Chapter 2: Developing a Monitoring Strategy
Chapter 2 Footnotes
1. The concentration of Iodine-131 in milk was found to be correlated with the frequency of testing. Strontium-90 was found in human bone tissue. Cesium-137 was found in human muscle tissue.
2. Rainier was not the first test to be conducted below the ground. The United States' 100th nuclear explosion was its first underground test. On July 26, 1957, "Pascal-A" was detonated at the bottom of a 499-foot open drill hole. Although Pascal-A marked the beginning of underground testing, above ground testing continued for another 6 years. With testing simultaneously occurring above ground, the release of radioactive material from underground explosions was at first not a major concern. Consequently, Pascal-A, like many of the early underground tests that were to follow, was conducted "roman candle" style in an open shaft that allowed the release of radioactive materials to the atmosphere.
3. Adapted from the "Nuclear Proliferation Status Report, July 1992", Nuclear Non-Proliferation Project, Carnegie Endowment for International Peace, Leonard S. Spector and Virginia I. Foran.
4. Displacements as small as 0.00000001 centimeters, the same order as atomic spacing, can be detected by seismometers.
5. To reduce the background noise caused by wind and other surface effects, seismometers are often placed in boreholes at a depth of about 100 meters. Seismic arrays (clusters of seismometers distributed over a fairly small area) also can be used to distinguish coherent small signals from the more random background noise. The signals from the various instruments within the array can be combined to enhance small signals.
6. The deepest underground nuclear explosions have been at depths of around 2.5 kilometers, and almost no holes (for any purpose) have been drilled to more than 10 kilometers, whereas most earthquakes occur at much greater depths. Similarly, many earthquakes occur in oceanic areas. If no acoustic signals characteristic of an explosion are detected, a nuclear explosion can be ruled out.
7. While a nuclear explosion releases its energy in less than 1/1,000,000 of a second, earthquakes typically rupture over several seconds or even several tens of seconds.
8. Ripple-firing is almost always used in quarry blasting and mining because it fractures rock more efficiently and in a more uniform fashion, and minimizes undesirable effects such as air blasts.
9. See for example, M.A.H. Hedlin, J.B. Minster and J.A. Orcutt, "The time-frequency characteristics of quarry blasts and calibration explosions recorded in Kazakhstan USSR", Geophysical Journal, Vol. 99, p.109-121, 1989.
10. Scientists were trying to recreate the "Sakhalin effect". Mines in the Far East Sakhalin Island were found to be cleared of methane gases after an earthquake created fissures and fractures in the surrounding rock.
11. Izvestiya, Moscow, June 26, 1992.
12. The automatic processing of this event showed a high frequency signal, visible on at least four subarrays, but with poor signal coherency across the full array. The automatic location estimate (45N, 34E) is somewhat different from the location of Yunokommunarsk (48.22N, 38.30E), but well within the uncertainty for an event with such low signal coherency. See NORSAR Sci. Rep. 1-92/93, November 1992.
13. Although the inhabitants of the town knew of the explosion, it was unclear whether all of them knew (or understood) that the explosion was nuclear rather than chemical.
14. Associated Press, Sunday, June 28, 1992.
15. NORSAR Sci. Rep. 1-92/93 November 1992.
16. Tests everywhere but underground are already prohibited by the 1963 LTBT which is monitored with high confidence. Satellites effectively monitor the atmosphere and acoustic sensors used for antisubmarine warfare can monitor testing in the oceans. It has been proposed that nuclear tests could be conducted secretly either in deep space or behind the sun. If such a scenario was considered to be a serious concern, satellites also could be deployed to monitor behind the sun or deep space. Alternatively, an agreement could be negotiated to conduct simple inspections of the few vehicles that go into deep space.
17. If the reason to test were extremely compelling, they might choose instead either to withdraw from a CTBT or test in an area or manner such that they could not be associated with the test.
18. A review of early U.S. experience indicates that at least a factor-of-two uncertainty in yield prediction is appropriate for the testing of a new device.
19. The minimum cavity radius required for full decoupling is proportional to the cube root of the explosion yield and inversely proportional to the cube root of the maximum pressure which the overlying rock can sustain without blowing out or collapsing.
20. Sykes, Lynn R., "Verification of Nuclear Test Bans with the Former Soviet Union: Dealing with Decoupled Explosions", EOS, p.58, April 20, 1993.
21. J.R. Murphy, J. Stevens, and N. Rimer, "Theoretical Simulation Analysis of Seismic Signals from Decoupled Explosions in Spherical and Ellipsoidal Cavities", EOS, p. 58, April 20, 1993.
22. Values of the pre-1971 releases refer to the Curies at the time of release. The containment failures of 1971-1988 are normalized to 12 hours after the event. The decay of an individual radioactive species is quantified by its half life - the time it takes for half of its nuclei to disintegrate. A mixture of fission products, however, has a more complicated decay pattern. The general rule of thumb for a nuclear explosion is that the total activity decreases by a factor of 10 for every sevenfold increase in time. In other words, if the gamma radiation 1 hour after an explosion has an intensity of 100 units, then seven hours later it will have an intensity of 10. Containment failures are unintentional releases of radioactive material to the atmosphere due to a failure of the containment system. They are termed "ventings", if they are prompt, massive releases; or "seeps", if they are slow, small releases that occur soon after a test. Late-time seeps are small releases that occur days or weeks after a test when gases diffuse through pore spaces of the overlying rock and are drawn to the surface by decreases in atmospheric pressure.
23. U.S. Congress, Office of Technology Assessment, "The Containment of Underground Nuclear Explosions", OTA-ISC-414 (Washington, DC: U.S. Government Printing Office, October 1989), Table 3-1, p.48.
24. Operational releases are deliberate and therefore could be controlled by a potential evader. Consequently, the time after the explosion has a strong effect on the amount of radioactivity.
25. "Announced United States Nuclear Tests" July 1945 through December 1991, Prepared by the U.S. Department of Energy, Nevada Field Office, Office of External Affairs, DOE/NV-209 (rev.12), May 1992, UC-700.
26. Note that the release of radioactive material is not due simply to burial depth. Compared to the larger yield tests, small tests are deeper relative to their size.
27. Of approximately 350 underground tests that took place in Kazakhstan between 1962 - 1989, roughly one of every three explosions accidentally vented into the atmosphere. In 30 cases, the radiation penetrated into populated settlements and areas where sheep were herded. See Kianitsa, Victor, "Test Anxiety", The Bulletin of the Atomic Scientists, p. 37-39, October 1993.
28. Ultimately, there even will be a level below which there will be debate as to what constitutes a nuclear test. For example, certain physics experiments involve nuclear materials and have measurable yields - at what level will these experiments be considered nuclear weapons tests?
29. See "The Politics of Verification: Limiting the Testing of Nuclear Weapons", by Gregory E. van der Vink and Christopher E. Paine, Science & Global Security, Vol.3, pp.261-288, 1993.
Nuclear Testing and Nonproliferation
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