special attention devoted to safety and environmental aspects of underground nuclear testing. 

The current report uses as its outline the structure of the OTA report, modified to accommodate 

the differences between Soviet and U.S. nuclear testing practices and containment experiences. 

The basic contract reports that were provided by the Russian authors of this study have been 

supplemented by other published information and some unpublished works, improved citations of 

the literature, and a number of illustrations. Most of this report is, therefore, based on a 

translation from Russian to American English that was subsequently edited. The original Russian 

reports are available upon request to W. Leith (email: wleith@usgs.gov).

Basic data on Soviet underground nuclear tests are published in the six volumes of "Nuclear 

Testing in the USSR." Volume 1 of this series (published by RFYaTs-VNIIEF, 1997, as an update 

to MINATOM, 1996; a nearly-identical version was also published by IzdAT, 1997) contains 

summary data for all Soviet nuclear tests, excluding hydronuclear tests. Volume 2 presents 

information on the technology of nuclear testing; Volume 3, on military and political aspects of 

nuclear testing; Volume 4, summary information for 115 of the so-called "Peaceful Nuclear 

Explosions," (PNEs); Volume 5, nuclear testing and the environment. Note that, the numbers of 

underground nuclear tests of various types reported in these publications are inconsistent and 

may, in places, differ from that presented herein: For example, for the Peaceful Nuclear 

Explosions (PNEs), Volume 2 (op c/f) lists 115 PNEs; while Volume 1 lists 124, and both Sultanov 

et al (1993) and Laushkin et al (1995) list 122 PNEs. The inconsistencies are apparently due to 

how tests were categorized. The categorization of underground nuclear tests used herein is that 

of Adushkin and Laushkin (Experience monitoring UNTs with the seismic network of the former 

USSR, FSSN, v.3,1996); this is shown graphically on the next page, as well as in Tables 1 and 2.

For the Semipalatinsk test site, a book reviewing nuclear testing there was published by MEDVIOEKSTREM in 1997. Additional data are available in several publications, including, for underground tests: Bocharov et al (1989), Adushkin et al (1995), and Leith (1998). A summary of the 

record of containment of underground nuclear tests at the Semipalatinsk test site is available in 

Gorin et al (1993). Summary data for Soviet nuclear tests in the atmosphere is available in 

Dubasov et al (1993), and height-of-burst and other data for atmospheric nuclear explosions are 

available in Andryushin et al (1998). The latter reference also includes a listing of hydronuclear 

experiments conducted at the Semipalatinsk test site. A number of these hydronuclear tests 

(which resulted in plutonium contamination of the local environment) were conducted in tunnels at 

the Degelen Mountain test site, and may therefore be on interest for containment studies.

For the Novaya Zemlya test site, books reviewing nuclear testing there were published by the 

Khlopin Radium Institute (1999) and IzdAT (2000). Additional information on nuclear test 

containment is available in Mikhaylov and Chemyshev (1991), Mikhaylov et al (1991), 

Chelyukanov and Savel'ev (1992) and in Andrianov and Bazhenov (1992). The latter includes 

detailed descriptions for a number of containment failures at Novaya Zemlya that (summarized in 

this report). In general, the containment record at Novaya Zemlya has been poor (and is 

described some in detail, herein); this is of concern since it is now the only declared Russian 

nuclear test site.
USGS Open File Report 01-312: Containment of Soviet Underground Nuclear Explosions

PNE shaft test (1) -Clivazh - 

NZTS borehole tests (6) - |

PNE tunnel tests (2) 

Dnepr 1 & 2

NZTS, tunnel tests (36]

PNE, boreholes (114)

STS borehole tests 

(133)

Distribution 

of 522 Soviet 

Underground 

Nuclear Tests

PNE, boreholes, STS (5)

STS tunnel tests (225)

Number of Soviet Underground Nuclear Tests, categorized in terms of test 

emplacement mode (tunnel, borehole, shaft), and color coded by location 

(STS = Semipalatinsk Test Site, 363 tests; NZTS = Novaya Zemlya test sites, 

42 tests; PNE = Peaceful Nuclear Explosions, 122 tests, including 5 PNEs on 

the STS). Hydronuclear tests are not included.
USGS Open File Report 01-312: Containment of Soviet Underground Nuclear Explosions

CHAPTER 1. The Nuclear Testing Program

1.1 Introduction

Conducting nuclear tests is one of the most important elements in the technology of creating and 

improving nuclear weapons. In 1963, due to the serious environmental consequences of nuclear testing 

in the atmosphere, hydrosphere and in near space, the USSR, USA and Great Britain signed the Treaty 

on Prohibiting Nuclear Weapons Testing in Three Media (in the atmosphere, in space and under water), 

also known as the Limited Test Ban Treaty. Currently, this Treaty is signed by 117 nations.

The 1963 Treaty ushered in a new stage in nuclear testing, in which nuclear tests were conducted only 

underground. Nevertheless, this did not obviate the question of the environmental consequences of 

nuclear tests. The results from early underground nuclear tests indicated that releases of radioactive 

materials into the atmosphere were possible. As a result, during the entire period of underground testing, 

serious research was conducted to guarantee the ecological safety of underground nuclear explosions. 

One of the primary directions of this research was to guarantee the so-called "camoufletic" (contained) 

nature of nuclear explosions, that is, to conduct underground explosions under conditions which 

guarantee keeping the primary radioactive by-products that are most dangerous to man, within the area 

immediately surrounding the explosion location.

The basis for providing containment of nuclear tests was the concept of creating a relatively impermeable 

barrier to the migration of the non-condensed radioactive gasses found in the explosion cavity under high 

temperatures and pressures. For this barrier, it was suggested to use the layer of rock above the 

underground explosion. As data were obtained on the level of rock damage in the close-in zone of the 

nuclear explosion, concepts improved about zones of irreversible behavior of the rock massif and of the 

rock composing it (the so-called "zonal" approach to describing the mechanical effects of an underground 

nuclear explosion, see below). It was established that, in addition to buckling/crushing zones of the rock 

and massif damage directly abutting the explosion containment cavity, there exists an area of damaged 

medium near the free surface (the spall damage zone) and in the vicinity of large, tectonic faults, which 

significantly reduces the insulating properties of the rock massif.

It is also asserted by Russian scientists that underground nuclear tests conducted in the USSR from 1985 

to 1990 support the conclusion that the task of guaranteeing containment of underground nuclear 

explosions has been successfully solved at the former Soviet nuclear test sites.

1.2 Definitions of Containment

The Limited Test Ban Treaty (LTBT) established an international requirement for adequate containment 

of the radioactive products of underground nuclear explosions. Article 1.1 (b) of this treaty prohibits an 

explosion that "...causes radioactive fallout [in Russian, "posadkha"] to be present outside of the territorial 

limits of the State under whose jurisdiction or control such explosion is conducted." Using this simple 

criterion, one might judge that the majority of U.S., Soviet, Chinese and French underground nuclear tests 

were "contained," but only to the extent that they were compliance with the LTBT. However, the U.S., the 

Soviets/Russians and the French have since developed more rigorous requirements for containment.

The U.S. defines successful containment as "such that a test results in no radioactivity detectable off-site 

as measured by normal monitoring equipment, and no unanticipated release of radioactivity on site within 

a 24-hour period following execution" . The U.S. further characterizes prompt (seconds to hours), highrelease containment failures as "venting", and late-time, small, slow radiation releases as "seeps" 

(associated with changes in atmospheric pressure; see OTA, 1989). Also defined are "controlled tunnel 

purgings," which are mostly small, intentional releases of gasses trapped in sealed tunnels, and 

"operational releases," which are also small releases upon post-test sampling (tunnel reentry or drillback). Ventings from early U.S. underground nuclear tests (e.g., DesMoines, 1962, and Baneberry, 1970)
USGS Open File Report 01-312: Containment of Soviet Underground Nuclear Explosions

account for the major radioactivity release (more than 25 million curies). Following Baneberry, the U.S. 

halted testing for some months to review its testing procedures and record of containment. After 

implementing changes in U.S. testing procedures following Baneberry, there have been only two ventings 

that released more than 1000 curies (Diagonal Line, 1971 and R;o/a, 1980), and only one seep releasing 

more than 100 curies (Tierra, 1984). Also since Baneberry, all but one U.S. underground nuclear test 

(Cannikin) were emplaced in relatively porous volcanic rocks or alluvium at the Nevada Test Site; i.e., in 

geologic environments quite different from those of the main Soviet nuclear test sites. These differences 

in test environments are reflected in contrasting containment practices between the two countries.

While the above definitions of containment are useful and can be used to review the available information 

on the containment of underground nuclear tests, under the Comprehensive Nuclear Test Ban Treaty 

(CTBT), the de facto criterion for "containment" will be undetectability by the radionuclide monitoring 

network of the International Monitoring System (IMS). Although there is no specific capability established 

for the IMS, it has been evaluated with respect to its ability to detect the venting of 10% of the radioactive 

gasses from a 1 kt underground nuclear explosion within 12 hours of the explosion (specifically, about 

1014 Bq of 133Xe; see the Working Papers of the Conference on Disarmament CD/NTB/WP-224 and 

CD/NTB/WP-283, 1995). In terms of the historically-used terms for describing nuclear test containment, 

this criterion would be categorized as a "prompt vent".

1.3 A Brief History of Nuclear Testing in the USSR

Nuclear testing in the USSR began with the test of the RDS-1 nuclear bomb1 , detonated on 29 August 

1949. The 22 kt charge was an implosion design with plutonium as the working substance. It was placed 

on a metal tower, 37.5 m high, at Training Test Site No. 2 of the USSR Ministry of Defense, a specially 

equipped field located 170 km from Semipalatinsk, Kazakhstan (at that time the Kazakh Soviet Socialist 

Republic). This test site later became known as the Semipalatinsk Polygon. In addition to testing the 

nuclear charge itself, approaches were developed in this experiment for recording the primary effects of a 

nuclear explosion in the atmosphere. Specially developed equipment was used to record the optical and 

electromagnetic effects, the parameters of the atmospheric shock wave and the yield of the explosion.

The organization responsible for instrumental observations of the physical and mechanical parameters of 

a nuclear explosion, including the development and creation of special recording devices, was headed by 

M.A. Sadovskiy, who later became an academician of the Russian Academy of Sciences and Director of 

the Institute of Physics of the Earth (IPE). The latter institution included the Special Sector (Spetssektoi1) 

with the independent rights of a structural subdivision. This Spetssektor was the leading scientific 

organization for studying the physics of nuclear explosions. The preparations for and the actual conduct 

of the first test determined the primary issues that had to be solved in the process of nuclear testing; it 

also determined the circle of organizations needed to participate in nuclear testing.

The term "underground nuclear test" can be defined as the near-simultaneous detonation of one or more 

nuclear charges inside one underground excavation (a tunnel, shaft or borehole). With this definition, of 

the 742 nuclear tests were conducted during the entire period of nuclear testing in the USSR, from 1949 

to 1990, 522 tests (70%) were conducted underground. This includes 122 underground nuclear tests that 

were conducted "in the interests of the national economy" (the so-called Peaceful Nuclear Explosions, or 

PNEs). Note that, because many Soviet tests included multiple nuclear devices, detonated within a few 

milliseconds to seconds, the number of nuclear charges detonated (approximately 969) was significantly 

greater than the number of underground nuclear tests. The composite energy yield (TNT-equivalent) of 

all Soviet nuclear tests is estimated at 285.4 megatons (Mt).

After the first atomic bomb test, it became clear that nuclear weapons would be constantly improved, and 

that it was necessary to organize a systematic nuclear testing program. Academician M.A. Sadovskiy led 

preparations for the technical task of designing the test site. In 1950, Training Test Site No. 2 (UP-2) 

became the Semipalatinsk Test Site. The test site territory had a specialized military unit assigned to it, 

as well as command and research services. The scientific director of the test site was M.A. Sadovskiy, 

who was previously the scientific director of UP-2.

1 The abbreviation "RDS" stands approximately for Made in Russia ["Russko Delano Sarna1]
USGS Open File Report 01-312: Containment of Soviet Underground Nuclear Explosions

Between 1949 and 1989, a total of 483 tests were conducted at the Semipalatinsk Test Site. This 

comprises nearly 65% of the overall number of nuclear explosions conducted by the USSR. For its entire 

existence, the Semipalatinsk Test Site was the primary location for conducting nuclear testing. The last 

nuclear test at the Semipalatinsk Test Site was conducted at the Balapan site on 19 October 1989. The 

data from this explosion are as follows:

Time of detonation:

Coordinates:

# of nuclear charges:

Total charge yield:

Charge emplacement depths:

Rock at the hypocenters:

Gas content of rock:

12:49:59.98 seconds

49°55'15"N ; 78°54'24"E

three

-85 kt

628, 592 and 556 m

siliceous sandstone

12% (by weight at 1000 degrees Celsius)

By the mid-1950s, it became necessary to establish a new test site for nuclear tests were being planned 

for water environments and for high-yield (megaton) nuclear charges. A test site was created on the 

territory of the Novaya Zemlya archipelago with the 31 July 1954 Decree of the Central Committee of the 

USSR Communist Party and the Council of Ministers of the USSR. Since its establishment, a total of 133 

nuclear tests were conducted on the Novaya Zemlya Test Site, including 88 explosions in the 

atmosphere, 3 explosions under water, and 42 underground nuclear explosions, of which 36 were 

conducted in tunnels and 6 in deep boreholes.

The first nuclear explosion at the Novaya Zemlya test site was conducted underwater at Chornaya Guba 

on 21 September 1955. It was at this test site that the USSR conducted on 30 October 1961 the highest 

yield nuclear test of any nation a ~50 Megaton charge exploded in the air at a height of 4000 m. The 

last test at Novaya Zemlya was conducted on 24 October, 1990, in tunnel A-13N. This was the last 

Soviet nuclear test (since then, no nuclear tests have been conducted by Russia). It is asserted by 

Russian scientists that, by the end of nuclear testing, the methodology for guaranteeing containment was 

so well developed that the last tests at Semipalatinsk and Novaya Zemlya, were conducted with 

practically total containment (i.e., with only an insignificant migration to the surface of light, noncondensible radioactive components in the form of inert gasses).

The number of nuclear tests conducted per year in the USSR is not equally distributed (see Figure 1).

o\j-

*" 7O- W ' u

d> *- 60 

o 50

c> 40-

w w

3

z 20-

10

o- El,

o1 ' 'cv '

0) 0)

1 H

0)

i

1

B

r

4

L

c

1

H^

n <

D i

^

!i '

i

I 

i?

p

X)

3)

^ 1

sj ^ ._.,,!

!' . , , ....... i 1- : : : ^ - = = j

* \

* A i." n

s Fl @ i R ; " fl i' I " Fl

^ allR" 1 " ! l ! If* ! 1 "W ' ^i '

^ pi! 1- ! s ;1 : S!ml M ili'pl i J^jj

CDCDh-h-h-l^-OOOOOO

o>o>o>o>o>o>o>o>o>

Year

Figure 1: Annual Number of nuclear tests in the USSR.
USGS Open File Report 01-312: Containment of Soviet Underground Nuclear Explosions

Figure 1: Annual Number of nuclear tests in the USSR.

The Soviets did not conduct nuclear tests In 1950 and 1952. This was related to the specifics of the initial 

stage of work in creating nuclear weapons. From 1959 until August 1961, the USSR did not conduct 

nuclear tests due to a moratorium on nuclear testing together with the USA and Great Britain. From 1963 

until March 1964, nuclear tests were not conducted because of preparations for concluding the Limited 

Test Ban Treaty and the transition to a program of underground nuclear testing. From August 1985 to 

February 1987, and from November 1989 to October 1990, nuclear testing and nuclear explosions were 

not conducted due to USSR participation in testing moratoria.

Table 1 presents a distribution of the quantity of nuclear tests and explosions according to the conditions 

in which they were conducted. It is clear that the greatest number of nuclear explosions were conducted 

in underground conditions (70%). Of these, 122 nuclear tests were conducted in the interests of the 

national economy, five of which were at the Semipalatinsk Test Site and three at Mangyshlak.

Table 1. Distribution of the number of nuclear tests and explosions according to 

the environmental conditions in which they were conducted.

Emplacement 

Conditions

Number of 

Explosions

Surface

32

Atmospheric

175

High-Altitude 

and Space

8

Underwater 

+ water surface

3+2

Underground

Tunnel 

and shaft

263+1

Borehole

258

Total

742

The transition to conducting underground nuclear tests occurred later in the USSR than in the United 

States. The first underground nuclear test at the Nevada Test Site, code named Uncle, was a 1.2 kt 

cratering explosion conducted on 29 November 1951, within the framework of the Jangle program (this 

explosion was also known as Jangle-4). Four years later, on 23 March 1955, a second cratering nuclear 

explosion, Ess (1 kt, part of Operation Teapot), was conducted at the Nevada test site. While the tests 

were not contained, since the charges were detonated at a shallow depth (5.2 and 20.4 m for Uncle 

Teapot explosions, respectively), these experiments were significant in terms of developing a 

methodology for conducting nuclear tests in underground conditions. The first U.S. contained nuclear 

explosion, Rainier, was conducted on 19 September 1957, using a proven device with a known yield of 

1.7kt.

In the USSR, preparations for conducting underground nuclear explosions began in 1957 (by the end of 

1957, the USA had already conducted 5 underground nuclear explosions: 3 in boreholes and 2 in tunnels, 

including Rainier). A large series of underground explosions of chemical (TNT) explosives weighing 1,10 

and 1000 tons was conducted in the clays and sandy loams in the steppes close to the settlement of 

Kabulsai, in the Kazakh SSR. The main task of these explosions was to study the "scale" effect for buried 

explosions, through which an increase in charge energy (and, correspondingly, the depth of the 

explosion) the law of geometric similarity of the excavation effect is broken, as a result of the increase in 

the role of the gravity force. It is necessary to account for this effect in order to guarantee the conditions 

of containment when conducting underground nuclear tests (see Section 2.4). These preparations 

continued into 1959, when in the rock massif of Tuya-Muyun (Kirghiz SSR), two trotyl (TNT) charges 

weighing 190 and 600 tons were exploded underground, in order to determine the conditions for 

containing large-scale nuclear explosions.

At the same time, in the rock massif of Degelen Mountain at the Semipalatinsk Test Site, Tunnel V-1 was 

being prepared for the first underground nuclear explosion in hard rock. In order to ascertain the 

technicaltasking, an experimental detonation of a 600-ton trotyl (TNT) charge was conducted in a nearby 

tunnel, V-2, on 5 June 1961 i.e., just before the nuclear explosion in tunnel V-1. The mechanical 

effects of this chemical explosion test, including the seismic signal, were studied in detail.

Four months later, after analyzing the results of the chemical explosion in tunnel V-2, the first fullycontained, underground nuclear explosion in the USSR was conducted on 11 October 1961, in tunnel V-1
USGS Open File Report 01-312: Containment of Soviet Underground Nuclear Explosions

(four years after Rainier). In this experiment, a nuclear charge with a yield of 1.2 kt was detonated at a 

depth of 118 m. Because the mechanical effects of this explosion turned out to be somewhat weaker 

than expected, the requirements for containment were fully achieved.

Note that, at about the same time, France (which had already conduced nuclear tests in the atmosphere) 

conducted its first underground nuclear explosion, code-named Agate, at the Reggane test site in the 

Sahara on 7 November 1961, with a yield of less than 20 kt. Thus, the USA, USSR and France had 

begun systematically conducting underground nuclear tests, in preparation for the LTBT. By 1962, the 

USA had conducted 58 underground nuclear explosions; the USSR, one test in underground conditions, 

and France, one underground explosion.

1.4 Limits on Nuclear Testing

The early nuclear testing in the atmosphere created globally-detectable quantities of radioactive byproducts in the atmosphere and, as a consequently led to the radioactive contamination of the Earth's 

surface well beyond the boundaries of the test sites.

In 1963, the Limited Nuclear Test Ban Treaty was concluded, requiring strict limitations on the release of 

radioactive by-products into the atmosphere during underground nuclear explosions (although no 

monitoring system was provided for in the Treaty). It was declared, that the concentration of radioactive 

by-products in air masses that pass beyond the territorial boundaries of a state conducting tests must not 

exceed the global background values of corresponding isotopes in the atmosphere. In addition to this, it 

was necessary to adhere to standards of radiation safety for the population. This, in turn, added practical 

limitations on the time of the onset of release of radioactive by-products from the explosion cavity into the 

atmosphere, even in those cases when this release was insignificant. These containment requirements 

could be achieved by: 1) the fundamental selection of the depth of emplacement of the nuclear charge, 

and 2) the development and implementation of special measures for sealing-off (stemming) the 

emplacement tunnels and boreholes.

By the early 1970s, it was clear that the limitations on underground nuclear explosions imposed by the 

LTBT did not guarantee the full measure of integrated radiation safety of the country that was testing the 

nuclear weapons, or of neighboring States, and in 1974, the USA and USSR reached agreement on 

limiting the yield of underground tests to 150 kt (Threshold Test Ban Treaty). Later, in 1976, the USA and 

the USSR signed the Treaty on Threshold Limitations for Underground Nuclear Explosions Conducted in 

the Interests of the National Economy (a.k.a. the Peaceful Nuclear Explosions Treaty). In accordance 

with this Treaty, the yield of a nuclear charge used for conducting peaceful nuclear explosions was limited 

also to 150 kt (in the case of a multiple-device explosion, the total yield of the charges could not exceed

1.5 Mt). Although the last two treaties were not ratified until 1990, both countries governed their nuclear 

activities according to the treaty conditions. Thus, the agreements reached in 1974 dictated that nuclear 

tests should be conducted only on designated test sites (although peaceful nuclear explosions were 

permitted at other locations), and the yield of the nuclear charge must not exceed 150 kt.

1.5 Types of Underground Nuclear Tests

The Soviet underground nuclear explosions can be divided into two groups, based on the geometry of the 

underground emplacement: 1) explosions conducted in near-horizontal excavations (adits or tunnels), 

and 2) explosions conducted in deep near-vertical boreholes. In total (excluding hydronuclear 

explosions), 258 Soviet nuclear explosions were conducted in boreholes, and 263 in tunnels. Table 2 

summarizes the numbers of nuclear explosions in tunnels and boreholes for the Semipalatinsk, Novaya 

Zemlya and the Peaceful Nuclear Explosion sites. From Table 2, it is clear that at Semipalatinsk, the 

portion of tunnel explosions comprised 62%, and at Novaya Zemlya, practically 85%. Underground 

Peaceful Nuclear Explosions, conducted in the interests of the national economy, were almost exclusively 

done in boreholes, with the exception of the Dnepr-1 and Dnepr-2 projects (tunnel-type emplacements) 

and the Klivazh project (a shaft-type emplacement).
USGS Open File Report 01-312: Containment of Soviet Underground Nuclear Explosions

Table 2. Comparison of the numbers of Soviet underground nuclear explosions 

conducted in deep boreholes, tunnels and mines (note that the numbers for 

Semipalatinsk include five PNEs conducted in boreholes).

Semipalatinsk

Tunnel

225

Borehole

138

Novaya Zemlya

Tunnel

36

Borehole

6

PNEs (beyond test sites)

Tunnel

2

Borehole

114

Mineshaft

1

At the Semipalatinsk test site (STS), explosions in tunnels were conducted in Degelen Mountain. At the 

northern Novaya Zemlya test site (NZTS or NZ), explosions in tunnels were conducted in rock massifs 

along the Matochkin Shar Strait. The excavated tunnel works ranged from 200 m to 2 km long, usually 

made with a diameter of about 3m. In accordance with the engineering requirements of a specific test, 

the system of underground works could be highly simple (one straight tunnel) or it could have a branching 

system of works. For example, in the test in Tunnel 704 at Degelen, one straight tunnel was used, with 

the charge placed at the end of the tunnel. In the complex test at Tunnel 169/2 (Degelen, 4 October 

1989), two diverging tunnels were used, with the goal of observing the effects of a simultaneous release 

of radiation along two beams out to the surface. A third example is the complex system of underground 

works used for the multiple-device test in Tunnel A-37 (11 October, 1982) at the northern Novaya Zemlya 

test site (see Spungin et al, 1998). Figure 2 shows a plan view of the tunnel complex for this 80-kt test, in 

which four charges of differing yields were detonated in separate drifts.

Figure 2. Plan of Tunnel A-37, northern Novaya Zemlya test site (Matochkin Shar). 

The sites marked ZR-1, ZR-2, etc. (for "zero room"), are the locations of the 

nuclear charges within the tunnel complex. Elevation contours are in meters.

10
USGS Open File Report 01-312: Containment of Soviet Underground Nuclear Explosions

In several cases after a test in a single, linear tunnel, a system of access drifts was excavated for 

research into the properties of rock at various distances and azimuths from the explosion source. For 

example, Figure 3 presents the plan for the underground works excavated in the rock massif, which was 

destroyed by the explosion in the "Tunnel V-1" experiment in 1961 at the Degelen test site (STS).

experimental 

boreholes

__ crushed zone f f \ n / / *JT i mm- \~*r / 7 / j *

access 

drifts ~ " " ' ' '" ' ' ~" ' ~ damaged zone

blockfractured 

zone

Tunnel V-1 

Main Drift

Figure 3. Plan view of the nuclear test-experiment, "V-1", of 11 October 1961 (Degelen 

test site). Note that the side access drifts were constructed after the test.

The nuclear charge was placed, as a rule, at the end of the tunnel in a specially equipped room, known 

as the "end box" (in U.S. usage, "zero room"). In some cases (for example, in tunnels 148 and Dnepr-1, 

when the underground works were used to direct the ejection of radioactive explosion products), the 

charge was placed at some distance from the end of the tunnel. Recording sensors were placed along 

the tunnel in specially made pits or recesses in the walls of the tunnel. All the recording equipment was 

placed either inside, near or close to the portal of the tunnel, or at distances of less than 1 km from it (i.e., 

close-in and remote measuring points). In the case of irradiation experiments (in which a radiation beam 

was directed to the surface), the tunnel was specially equipped so that, immediately after the radiation 

beam exited to the portal area where the test objects were placed, the tunnel was closed off, so as to 

protect the test objects from debris, as well as to contain the radioactive by-products of the explosion.

After conducting a nuclear explosion, the tunnels were generally studied from the portal to the innermost 

stemming, which was not equipped with a hermetically sealed pass-through. Such studies made it 

possible to obtain information on the level of damage of the rock at various distances from the explosion, 

and of the underground works. In several experiments, the working tunnels were completely opened up 

in order to gain access into the containment cavity.

11
USGS Open File Report 01-312: Containment of Soviet Underground Nuclear Explosions

To conduct nuclear explosions in flat terrain, vertical boreholes about 1 meter in diameter were drilled (the 

actual diameter of the hole varied with depth). Depths ranged from 200 m to 2 km for different tests. In 

several experiments, after the nuclear explosion, several investigation boreholes were excavated in order 

to study the properties of the damaged rock. For illustration, Figure 4 below presents the plan of the 

borehole in the "Borehole 102" experiment at the Balapan test site (Semipalatinsk). The boreholes made 

after the explosion, including one, which had a very complex shape, intersected the rock located in the 

various zones of the underground nuclear explosion. By analyzing the core material of these boreholes, it 

was possible to ascertain the characteristics of the rock and of the massif in zones of rock 

buckling/crushing, the damaged rock zone, and also in fracture zones (for induced and block fracturing).

1.6 Locations Where Nuclear Tests Were Conducted

Nuclear tests were conducted in specially equipped areas of the Semipalatinsk and Novaya Zemlya Test 

Sites (Figures 5 and 6). In addition, 122 underground nuclear explosions were conducted outside of 

these main test sites (Peaceful Nuclear Explosions, or PNE's, conducted "in the interests of the national 

economy"). PNE test locations span a vast region of the former Soviet Union (in Siberia, Central Asia 

and in the European part of Russia, see Figure 7) and a wide range of geological environments.

- - 200 m

^ clav

gravel sediments 

spall zone

l_-400m

cavity

zone of rock 

contortion

damaged zone

high-density 

fissure zone

block fractured 

zone

Figure 4. Structure of the central zone of the explosion in borehole 102. 

The vertical lines labeled "B" are the post-test exploratory boreholes.

12
USGS Open File Report 01-312: Containment of Soviet Underground Nuclear Explosions

Figure 5. Semipalatinsk nuclear testing 

"Polygon", showing the location of the 

Degelen and Balapan underground test 

sites, and the atmospheric test site 

("Experimental Field").

Figure 6. Novaya Zemlya nuclear testing 

Polygon, including the underground 

test sites at Matochkin Shar and 

Krasino, and the atmospheric test 

site at Chernaya Cuba.

13
USGS Open File Report 01-312: Containment of Soviet Underground Nuclear Explosions

Figure 7. Map of the former USSR, showing where "Peaceful Nuclear Explosions" 

were conducted outside of the main nuclear test sites (black dots). Five 

PNEs were also conducted on the Semipalatinsk Test Site.

Distribution of underground nuclear explosions by location:

Location Number of tests 

Semipalatinsk Test Sites 363* 

Novaya Zemlya Test Sites 42 

outside of declared test sites 117**

* including 5 PNEs conducted on the STS

** at sites in the Russian Federation; European Russia; Asiatic Russia; Ukrainian 

SSR, Kazakh SSR; Uzbek SSR; and Turkmenskaya SSR

1.7 Underground Testing at the Semipalatinsk Test Site

The Semipalatinsk Test Site was the primary location for conducting nuclear tests in the USSR. Of a total 

of 742 Soviet nuclear tests, 483 were conducted at STS. The existence of a good infrastructure at STS, 

and sufficiently mild climatic conditions (compared to the Novaya Zemlya Test Site), permitted conducting 

nuclear tests there at any time of year. These factors also permitted "non-standard" configurations for 

underground tests, including nuclear detonations with an intentional release of radiation to the surface.

14
USGS Open File Report 01-312: Containment of Soviet Underground Nuclear Explosions

During the early period of nuclear testing (from 29 August 1949 to 25 December 1962), mainly aerial 

nuclear explosions were conducted at STS (this also includes surface nuclear explosions which, in many 

respects, can be considered "atmospheric" explosions). Aerial explosions were conducted within the 

boundaries of the Experimental Field (Figure 8; see location on Figure 5).

During this early testing period of activity at the 

STS, it should be noted that it was also here 

that the Soviets first dropped a nuclear bomb 

from an airplane (18 October 1951), and also 

first conducted a thermonuclear explosion, with 

a yield of 450 kt (12 August 1953). In this 

same period at STS, the first underground test 

of a nuclear charge (tunnel V-1) was 

conducted, as was the first underground test 

for the purposes of studying the effects of 

radiation on military equipment with the 

release of radiation to the surface (tunnel A-1).

After the 1963-1964 moratorium on nuclear 

explosions, the nuclear testing program was 

conducted under the conditions stipulated by 

the Limiteid Test Ban Treaty. Since the 15th of 

March, 1964, underground nuclear explosions 

were conducted only in tunnels or deep boreholes.

Figure 8. View of towers constructed for recording the effects of atmospheric nuclear tests 

at the "Experimental Field" at the Semipalatinsk Test Site.

Figure 9. The Soviet nuclear explosion, "Shagan," of 15 January 

1965, designed to create a crater 

and dam a water reservoir.

On 15 January 1965, on STS but away from the active sites, 

the first underground nuclear explosion in a borehole was 

conducted beneath the Shagan riverbed. This explosion was 

designed to create an ejection crater (Figure 9), and is 

considered to be the first nuclear explosion for peaceful 

purposes in the USSR. In this experiment, the technology 

was developed for using the excavation action of nuclear 

explosions in the interests of the national economy. In 

particular, as a result of the explosion (conducted in borehole 

1004 at 178 m depth), a crater was formed, 415 m in 

diameter, 100 m deep, with a volume of 6.4 million cubic 

meters. After it filled with water, this was used as a water 

reservoir for the dry Kazakh steppe. (Actually, the volume of 

the reservoir was significantly greater than the volume of the 

crater, since the raised lip of the crater that was formed 

during the explosion served well as a dam, and a second 

reservoir was formed adjacent to the crater).

The most powerful nuclear explosion conducted in a tunnel at 

the STS was the "Tunnel E-1" experiment (13 February 

1966), in which the charge yield was 125 kt. The most 

powerful test in a borehole at the Balapan test field was the 

"Borehole 1061" experiment (2 November 1972) in which a 

165 kt charge was tested. It was also at the STS where the 

methodology for conducting a salvo (multiple-device) 

explosion in a single tunnel was tested (at Tunnel 14, on 3rd 

December 1966), and where the USSR first conducted a 

multiple (salvo) explosion in two tunnels (Tunnels Z-2 and 

140, on 10 December 1972).

15
USGS Open File Report 01-312: Containment of Soviet Underground Nuclear Explosions

The geological structure of the two main underground test areas at STS differ from one another, in terms 

of the amount of tectonic (natural) fracturing present in the rock massifs. The Degelen rock massif, where 

nuclear tests were conducted in tunnels, is highly fractured and characterized by the presence of a 

noticeable layer of weathered rock, whose physical and mechanical properties differ significantly from the 

properties of the bedrock. The Degelen area is also characterized by the presence of a large number of 

tectonic faults and extensive fractures. Each of the excavated tunnels in the Degelen rock massif 

intersects, as a rule, several level IV-VI tectonic faults.

This makes the task of containing the by-products from an underground nuclear explosion in a rock 

massif of special current interest. It should be noted that the primary containment conditions for 

underground nuclear explosions were obtained from the results of the Semipalatinsk experiments. It was 

here that the primary correlations were established; these determine the effect of tectonic damage on the 

laws governing the release into the atmosphere of by-products from an underground nuclear explosion.

1.8 Announcement of Nuclear Tests

The organizational system for nuclear testing in the USSR stipulated informing the administrative 

organizations and the nation's population of the conduct of underground nuclear explosions. Informing 

the administrative organizations was dictated by the necessity of appropriating the corresponding 

financial funding, as well as the means for engineering the tests (communications, utilities, ensuring 

safety, messages, and so forth). Since the system for setting up and organizing nuclear explosions was 

located in two USSR ministries (Ministry of Defense (MOD) of the USSR and USSR Minatom), the Office 

of the Council of Ministers of the USSR developed the measures for ensuring nuclear testing. The 

Council of Ministers developed a list of necessary documentation of oral and written reports on 

completing all work related to the nuclear test.

A special Decree of the Council of Ministers regulated the sequence of announcing the nuclear 

explosions within USSR territory. Thus, in the first quarter of each year, a Joint Decree of the USSR 

MINATOM and the USSR MOD determined the plan for nuclear testing in the current year. This same 

Decree had an appendix, which laid out the plan for specific measures to ensure safe testing. All 

changes in the operational plan of measurements or the schedule of testing were reported without delay 

to the USSR Council of Ministers by MINATOM and MOD.

After completing all preliminary measures and completing preparations for each test, a Representative of 

the State Commission on Testing prepared a special report to the USSR Council of Ministers and to the 

CPSU Central Committee on the readiness to conduct the test. This report contained a description of the 

nature and purpose of the test, as well as a request for approval to conduct the test. After the decision is 

made to conduct the test, the Council of Ministers and the USSR Defense Council inform the leadership 

of the appropriate test site. At the same time, no later than two days before the planned test, the 

administrative leadership, and before that, the party leadership of the region abutting the test site were 

also informed of the test. The fact that information on conducting the nuclear test was transferred and 

accepted was documented for all stages in the announcement process.

A planned test was announced to the population living in population centers close to the test site only one 

day prior to the test. Information on conducting nuclear tests and peaceful nuclear explosions was not 

accessible to the general population. After the nuclear tests were conducted, the USSR population was 

periodically informed by way of informational messages in official periodicals (e.g., the "Pravda" and 

"Izvestiya" newspapers). Regular publications on conducted tests began to appear only in 1987.

During the time of atmospheric testing, while there were generally no messages published, there were 

several exceptions. For example, on 8 August 1953, TASS announced in the "Izvestiya" newspaper the 

planned, 12 August 1953 test of the first hydrogen bomb at STS. In October, 1961, the General 

Secretary of the CPSU, N.S. Khrushchev, made an announcement at the 22nd Congress of the CPSU 

regarding the planned, 30 October 1961 test of the most powerful hydrogen bomb in the world (the 

number 100 megatons was stated). Indeed, such a test was conducted at Novaya Zemlya, but with an 

actual yield of 58 Mt (apparently, at the last moment, it was decided to conduct the test with a less-thanfull yield). When the nation's population was informed of the test, the actual charge yield was not noted.

16
USGS Open File Report 01-312: Containment of Soviet Underground Nuclear Explosions

Often, a yield range was stated (for 

example, "charge yield of up to 20 kt"). 

However, as a rule, the purposes of 

the test were announced.

1.9 Detonation Authority and 

Procedures

The task of carrying out nuclear tests 

was entrusted to specially-created 

subdivisions of the Ministry of Atomic 

Energy (specifically, the Ministry of 

Medium Machine Building, MMMB, of 

the USSR, later MINATOM), and the 

Ministry of Defense (MOD). A specialized Directorate of the MOD was 

created in 1949. The Chief 

Directorate of the MMMB, made up of 

military specialists, was created in 

1957. The tasking of this Directorate 

included the special acceptance of 

nuclear char-ges, populating military 

units with specialists on using nuclear 

charges, and conducting nuclear tests.

Figure 10. The ~118 kiloton nuclear device that was detonated by the Soviets on 14 September, 1988, as part of 

the "Joint US-USSR Verification Experiment, in borehole 1350 at Balaoan fSemioalatinsk test site).

In addition to MINATOM and MOD, a wide range of organizations belonging to various agencies also 

participated in the fielding and evaluation of nuclear tests (Figure 11). These organizations, first and 

foremost, the Academy of Sciences of the USSR, researched the physical effects of the nuclear 

explosion, as well as its damaging effects. The State Commission on Nuclear Testing and the 

Interagency Commission on Seismic and Radiation Safety of Nuclear Explosions played an important role 

in organizing and conducting the tests (these commissions had different names at different times).

The main task of the State Commission was to provide quality and timely nuclear tests and to obtain the 

physical characteristics of the tested nuclear charge, as well as other information stipulated by the test 

program. The State Commission was also responsible for maintaining secrecy of the testing. The 

Commission was staffed by representatives from MINATOM and MOD, and included a scientific director 

who developed the charge, and representatives of associated institutes from MINATOM and other 

agencies. It also included representatives of the organizations who produced the charge and of the 

customer.

The Interagency Commission was responsible for ensuring nuclear test safety. At special meetings of 

this commission, the conditions for conducting the explosion were examined (when conducting 

underground explosions, special attention was given to the issue of containment of radioactive explosion 

by-products under the ground). According to the results of their examination of a specific test design, 

either the selected explosion parameters were deemed permissible, or corrections were added to the 

construction of the underground works and stemming components. At the same time, these Commission 

meetings also developed the requirements for the meteorological situation at the time of the nuclear test.

The Interagency Commission included specialists from various agencies: MOD, MINATOM, USSR 

Academy of Sciences and the Hydrometeorological Service of the USSR. After preparing the appropriate 

conclusions, the possibility of conducting the test was examined at a high government level in the USSR 

Council of Ministers and the CPSU Central Committee. Both commissions began their work two or three 

months before the specific nuclear test. A special role befell the State Commission on the eve of the test. 

Several days before the nuclear test, this commission examined the preparedness of all participating 

services and the state of completion of the special measures for ensuring the test.

17
USGS Open File Report 01-312: Containment of Soviet Underground Nuclear Explosions

The primary members of the Interagency Commission on Ensuring Test Safety participated in all 

meetings of the State Commission, which occurred in the initial test preparatory period. The last meeting 

of the commission occurred on the eve of the nuclear test. This was after the "Dry Run" test, in which the 

preparedness of all services and the operation of all equipment was verified in a mode that was as close 

as possible to conducting the actual test (e.g., the operation of all services and equipment was verified 

minute by minute). At this final meeting of the State Commission, information concerning the 

meteorological situation was heard, and the final decision was taken on the possibility of conducting the 

nuclear test in the given specific situation.

Immediately after a test was conducted, the State Commission collected the operational data, which 

characterized the test results. A commission meeting was convened to look over issues related to the 

achieved charge yield as compared to the planned yield; the results of studying the action of the 

explosion, and the radiation situation in the test location and in the region. At this meeting, a short report 

was made to the government on the results of the test (a more complete report was prepared after 

detailed processing of the obtained data).

TEST 

PERFORMANCE

USSR Council 

of Ministers

Communist Party 

of the Soviet Union

State Commission 

on Nuclear Testing

TEST 

SAFETY

Interagency Commission on 

Seismic and Radiation Safety

Ministry of Medium 

Machine Building

Ministry of 

Defense

Academy 

of Sciences

HydroMeteorological 

Service

Figure 11. Diagram summarizing the authority and interactions of the 

various Soviet organizations participating in the conduct of nuclear 

tests, as described in the text. Note that the Chair of the State 

Commission on nuclear testing would change, depending on the 

purpose of the test. For example, if the experiment was a radiation 

effects test, the Chair would come from the military, while if it was a 

device performance test, the Chair would be from one of the weapons 

laboratories. Also, occasional participating organizations include 

(depending on the test purpose): Ministry of Electronics; Ministry of 

General Machine Building; Ministry of Heavy Machine Building; or 

Ministry of Aviation.

18
USGS Open File Report 01-312: Containment of Soviet Underground Nuclear Explosions

Chapter 2 CONTAINMENT OF UNDERGROUND NUCLEAR TESTS

2.1 What Happens During an Underground Nuclear Explosion

From the point of view of ensuring underground nuclear test containment, it is interesting to examine the 

two main processes which accompany a nuclear explosion in a rock massif: 1) the formation of a zone of 

irreversible deformation of the solid medium (the containment cavity, the zones of buckling/crushing, 

crushing and fracture formation); and 2) the formation of highly compressed radioactive gasses in the 

containment cavity. It should be noted that both these processes occur essentially simultaneously.

Formation of highly compressed gasses in the containment cavity

The process of forming an explosive source during the detonation of a nuclear device is comprised of the 

formation of a cavity, which fills with gaseous by-products at high pressure. Estimates show that at the 

moment when the cavity reaches its maximum size (after roughly 0.1 sec/kt1 '3), the pressure within is 

equal to roughly 150-200 atm, and the temperature is 4000-5000 degrees Celsius. The processes of 

condensation of a portion of the gasses and the mass transfer of substances lead to a situation where 1- 

10 sec/kt1 '3 after the explosion, a dynamic equilibrium of the gaseous mixture is established. At this time, 

the temperature of the gaseous by-products is 1500-2100 degrees Celsius, and the pressure settles to 

the pressure level of the non-condensable gasses.

The overall quantity of non-condensable gasses, M, is determined by the relation: 

M = TI G q

where t] is a coefficient characterizing the gas-forming properties of the rock, G is the specific mass of the 

rock participating in the gas formation, and q is the yield of the explosion. The formation of gas is 

determined by the physical-chemical composition of the rock and is related to the vaporization of rock on 

the wall of the cavity, the melting of the rock with subsequent vaporization of the water contained in it, and 

the thermal decomposition of the minerals. It also results from the strong compression of the rock 

(beyond the cavity) by the shock wave.

Of the gaseous by-products that arise in the process of cavity formation, only the non-condensable 

portion filter through the permeable space of the rock massif. The formation of non-condensable gas 

during the explosion occurs in the zones of vaporization, melting and thermal decomposition of the rock. 

Table 3 presents the numbers characterizing the quantity of vaporized and melted material during a 

nuclear explosion in several rock types. The experiment results indicate the fact that the zone of gas 

release in dense, hard rock has a mass of close to (2-4) x 105 kg/kt, and in alluvium, 7 x 105 kg/kt.

Table 3

Rock Type

Dry granite

Moist tuff (18-20% H20)

Dry tuff

Alluvium

Rock salt

Specific mass of vaporized material 

(in tons per kt yield)

69

72

73

107

150

Specific mass of the melted 

material (in tons per kt yield)

300 +100

500+150

200 -300

650 +50

800

The nature of the gas release depends on the type of rock. In silicate rocks (quartzites, granites, tuffs 

and alluvium), that contain water in the pore spaces, non-condensable gas is represented by water vapor. 

In carbonate rocks (limestones, dolomites, and some types of quartzites), the principal mass of the noncondensable gas is comprised of carbon dioxide, which is released as a result of the thermal 

decomposition of the rock.

19
USGS Open File Report 01-312: Containment of Soviet Underground Nuclear Explosions

The gas temperature in the cavity should be considered to be equal to the melting temperature of the rock 

in silicate type rock (Table 4) and equal to the temperature of the thermal decomposition of the rock in a 

carbonate type rock. (Actually in the case of carbonate rock, a competition occurs between the 

processes of vaporization, melting, and thermal decomposition; nevertheless, the non-condensable 

gasses are represented, mainly by carbon dioxide).

Table 4

Rock Type

Melting Temp., °C

Shale, Porphyrite

1220-1450

Granite

1340-1380

Quartzite, Sandstone

1400-1750

Aleurolite, Argillite

1120-1170

The thermal decomposition of dolomites and limestones occurs at temperatures of 825 to 900 degrees 

Celsius. Calculations confirm the fact that the mass of dolomite, which undergoes thermal decomposition 

during an underground nuclear explosion, is close to 180 tons per kiloton of nuclear charge. The 

temperature of the gasses in the cavity reaches close to 2200 degrees Celsius. As we see, the 

temperature of the non-condensable gasses in the cavity in the case of a carbonate type rock is higher in 

comparison with silicate type rock. This can be explained by the difference between the molecular 

weights of carbon dioxide (u=44) and of water (u=18). In practice, gas formation may occur 

simultaneously as a result of water vaporization, and as a result of the thermal decomposition of the 

minerals. It is namely by this method that it occurs at the Novaya Zemlya and Semipalatinsk test sites.

At NZ, the rock massifs are represented by shales, sandstones and quartziitic sandstones with some 

limestone content. The shales, which are most widespread, have the following mineral composition:

KAL3Si3Oio(OH)2 15-35%

SiO2

Mg3Si4010(OH)2 

FeS2 

Dolomite 

free water

15-25%

10-30%

3-30%

0.1-3%

2-25%

0.05-0.8%.

At the Balapan test area on STS, the rocks are represented by siltstones, sandy tuffs, argillites, 

porphyries and carboniferous shales. As a whole, these rocks contain the following minerals:

Quartettes

Dolomites

Mg3Si205(OH)4

CaAI2Si2Oa

Mg3Si4Oio(OH)2

free water

20-50%

5-15%

1-45%

10-30%

1-20%

0.8-1.2%

The variation in mineralogical compositions is the main feature of the rock at STS and NZ. Practically all 

minerals contain hydroxyl and carbonate groups. As a result of the thermal decomposition of these 

minerals, gasses form: Co2, H 20, S2, H2S and others (along with infusible oxides: SiO2, MgO, AI2O3 and 

others).

As a result of comparative evaluations, it was found that the gas release at the NZ sites as a result of 

thermal decomposition of the shales occurs in a volume of rock massif, which is characterized by a mass 

of roughly 300 tons per kt of nuclear explosion. The equilibrium state of the gas and the cavity is upheld 

in this case due to the water vapor formed as a result of the decomposition of sericite, which appears 

during the moment of highest pressure of the saturated vapors of all the minerals comprising the shale.

20
USGS Open File Report 01-312: Containment of Soviet Underground Nuclear Explosions

To simplify the calculations, it is permissible to consider only carbon dioxide and water as the principal 

components. The molecular weight of the non-condensable gas will be equal, in this case, to:

|a = r\l(r\co2/. Hco2 + TI^O/MWO) 

In general, it is necessary to consider also the presence of the free water in the rock. In this case:

T\ = Tlw + T1H20 + T1C02

where T]w is the specific content (weight) of free water. 

Formation of the zone of irreversible behavior of the rock

The migration of gaseous by-products from an underground nuclear explosion, which, in the final count, 

determines the containment of the underground explosion, occurs along a permeable channel, which 

either existed initially in the rock massif, or was formed as a result of the explosion. As a result of the 

vaporization and melting of the rock at the focus of the explosion, and the subsequent displacement of 

the medium at great distances as a result of the shock and compressional waves, a containment cavity 

forms at the focus of the explosion. It is free from the rock volume, and filled with gaseous materials.

In the area located beyond the cavity, the medium remains solid. However, as a result of the intense 

compression in the explosive wave, the rocks undergo intense changes. Their physical-mechanical 

properties and structure change noticeably. .At greater distances, the rock is damaged due to the 

formation of rather fine pieces (crushing zone). Then, with increased distance from the focus of the 

underground explosion, the size of the pieces are such that one can speak of the formation of new 

fractures in the rock massif.

Thus, the main zones of irreversible behavior of the medium, from the point of view of containment of the 

underground explosion are: the containment cavity, and the zones of rock buckling/crushing, crushing 

and fracture formation (Figures 3 and 4). It is specifically these zones that directly affect the migration of 

gaseous explosion by-products. The possibility of ensuring containment of an underground nuclear 

explosion is determined by the initial parameters of the gaseous explosion by-products in the containment 

cavity and the permeability of the rock massif in the area directly abutting the containment cavity.

Similar investigations into the mechanical state of the rock and rock massif in the vicinity of the underground explosion, which were conducted using special excavations in the rock after the explosion (adits 

and deep boreholes) showed that the parameters of the zone of irreversible behavior of the medium is 

defined by the initial physical-mechanical properties of the rock and of the massif; these are as follows:

Degelen Site

Zone Cavity Rock buckling/crushing Rock crushing Fracture formation

relative 

size, m/kt1 '3 7-10 10-16 20-25 35-40

Balapan Site

Zone Cavity Rock buckling/crushing Rock crushing Fracture formation

relative

size, m/kt1 '3 10-14 14-18 25-30 50 

Increase in 

Massif 

Permeability1 3-8 x . 1.8-4x 1.3-3.8 x 1.27-Sx

Note here that ensuring containment of underground nuclear explosions is based on a prediction of the 

dimensions of the main zones of irreversible deformation of the rock massif during the explosion.

1 For the cavity, the estimated permeability increase is for that of the rock fill resulting from cavity collapse.

21
USGS Open File Report 01-312: Containment of Soviet Underground Nuclear Explosions

2.3 How Nuclear Explosions Remain Contained

Radioactive materials that are produced in a nuclear explosion consist of a rock melt with materials of the 

nuclear device and gaseous products. As the containment (camouflet) cavity expands, a considerable 

fraction of the nuclear material is converted to the solid state as a result of cooling of the melt and 

condensation of some of the gaseous components.

A certain amount of the radioactive products, mostly inert gases, as well as some products of dissociation 

of rocks and water vapor, remains in gaseous form. The nature of gas release depends on the type of 

rock: in rocks of silicate type (quartzites, granites, tuffs, alluvia) that contain water in the free state, the 

uncondensed gas is represented by water vapor, in rocks of carbonate type (limestones, dolomite, some 

types of quartzites), most of the uncondensed gas is carbon dioxide that is released as a result of thermal 

dissociation of rock.

Uncondensed gaseous radioactive products of an underground nuclear explosion that have accumulated 

in the underground cavity following the first instant of the explosion begin to filter through the geological 

medium. There are several factors that contribute to this:

1 - elevated permeability of rocks in the near zone of the explosion;

2 - the presence of tectonic disturbances (faults and fractures) whose permeability is 

also increased by explosive action;

3 - inadequate isolation of the underground excavation (tunnel, borehole).

At the same time, it should be noted that a certain fraction of the uncondensed radioactive gas remains 

underground due to the following factors:

1 - relatively low pressure of explosion products in the containment cavity (while the 

initial pressure is a few hundred MPa, the pressure of uncondensed gases at the 

instant that they begin filtering out of the cavity is on the order of 1-10 atm 

depending on the gas-forming properties of the rocks).

2 - rather high porosity of the rock mass broken by the explosion (volume of voids 

formed is comparable to the volume to which uncondensed radioactive gases 

expand when pressure falls from the initial level to atmospheric);

3 - with appropriate selection of the depth of burial of the device, the layer of ground 

situated above the charge chamber (especially the layer of unbroken rock) is 

good insulating material that prevents propagation of gaseous explosion products 

toward the free surface.

4 - well executed stemming systems (and other measures to isolate underground 

excavations) likewise serve as a good insulator to stop propagation of 

uncondensed gases toward the surface of the ground.

In contrast to soft rocks like tuff, no high-density layer is formed in hard rocks in the vicinity of the 

containment cavity. The region of crushing of hard rocks is in direct contact to the wall of the containment 

cavity. This somewhat decreases the isolating properties of rocks (the absence of an extra barrier in the 

form of a compacted rock layer allows uncondensed gases to filter out into the broken medium in the 

early instants following the explosion).

However, as the filtration front expands, the gas pressure in the permeable space drops rapidly due to 

geometric expansion of the flow, as well as to partial cooling as a result of contact with considerably less 

heated rock. Simple estimates show that if there are no channels for preferred filtration of uncondensed 

radioactive products of the nuclear explosion (for example in spherically symmetric filtration), the entire 

mass of these products fills the pore space of the medium broken up by the blast (Figure 12). Thus, the 

pore space of the broken medium is a reliable reservoir that accumulates radioactive gases.

22
USGS Open File Report 01-312: Containment of Soviet Underground Nuclear Explosions

100

MIM0 (%)

75

50

25

13579 riP0

Figure 12. Relative mass of gaseous products of underground explosion filtered to 

distances exceeding rtRo (M0 is the mass of gases in the containment cavity at the 

initial instant; r and R0 are respectively the distance from the explosion and the 

radius of the containment cavity); 1 calculation for a 2 kt explosion using results 

of measurement of permeability of the rock mass (experiment Dnepr-1); 2-5 

calculation for medium with constant porosity m,%:2 1,3 2,4 4, 5 6.

Of course, everything is a lot more complicated in practice. Actual filtration of explosion products is 

typified by pronounced directionality (uncondensed gases generally filter preferentially toward the free 

surface). Tectonic breaks (tectonic faults and cracks of various scales) make a major contribution to 

delivery of gaseous products to the free surface of the earth. Nevertheless, in property selecting the 

location of the charge chamber and depth of the device, the insulating properties of overlying rocks may 

be used to advantage.

2.4 Selecting Location Depth and Spacing

Reviewing a Test Site Location

To ensure containment of underground nuclear tests, the location of the device is chosen from results of 

a careful study of the geological features of sites. This is supported by continual work of geological field 

parties in the investigation of all sites of proving grounds that are potentially suitable for conducting 

underground nuclear tests. The rock and geological conditions of specific sites are investigated by 

studying experimental boreholes and geophysical measurements made on the surface of rock masses.

From results of studying rock specimens taken from the surface of rock masses and coring of 

experimental boreholes, rock composition and the physical and mechanical properties of rocks are 

determined, including the gas content. The tectonic characteristics of a section are determined from 

results of investigation of outcroppings of rocks and underground excavations that are cut through on 

adjacent sections. The number, rank and extent of tectonic fractures in the rock mass, natural fracturing 

of rocks and thickness of the weathered layer are determined.

23
USGS Open File Report 01-312: Containment of Soviet Underground Nuclear Explosions

Tectonic faults are studied especially carefully. The width of the fault, size of the fault-affected zone, rank 

of the fault and probable mechanical properties of the filler are determined (all of these characteristics are 

more precisely determined after cutting an underground excavation). An estimate is made of the filtration 

properties of tectonic faults, and their possible shifts as a result of blasting effects of various scales.

Based on results of the geological study of a specific section, recommendations are made on location of 

the charge chamber. Following this, options for the planned test are considered with allowance for the 

thickness of the layer of overlying rocks and the specific properties of the rock mass. The yield of the 

device and conditions of setting off the explosion are selected. This is done by planning organizations, 

after consultations with research institutes that work on problems involved in organizing safe underground 

tests.

Results of hydrogeological studies of sites are a very important factor in test safety. Experimental 

boreholes are used to determine the level of subsurface water, intensity of subsurface water flows and 

their direction. Added to these are data from years of hydrogeological observations. The degree of water 

encroachment of the rock mass has a considerable impact, both on the initial parameters of gas formation 

during an underground nuclear explosion, and on the rate of transport of radioactive products of explosion 

with subsurface waters. Data from geophysical studies of the rock mass can reveal anomalous 

inhomogeneities of the structure of rocks and the extent of fracturing of the rock mass as a whole.

In special cases, seismic profiling of surface sections of rocks is done to determine the thickness of the 

weathered layer of rocks and the specific seismic properties of the rock mass at different depths, 

characterizing the degree of fracturing of the medium. With allowance for all data of geological study by 

the design organization, a decision is made on a subterranean excavation (tunnel) for conducting a 

specific test. In the course of cutting the tunnel, a set of measures is carried out to determine the 

properties of rocks on different sections of the tunnel, and especially in the vicinity of location of the 

charge chamber. Rock samples are taken for this purpose and studied under laboratory conditions.

After the tunnel has been cut, careful studies are done on subsurface tectonic faults and fractures, as well 

as on the jointing of the rock mass. Systems of cracks and their parameters are determined. More 

detailed investigations are made of the seismic properties of the rock mass by seismic shooting of the 

mass situated above the tunnel. This is done by recording seismic waves elicited by a series of 

detonations of chemical explosives at several points on the surface of the rock mass. The seismic waves 

are recorded by a group of sensors placed in the tunnel itself. The seismic cross section of the tunnel is 

plotted from the results of seismic shooting.

Results of detailed geological studies, done after excavating the tunnel with allowance for the 

recommended yield of the device and depth of burial, are examined at an interdepartmental commission 

on safety of underground nuclear tests (see section 1.9). Before convening the commission, experts 

make estimates of the dimensions of zones of irreversible behavior of the rock mass, considering 

possible variations in the yield and device.

Selecting Location and Depth

In selecting the depth of burial of nuclear devices for underground testing, two basic conditions are 

considered: 1) guarantee of standards of radiation safety for test participants and citizens of centers of 

population adjacent to the proving grounds, and 2) observance of the requirements of the Moscow Treaty 

of 1963 (Limited Test Ban Treaty) prohibiting radioactive fallout beyond the limits of state borders, or 

more precisely, that the concentration of corresponding radioactive isotopes not exceed global 

background levels in air currents going beyond the limits of the state territory.

It is these conditions that determine the concept of the degree of containment of underground nuclear 

explosions. The aforesaid conditions are met by suitable selection of the depth of burial of nuclear 

devices and appropriate sealing of tunnels and boreholes.

When determining the depth of burial of devices, attention has been given to considerations of possible 

mechanisms of emission of radioactive explosion products into the atmosphere. As has already been

24
USGS Open File Report 01-312: Containment of Soviet Underground Nuclear Explosions

noted previously, the mechanisms of escape of radioactive explosion products into the atmosphere are 

determined by the geological structure of a specific rock mass and the physical and mechanical 

properties of both rocks and rock masses. Thus, the depth of burial of devices are selected with 

allowance for geological conditions at the location where the test is being planned.

The first underground tests of nuclear devices in the USSR were done at the Degelen Mountain Complex 

of Semipalatinsk Test Site (STS). In preparing and conducting these tests (specifically, the first 

underground explosion, in tunnel V-1 (11 October 1961), and the second explosion, in tunnel A-1 (2 

February 1962)), the depth of burial of the device was established from experience studying the 

mechanical action of the large chemical explosions that were detonated in Tuya Muyun Mountain (with 

masses of 190 and 660 metric tons) and the chemical explosion detonated on 5 June 1961 directly in 

Degelen Mountain (with a mass of 600 metric tons of TNT).

In determining the depth of burial of nuclear devices, the usual law of energy scaling was used, in 

accordance with which the depth of the explosion is:

H~q113 (1)

Where H is the depth and q is the energy of the explosion. As a result, the first Soviet nuclear explosion 

was placed in tunnel V-1 at a scaled depth, H/q1 '3, of 100 m/kt1 '3, and the explosion in tunnel A-1 at 110 

m/kt '3. The required conditions of containment were met under these conditions: specifically, the slow 

discharge of radioactive gases (Xe and Cs) into the atmosphere occurred several hours after the 

explosion and no transport of the primary radioactive products (Kr and Sr) beyond the test site 

boundaries.

There were no underground tests in 1963. Tests were renewed in March 1964 under Degelen Mountain 

conditions. Five underground nuclear tests were conducted in 1964. Experience conducting 

underground tests at Degelen Mountain in 1964-1965 showed that use of scaling law (1) to determine the 

depth of burial of charges was not always successful from the standpoint of ensuring containment of 

tests. For example, analysis of experimental data for these two years showed that for some relatively 

high-yield explosions (yields from 10-100 kt) at 60-67 m/kt1 '3 there was no emission of radioactive 

explosion products into the atmosphere (slow discharge of radioactive gases was observed several hours 

or days after the explosion), whereas for lower-yield explosions (q ~ 1 kt), emission of radioactive 

products through ground zero and corresponding fallout of radioactivity along the trail of the cloud was 

observed even for greater values of scaled depth, 67-70 m/kt1 '3.

For this reason, the rules of selecting the depth of the explosion were changed with allowance for 

intensification of the role of gravity of the ground when the scale of the explosion is increased, and the 

law

H = 70q1134

was taken as basic for Degelen Mountain, where H was in meters and q in kt. This relation was 

recommended for devices with yield of less than 200 kt placed in end-boxes of dimensions corresponding 

to an energy density greater than 10~2 kt/m3 and a moisture content in the rock of less than 1%.

In the case of moisture content in rocks of more than 1 %, the relation

H = 70 [(1 + 0.36^11.36)q]1'34 

was used, where r\ is the moisture content of rocks in percent.

All subsequent experience in underground nuclear testing at Degelen Mountain has shown that selection 

of depths of burial of devices with yield on the order of 1 kt in accordance with the aforesaid relations has 

enforced conditions of containment and accordingly has met the requirements of the Limited Test Ban 

Treaty. For devices smaller than 1 kt, depth was set individually for each specific experiment.

25
USGS Open File Report 01-312: Containment of Soviet Underground Nuclear Explosions

OEWOflHAH BHPAEOTKA -

u

BAKyyMHHH EOKC

OB1>EKT 106K

Figure 13. Plan view of tunnel 108k, Degelen test site. It was at this site that a 

nuclear device was left sealed underground, when the Russians abandoned the 

test site in the early 1990s. In 1995, the device was destroyed in place by a 30 

kg high-explosive charge.

Underground tests of nuclear devices in boreholes was started in the USSR in 1966. The first test was 

done on 18 December 1966 on Murzhik site (STS) in hole 101 . At the Balapan test site, the first test was 

done on 19 June 1968 in hole 1053. By this time, considerable experience had been accumulated in 

underground nuclear explosions. It was known from this experience that the depth of burial of the nuclear 

device has to be selected with allowance for geological conditions.

The geological conditions of the Murzhik and Balapan test sites were very complicated, characterized by 

a variety of rocks types, ranging from relatively weak siltstones, shales and argillites to rather strong 

porphyrites, tuff-sandstones and quartzites. Rocks occurred as steeply dipping layers and were 

intersected by numerous tectonic faults of various ranks up to regional. Rocks also typically had a 

considerable moisture content and a high content of gas-forming minerals (from 4% to 18%). The rocks 

are covered on top by Quaternary deposits in the form of loams and sand clay from a few meters to 50- 

100 m thick. Therefore, rather deep placement of devices was settled on from the very beginning of 

nuclear tests at these sites. The relation:

was used for estimates of the depth of burial of devices.

In accordance with this relation, the minimum permissible depth of an explosion was determined for which 

radioactive products of the explosion were not discharged into the atmosphere. As experimental data 

were accumulated, it was proposed that this relation be used for large explosions with yield on the order 

of 100 kt, and for rocks with gas content of less than 6%. In other cases, for devices with yield on the 

order of 10 kt or less, and also when devices were placed in rocks with gas content of more than 6%, the 

depth of the explosion was determined from the relation:

H = 110 [(1 + 0.36n;/3.76;q/w34

On the whole, the relations given for determining depth of underground nuclear explosions in boreholes at 

Semipalatinsk have ensured containment and enforcement of requirements of the Moscow Treaty of 

1963.

2.6 The Containment Evaluation Panel

One of the main stages in determining the level of containment of a planned underground nuclear 

explosion in the USSR was the examination of the explosion design at the Interagency Commission on 

Radiation and Seismic Safety of Nuclear Explosions, which was specially created by the Government of

26
USGS Open File Report 01-312: Containment of Soviet Underground Nuclear Explosions

the USSR. The Commission included representatives from scientific-research organizations of the USSR 

Ministry of Defense, USSR Minatom, and the USSR Academy of Sciences. The main staff of the 

Commission (roughly 25 experts) was named every 3 years and comprised the permanent members of 

the Commission. In particular, from the USSR Academy of Sciences, M.A. Sadovskiy, V.N. Rodionov, 

V.V. Adushkin and A.A. Spivak all served, at various times, as permanent members over a long period. 

When necessary, or when special questions were being examined, the commission also named 

temporarily enlisted experts.

The Chairman of the Commission was the representative from either the USSR MOD or Goskomgidromet 

[the State Committee on Hydrometeorology). At various times the commission was headed by Izrael', 

lu.A.;, Fillipovskiy, V.I.; and Petrov. V.N. The main purpose of the commission was to make a detailed 

examination of the issues related to ensuring safety of personnel and populace when conducting an 

underground test. The commission first heard the report from the chief engineer for test design. Most 

attention was given to the issue of selecting the location for the charge, the depth of the explosion and the 

geological structure of the portion of the rock massif in which the test was planned.

As a rule, the Commission met for a specific test after the underground works were excavated (tunnels or 

boreholes). This was a time when the Commission would have at their disposal the technical 

characteristics of the rock massif at the explosion location (i.e., the properties of the massif and its rock 

components as determined by studying samples taken during the excavation of the underground works). 

When evaluating the possibility of conducting a test, the following factors were taken into consideration:

- the gas-forming properties of the rock at the proposed charge location;

the presence or absence of tectonic disturbances both near the charge emplacement 

location and along the underground works;

the reaction of the tectonic disturbances to explosive action;

the conformity of the location of the first and second stemming to the predicted 

dimensions of the zones of irreversible deformation of the rock and the massif, given 

the planned charge yield and for the case of incomplete actuation;

the conformity of the charge emplacement depth which was suggested by the 

designers according to the specific conditions of conducting the explosion.

The design of the test had to correspond completely to the requirements of the method for determining 

the containment of the underground nuclear explosion. The conclusion to conduct the nuclear test was 

made as a result of discussions concerning the design of the explosion and as a result of examining the 

past experience in conducting underground explosions with similar conditions. When discussing a specific 

design, changes were made if necessary (for example, recommendations to move the charge placement 

location). In this case, the design was examined again after it was redone and after the appropriate 

mining work was completed, which gave additional data on the rock and massif properties.

After the final approval of the design at the Interagency Commission on the Safety of Underground 

Nuclear Testing, the conclusion was presented to the State Commission on Nuclear Testing, which then 

made the decision on the readiness for conducting the test based on the conclusion of the Interagency 

Commission.

2.7 Containing Vertical Shaft Tests

The containment of nuclear explosions conducted in deep boreholes was ensured by employing special 

borehole stemming methods. A plan for a typical borehole prepared for conducting underground nuclear 

tests is shown in Figure 14.

In order to hermetically seal off the nuclear charge, the first section of the borehole, which falls in the 

rock-crushing zone, is filled with rubble. In this section, it is not necessary to fully pack the charge with 

grout, since the rock massif will be similar to rubble after the explosion. At the same time, when filling-in

27
USGS Open File Report 01-312: Containment of Soviet Underground Nuclear Explosions

f t

12-

1

2

-8

Figure 14. Typical borehole plan for 

conducting an underground 

nuclear test: 1- 1420mm 

borehole; 2-1120 mm steel pipe; 

3-1000 mm borehole; 4-168 mm 

casing; 5- cement grout; 6- 89 mm 

casing; 7- rubble; 8- charge; 9- 

unloading device; 10- elevator; 11- 

dynamic device; 12- additional 

plug of rubble.

with rubble, it is possible to cause mechanical damage to 

the charge itself (or the devices leading to it). This may 

also occur when cement grouts solidify (if such grouts are 

used). The remaining section of the borehole is cemented 

fully along its entire depth.

When the borehole is severely flooded, which was 

sometimes the case at the STS Balapan site, often the 

upper section of the borehole for 30-100 m was left as it 

was, full of groundwater. This type of construction, with 

the correctly selected depth for charge emplacement, 

ensured good explosion containment in the majority of 

cases.

2.8 Containing Horizontal Tunnel Tests

When conducting nuclear tests in horizontal underground 

works, the stemming complex consists of several sections 

of stemming, located at various distances from the 

explosion location, and several devices, which ensured 

additional isolation of the explosion (Figures 15).

Equipping Tunnels for Standard Nuclear Tests

In standard nuclear tests (for the purposes of device 

improvement, for studying the physical processes occurring during an explosion or for studying the action of the 

explosion), the stemming complex consisted of a first 

section, located directly at the charge chamber (Fig. 15). 

This stemming section functions to prevent the initial 

pressurized release of explosion by-products into the 

tunnel. The length of this section is determined by a 

calculation wherein the device yield and rock massif 

properties are accounted for, as is the presence of 

tectonic disturbances (faults) of varying scales. As a rule, 

the length of this section is equal-to or greater than the 

radius of the rock-crushing zone for a specific explosion 

yield. The structure of the first stemming section is shown 

in Figure 16. This stemming is composed of concrete 

elements with rubble backfill between them.

The second stemming section is an actuating element, 

that can withstand the excess pressure that is formed in 

the section of the tunnel outside the first stemming section 

as a result of the partial migration of explosion by-products 

from the cavity along the permeable channel of the rock-crushing zone and of the zone of induced massif 

fracturing. The second stemming section is designed for strength relative to the compression wave from 

the explosion and relative to the pressure from the explosion by-products, which penetrate into this tunnel 

section from the cavity. The specific construction of the second stemming section is shown in Figure 16. 

This section is made of concrete "keys" (concrete walls that are not only partitioning but are also 

embedded ("keyed") into the rock massif). A cement grout is pumped in between the concrete keys. The 

method of pouring concrete most often used is wherein the space is filled with different grades of 

concrete.

28
USGS Open File Report 01-312: Containment of Soviet Underground Nuclear Explosions

Figure 15. Typical plan of a tunnel for conducting a nuclear charge test: 1- 

chamber for emplacing the charge; 2- first section of the stemming complex; 3- 

second stemming section; 4- second, additional stemming section; 5- 

hermetically sealing walls; 6- tunnel portal; 7- rock massif surface.

Outer Stemming Section 

1

Inner Stemming Section

\\ \

Figure 16. Stemming Sections. Stemming complex plan: 1- concrete keys; 2- 

crushed rock stemming ; 3- individually-concreted sections; 4- explosion 

chamber. The length of concrete keys along the tunnel is nominally 3 meters, 

and the length of the individually concreted sections is nominally 1- to 2.5 

meters, but these vary with the yield and rock mass conditions.

The cable lines between the explosion chamber and the tunnel portal are placed in special metal boxes 

and are filled in with cement grout in places where the boxes pass through the stemming complexes. 

When this occurs, each cable is fitted with a gas-blocking device, which inhibits the release of gasses 

along the cable.

In order to prevent the venting of gasses from the tunnel in cases where the gas penetrates beyond the 

second stemming section, two hermetic elements are installed in the tunnel section after the first 

stemming. The hermetic elements are partitions, which are made of metal and have special so-called 

hermetic man-ways, specially structured doors, which ensure that the partitions are sealed during the 

explosion, and that personnel have access to the tunnel section located beyond the second stemming for 

dismantling recording equipment and for studying the action of the explosion. When necessary (in nonstandard test conditions), additional elements are installed in the tunnels; these are like an additional, 

second stemming section (see Figure 16), made of concrete buffers and actuating sections, which 

reinforce the tunnel walls.

When the stemming location and the charge depth are correctly selected according to the geological 

conditions, all these measures for hermetically sealing the tunnel prevent the possibility of a dynamic 

release of radioactive explosion by-products out to the ground surface. In such cases, some leakage of 

short-lived inert gasses is permissible in quantities wherein the exposure dose of gamma radiation

29
USGS Open File Report 01-312: Containment of Soviet Underground Nuclear Explosions

beyond the test site boundaries does not exceed the fluctuation range values of the natural radiation 

background.

Equipping tunnels for conducting irradiating experiments

A highly important avenue of research was the study of the damaging factors of irradiation, which 

accompanies a nuclear explosion. Of great interest was the effect of irradiation (neutron, gamma quanta, 

x-ray) on the operability of various-purpose technical equipment, of military technical objects, including a 

nuclear warhead, and biological subjects. The physical irradiation experiments are the most complex and 

potentially dangerous type of nuclear test.

In order to obtain the maximum possible irradiation area, the USSR used the following plan for an 

irradiation experiment. The detonation of the nuclear charge was done so as to create a short-lived 

release of radiation out of the explosive chamber to the ground surface. The equipment and objects 

under study were placed in front of the portal. The irradiation cross-section reached 100 m2. The plan for 

equipping the tunnel for irradiation experiments hardly differed from the tunnels in which the usual tests 

were conducted. However, the necessity of releasing the radiation out of the explosive chamber to the 

ground surface defined several features of the stemming complex.

When conducting irradiation experiments, it is necessary to cut off the radioactive explosion by-products 

after the radiation passes along specially-made Line of Sight (LOS) pipes. Radiation releases occurred 

along small cross-section pipes, with a diameter of 0.4 to 1 m, which represented a special, metal duct. 

This duct passed through the first stemming. The same ducts passed through all the elements of the 

other stemming complexes. That portion of the LOS that was located directly at the explosive chamber 

was constructed so that the aerial shock wave would not collapse it. To some degree, this held back (for 

roughly 0.05 to 0.1 msec) the distribution of the explosion by-products into the remaining LOS section.

To prevent the release of explosion byproducts out to the ground surface, so-called 

explosive doors and fast-acting closures were 

installed where the main stemming was and in 

additional locations. The explosive door was 

used in the tunnel space located directly after 

the first level stemming. Its principal role was 

to close down the LOS pipe. The explosive 

door was a cylindrical charge of chemical 

explosive which encircled the LOS pipe. The 

explosive door closed down the LOS pipe in 

0.8 to 1.4 msec. It should be noted that 

despite the fact that in the majority of cases 

absolute LOS pipe closure was not achieved, 

the use of the explosive door permitted a 

significant reduction in the flow of explosion 

by-products into the space between the first 

and second stemming.

Figure 16. Tunnel entrance at Degelen mountain, 

with supports visible for a large-diameter lineof-sight pipe. Such structures, evacuated, 

were used to direct a beam of radiation to test 

objects located outside of the tunnel complex. The fast-acting closures (as a rule, one or two) 

were installed in the tunnel at a seismically 

safe distance, where the compression wave 

amplitude did not exceed the amplitude of damage of the rock or the structures. The operating time of 

the closures had to be less than the arrival time of the compression wave to the closure location. This 

ensured the stable operation of the fast-acting closure before the arrival of the compression wave 

(seismic signal). The fast-acting closure cut off the radioactive gasses in both situations where the 

gasses were dynamically released into the tunnel in a containment failure, and during filtered seepage of 

the gasses along the tunnel. The fast-acting closures were thick-walled metal structures, which partially 

partitioned the tunnel and fully closed off the tunnel at defined moments of time. The tunnel was closed 

off by firing powder boosters at specifically calculated moments of time.

30
USGS Open File Report 01-312: Containment of Soviet Underground Nuclear Explosions

Figure 17. Structures supporting a test object (a rocket motor) outside of tunnel 

169/2 at Degelen Mountain. In this experiment (4 Oct. 1989), radiation was 

channeled through a flexible bag filled with a special gas, and its crosssection was modified by the crescent-shaped device.

The principal technical characteristics of the fast-acting closures are as follows: 

dimensions of closed-off pipe: 2.55 x 2.55 m 

time from firing to complete closure of the pipe: 43 msec; 

time to close off the pipe: 29 msec; 

dimensions of the casing: 9.2 x 3.3 x 2 m; 

maximum speed of closure shield: 100m/sec.

Falling closures were also used additionally in a number of experiments to close off the tunnel within 1 

sec after the explosion (in order to cut off the radioactive by-products). The falling closure was a thickwalled metal-concrete structure, which closed off the tunnel by falling under the force of gravity.

Additional measures to contain radioactive explosion by-products in the tunnel

In complex nuclear test in tunnels, additional structures were used to close the tunnel in order to localize 

the radioactive explosion by-products in the tunnel. In a series of experiments, a gas release blocking 

system was used. This system was installed at the exit out of the tunnel and was made up of several 

flexible casings, which filled up with high-pressure air immediately after the explosion and provided a 

relatively hermetic seal to the entire tunnel cross-section. This permitted the explosion by-products to be 

held in the tunnel at a low pressure, such that the by-products could filter into this tunnel section through 

migration channels (damaged massif, or tectonic faults). In the case of an accidental release of explosion 

by-products through the tunnel, several experiments used a foaming material, which filled in a section of 

tunnel volume.

31
USGS Open File Report 01-312: Containment of Soviet Underground Nuclear Explosions

2.9 Types of Radiation Releases

The release of radioactive by-products from an underground nuclear explosion to the ground surface can 

occur in several ways. In the most favorable case, when the emplacement depth was correctly selected 

in accordance with the specifics of the geological structure of the rock massif, and when the stemming 

and hermetically-sealing complexes operated successfully, the release of explosion by-products to the 

ground surface may only occur simply as a result of filtration through the rock massif (Figure 18).

Figure 18. Schematic illustration of gas migration through the damaged rock 

massif: 1- underground works; 2- zero room; 3- damage zone radius; 4- spall 

zone; 5- tectonic faults; 6 and 7- first and second stemming.

Indeed, any rock massif has a finite (non-zero) permeability. Thus, if the porosity of the massif is such 

that it is unable to contain the expanding explosion by-products in the space between the containment 

cavity and the free surface, a portion of the by-products (generally very small) can reach the ground 

surface. In this case (Figure 18), the migration path for the by-products out of the cavity lies through the 

damaged-rock zone, which is characterized by an increased permeability, then through the rock massif 

itself and on through the spall damage zone. With correct selection of the depth of emplacement of the 

nuclear charge, the case in which explosion by-products are released through the massif into the 

atmosphere occurs in the absence of conditions that tend to "weight down" the explosion for example, 

when the stemming fails or the actual yield is much smaller than predicted.

In this case, if the rock massif in the vicinity of the explosion is damaged by a tectonic fault (Figure 19), 

the primary migration of explosion by-products toward the ground surface can occur faster as compared 

to the case of filtration through the massif. This is possible when the characteristics of the fault are such 

that its permeability increases as a result of the explosive action, thereby exceeding the permeability of 

the rock massif in the area between the damage zone within the medium and the free surface.

Another case is possible wherein the radioactive explosion by-products end up in the tunnel space 

located between the first and second stemming. In individual cases, this can lead to a primary migration 

of by-products along the tectonic fault intersecting the tunnel in this section (Figure 20). As a rule, the 

pressure of the gaseous explosion by-products in the space between the first and second stemming is not 

great (does not exceed 0.2 to 2 atm). However, considering that the filtration path of the gasses toward 

the free surface in this tunnel section is shorter and the permeability of the tectonic faults as a result of 

the explosion can increase, this case must be considered undesirable. Similar cases of release of 

explosion by-products into the atmosphere can be observed as well in deep borehole explosions.

The last variant of release of explosion by-products into the atmosphere is related to an accidental 

venting through the tunnel portal (Figure 21) or along the borehole.

32
USGS Open File Report 01-312: Containment of Soviet Underground Nuclear Explosions

Figure 19. Illustration of gas release through a tectonic fault: 1- tunnel works; 2- 

zero room; 3- damage zone radius; 4- spall zone; 5- faults; 6 and 7- first and 

second stemming; 8- outer boundary of area in which the gas is moving 

through the damaged rock massif; 9- gas flow through the tectonic fault.

Figure 20. Illustration of gas release through a tectonic fault that intersects the 

tunnel between the first and second stemming sections: 1- tunnel works; 2- 

zero room; 3- damage zone radius; 4- spall zone; 5- tectonic faults; 6 and 7- first 

and second stemming; 9- gas flow through the tectonic fault.

Figure 21. Illustration of gas release through the tunnel by migration around the 

stemming plugs: 1- tunnel works; 2- zero room; 3- damage zone radius; 4- spall 

zone; 5- tectonic faults; 6 and 7- first and second stemming; 9- gas flow through 

the tunnel and surrounding rock.

33
USGS Open File Report 01-312: Containment of Soviet Underground Nuclear Explosions

2.10 Record of Containment

The degree of containment of a 

specific underground test is 

determined from results of 

instrumental observations of the 

radiation environment at the test site. 

For this purpose, the intensity of 

radioactive emission is recorded at the 

time of the explosion, and for several 

hours thereafter, by sensors placed on 

the surface of the rock over the tunnel 

or bore hole. Radiation observations 

are also made from the air by using a 

helicopter and specially equipped 

flying laboratory.

On the day following the explosion, a 

radiation survey is done at the mouth 

of the tunnel and on the section of the 

emplacement tunnel situated after the 

second stemming. At the same time, 

the radiation environment on the 

surface of the rock mass is studied in 

detail, and points of emission of 

radioactive gases into the atmosphere 

are determined. Channels of 

preferential migration of gases through 

the broken rock mass or through 

tectonic faults are established from the 

intensity of gamma radiation.

Statistics show that predictions by the 

interdepartmental commission of the 

level of containment of tests are 

generally confirmed. Given below are 

basic statistics of emission of products 

into the atmosphere when conducting 

tests at Semipalatinsk and Novaya 

Zemlya Test Sites.

Total number of explosions studied in detail

Discharge into the atmosphere through ground zero 

Discharge of products through the excavation 

Discharge of products through tectonic faults 

Very faint signs of radiation ("full containment")

Figure 22. Radioactive gas sampling equipment used at 

a tunnel in Degelen mountain by the Russian Institute 

for Radiation Safety. The person in the photograph is 

Dr. Yuri Dubasov of the Khlopin Radium Institute, St. 

Petersburg.

123

73

36

14

NZTS 

42 

24

1

3 

14

It should be noted here that radioactive gases do get into the atmosphere in small amounts. Most of the 

products of explosion settle out in the containment cavity and in the section of the excavation before the 

first stemming.

34
USGS Open File Report 01-312: Containment of Soviet Underground Nuclear Explosions

2.11 "Tired Mountain" Syndrome

The underground detonation of nuclear explosions considerably alters the properties of the rock mass. 

Fracturing and rock breakage are extensive and markedly increased, and permeability is appreciably 

increased both in the rock mass itself and along isolated tectonic faults. For example, in the Dnepr-1 

blast, the permeability of the rock mass was increased several times (near the containment cavity, 

permeability was increased by a factor of 40). The permeability of tectonic faults was increased by a 

factor of 2-12 on sections situated at a relative distance of up to 150 m/kt1'3 from the site of the explosion.

From results of engineering geology and geophysical research done to study the effect of tunnel 

explosions on the rock mass, the following zones have been distinguished (illustrated in Figures 3, 4; 

quantitative characteristics are given in Figures 24-27).

 The cavity usually has an ellipsoidal shape that is asymmetric relative to the center with average 

relative size of 7-14 m/kt1'3 depending on the strength properties of rocks.

 The collapse column is formed above the cavity, as a result of caving of broken rock situated above 

the confined underground explosion. The medium is characterized by a loosened rock mass with 

cleavage dimension close to that observed in the main zones of irreversible deformation of the 

medium. The height of the collapse column is 40-110 m. The dimension of fragmental material 

ranges from clay particles in the lower part to 10-15 cm or more on the outer boundary. The hydraulic 

conductivity of the rock mass in the collapse column may go as high as 200 Darcy. The porosity of 

fragmental material in the collapse column reaches 25%. Formation velocities are 2270 m/s.

 The dome of stable equilibrium (or "chimney") is formed in contained underground explosions, and is 

characterized by the fundamental layering of rocks above the void over the collapse column. Its 

existence is determined mainly from the falling of the drill bit during reentry.

 The zone of crushing is in direct contact with the cavity and stretches to distances of 12-14 m/kt1'3 

from the center of the explosion (relative thickness of up to 3.7 m/kt1'3'. Rocks in this zone are 

pulverized, and readily break down to a sandy material under slight mechanical action. The strength 

and elastic properties of the rock are drastically reduced. The total porosity is 2-6 times the initial 

level, and the permeability of the rock is dramatically increased, to 0.4-1.13 Darcy.

 The zone of elastic deformation can be traced to distances as far as 14-70 m/kt1'3 . In this zone, in 

addition to displacements of blocks of rock, a relatively intense crushing of the rock proper is 

observed, along with the formation of new fractures (Figure 27). Within the confines of this zone we 

can distinguish sub-zones of fracturing (out to distances of 20-25 m/kt1 '3) and new cracks.

In the sub-zone of fracturing, the rock mass is fractured by new and reactivated natural cracks, 

and composed of blocks with individual dimensions from 2-3 to 5-7 cm. The total porosity of the 

rock mass reaches 10.5 %. The porosity of the rock mass is increased by a factor of 2-3 as 

compared with the initial level. The coefficient of filtration of the rock mass averages from 0.25 to 

0.2 m/day, based on experimental pumping data.

-In the sub-zone of new cracks (to distances of 35-40 m/kt1 '3), the total number of cracks 

increases by a factor of 2-4. The rock mass acquires a pronounced block structure. The strength 

of the rock gradually increases from the center of the explosion toward the periphery, and elastic 

properties also become near natural.

-Observed farther out is a zone of intense cracking that extends to relative distances of 50-55 

m/kt1 '3. This zone is characterized by occurrence of new cracks along natural microcracks, 

structural elements of rocks and zones of mechanical weakening. Strength properties of the rock 

are reduced by 20-30%, acoustic properties by 10-25%. The hydraulic conductivity of the 

medium is increased by a factor of as much as 1000, the greatest increase being noted along the

35
USGS Open File Report 01-312: Containment of Soviet Underground Nuclear Explosions

3.

3.

strike of the rocks. Formation of secondary cracks in this zone is observed in the direction of 

weakened tectonic zones. The number of cracks estimated from coring ranges from 4-6 per 

running meter to innumerable. The water permeability of the rocks is considerable, ranging from 

0.001 to 10 m/day. The total porosity of the rock mass according to geological data is 10-25%.

-The zone of block cracking (zone of renewed cracks) is symmetric in shape, copying the zone of 

intense cracking in general outline. The radius of the zone in the plan view reaches 65-70 

m/kt1'3. The strength properties of rocks in the zone are reduced by 10-15%, and acoustic 

properties by 5-15%. The hydraulic conductivity of the medium ranges from 0.05 to 10 D.

Farther out, we can distinguish a zone of inelastic deformations of rock mass (situated at distances to 

120-130 m/kt1'3, and in isolated directions may reach 150 m/kt1'3). In this distance range, only 

occasional new cracks are encountered. Fissure opening is greatest for gently sloping cracks, while 

individual cessations, chips and displacements of blocks are observed along steep cracks. The width 

of fissure opening is more often 2-10 mm, and in the most weakened zones 10-50 mm. The 

velocity of longitudinal waves in the rock mass is 5-10% less than the initial level. Permeability is 

near natural. In the region continuous with the outer boundary of the zone of irreversible behavior of 

rocks there is a ubiquitous sub-zone of reactivated cracks (at 50-60 m/kt1'3).

Zone of local inelastic deformations (to distances of 200-220 m/kt1'3). 

deformations are instrumentally observed on structural fractures.

In this zone, inelastic

Zones of spelling fracture are formed in numerous underground explosions on the interface of media 

with differing acoustic impedance. On the free surface, spalling fractures are observed to occur at 

epicentral distances of 100-200 m/kt1 '3 (and, in isolated cases, out to 1000 m/kt1 '3). The depth of 

spalling fractures is determined by the specific structure of the rock mass at the location of the 

explosion (presence of tectonic fractures and other boundaries between rocks of different material 

composition) and is 10-32 m/kt1'3.

0.8 

0.6

^X 0.4

U

0

-0.2

0 250 

Scaled Distance,

500 

m/kt 1/s

Figure 24. Relative strength, C, of rock samples taken at different 

scaled distances rlq (q - yield) from the explosion, for tunneltype emplacements: 1 8 Dec 67; 2 23 May 68; 3 30 Dec 

71; 4 Dnepr-1; 5 16 Dec 74; 6 15 Apr 84; 7 22 Apr 88.

36
USGS Open File Report 01-312: Containment of Soviet Underground Nuclear Explosions

4. The zone of deformation of the free surface is generally represented by formation of residual cracks 

in the rock mass. In some experiments, this zone is characterized by upheaval of the rock mass, 

often with formation of a subsidence crater in the central part. The relative radius of the zone of rock 

upheaval is 60-140 m/kt1'3. The height of the upheaval mound is 0.7-2 m/kt1 '3.

10 o -1 n -2 A -3 A -4 O -5 -6 * -7

<J "S. 

<J

0.1

0.01

50

Scaled Distance, m/kt

100

7/3

Fig. 25. Ratio of longitudinal velocity of wave propagation, 

C, to its initial value, C0. Data from experiments: 1 8 

Dec 67; 2 23 May 68; 3 30 Dec 71; 4 Dnepr-1; 

5 16 Dec 74; 6 15 Apr 84; 7 22 Apr 88.

10

o -1 n -2 A -3 A -4 o -5 -6 * -7

i' 1

0.1

0.01

;° i& «o

ft0 20 .40 60 

Scaled Distance, m/kt 7/3

Fig. 26. Relative change in velocity of propagation of 

longitudinal (p-) waves in rock mass after explosion; 

experiments: 1 8 Dec 67; 2 15 Apr 84; 3 17 Jul 87; 4 

 23Nov88.

37
USGS Open File Report 01-312: Containment of Soviet Underground Nuclear Explosions

100 1000

Scaled Distance, m/kt 1/3

Fig. 27. Average fracturing of the rock mass following the 

explosion: 1 8 Dec 67; 2 23 May 68; 3 Dnepr-1; 4 

15 Apr 84; 5 22 Apr 88

These changes in properties of rocks and rock masses in the vicinity of previously conducted 

underground explosions impose certain requirements on selection of a location for conducting 

underground tests. The location of a new test must be chosen such that zones of increased fracturing of 

the rock mass from previously conducted explosions do not intersect with the planned explosion. 

However, even with such a site selection, the new test is not always fully contained. For example, in the 

case of emplacement in Degelen tunnel 113 (16 Feb 73), leakage of gaseous products was observed 

through ground zero of tunnel 510, where a test had been conducted previously (28 Jun 70). A similar 

phenomenon was observed at the Novaya Zemlya test site, where the gaseous products of an explosion 

in tunnel A-3 (7 Nov. 68) escaped into the atmosphere through an adjacent tunnel (A-8) in the same rock 

mass. In the subsequent test in tunnel A-8, on 27 Sep 71, allowances were made for the nearby location 

of tunnel A-3.

2.12 Statistics of the Containment History of Soviet Tests

As detailed in Chapter 1, a total of 363 underground nuclear explosions were conducted at the 

Semipalatinsk test site more than 70% of the total number of underground tests conducted by the 

USSR. The first underground nuclear tests at Semipalatinsk were conducted in tunnels within Degelen 

mountain, where a total of 225 underground nuclear explosions were conducted between 1961 and 1989.

A summary of the record of containment of underground nuclear tests at the Semipalatinsk test site is 

available in Gorin et al (1993), who characterized containment using the following terminology:

38
USGS Open File Report 01-312: Containment of Soviet Underground Nuclear Explosions

WG - Explosion with ejection of soil; accompanied by the destruction and movement of 

rock in the epicentral zone and the escape of radioactive by-products into the 

atmosphere in aerosol and gaseous phases; an ejection crater forms at the surface.

VKP - Fully contained explosion; accompanied by the formation of an underground cavity 

with corresponding compaction, crushing and fracturing of the rock around it, but the rock 

chimney prevents the escape or leakage of gaseous by-products into the atmosphere.

VNK (RIG) - Incompletely contained explosion; accompanied by the joining of the fracture 

zone and spalling damage to the earth's surface within the epicentral zone of the 

explosion, with insignificant ventilation into the atmosphere, as a rule, of short-lived 

radionuclides - inert gases (RIG): 85Kr (T1/2 = 4.5 hrs, where T1'2 is the half life of the 

radionuclide); 87Kr(T175 = 76.3 min), 8BKr(T1/2 = 2.84 hrs), 131Xe (T1/2 = 11.9 days), 133Xe 

(T1/2 = 5.2 days, 133mXe (T1/2 = 2.2 days), l35Xe (T1/2 = 9.09 hrs), ^ 35mXe (T1/2 = 15.3 min), 

l38Xe(T1/2 = 14.17min);

VNK (NRS) - Incompletely contained explosion, with an irregular radiation situation 

(MRS), accompanied by early and pressurized dynamic release into the atmosphere of 

explosion by-products in the gas- and pressure-forming phase, caused by a random 

failure of the normal process of conducting a test or by unforeseen consequences of its 

design.

Statistically, Gorin et al (op c/f) presented the containment record for Semipalatinsk underground 

explosions as follows:

50% VKP

49% VNK (RIG), including 4% VNK (NRS)

1% VVG

emphasizing that only one test resulted in identifiable amounts of radioactive fallout beyond the 

boundaries of the former USSR. This was the test "Shagan" (January 15, 1965, characterized as WG), 

which was conducted to develop nuclear-explosion technologies for creating artificial reservoirs by rock 

mass excavation. The remaining explosions therefore fulfilled the requirements of the Limited Test Ban 

Treaty for the criterion of "radioactive fallout".

Experience from the observation of the radiation consequences of these explosions has shown that the 

time of emergence of radioactive gases for most of the explosions in Degelen tunnels ranged from tens of 

minutes to several hours or days. Such a situation is owing to the extremely low gas-forming properties 

of the granites and quartzite porphyries comprising the main rock mass at Degelen. These are silicate 

rocks, with a mineral composition is dominated by quartz (20-40%), feldspar (60-70%) and plagioclase 

(15-25%). The gas-forming properties of these rocks are due solely to the content of moisture that is in 

pores and cracks of the rock mass in its natural state, and is generally low, ranging from 0.03 to 1.7%. In 

most experiments, the moisture content was 0.1-1%, and the excess pressure from water vapor in the 

shot cavity after condensation of rock vaporized by the nuclear explosion reached 1.2 to 3 atmospheres.

Sometimes when the moisture content in the rock increased to 1.5-2% in the spring, the water vapor 

pressure increased to 5-10 atm. Under such conditions, despite the small size of the shot cavity, the 

elevated permeability of fracture zones and the opening of tectonic fractures, there was no pressurized 

discharge of radioactive gases into the atmosphere. In many cases, the excess water vapor pressure 

was easily accommodated and condensed in cracks and pores formed by the explosion. Pressurized 

discharge of gases was also blocked by a melt with considerable mass of 300-400 metric tons per kt 

formed on the walls of the cavity and filling cracks near it.

Nevertheless, the time of emergence of radioactivity was considerably influenced by the ratio of depth of 

charge, W, to the cube root of yield of the device M//g1'3 (i.e., the normalized or "scaled" depth). The fact 

is that, in the range of Wlq113 = 55-80 m/kt1'3 , in the region of an epicenter on the slope of a hill, a spalling 

crater was formed, reducing the thickness of the rock mass over the device. For example, at a scaled 

depth (Wlqw) of 55-70 m/kt1'3 the dimensions of the spalling crater were appreciable: radius R = (0.3-

39
USGS Open File Report 01-312: Containment of Soviet Underground Nuclear Explosions.

0.4)Wand depth H = (0.15-0.2) W. The table below gives examples of explosions under such conditions, 

and shows the time t0 of emergence of radioactive gases into the atmosphere.

Tunnel

Rock

Wlqw, m/kt1'3

TI, %

to

E-1

Granite

59

0

24 h

13

Quartz 

Porphyrites

61

0.6

12min

A-5

Granite

62

1.4

1.5 h

V-2

Granite

65

1.0

9min

17

Granite

67

0.3

3.5 h

1

Quartz 

Porphyrites

68

0.8

4.1 h

A-p

Granite

68.5

0.1

1 h

11

Granite

68

0.5

8h

When the normalized depth of explosions was in a range of 7Q-80 m/kt , the size of the spading crater 

was reduced: radius (0.15-0.3)W, depth (0.07-0.15) W. The table below gives examples of explosions 

under such conditions, and shows times of emergence of radioactive gases into the atmosphere.

Tunnel

Rock

Wlqm

m/kt1 '3

n,%

to

Z-5

Quartzite 

porphyries

70

0.12

14 h

14

Granite

70.5

0.6

2.5 h

Zh-3

Granite

72

0.8

3.3 h

Zh-1

Granite

72

0.2

3.5 h

19

Granite

72

0.6

5h

Z-1

Quartzite 

porphyries

74

0.1

18h

And finally, in explosions with depth of charge placement greater than 80 m/kt1 , no spalling crater was 

formed. Times to of emergence of radioactive gases under these conditions are given below for some 

explosions at the Degelen test site.

Tunnel

Rock

Wg1 '3, m/kt10

TI, %

to

A-4

Quartzite 

porphyries

87

1.2

130 h

A

Granite

91

1.7

30 h

Zh-2

Granite

92

0.8

Several days

A-3

Granite

93.5

1.2

14 h

V-1

Granite

97

1.0

3.5 h

Z-3

Quartzite 

porphyries

133

1.6

18 h

The data presented show that as the normalized depth of explosion increased, so did the time of 

emergence of radioactive gases as a whole, and with the exception of a few explosions conducted during 

the early years of testing at depths of 55-65 m/kt1 '3, it was hours or days.

Consequently, the excess pressure of water vapor in the shot cavity was insufficient for pressurized flow, 

and radioactive gases escaped by the mechanism of thermal diffusion. In such a situation, slow 

displacement of warm gases upward through cracks in the rock mass was also aided by a "furnace effect" 

due to the difference in atmospheric pressure on the level of the tunnel and the upper section of the 

slope. In many cases, emergence of radioactive gases into the atmosphere was due to a change of 

atmospheric pressure. Let us also note that for times of emergence of gases of less than 1-3 hours, 

radioactivity in most explosions first appeared at the epicenter of the explosion on the slope. For later 

times of emergence, the first occurrence of radioactivity was noted at the mouth of the tunnel, and later in 

the region of the epicenter as well.

To make the picture complete, we note that for some nuclear explosions in tunnels of Degelen site, earlier 

emergence of radioactive gases into the atmosphere was recorded (t0 < 3.5 min). Such a situation 

occurred in 5 to 7 explosions (e.g., A-8sh, A-6sh, 11-p, 608-p and others). These were mainly low-yield

40
USGS Open File Report 01-312: Containment of Soviet Underground Nuclear Explosions

explosions, and were "repeat" shots; i.e., conducted within previously used tunnels of short length. The 

absolute depth of burial of the device was therefore also relatively shallow.

Beginning in 1965, underground nuclear explosions at STS started being conducted at Murzhik and 

Balapan sites. In all, 138 underground nuclear tests were conducted in the period of 1965-1989 in STS 

holes. Of these, 5 were under a program of peaceful explosions, including with formation of ejecta 

craters, 21 tests in holes at the Murzhik site, and 112 at Balapan.

The Balapan test site is situated in the eastern portion of the STS, and occupies an area of roughly 1000 

km2 . It is a flat plain with absolute elevations ranging from 240 to 350 m. Geologically, the structure of 

Balapan site is fairly complicated: the stratigraphic cross section is represented by faulted and 

metamorphosed volcanic-sedimentary layers in the form of alternating banks intersected by sub-vertical 

tectonic fractures of various orders. These folded structures are covered by sand-clay sediments, 

ranging in thickness from 3-10 m to 80-100 m.

The table below gives data of investigation of the mineralogical composition (in percent by weight) of 

sandstone and siltstone rocks taken from holes 101 and 1003 at the depth of charge placement.

Test Location

Hole 101

Hole 1003

Rock

Sandstone

Siltstone

T!

12.8

5.4

T|C02

6.0

3.6

11H20

6.8

1.8

SiO2

48.6

70.7

MgO

23.2

8.4

AI203

7.0

8.5

CaO

8.4

6.7

In this table, the quantity TJ denotes the total gas content of the rock, r\Co2 is the fraction of carbon dioxide 

that is formed, and TJHZO is the fraction of water vapor formed from minerals of the rock.

With respect to the time of the beginning of emergence of radioactive products of the explosion into the 

atmosphere and corresponding radiation effects, all explosions in holes can be divided into three groups.

 Early escape of radioactive gases into the atmosphere ranging from 10 s to 20 min was 

recorded in 30 borehole explosions. The normalized depth of burial of the device in this 

group ranged very widely, from 70 to 960 m/kt1 '3. The total gas content of the rocks where 

the nuclear devices were placed ranged from 4.5% to 18%.

This group included 4 containment failure "accidents" with very early time of emergence: an 

explosion in hole 1204 (at Wlq113 = 72 m/kt1 '3 there was a gas breakthrough of the dome at 

the 12th second) and an explosion in hole 1007 (at Wlq =118 m/kt1 '3 there was a gas 

breakthrough of the dome at the 20th second and ignition of gases in the atmosphere), and 

also explosions in holes 1301 and 1069 where the stemming and casing were blown out at

Wlq = 364 m/kt 1 '3 and W/g1 '3 = 450 m/kt 

dislodging explosions: in hole 101 at Wlq m/kt1 '3

respectively. Also included in this group are two

1/3 = 50.7 m/kt1 '3 and in hole 125 at Wlq1 '3 = 56.2

In the other 24 shots of this group, radioactive gases escaped through man-made breaks 

produced during preparation of the explosions: through sampling ways, through the tubingcasing annulus and intercable space, through the emplacement and core holes.

Later escape of radioactive gases ranging from 25 to 60 minutes was observed in 40 

explosions, from 1 hour to 5 hours in 30 explosions, and from 5 hours to 25 hours in 10 

explosions. The normalized depth of explosions of this group also ranged over wide limits 

(from 88 to 236 m/kt1/3), and the gas content of the rock was 2.6-14.4%.

With respect to these indices, the conditions of conducting explosions were practically the 

same as for the preceding group. In this most numerous group of 80 hole shots, radioactive 

gases propagated for a rather long time inside the rock mass through cracks and gaps 

between blocks without encountering direct channels of exit to the atmosphere.

41
USGS Open File Report 01-312: Containment of Soviet Underground Nuclear Explosions

As a result, the radiation consequences of these explosions could be minimized, and 

conditions of radiation containment could be observed (absence of propagation of radioactive 

products beyond national territorial limits).

Clearly, in explosions of this group the movement of gases in the rock mass was of filtration 

type, and occurred under the action of excess pressure in the shot cavity. The said later 

escape of gases was usually observed over a rather wide region of the epicentral zone, 

sometimes after formation of the cave-in column, and sometimes through the bottom of the 

subsidence crater (for example, hole 1066). In some explosions, on the concluding stage of 

the filtration process, gas escaped into the atmosphere through sites of location of core holes 

or research wells.

 In the third group of 23 explosions, there was no emission of radioactivity into the 

atmosphere. The normalized depth of explosions of this group ranged widely: from 96 to 

225 m/kt1 '3, and the gas content of host rock reached 4-12%. With respect to these indices, 

the explosions of this group were practically the same as for the first and second groups, and 

are of little help in explaining the absence of gas escape into the atmosphere.

In our opinion, the reason that gases do not escape into the atmosphere in this group of 

explosion is the sealing action of the upper sand-clay layer, along with a high-quality 

stemming system and the sealing of other components in the epicentral zone. Indeed, the 

conditions of conducting these explosions differ only in terms of the thickness of a 

considerable layer of drift sediments, ranging from 25 to 90 m. For the explosions with 

escape of radioactive products into the atmosphere, the thickness of the drift was 3-30 m, 

and in only 10 shots was this layer 40-70 m thick. It is probable that the stemming was not 

of high quality in these detonations.

Thus, analysis of the specifics of propagation of radioactive gases in borehole shots at Balapan site has 

shown that geological factors play an significant role in the evolution of radiation effects following an 

explosion. For example, even at a considerable scaled depth of burial (more than 100-150 m/kt1 '3), under 

conditions of rocks with high gas-forming properties and complex geological structure of the rock mass, 

escape of radioactive gases into the atmosphere may not be avoided.

Figure 28. Satellite photograph of a nuclear test 

site at Balapan (left) and an enlarged detail of 

the borehole test area. Light lines are dirt 

roads to the site.

42
USGS Open File Report 01-312: Containment of Soviet Underground Nuclear Explosions

Containment of underground nuclear explosions at the Novaya Zemlya test sites was especially 

problematic. This was due initially due to the presence of carbonate rocks in the stratigraphic section 

(resulting in large volumes of non-condensable gasses. However, even when carbonate rocks were 

avoided (for tests at Matochkin Shar), the rock still included a significant amount of water, including 

intragranular water. The following table summarizes the major releases (over 1000 Ci) for underground 

nuclear tests on Novaya Zemlya (data taken from Andrianovand Bazhenov, 1992).

Test No.

A7.A9

A1.A2

A6

A26

A16

B

A12

A3

A11

G

A7P

A24

A37A

A37

Date

14-Oct-69

27-Oct-66

14-0ct-70

25-Oct-84

28-Aug-72

25-Oct-64

21-Oct-75

07-Nov-68

29-Aug-74

18-Sep-64

09-Oct-77

08-May-88

02-Sep-87

11-Oct-82

release (Ci)

large

10,000,000

2,000,000

1,081,081

1,000.000

1,000,000

297,297

10,000

4,865

3,784

2,973

1,081

1,000

1.000

dose rate note

» 200 R/h significant vent

7 R/h megaton class,

250 R/h megaton class

500 R/h

100 R/h megaton class

1.5 R/h low yield

250 R/h megaton class

5 R/h

< 3 R/h megaton class

2 R/h low yield

1000 R/h at adit

<1 R/h

> 500 R/h significant vent

0.25 R/h

2.13 A Few Exam pies

Presented below are a few examples typical of the majority of underground nuclear explosions in which 

radiation consequences have met safety standards.

Tunnel 215. Deqeten Test Site (Semioalatinsk)

The explosion was conducted on 30 May 1983. The tunnel is cut in a quartz porphyry rock mass. 

Length of the tunnel is 780 m. Two nuclear devices with total yield of about 20 kt were detonated 

in the tunnel. The depth of emplacement of the devices was at 245 m and 180 m, with slant 

depths (line of least resistance, or LLR) of 221 m and 136 m respectively. Inside the tunnel, 

numerous tectonic cracks and faults opened along its entire length. Angles of dip of these 

fractures ranged from 40 to 80°. Several faults were rather large, having a width of 10-50 cm, 

and were filled with small-block material. Smaller faults 1-3 cm thick were cemented with 

frictionally produced kaolinite.

External manifestations of mechanical action of the underground explosion were characterized by 

an initial rate of elevation of the surface at ground zero of 11.5 m/s and height of elevation of the 

dome of 7-8 m. At isolated spots the height of ejecta was 15-20 m. Movement of individual large 

blocks could be clearly seen. The relative displacement of these blocks in the tunnel was 0.2-0.3 

mm, and on the surface of the rock mass, displacements at points of emergence of large faults 

measured from 2-3 cm to 6-10 cm.

In an explosion in tunnel 215, instrumental observations were made of the movement of 

radioactive products through the tunnel and their emergence into the atmosphere. The dynamics 

of movement of radioactive products through the tunnel was as follows: radioactive products 

penetrated through the first section of the stemming system within 10s after detonation, and were

43
USGS Open File Report 01-312: Containment of Soviet Underground Nuclear Explosions

recorded at a level of 10,000 roentgens per hour. Within 30 s, radioactive products were 

recorded beyond the second section of the stemming with level reaching approximately 10 

roentgens per hour. Radioactivity showed up within 50 s beyond the first pressure wall at a level 

of less than 0.1 R/h. Radioactive products did not reach the mouth of the tunnel.

Thus, levels of radioactivity were reduced by 3-4 orders of magnitude after filtering through each 

component of the stemming system. In the region of the epicenter, radioactive gases were 

recorded within 2 hours after the explosion with maximum levels reaching 0.1-1 mR/h.

Tunnel K-85, Deaelen Test Site (Semipalatinsk)

The explosion was conducted on 16 October 1987. The tunnel is cut in heavily fractured quartz 

porphyry. Length of the tunnel is 210 m. There are 10 tectonic faults lengthwise of the tunnel, of 

which the two closest to the mouth of the tunnel are 10 cm and 1.5 m thick, the other 8 ranging in 

thickness from 0.5 to 1-2 cm. The filler is frictionally produced kaolinite. Yield of the explosion 

was roughly 1 kt, LLR 82 m.

Light-spot fiducial points were placed in the region of ground zero to record the initial rate of 

elevation of the free surface. The initial rate of elevation of the dome at the epicenter was 25 mis. 

The maximum height of elevation of the dome at the epicenter was about 30 m. The dimension 

of the dome along the slope was roughly 150 m.

The epicentral zone of the blast was heavily fractured. A subsidence crater was formed. A 

mainline crack was formed in the lower part of the slope from 0.5 to 1 m wide and as long as 200 

m. Inside the tunnel at a distance of roughly 70 m from the mouth there was a bend in the rails 

and cable duct, and it was above this location that the said mainline crack appeared on the slope.

Radioactivity sensors were placed along the tunnel. Radioactivity levels of about 1000 R/h were 

recorded near the first section of the stemming. Near the pressure wall tens of R/h, and at the 

mouth of the tunnl units. A radiation service helicopter flying at an altitude of 300-400 m 

around a circle with radius of 1.5-2 km recorded radioactivity of approximately 500 ^R/h at 72 s in 

the direction of wind blowing at 3.5 m/s.

This level of radioactivity persisted with slight fluctuations for about 10 minutes. At the tenth 

minute, the radioactive level began to rise in the area near the mouth of the tunnel. A 

considerable increase in the level of radioactivity (up to 100 mR/h) was recorded by the helicopter 

at the 15th minute.

Hole 1087. Balaoan Test Site (Semipalatinsk)

The shot was conducted on 12 October 1980. Hole 1087 is situated 3.5 km to the north of manmade Lake Shagan produced by a cratering detonation in hole 1004. Two devices with total yield 

of 100 kt were detonated in the hole. The devices were placed at depths of 440 and 510 m. 

Emplacement of the upper device was in tuffaceous-sandstones, and the lower device in flinty 

siltstones. The density of rocks around the devices was 2650-2700 kg/m3, and the velocity of 

longitudinal waves was 4.6-5.1 km/s. Capping the rock mass was a clay layer about 50 m thick.

Under the action of the explosion, the initial rate of rise of the surface was 10 m/s. The outlines of 

the raised dome were uneven, and there was an abundance of vertical jets. The maximum height 

of the main mass of the dome was 10-15 m. Isolated jets rose above the dome as high as 20 m. 

After the dome had settled, rock upheaval was formed over an extensive area with radius of 

roughly 1 km. A mound about 1 m high and 400 m in radius appeared in the epicentral area.

A subsidence crater 0.6 m deep and 150 m in radius was formed in turn in the center of the

mound. Escape of radioactive gases into the atmosphere was recorded within 66 minutes. The

. gas escaped through cracks in the upheaval mound and inside the subsidence crater. The

measured level of radioactivity reached about 10 mR/h. The duration of active discharge of

44
USGS Open File Report 01-312: Containment of Soviet Underground Nuclear Explosions

radioactive gases was 1 hour and 15 minutes. Within 24 hours, radioactivity in the epicentral 

zone was roughly

Hole 1066. Balaoan Test Site (Semipalatinsk)

The shot was conducted on 23 July 1973. A nuclear device with yield of 150 kt was detonated at 

a depth of 465 m. The charge emplacement was in granites with inclusions of biotite. Density of 

the rock was 2630 kg/m3, porosity 2.3%, velocity of longitudinal waves 5.14 km/s. Gas-forming 

properties of the rock with respect to weight were 3.66%, including moisture content on a level of 

0.3-0.5%. The rock mass was covered over by a layer of loam drifts 13m thick at the epicenter.

From results of high-speed cinematography the initial rate of rise of the free surface was 

measured at 21.2 m/s. The maximum height of rise of the dome at ground zero was 19 m. 

Isolated peak-like ejecta 5-10 m high could be seen in the epicentral part of the dome. A dust 

cloud was formed over the dome under the action of a stream of displaced air, persisting due to 

the complete absence of wind, and rising to a height of 50 m.

After the dome had settled, a subsidence crater was formed in the epicentral zone with radius of 

110 m and maximum depth of 14 m, the radius of the crater with respect to the crest of the 

upheaval region reached 150 m, the maximum height of upheaval averaged 9 m, and the radius 

of the upheaval region reached 500-600 m.

Radioactive gases escaped into the atmosphere 25 hours after the shot. In the first hours after 

radioactivity was noted in the atmosphere, slow free-flow discharge of radioactive gases was 

observed, mainly through annular cracks formed on the periphery of the subsidence crater. 

Filtration of gases ended after about a day. During filtration of radioactive gases, levels of 

radiation were 200-300 mR/h. After filtration had ended, the radiation background within the 

confines of the subsidence crater and on the crest of the upheaval mound was 10-50 mR/h for 

the first few days.

Figure 29. Drill rig, of the type 

used for drilling the nuclear 

test emplacement borehole. 

Normally, the emplacement 

borehole has a diameter of 

-900 millimeters, and was 

drilled to depths ranging from 

200 to about 1000 meters. 

The rig shown was that used 

to drill the hole for the Soviet 

nuclear test of the US-USSR 

Joint Verification Experiment, 

conducted at the Balapan test 

site in 1988.

45
USGS Open File Report 01-312: Containment of Soviet Underground Nuclear Explosions

Chapter 3. MONITORING ACCIDENTAL RADIATION RELEASES

3.1 Criteria for Conducting a Test

As has already been noted, the decision regarding the feasibility of conducting an underground nuclear 

test was made with allowance for the probable level of safeguards, both for keeping gaseous products of 

explosion under the ground, and for the specific weather situation at the proposed time of the shot. The 

latter is a very important factor for ensuring safety of underground nuclear tests, as the movement of air 

masses determines the nature and quantitative characteristics of transport of gaseous explosion products 

when they escape into the atmosphere. Specifically, the propagation of explosion products over the 

territory adjacent to the nuclear test site determines, in case of an accident, the doses received by 

individuals and the general populace.

The usual technology of conducting an underground test calls for ensuring full containment of the 

explosion, confining the radioactive products of the explosion underground. In doing so, an allowance 

has been made for the probability of escape of a small amount of radioactive materials in gaseous form at 

some time after the explosion. To develop requirements for radiation safety, a State Radiation Safety 

Service was set up in the USSR on 21 August 1947, even prior to the first nuclear tests (1947). This 

Service was transferred to the system of the Ministry of Public Health of the USSR, in the entity of the 

Third Medical Administration. This Administration was responsible for ensuring radiation safety for the 

entire period of nuclear testing.

The legal basis regulating the irradiation of personnel and the populace as a result of nuclear testing has 

been "Sanitary Rules of Working With Radioactive Substances and Sources of Ionizing Radiation." 

These rules were first introduced legislatively in 1961. In accordance with these rules, exposure of the 

population was permitted up to 0.5 rem per year. Over the years, these rules were revised and 

expanded; yet, the basic figures remained the same. For example, "Interim Sanitary Requirements on 

Ensuring Safety of Workers and the Populace When Using Underground Nuclear Explosions for Needs of 

the National Economy" were developed and approved in 1967. These sanitary requirements, as well as 

the subsequently developed, "Standards of Radiation Safety" of 1969, 1976 and 1987, established the 

same "permissible exposure dose" of the populace at 0.5 rem per year. It was under these standards that 

underground nuclear tests were done in the USSR. Guidance for test site personnel were taken from 

"Rules for Working with Radioactive Substances and Sources of Ionizing Radiation," effected in 1963 by 

order of the USSR Defense Ministry and renewed in 1976. The permissible "emergency levels of 

exposure" for personnel were, in practice, allowed to be used only in exceptional cases and by a special 

written decision of the Director of Tests.

In some cases, provisions had not been made for eliminating the probability of escape of radioactive 

gases to the atmosphere, creating the possibility of a radiation environment beyond the confines of the 

proving grounds with emission doses exceeding permissible levels. In these cases, the USSR Ministry of 

Defense, in cooperation with the Ministries of Nuclear Power and the Public Health, would be obligated to 

issue to the proving grounds a special permit for conducting the test with indication of the permissible 

external and internal exposure doses. It was mandatory that this information, as well as a list of 

additional measures to ensure safety, be included in a coordinated and approved "List of Measures on 

Ensuring Safety When Conducting Tests of Classified Items at Proving Grounds."

There were also other important requirements that had to be met before underground nuclear tests could 

be conducted. For example, a test was prohibited if the wind was blowing toward sites where instrument 

structures were located and personnel would be working, or toward residential sectors of proving grounds 

(so-called "classified areas"). Favorable weather was defined as an anticyclone (high pressure) 

environment, with transport of air masses toward unpopulated areas, temperature conditions ensuring 

rapid rise of gases to considerable altitudes, and their dilution by atmospheric masses. The USSR Stefe 

Committee for Hydrometeorology was responsible for the selection of adequate weather conditions.

During the conduct of a test, radiation monitoring was done both on the test site (by equipment installed in 

helicopters and vans), and in the surrounding territory. In the sector of possible propagation of air

46
USGS Open File Report 01-312: Containment of Soviet Underground Nuclear Explosions

masses from the region of ground zero, radiation observations were made by air reconnaissance patrols 

at distances out to 500 km and (if required) to the borders of the USSR.

3.2 Examples of Containment Failures

In some underground nuclear tests, the normal testing process was not followed, and unforeseen 

radiation situations occurred. Such situations usually occurred during the early and free-flow discharge of 

radioactive explosion products into the atmosphere. On the whole, these explosions were very few; less 

than 5% of the total number of tests. A few such explosions with unplanned radiation releases occurred 

when conducting borehole shots. Described below are two borehole shots where the emission of 

radioactive gases occurred as a result of breakthrough of the dome and rapid formation of a cave-in 

column. In tunnel emplacements, accidents rarely occurred, and only when conducting low-yield 

detonations (1 or 2 orders of magnitude less than a kiloton). Two experiments are described that 

exemplify such explosions.

Hole 1204. Balapan Test Site (Semioalatinsk)

The explosion was conducted on 10 December 1972. A 150 kt nuclear device was placed at a 

depth of 378 m in tuffaceous sandstones with interbedded porphyrite. The rocks were 

characterized by moderately heavy fracturing, and had a bulk density of 2680 kg/m3, a porosity of 

2.4% and a longitudinal p-wave velocity of 4.63 km/s. The gas production of the rocks was 1- 

1.3% at 100°C and 10.8% at 1000°C. Thickness of surface deposits at ground zero was 40 m, of 

which 20 m was clay, covered with 20 m of sand, clay and gravel. Light-spot fiducial points were 

used to measure the initial rate of movement and height of rise of the dome at ground zero, which 

were 25.8 m/s and 32 m respectively. Within 12 seconds of the explosion, at a distance of 40 m 

from the epicenter, there was intense venting of cavity gases into the atmosphere with velocity of 

about 70 m/s. At 40-50 seconds, the gas column had risen to an altitude of 300-350 m. Within 

the next 18.4 s, there was another, weaker breakthrough of gases. Ultimately, an upheaval 

mound was formed in the epicentral region, with volume of about a million cubic meters, a radius 

of 560 m at the base, and an average height of 9.8 m. A subsidence crater 110 m in diameter 

and 36 m deep was formed in the central part of the upheaval region. Thus, in this explosion 

there was an early (12 s) and pressurized breakthrough of radioactive gases into the atmosphere. 

After 1.8 minutes, a radioactive cloud had formed above ground zero at altitude of about 350 m, 

moving in the direction of the wind at about 5-7 m/s. The cloud included short-lived radionuclides 

of inert gases: krypton with half-lives ranging from 76.3 minutes to 4.5 hours, and xenon with 

half-lives ranging from 14-15 minutes to 2-5 days. A radioactive trail with strontium and cesium 

fallout was formed on the surface of the ground in the direction of motion of the cloud. This 

explosion resulted in an unplanned radiation situation that led to irradiation of direct participants in 

the test beyond the established safety standards.

Hole 1207. Balaoan Test Site (Semioalatinsk)

The explosion was conducted on 31 May 1974. A nuclear device with yield of about 40 kt was 

placed at a depth of 316 m. The host rocks of the emplacement were carbonaceous shales with 

density of 2710 kg/m3, porosity of 1.2% and velocity of longitudinal waves of 4.4 km/s. The 

carbonaceous shales were typified by high gas-forming properties, having total gas content of 

10.8%, of which 10% by weight was water vapor, and 0.8% carbon dioxide. Under the action 

of the explosion, the free surface started to move with initial velocity of 13.5 m/s. A dome was 

formed with height at the epicenter of 10 m and diameter of about 600 m. Within a few seconds, 

the dome had fallen to a height of 4-5 m. After roughly 10 minutes, the central part of the dome 

began to settle, forming a subsidence crater 200 m in diameter and 40 m deep 15 minutes after 

the explosion. Within 26 minutes after the explosion, escape of radioactive gases through cracks 

in the bottom of the subsidence crater was recorded. Suddenly at the 30th minute after the 

explosion, cavity gases broke through the bottom of the crater, mixed with oxygen in the air and 

began to bum. A fireball was formed that began growing rapidly in height and toward the sides, 

reaching an altitude of several hundred meters. Flame jets began springing up around the 

periphery of the upheaval region, and then through cracks on the free surface. The area on

47
USGS Open File Report 01-312: Containment of Soviet Underground Nuclear Explosions

which flame jets were springing up gradually increased. Radioactivity levels began to rise. 

Within 35 minutes after the explosion, test participants left the observation post. By that time, 

levels of radioactivity had reached 0.5 R/h. The occurrence of flame jets in the region of the 

epicenter on an area with radius of roughly 1-1.5 km lasted for 2 hours. The cause of occurrence 

of flame jets was that at the source of the explosion, as a result of strong heating of 

carbonaceous shales interbedded with coal, and occurrence of water vapor, chemical reactions of 

the type

C + HZO = CO + H2

began taking place, i.e. carbon monoxide and hydrogen were produced. Gaseous hydrogen and 

carbon monoxide began to emerge into the atmosphere under the action of excess pressure, 

where they were ignited, mixing with oxygen of the air.

Tunnel 204-2. Test II. Deaelen Test Site (Semioalatinsk)

The explosion was conducted on 5 December 1980. The tunnel was constructed in quartz 

porphyries. A low-yield device of roughly 0.1 kt was placed at a depth of 36 meters, with LLR of 

33 meters. Immediately after the explosion (within approximately 1-2 s), there was an early 

breakthrough of gaseous products into the atmosphere through a tectonic fracture on the surface 

of the slope. This fracture cut through the tunnel between the first and second stemming plugs. 

Hence, products of explosion were thrown by the force of the blast through the first section of the 

stemming system and leaked out through the tectonic fracture. As the gases escaped, they were 

ignited in a ravine cutting across the slope in the region of emergence of the tectonic crack onto 

the surface.

Tunnel 609. Test II. Deaelen Test Site (Semioalatinsk)

The explosion was conducted on 10 April 1976. 

The tunnel was constructed in granites. A low-yield 

device of about 0.1 kt was 

placed at a depth of 130 m 

with LLR of 100 m. Early 

escape of radioactive 

explosion products through 

the tunnel occurred within 

12s after detonation of the 

device. Levels of radioactive contamination near the 

mouth of the tunnel were 

2.5 R/h.

Figure 30. View of a structure at tunnel 169/2 

constructed to hold a 

gas-filled bag used in a 

radiation effects experiment. In this test, radiation was directed out 

two diverging tunnels 

from a centrally-located 

device.

48
USGS Open File Report 01-312: Containment of Soviet Underground Nuclear Explosions

Hole Yu-4. Krasino Test Site (Novava Zemlva)

The shot was conducted in borehole "Yu-4" at the Krasino (southern Novaya Zemlya) testing 

area, on 27 Sep. 1973. The yield is estimated at 100 kt; and the, about 190 m/kt1'3: The test was 

of an unexpectedly small device at great depth. Apparently, the venting occurred as a result of 

tectonic motion on an unidentified fault, which opened a passageway for the gasses to reach the 

surface [4]. Fault displacement was about 1 meter. The area contaminated was about 1.5 x 7 

km; radiation readings made in 1990 were 25 microrem/hr of Cs-137 and Sr-90; fallout was 0.1 

Ci/km2.

Tunnel A-9. Matochkin Shar Test Site (Novava Zemlva)

The nuclear test at tunnel site A-9 (Matochkin Shar testing area) was part of a double event at the 

northern testing area, on 14 Oct. 1969. The yield estimate of both events is 140 kt; the scaled 

depth of burial of A-9 was about 100 m/kt 1 '3. Venting occurred by the explosive escape of gasses 

along a fault (apparently, without fault motion) that cut the tunnel between the two main stemming 

blocks and the blast door (see Figure 20). The failure mechanism apparently involved a moisture 

lens in the permafrost layer. About 10% of the radioactive gas escaped and personnel were 

evacuated. Containment practices were apparently changed because of this event.

Tunnel A-37. Matochkin Shar Test Site (Novava Zemlva)

The nuclear test at tunnel site A-37A (Matochkin Shar testing area) took place on 2 Aug. 

1987. The yield estimated at 70 kt; the SDOB about 95 m/kt1 '3 . Like the 1969 test, 

venting occurred by escape of gasses along a fault (apparently, without fault motion) that 

cut the tunnel between the two main stemming blocks and the blast door (see Figure 

20). About 10% of the radioactive gas escaped. An extensive description of the 

radiological conditions caused by this event given by Andrianov and Bazhenov (1992).

3.3 Groundwater Contamination

The territory of the Semipalatinsk Proving Grounds is characterized by complicated hydrogeological 

conditions. Hydrogeology here is represented by several aquifers (this is especially typical of Balapan 

site), as well as fissure water (Degelen Mountain) and seasonal precipitation. Degelen Mountain has 

several streams that flow through ravines and valleys, and also several springs.

In order to develop approaches and recommendations on preventing the transport of radioactive 

explosion products in the groundwater, the Institute of Dynamics of Geospheres of the Russian Academy 

of Sciences, in cooperation with the geological service of the proving grounds, carried out a special 

research program. This program was focused on determining the principles governing the influence that 

underground explosions have on the hydrogeological environment, both regionally and for individual test 

sites. Studies were done in more than 800 test holes drilled both on the territory of the proving grounds 

and outside its boundaries. Water samples were taken periodically in most holes. In some of the holes 

closest to epicenters of explosions, more detailed studies were done. These involved determinations of 

changes in the ground water regime as a result of an explosion, and changes in the chemical composition 

of water, including the presence and quantitative characteristics of any radioactive materials detected.

Efforts to study ground water began after the first underground explosions were conducted at the 

Semipalatinsk test site. A very thorough study was done on the radiation situation with ground water for 

the first shots in boreholes 1003 and 1004. Test holes were investigated, and also the water from wells in 

populated areas, such as Sarapan, Musa, Karabas and Chagan. Water samples taken from holes and 

wells contained isotopes of strontium, ruthenium, barium, zirconium, cerium, iron and cesium. The 

amount of these isotopes was below the permissible level defined by "Standards of Radiation Safety."

49
USGS Open File Report 01-312: Containment of Soviet Underground Nuclear Explosions

3.4 How Safe is Safe Enough?

Radiation monitoring, as has been noted above, includes several measures:

 detailed study of the radiation environment on test sites with recording of the time of 

emergence of gaseous explosion products into the atmosphere and their amount;

 detailed radiation monitoring of proving ground territory and ground water in each test,

 aircraft monitoring of nearby and remote territories.

Experience shows that with such an arrangement of radiation monitoring systems, it is almost impossible 

to miss a leak of radioactive gases into the atmosphere or transport of radionudides with ground water.

However, variability in the properties of actual rock masses and in the conduct of a specific underground 

nuclear tests preclude any guarantee of achieving complete containment of an underground explosion. 

Experience shows that, no matter how careful the analysis of conditions of conducting the test, or how 

rigorous the approach to selecting the site and depth of emplacement of the device, there still may be 

cases of escape of gaseous products of explosion into the atmosphere, albeit small in volumes. Actually, 

methods used for diagnosing the rock mass (e.g., seismic surveying) give a generalized picture of 

fracturing of the medium, but are not capable of distinguishing important details such as the opening 

("penetrability") of an individual tectonic fault or large crack. This information may not be fully obtained, 

even by detailed studies of tectonic fractures in a tunnel.

The situation becomes much more complicated when tests are done in a rock mass where underground 

explosions have been done previously. In this case, precise estimates must be made of the dimensions 

of zones of fracture due to the previous and planned shots. Despite considerable experience and a great 

deal of experimental results, it is difficult to determine the exact boundaries of the zone of fracture of an 

underground explosion, since individual features of the structure of each specific rock mass may 

appreciably affect both the dimensions of the fracture zone and the zone affected by the explosion.

Ensuring the containment of an explosion requires considerable expenditures (e.g., for drilling a very 

deep hole and implementing special, high-cost measures to seal it). For example, when organizing tests 

in tunnels, cost considerations resulted in grouping the tunnel portals to the extent possible This made it 

difficult to space the epicenters of neighboring shots far apart. A similar tradeoff happens when selecting 

the depth of an explosion. In order to achieve large depths, very long tunnels would have to be driven, 

which was economically inadvisable. Further, when the boundaries of the proving ground are limited, 

care had to be exercised in using up the sites that were suitable for underground tests.

All this brings up the question, "Where are the reasonable limits to ensuring full containment (or radiation 

safety) of nuclear tests?" Some scientists assert that, given appropriate selection of geological 

conditions and a high-quality stemming system, the short-term escape of radioactive gases into the 

atmosphere can be almost entirely eliminated. Success depends not only on results of analysis of 

geological and engineering characteristics of a specific planned test, but also on experience and, in part, 

on the intuition of the decision-making experts. When selecting the conditions for conducting a nuclear 

test, the primary consideration is the possible negative impact of radiation on the health of people living 

near the proving grounds, and the personnel working thereon. During Soviet underground nuclear 

testing, the conditions for conducting a test were considered acceptable if the dose of the exposure to 

personnel and the population of nearby settlements did not exceed permissible levels, even in case of an 

accidental release.

Acknowledgements

We are grateful for reviews of the manuscript that were provided by Randy Beaty, Al Bezek, Rod Matzko, 

Paul Orkild, Gregory van der Vink, and two anonymous reviewers, and for the substantial technical assistance and review provided by Alexander Spivak.

so
USGS Open File Report 01-312: Containment of Soviet Underground Nuclear Explosions

Bibliography and References

Adushkin, V.V., and others, 1993, Description of the Environmental State on the Russian Nuclear Test 

Site (Novaya Zemlya), report to the Defense Nuclear Agency, P.O. DNA001-92-M-0714

Adushkin, V.V., and A.A. Spivak, 1994, Geologic Characterization and Mechanics of Underground 

Nuclear Explosions, report to the Defense Nuclear Agency. Alexandria, VA, 796 p.

Adushkin, V.V., and A.A. Spivak, 2001, Characterization of the Release of Radioactive Underground 

Explosion Products into the Atmosphere, preprint, RAS/IDG, xxx pp.

Agreements and Protocols Between the Union of Soviet Socialist Republics and the United States of 

America "On Limiting Underground Nuclear Weapons Tests", 1974, and "On Underground Nuclear 

Explosions for Peaceful Purposes", 1976, Catalogues of the Council of Peoples'Deputies, USSR and 

the USSR Supreme Soviet, 1991. No. 21.

Andrianov, K. N. and Bazhenov, 1992, Nuclear Explosions in the USSR. Vol. 1: Northern Test Site, V. N. 

Mikhaylov, ed., International Commission on ... Underground Nuclear Explosions, V. G. Khlopin 

Raduim Institute (Moscow).

Bocharov, V.S., S.A. Zelentsov and V.I. Mikhaylov, 1989, Characteristics of 96 underground nuclear 

explosions at the Semipalatinsk nuclear polygon, Atomnaya Energiya, v. 67, n. 3, p. 210-214

Chernyshev, A., 1991, On the preparation for conducting nuclear explosions at the northern test site 

(Novaya Zemlya), unpublished, Canadian Centre for Arms Control, 56 pp. (transl. L. Bykowski, DNA 

Springfield Res. Fac., 1991).

Chukhin, S.G., 1992, The Truth of Chagan, Energiya, No. 12.

Department of Energy, 1994, United States Nuclear Tests, Pept. DOE/NV-209 (Rev. 11), Dec. 1994.

Dubasov, lu.V.; Matushchenko, A.M.; Filonov, N.P. etal., 1993, Semipalatinsk Test Site: Evaluating the 

Radioecological Consequences, Bulletin of the Center of Public Information on Atomic Energy, 

Special Issue, 20 January 1993.

Dubasov, Yu.V., and others, 1998, Chronology of nuclear tests conducted in the USSR in the 

atmosphere, space and underwater (1949-1962), Atomnaya Energiya I Oborona, pp. 36-43.

Gorin, V.V., Semipalatinsk Test Site: Chronology of Underground Nuclear Explosions and their Initial 

Radiation Effects (1961-1989), Atomnaya Energiya, v. xxx, n. xxx, p. xxx.

Higgins G.H. Nuclear explosions data for underground engineering applications," in Peaceful Nuclear 

Explosions, IAEA Vienna, 1970, p. 111-122.

Izrael', lu.A., 1974, Peaceful Nuclear Explosions and the Environment, Gidrometeoizdat, Leningrad.

Laushkin, V.A., S.I. Oreshin and V.M. Ovtchinnikov, 1995, Regional analysis of former Soviet Union 

peaceful nuclear explosions recorded in the former Soviet Union, contract report EOARD SPC-94- 

4065, RAS/IDG, 53 pp.

Leith, W., 1988, Degelen nuclear test and tunnel data. Technical Memorandum to the Defense Special 

Weapons Agency, dated June 26, 1998, 10 pp. (revised 7/1/2001).

Matushchenko, A.M.; Bazhenov, V.N.; Dumik, V.P.; et al. Underground Nuclear Tests: Conditions for 

Conducting them per the Criteria of the Moscow Treaty 1963, Information Bulletin. 1992. No. 9. 

(Center of Public Information on Atomic Energy.)

Mikhaylov, V.N., 1991, Untitled report, General Region Characteristics (Novaya Zemlya), unpublished, 

Canadian Centre for Arms Control, 10 pp.

Mikhaylov, V.N., and others, 1992, Chronicle and phenomenology of nuclear tests on the Novaya Zemlya 

test range, pp. 1-14 in Proc. Conf., The Radiological and Radiation Protection Problems in Nordic 

Regions, Nordic Soc. For Radiation Protection, Oslo.

51
USGS Open File Report 01-312: Containment of Soviet Underground Nuclear Explosions

Nuclear Testing in the USSR: General Characteristics Concerning the Organization of Nuclear Tests in 

the USSR. V.N. Mikhaylov, dir., IzdAT, 1997, 304 pp.

Nuclear Testing in the USSR, Vol. 1, LA. Andryushin and others, eds., RFYaTs-VNIIEF, 1997, 95 pp.

Nuclear Testing in the USSR, Vol. 2, Technology of Nuclear Testing, LA. Andryushin and others, eds., 

RFYaTs-VNIIEF, 1997, 320 pp.

Nuclear Testing in the USSR, Vol. 4, Peaceful applications of underground nuclear explosions V.I. 

Mikhaylov, ed.. RFYaTs-VNIIEF, 1997, 155 pp.

Nuclear Testing in the USSR, Vol. 3: Nuclear Weapons, Military and Political Aspects, LA. Andryushin 

and others, eds., RFYaTs-VNIIEF. 2000, xxx pp.

Nuclear Testing in the USSR, Vol. 5: Nuclear Tests and Ecology, LA. Andryushin and others, eds., 

RFYaTs-VNIIEF. 2000, xxx pp.

Nuclear Testing in the USSR, Vol. 6, Legacy of the Atomic Era, LA. Andryushin and others, eds., 

RFYaTs-VNIIEF. 2000, xxx pp.

Nuclear Explosions in the USSR: Northern Test Site: Nuclear Explosions, Radiology, Radiation Safety. 

Vol 1. (Information Handbook); Edited by V.N. Mikhailov, G.E. Zolotukhin, A.M. Matushchenko. St. 

Petersburg, NPO "V.G. Khlopin Radium Institute," 1992.195 pp. [transl. JPRS-UEQ-93-009-L]

Nuclear Testing in the USSR: Semipalatinsk Polygon, N.P. Voloshin and others, eds., MEDBIOEKSTREM, 

1997,320pp.

Olsen E.W. Time history of the cavity pressure and temperature following a nuclear detonation in 

alluvium.- J. Geophys. Res., 1967, No.20, p. 5037-5041.

Schoengold C.R., DeMarre M.E., Kirkwood E.M., Radiologicel effluence released from U.S. continental 

tests, 1961 through 7992, U.S.Department of Energy. Nevada Operation Office. Las Vegas, Nevada. 

1996.276pp.

Spungin, V.G., and L.S. Panteleev, 1998, Effect of the block-fault structure of a rock mass on its 

destruction due to underground nuclear explosions: A case study of the Novaya Zemlya test site, 

Environmental Geosci., v. 1, n. 2, pp. 118-126.

Sultanov, D.D., 1993, Investigation of seismic efficiency of Soviet peaceful nuclear explosions conducted 

in various geological conditions, RAS IDG, 220 pp.

Sultanov, D.D., Murphy, J.R.; Rubinstein, K.D., 1999, A seismic source summary for Soviet peaceful 

nuclear explosions, Bull. Seismol. Soc. Am., v. 89, n. 3, pp. 640-647

Terminology Dictionary for Issues Concerning the Use of Underground Nuclear Explosions for Peaceful 

Purposes: Glossary, O.L. Kedrovskiy, M.P. Grechushkina, L.B. Prozorov, eds., Moscow, 1981.

Treaty on Prohibiting Nuclear Weapons Tests in the Atmosphere, in Space and Under Water, in 

Catalogues of the USSR Supreme Soviet, No. 42,16 Oct. 1963.

USSR Nuclear Tests. Hydronuclear Experiments. Plutonium Inventory, LA. Andryushin and others, eds., 

RFYaTs-VNIIEF, 1997-98, 22 pp.

USSR Nuclear Weapons Tests and Peaceful Nuclear Explosions 1949 through 1990, LA. Andryushin and 

others, eds., RFYaTs-VNIIEF, 1996.63 pp.

52