Abstract
With an advanced, safe, and reliable nuclear arsenal as well as a supportive president, the U.S. Senate has no reason to continue allowing the comprehensive Test Ban Treaty to languish.
Nearly 10 years ago, the U.S. Senate failed to give its consent to ratify the Comprehensive Test Ban Treaty (CTBT), an international agreement that commits its member states to ceasing all nuclear explosive testing. The Senate defeated the CTBT in a 51-48 vote that split largely along party lines. (The lone Senate holdout: West Virginia Democratic Sen. Robert Byrd, who voted “present” to protest the limited time allotted for the debate.) It was the first failure to ratify a major treaty since the Treaty of Versailles, which established the League of Nations. Then-Delaware Democratic Sen. Joseph Biden declared, “This is the most serious mistake the Senate has ever made.”
But today, due to changes in the makeup of the Senate, support from President Barack Obama and now-Vice President Biden, and increasing bipartisan support from senior officials of past administrations, there is a growing consensus that the CTBT could be ratified early in the Obama administration. Logistically, the treaty remains on the calendar of the Senate Foreign Relations Committee and could be ratified if 8 Republicans and all 59 Democrats currently in control of the Senate vote in favor of it.
At the time of the 1999 vote, Republican opposition mainly was driven by ill-founded concerns that the treaty was not sufficiently verifiable, as well as a belief that further testing would be needed to keep the U.S. nuclear arsenal safe and reliable.
The CTBT's intent is to prevent further proliferation of nuclear weapons to non-nuclear weapon states and to restrain countries with existing nuclear arsenals from developing more sophisticated designs that would likely require further nuclear testing. It also symbolizes a broader commitment by the nuclear weapon states to halt further nuclear weapons development and to work toward the eventual elimination of their nuclear weapons. As such, its negotiation and entry into force was a key promise to the non-nuclear weapon states in exchange for their support of the indefinite renewal of the Nuclear Non-Proliferation Treaty (NPT) in 1995.
Although there is widespread international support for the CTBT, the United States remains a key holdout. As of January, 180 countries have signed the treaty, and 146 countries have ratified it. In order for it to enter into force, though, 44 key countries listed in Annex 2 of the treaty must ratify it. So far, 35 of these 44 nations have done so; besides the United States, the other nine holdouts include China, Egypt, India, Indonesia, Iran, Israel, North Korea, and Pakistan. Each of these nations have its own unique reasons for resisting ratification, and some are simply waiting for others to ratify first. Needless to say, U.S. ratification of the CTBT would put tremendous pressure on these remaining states to do the same.
The Bush administration emphatically opposed the CTBT, arguing that further testing may someday be needed to maintain the reliability of the arsenal. As a result, the administration reduced funding to the CTBT monitoring organization and even considered legal attempts to reverse the U.S. signature to the treaty. (“Once a treaty has been presented to the Senate … an affirmative vote to return the treaty to the executive is required to remove it from the Senate calendar,” State Department lawyers concluded in a 2001 legal brief.) Nevertheless, the Bush administration continued to abide by the CTBT's terms; the United States has not conducted a nuclear test since 1992. In other words, Washington has, de facto, taken on the CTBT's obligations, without gaining the substantial benefits from its entry into force.
During the recent presidential campaign, Obama stated that he would “reach out to the Senate to secure the ratification of the CTBT at the earliest practical date and then launch a diplomatic effort to bring onboard other states whose ratifications are required for the treaty to enter into force.” In the Wall Street Journal, even the unlikely quartet of former secretaries of state Henry Kissinger and George Shultz, former Defense Secretary William Perry, and former Georgia Democratic Sen. Sam Nunn have described a vision of a “world free of nuclear weapons” and called for “a process for bringing the [CTBT] into effect.”
To my way of thinking, there are three reasons why the Senate should ratify the CTBT:
During the Cold War, the United States conducted more than 1,000 nuclear tests. As a consequence, Washington has a highly developed nuclear arsenal–an estimated 5,000 thermonuclear warheads at last count–of high-yield, lightweight designs that can be delivered by missiles or bombers over intercontinental distances. Only Russia, which conducted an estimated 715 nuclear tests during the Cold War, has a comparable nuclear arsenal in size and capabilities. In contrast, China has conducted 45 nuclear tests; India and Pakistan each have conducted six nuclear tests; and North Korea has conducted only one low-yield test. These countries and other would-be nuclear weapon states have far more to gain by a resumption of nuclear testing than the United States does.
A test ban will not prevent emerging countries from developing first-generation fission weapons similar to those used on Hiroshima and Nagasaki, but it will prevent existing nuclear powers from modernizing their arsenals with more sophisticated thermonuclear designs.
By itself, a test ban will not prevent emerging countries from developing first-generation fission weapons similar to those used on Hiroshima and Nagasaki. After all, the Hiroshima weapon was never tested before it was used. But a comprehensive test ban will prevent existing nuclear powers from modernizing their arsenals with more sophisticated thermonuclear designs. It will also impede emerging countries from developing more advanced fission weapons. (Most nuclear weapons in the arsenals of the major nuclear powers are two-stage thermonuclear weapons that derive their explosive energy from the combined power of nuclear fission and fusion; an initial fission reaction generates the high temperatures needed to trigger a secondary–and much more powerful–fusion reaction.)
An existing nuclear power would need to test any new, more advanced warhead design with a series of nuclear explosive “proof” tests in order to have high confidence in its reliability. Without such tests, military planners would be unlikely to deploy a warhead with truly new capabilities. A comprehensive test ban would therefore prevent the continuous development of new types of nuclear weapons–a process that characterized the Cold War.
For example, China is thought to possess about 20 ballistic nuclear missiles with single warheads that could reach the United States. Such a minimal deterrent has long been a part of official Chinese policy. However, China is concerned about U.S. efforts to develop an antiballistic missile system aimed at Asia. In order to counter this threat to its deterrent, China may be tempted to modernize its arsenal and produce the small, lightweight warheads necessary to place multiple warheads on a single ballistic missile. Such missiles would increase Beijing's nuclear capabilities against the United States. A nuclear test ban would hinder China's attempts to develop multiple-warhead missiles.
In South Asia, both Pakistan and India have committed to a testing moratorium since they tested nuclear weapons weeks apart from each other in 1998. Pakistan's arsenal is generally believed to be composed of first-generation nuclear warheads that utilize only nuclear fission. India claims to have tested a thermonuclear device with a yield of 43 kilotons. With further testing, both Pakistan and India might be able to develop more efficient boosted fission weapons, which would be easier to place on mid- to long-range nuclear missiles. Since missile flight times between India and Pakistan are as short as five minutes, such improvements could generate a dangerously unstable nuclear arms race in South Asia.
It's also worth noting the domino effect renewed nuclear testing could have. For instance, if the United States were to resume nuclear testing, it is likely that both Russia and China would respond with testing programs of their own. And if China tests, India and then Pakistan might resume their testing programs, too. Such a breakdown in the testing moratorium might encourage other states to withdraw from the NPT, giving them the right to pursue nuclear weapons and the means to produce them.
The IMS has been under development for a decade and is now approaching completion. Ultimately, it will consist of 337 worldwide facilities along with a data-analysis center in Vienna. As of January, approximately 70 percent of the stations have been certified and are in operation; another 10 percent are in the final testing phase. In addition, thousands of regional seismic stations–not part of the IMS but available to scientists–can contribute to the detection of explosive events.
All experts agree that the IMS has the capability to detect and identify at least 1-kiloton explosions anywhere in the world if no special efforts are made to conceal the explosion.1 According to the National Academy of Sciences, the IMS can detect underground nuclear explosions as small as 0.1 kilotons–less than 1 percent of the Hiroshima weapon–in hard rock, over most of the globe. In some key locations such as the Russian, Chinese, and U.S. nuclear test sites, the limit is as low as 0.02 kilotons, the equivalent of only 20 tons of TNT. Test explosions at this level would have little military value.
Take, for example, North Korea's October 2006 nuclear test. The best estimates of the magnitude 4.2 event on the Richter scale indicated a total yield of about 0.5 kilotons–less than 5 percent of the energy released in the Hiroshima weapon. The event was detected by at least 31 seismic stations around the world, including 21 IMS seismic stations. The seismic signature of the event had the high-frequency characteristics of an explosion, rather than an earthquake. The low yield suggests that the North Korean weapon did not explode with the intended yield typical of firstgeneration nuclear weapons. In any case, it demonstrated that the IMS system is able to detect and identify sub-kiloton nuclear explosions in key nations of concern. In addition, a radionuclide station located in Yellow-knife, Canada, detected unusually high levels of radioactive xenon 133 originating from the Korean peninsula, a clear signature of a nuclear explosion. Xenon is a noble gas that does not chemically bind with other materials and therefore, tends to leak even from well-contained underground nuclear explosions.
All experts agree that monitoring stations have the capability to detect and identify at least 1-kiloton explosions anywhere in the world if no special efforts are made to conceal the explosion.
Since the early 1960s, theories have been proffered that a determined country might be able to muffle the seismic signature of a test explosion by detonating it in a large underground cavity so that the air absorbs much of the explosive energy–an exercise termed “decoupling.” It has been shown in small tests that decoupling can reduce the strength of seismic signals by a factor of about 70.2 But larger tests of military significance would likely be detected. To fully decouple, a weapon would have to be detonated in a cavity with a diameter greater than 50 meters for a 1-kiloton explosion. Such cavities are difficult to construct without being detected; plus, there is no way to guarantee that the release of characteristic radioactive gases from such a test wouldn't be detected, as in the North Korean example. Not to mention, these decoupling scenarios would probably be beyond the reach of all but the most advanced countries, most of which already have sophisticated nuclear weapons.
The United States already has the tools it needs to maintain the long-term safety and reliability of the nation's nuclear deterrent through the Stockpile Stewardship Program. As part of the program, the nuclear weapons laboratories conduct an extensive series of non-nuclear tests on both production-line and stockpiled warheads to determine if there are any problems with the warheads themselves, their components, or their production procedures. The vast majority of weapon components do not involve the core nuclear explosive package anyway. And if a problem is found, these non-nuclear components can be replaced or upgraded without conducting a nuclear test.
In addition, the weapons laboratories can verify the behavior of the weapon's core nuclear components by conducting non-nuclear “hydrodynamic” tests. These experiments simulate the detailed dynamic behavior of the primary device without initiating a nuclear explosion. Weapon scientists replace the fissile plutonium 239 pit with an identical pit made with an inert, or non-fissile, isotope of plutonium. The high-explosive shock wave compresses the pit, makes it denser, and even liquefies it–hence the name, hydrodynamic experiment–just as in the implosion of the actual nuclear device. The only difference is that a nuclear chain reaction does not occur because the pit doesn't contain fissile material. Nevertheless, this method allows scientists to learn about the hydrodynamic behavior of the weapon without conducting an actual nuclear explosion.
One key concern has been the possible degradation over time of the weapon's core plutonium components–the so-called pits. In principle, the high-energy particles produced by the radioactive decay of the plutonium could damage the metal in the pit and affect its behavior. But this concern was alleviated in late 2006, when the Jasons–an independent panel of scientists and engineers that has long advised the U.S. government on nuclear weapon issues–assessed data from plutonium “accelerated aging” experiments. Based on data provided by the laboratories, the Jasons concluded that the core plutonium components in U.S. nuclear warheads have lifetimes of at least 85 years, and possibly much longer. Since the oldest warheads were built in the 1970s, the core nuclear components of current warheads will remain vital for at least another 50 years.
As a result of the information gained through stockpile surveillance, hydrodynamic tests, and other allowed experiments, the directors of the nuclear weapons laboratories have certified each of the country's weapon types to be safe, secure, and reliable every year since 1997. In turn, every defense and energy secretary during this same time period has issued formal memoranda to the president that the U.S. nuclear stockpile continues to be safe and reliable.
Given that the United States has the capability to maintain its nuclear deterrent without further nuclear testing and that the CTBT is effectively verifiable, Washington is clearly better off with the treaty in force than without it. In fact, ratifying it would serve as a symbolic and practical end to the arms races, as it represents a clear end to the continuous cycle of design, development, and testing of new nuclear weapons that characterized the Cold War.
Footnotes
1.
2.
A. L. Latter, R. Lelevier, E. Martinelli, W. McMillan, “A Method of Concealing Underground Nuclear Explosions,” Journal of Geophysical Research, March 1961, vol. 66, p. 943.