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November/December 1998
Vol. 54, No.6
NRDC Nuclear Notebook
Known Nuclear Tests Worldwide, 1945-98 Since the last update of "Known Nuclear Tests Worldwide" (see May/June 1996 "Nuclear Notebook"), several tests have occurred and additional information has become available about several nations' nuclear programs. From 1945–98 we list 2,051 tests by seven nations, with the United States and Soviet Union accounting for 85 percent. Almost 26 percent of the tests (528) were conducted in the atmosphere. In one of the tables below ("Known Nuclear Tests Worldwide"), we present what we believe to be a complete list of all nuclear tests by the five declared nuclear weapon states (as recognized by the Nuclear Non-Proliferation Treaty) and India and Pakistan. Another table ("Indian and Pakistani Tests: Facts and Figures") presents some preliminary information about the Indian and Pakistani tests. If we use the definition of a test adopted by the United States and the Soviet Union/Russia (a single explosion, or two or more explosions fired within 0.1 second within an area with a diameter of two kilometers), then the number of Indian tests in May 1998 was three and the number of Pakistani tests was two. As we will discuss below, the precise number of devices the Indians and Pakistanis may have used and the precise number that were detonated is unclear. More information is needed to accurately determine what transpired. Questions about Indian tests. India first tested a device on May 18, 1974. Advertised as a "Peaceful Nuclear Explosion" it obviously had military application and India may have produced a small stockpile based on a basic fission design. The test, code named "Smiling Buddha," was carried out in a 107-meter deep shaft at the Pokharan test site in the Rajasthan desert in western India, nine kilometers north-northwest of the village of Khetolai (an especially useful article by Vipin Gupta and Frank Pabian in Science & Global Security (1996, volume 6, no. 2) locates the site). Initially the Bhabha Atomic Research Center claimed the explosive yield of the test was 12 kilotons. Later they reduced their estimate to eight kilotons. The magnitude of the seismic waves from the 1974 test, when combined with its announced depth and the formation of a subsidence crater at the surface, strongly suggested that the actual yield was less than five kilotons. At least one reputable Indian journalistic account placed the yield as low as two kilotons. With regard to the 1998 tests, Indian officials claimed to have detonated three different devices on May 11: a "thermonuclear device" with a yield of 43 kilotons (code-named Shakti 1), a fission device with a yield of 12 kilotons (Shakti 2), and a low-yield device (Shakti 3) on the order of 200 tons (0.2 kilotons). According to Indian scientists, the blasts were set off simultaneously in three separate shafts. The two larger devices were in shafts one kilometer apart in an east-west direction, some three kilometers southwest of the 1974 test. The sub-kiloton device was in a shaft 2.2 kilometers away. (We have relied on three important articles analyzing the tests, one in the May 1998 issue of Arms Control Today, a second in the September 1998 issue of Seismological Research Letters, and a third in the September 25, 1998 issue of Science.) If these devices actually produced the yields claimed by Indian weapon scientists, we would expect to observe a seismic signal corresponding to 55 kilotons, or magnitude 5.76 on the Richter scale. Sixty-two seismic stations reporting to the prototype International Data Center recorded the seismic signal, and the average magnitude was calculated as 5.0, with some estimates as low as 4.7. In well understood regions where tests have taken place, seismologists have learned that a 5.0 magnitude in a stable region would indicate a probable yield of 12 kilotons, with the range possibly as low as five kilotons and as high as 25 kilotons. A mid-point of 12 kilotons is less than one-quarter of what Indian weapon scientists claimed. Of major significance is the Indian claim that it set off a "thermonuclear" device. Some experts initially suggested that this might mean India was "boosting" fission bombs by using tritium, a hydrogen isotope. Using a very loose definition, a "boosted" fission device could qualify as "thermonuclear." Indian scientists tried to dispel that interpretation at a press conference, where they correctly defined a hydrogen bomb as one with two stages, in which a fission primary sets off a hydrogen-fueled secondary; they claimed that was what they had tested. When challenged that a 43-kiloton "thermonuclear" bomb was too small to qualify, they stated that they reduced the yield because the village of Khetolai was only five kilometers away. (It was later reported that more than 40 percent of the structures in the village had sustained some damage.) The first successful tests of a modern hydrogen bomb by each of the five declared powers had yields of 1.6 megatons to over 10 megatons. All were detonated in the atmosphere in the 1950s and 1960s, although the United States and Soviet Union both conducted multi-megaton underground tests. It is technically feasible to scale back or "defuel" the second stage of a high-yield hydrogen bomb to perhaps 10–20 kilotons, but it is a sophisticated procedure and not something likely to be attempted on a first (and possibly last) thermonuclear test. It is also possible to design two-stage thermonuclear weapons with very low-yield secondaries that would correspond to the observed yield of the May 11 test. But this potential explanation is vitiated by the fact that the observed yield corresponds rather well with India's announced yield of 12 kilotons for a "fission device" involved in the test. The simplest explanation of the available evidence suggests that either a thermonuclear second stage, or perhaps the entire thermonuclear device, failed to explode. Several explanations are possible, however, and without more information it is impossible to conclude which is correct. India claimed that it conducted two additional tests on May 13, announcing the yields as 0.2 kilotons (200 tons) and 0.6 kilotons (600 tons). Although these tests are small by nuclear standards, they should have registered on some of the seismometers in the region, but they did not. The nearest station that reports its data publicly is in Nilore, Pakistan, 750 kilometers away from the Indian test site. Based on the recorded signal-to-noise ratio for the earlier May 11 test, the limit of detection capability at Nilore for an explosion at Pokharan is calculated to be 10–15 tons for normally "coupled" explosions in most geologic media, and perhaps 100–150 tons for explosions in very porous (and dry) media, such as the "sand dunes" mentioned by the Indian press accounts of the May 13 event. Even assuming the latter "partial decoupling" scenario, the claimed yield of 600–800 tons for this event should have produced signals detectable at Nilore. The absence of any seismic record for this test suggests that the actual yields were either far lower than planned, or that the announced yields were intended to confuse and mislead foreign observers as to the actual purpose of the tests, which may have been deliberately kept low to calibrate and validate computer models of the very early stages of nuclear device performance. As in the case of the May 11 tests, without further information from Indian officials, it is difficult to say with any degree of certainty what purposes were served by these explosions, or whether one or both occurred at all. Questions about the Pakistani tests. In response to the Indian tests, Pakistani Prime Minister Nawaz Sharif announced that five devices had been exploded on May 28. These explosions took place in Baluchistan very near the Afghanistan border, apparently in a horizontal tunnel. A sixth detonation was announced on May 30, conducted some 100 kilometers to the southwest according to seismic analysis, apparently in a vertical shaft. Pakistani officials, like their Indian counterparts, seem to have exaggerated the number and size of the explosions, announcing the first day's yield as 40–45 kilotons (including one test of 30–35 kilotons) and a yield of 15–18 kilotons for the sole test on May 30. Analysis of the seismic data does not support these claims. The average magnitude reported by the 65 stations recording the event on May 28 was 4.9, indicating an explosive yield in the 6–13 kiloton range. Fifty-one stations recorded the event on May 30, with an average magnitude of 4.3, indicating an explosion in the 2–8 kiloton range. As in the Indian case, much more information is needed to determine exactly how many devices were used, how many went off, and the nature of their designs. Indian and Pakistani tests: facts and figures
| Date |
GMT |
Coordinates |
Yield (est. range) |
| Indian Nuclear Tests |
| May 18, 1974 |
02:34:55 |
27.095 N 71.752 E |
2-5 kilotons |
| May 11, 1988 |
10:13:44 |
27.078 N 71.719 E |
12 kilotons* (9-16 kilotons) |
| May 11, 1998 |
10:13 |
? |
?* |
| May 13, 1998 |
06:51 |
? |
?** |
| |
| Pakistani Nuclear Tests |
| May 28, 1998 |
10:16:17 |
28.830 N 64.950 E |
9 kilotons*** (6-13 kilotons) |
| May 30, 1998 |
06:54:06 |
28.495 N 63.781 E |
4 kilotons (2-8 kilotons) |
Local time in India is five-and-one-half hours later than gmt; in Pakistan, local time is five hours later than gmt. *The Indian government announced that three nuclear devices were detonated simultaneously in three shafts, two of which were a kilometer apart; the third was 2.2 kilometers away. We count these as two tests. **Seismic records do not discriminate the explosions of two devices (announced by Indian scientists as being 0.2 and 0.6 kilotons), one or both of which may not have detonated.
***Pakistani officials announced that five nuclear devices were tested. Seismic records do not discriminate these and it is possible that only one device was detonated.
Last Nuclear Test
| Soviet Union (Russia) |
October 24, 1990 |
| United Kingdom |
November 26, 1991 |
| United States |
September 23, 1992 |
| France |
January 27, 1996 |
| China |
July 29, 1996 |
| India |
May 13, 1998 |
| Pakistan |
May 30, 1998 |
Known Nuclear Tests Worldwide, 1945-98
| Year |
U.S.
|
U.S.S.R.
|
U.K.
|
France
|
China
|
TOTAL
|
| |
A
|
U
|
A
|
U
|
A
|
U
|
A
|
U
|
A
|
U
|
|
| 1945 |
1
|
|
|
|
|
|
|
|
|
|
1 |
| 1946 |
2
|
|
|
|
|
|
|
|
|
|
2 |
| 1947 |
0
|
|
|
|
|
|
|
|
|
|
0 |
| 1948 |
3
|
|
|
|
|
|
|
|
|
|
3 |
| 1949 |
0
|
|
1 |
|
|
|
|
|
|
|
1 |
| 1950 |
0
|
|
0 |
|
|
|
|
|
|
|
0 |
| 1951 |
15
|
1 |
2 |
|
|
|
|
|
|
|
18 |
| 1952 |
10
|
0 |
0 |
|
1 |
|
|
|
|
|
11 |
| 1953 |
11
|
0 |
5 |
|
2 |
|
|
|
|
|
18 |
| 1954 |
6
|
0 |
10 |
|
0 |
|
|
|
|
|
16 |
| 1955 |
17
|
1 |
6 |
|
0 |
|
|
|
|
|
24 |
| 1956 |
18
|
0 |
9 |
|
6 |
|
|
|
|
|
33 |
| 1957 |
27
|
5 |
16 |
|
7 |
|
|
|
|
|
55 |
| 1958 |
62
|
15 |
34 |
|
5 |
|
|
|
|
|
116 |
| 1959 |
0
|
0 |
0 |
|
0 |
|
|
|
|
|
0 |
| 1960 |
0
|
0 |
0 |
|
0 |
|
3 |
|
|
|
3 |
| 1961 |
0
|
10 |
58 |
1 |
0 |
|
1 |
1 |
|
|
71 |
| 1962 |
39
|
57 |
78 |
1 |
0 |
2 |
0 |
1 |
|
|
178 |
| 1963 |
4
|
43 |
0 |
0 |
0 |
0 |
0 |
3 |
|
|
50 |
| 1964 |
0
|
45 |
0 |
9 |
0 |
2 |
0 |
3 |
1 |
|
60 |
| 1965 |
0
|
38 |
0 |
14 |
0 |
1 |
0 |
4 |
1 |
|
58 |
| 1966 |
0
|
48 |
0 |
18 |
0 |
0 |
6 |
1 |
3 |
|
76 |
| 1967 |
0
|
42 |
0 |
17 |
0 |
0 |
3 |
0 |
2 |
|
64 |
| 1968 |
0
|
56 |
0 |
17 |
0 |
0 |
5 |
0 |
1 |
|
79 |
| 1969 |
0
|
46 |
0 |
19 |
0 |
0 |
0 |
0 |
1 |
1 |
67 |
| 1970 |
0 |
39 |
0 |
16 |
0 |
0 |
8 |
0 |
1 |
0 |
64 |
| 1971 |
0 |
24 |
0 |
23 |
0 |
0 |
5 |
0 |
1 |
0 |
53 |
| 1972 |
0 |
27 |
0 |
24 |
0 |
0 |
4 |
0 |
2 |
0 |
57 |
| 1973 |
0 |
24 |
0 |
17 |
0 |
0 |
6 |
0 |
1 |
0 |
48 |
| 1974 |
0 |
22 |
0 |
21 |
0 |
1 |
9 |
0 |
1 |
0 |
55* |
| 1975 |
0 |
22 |
0 |
19 |
0 |
0 |
0 |
2 |
0 |
1 |
44 |
| 1976 |
0 |
20 |
0 |
21 |
0 |
1 |
0 |
5 |
3 |
1 |
51 |
| 1977 |
0 |
20 |
0 |
24 |
0 |
0 |
0 |
9 |
1 |
0 |
54 |
| 1978 |
0 |
19 |
0 |
31 |
0 |
2 |
0 |
11 |
2 |
1 |
66 |
| 1979 |
0 |
15 |
0 |
31 |
0 |
1 |
0 |
10 |
1 |
0 |
58 |
| 1980 |
0 |
14 |
0 |
24 |
0 |
3 |
0 |
12 |
1 |
0 |
54 |
| 1981 |
0 |
16 |
0 |
21 |
0 |
1 |
0 |
12 |
0 |
0 |
50 |
| 1982 |
0 |
18 |
0 |
19 |
0 |
1 |
0 |
10 |
0 |
0 |
49 |
| 1983 |
0 |
18 |
0 |
25 |
0 |
1 |
0 |
9 |
0 |
0 |
55 |
| 1984 |
0 |
18 |
0 |
27 |
0 |
2 |
0 |
8 |
0 |
1 |
57 |
| 1985 |
0 |
17 |
0 |
10 |
0 |
1 |
0 |
8 |
0 |
2 |
36 |
| 1986 |
0 |
14 |
0 |
0 |
0 |
1 |
0 |
8 |
0 |
2 |
23 |
| 1987 |
0 |
14 |
0 |
23 |
0 |
1 |
0 |
8 |
0 |
0 |
47 |
| 1988 |
0 |
15 |
0 |
16 |
0 |
0 |
0 |
8 |
0 |
0 |
40 |
| 1989 |
0 |
11 |
0 |
7 |
0 |
1 |
0 |
9 |
0 |
1 |
28 |
| 1990 |
0 |
8 |
0 |
1 |
0 |
1 |
0 |
6 |
0 |
1 |
18 |
| 1991 |
0 |
7 |
0 |
0 |
0 |
1 |
0 |
6 |
0 |
0 |
14 |
| 1992 |
0 |
6 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
2 |
8 |
| 1993 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
1 |
1 |
| 1994 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
2 |
2 |
| 1995 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
5 |
0 |
2 |
7 |
| 1996 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
1 |
0 |
2 |
3 |
| 1997 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
| 1998 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
5** |
| TOTAL |
215 |
815 |
219 |
496 |
21 |
24*** |
50 |
160 |
23 |
22 |
2,051 |
A = atmospheric U = underground *Includes one Indian test in 1974 **See "Indian and Pakistani Tests: Facts and Figures" ***All U.K. underground tests were conducted in the United States
Total nuclear test megatonnage
| |
Atmospheric |
Underground |
Total |
| United States |
141.0 |
38.0 |
179.0 |
| Soveit Union |
247.0 |
38.0 |
285.0 |
| United Kingdom |
8.0 |
0.9 |
8.9 |
| France |
10.0 |
4.0 |
14.0 |
| China |
21.9 |
1.5 |
23.4 |
| India |
- |
0.014-0.017 |
0.014-.017 |
| Pakistan |
- |
0.014-0.017 |
0.014-.017 |
| Total |
427.9 |
82.428-.434 |
510.328-.334 |
Tests by location
| Nevada |
935 |
| Kazakhstan |
496 |
| Russia |
214 |
| Mururoa Atoll |
175 |
| Enewetak |
43 |
| China (Lop Nur) |
41 |
| Christmas Island |
30 |
| Bikini |
23 |
| Algeria |
17 |
| Johnston Island |
12 |
| Australia |
12 |
| Fangataufa Atoll |
12 |
| India |
4 |
| Pacific Ocean |
4 |
| Malden Island |
3 |
| So. Atlantic Ocean |
3 |
| Alaska |
3 |
| New Mexico |
3 |
| Pakistan |
2 |
| Mississippi |
2 |
| Colorado |
2 |
| Ukraine |
2 |
| Uzbekistan |
2 |
| Turkmenistan |
1 |
| Total |
2,051 |
Nuclear Notebook is prepared by Robert S. Norris and William M. Arkin of the Natural Resources Defense Council. Inquiries should be directed to nrdc, 1200 New York Avenue, N.W., Suite 400, Washington, D.C., 20005; 202-289-6868. |