Silencing the Bomb: One Scientist’s Quest to Halt Nuclear Testing

THE CTBT TASK FORCE AND THE 2002 AND 2012 REPORTS OF THE NATIONAL ACADEMIES

THE CTBT TASK FORCE

In January 2000, U.S. Secretary of State Madeleine Albright announced that former chairman of the Joint Chiefs of Staff, retired General John Shalikashvili, had agreed to serve as an adviser to President Clinton and to her in order to spearhead the administration’s effort to achieve bipartisan support for ratification of the Comprehensive Nuclear Test Ban Treaty (CTBT) after its defeat in the U.S. Senate the year before.

Shalikashvili agreed to reach out to senators to find ways to narrow differences over the CTBT. He met for the first time in March 2000 with his CTBT task force. In a speech that month he stated, “I remain convinced that the United States will be safer with this important treaty than without it. True, potential proliferators can make simple fission bombs without testing. But a test ban makes it much harder to get nuclear weapons down to the sizes, the shapes and the weights most dangerous to us: deliverable in light airplanes, rudimentary missiles, or even in a terrorist’s luggage.”

On April 20, Shalikashvili indicated that it might well be necessary to attach conditions and understandings to the U.S. signing statement for the CTBT to convince senators to agree to ratification of the pact. The main concerns that he found after meeting with various senators who had voted against the CTBT in 1999 were: (1) the Treaty should not be of indefinite duration; (2) the United States should wait until the Stockpile Stewardship Program is completed; and (3) a treaty with a zero yield cannot be verified. He commented that he did not expect the Senate to act on the treaty in the remainder of 2000 and that his goal was to work toward developing “a more reasoned judgment” in the next administration.

FIRST STUDY BY THE NATIONAL ACADEMIES

To support his efforts, General Shalikashvili commissioned several studies, including one started in April 2000 with the U.S. National Academies to address major technical issues that had arisen during the 1999 Senate debate. Its mandate was confined to a specific set of important technical questions. The Academies were not asked to provide an overall “net assessment” of whether the CTBT was in the national security interest of the United States, which they did not do. The official government sponsor of the first study was the Department of State, with additional funding from the Department of Energy, the National Academy of Sciences (NAS), and several U.S. foundations.

For this study and another a decade later, the NAS turned to its standing Committee on International Security and Arms Control (CISAC), created in 1980. In 2000 CISAC picked members of the first CTBT study, with John Holdren of Harvard University as chair. Holdren, who later became President Barack Obama’s science adviser, had been involved for many years in arms control and energy issues. The committee contained members with special expertise, including those from academia, high-ranking retired military officers, persons involved in past arms control negotiations, and former officials of the weapons laboratories. The members also were chosen with regard for appropriate balance, including geophysicist Raymond Jeanloz from UC Berkeley and my seismological colleague Paul Richards from Columbia University.

After the committee signed off on a draft document in December 2000, its report, Technical Issues Related to the Comprehensive Nuclear Test Ban Treaty, then entered an extended process of multiagency classification review and peer review by the National Academies. The committee held extensive unclassified and classified meetings. General Shalikashvili was briefed by the committee at the classified level prior to the end of Clinton’s presidency. An unclassified report with a classified annex was published in 2002 during the Bush administration.

The report addressed three main concerns:

1. The capacity of the United States to maintain confidence in the safety and reliability of its nuclear stockpile in the absence of nuclear testing

2. The capabilities of the international nuclear test monitoring system and possibilities for decoupled nuclear explosions

3. Additions to their nuclear weapons capabilities that other countries could achieve through nuclear testing at yield levels that might escape detection—as well as the additions they could achieve without nuclear testing at all—and the potential effect of such additions on the security of the United States

By 2002 considerable advances had been made in stockpile confidence, nuclear monitoring, and dealing with evasive testing. The headline of the press release for the report published in 2002 was “Verification Capabilities Are Good, Cheating Possibilities Are Limited, and Safety and Reliability of U.S. Weapons Can Be Maintained Without Nuclear Tests.”

The 2002 report stated that a weapon’s reliability is dominated by the nonnuclear components of the entire system, such as electronics, which are testable under a CTBT. Stockpile stewardship by means other than nuclear testing is not a new requirement imposed by the CTBT; it has always been the mainstay of the U.S. approach to maintaining confidence in stockpile safety and reliability. Since 1996, much more had been learned under the Stockpile Stewardship Program about the stability of plutonium on time scales of many decades. Its stability is crucial to the functioning of the primary (fission) stage of thermonuclear weapons.

New data for nuclear monitoring had become available by 2002 when the International Monitoring System (IMS) was only partly in place. In addition, modern digital seismic data became available in near real time from hundreds of other global stations that were not part of the IMS. The capacity of computers to handle huge amounts of data, especially seismic waveforms, increased tremendously as well. Monitoring Russia and China became possible by 2002 once data started flowing from stations within those countries, something the United States had long considered essential for monitoring a full test ban. Data also became available from countries surrounding Russia and China, such as Mongolia, Kazakhstan, and Kirgizstan.

The new government of Kazakhstan worked to destroy tunnels and shafts at the former Soviet nuclear test site in the eastern part of its country. As part of that program, Kazakhstan detonated three large chemical explosions at varying depths to explore how much their seismic magnitudes changed with depth. All three were detected at stations of the International Monitoring System as far away as 4600 miles (7500 km).

The 2002 report concluded, “Taking all factors into account and assuming a fully functional IMS, we judge that an underground nuclear explosion cannot be confidently hidden if its yield is larger than 1 or 2 kilotons.” This was the capability I had claimed in my 1996 paper “Dealing with Decoupled Nuclear Explosions Under a Comprehensive Nuclear Test Ban Treaty.”

William Leith of the U.S. Geological Survey and I debated the feasibility of conducting hidden decoupled nuclear tests of various yields at one meeting of the committee on August 10, 2000. Leith’s expertise was based almost solely on his unpublished global catalog of very large holes in the ground. He argued before the CTBT committee and in a USGS Open File Report in 2001 that huge underground holes could be used for evasive decoupled testing of nuclear devices of 10 kilotons and larger.

Leith’s catalog, however, listed many huge holes that were open to the atmosphere, such as a giant sink (karst) hole in the jungles of Indonesia, which were not suitable for clandestine nuclear testing. Other buried openings on his list, such as the Norwegian skating rink for the Olympic games, were so shallow that their tops would be blown off even by very small nuclear explosions. Nevertheless, his views were repeated and quoted by Cyrus Knowles, Don Linger, and others of the former Defense Nuclear Agency and Larry Turnbull of the Arms Control Intelligence Staff. Fortunately, the relevant part of the 2002 NAS report, which I did not write, accepted my views on decoupling and not those of Leith.

A summary conclusion of the 2002 report stated that to get the large efficiency gains and weight reductions associated with boosting, an inexperienced state would need to test repeatedly at yields well above a kiloton, which it would not be able to conceal reliably. It also noted that considerable weapon design experience would be required to achieve low yields.

OTHER DEVELOPMENTS IN 2000

By mid-2000, all members of NATO except the United States had ratified the CTBT. In June 2000, the Russian Federation also ratified it, along with the bilateral strategic arms limitation treaty, START II, after seven years of delays. That treaty, ratified by the U.S. Senate in 1996, committed each side to cut its nuclear arsenal down to between 3000 and 3500 warheads, or about half the number allowed by START I. When he became president, George W. Bush gave notice to Russia that the United States would no longer adhere to the Anti–Ballistic Missile (ABM) Treaty and would build an ABM system; Russia then withdrew from START II.

On July 19, 2000, I attended the Stanford Center for International Security and Cooperation–Lawyers Alliance for World Security roundtable discussion on the CTBT in Palo Alto, California. General Shalikashvili attended, along with Republican senator Charles Hagel of Nebraska. Although Hagel had voted against the CTBT in 1999, he thought that much more time and debate should have been devoted to the treaty. In 2013 and 2014, he was secretary of defense. He and Shalikashvili showed great interest in what was said at the meeting about verification and stockpile stewardship.

Meanwhile, in early 2000, Sandia Lab Director Paul Robinson continued to claim difficulties in maintaining nuclear weapons without tests and to advocate the development of new nuclear weapons. He said that not doing so was tantamount to a policy of “self-deterrence” by the United States, in which the country would be giving up flexibility to respond to crises in a world with many nuclear powers. The Sandia National Laboratories is now a wholly owned subsidiary of the Lockheed Martin Corporation. Its primary mission is to develop, engineer, and test the nonnuclear components of nuclear weapons.

On March 29, 2000, the Albuquerque Journal reported that Robinson’s assertions were challenged by retired vice president of Sandia, Bob Peurifoy. Peurifoy said the weapons labs simply needed to focus on their mission of maintaining existing weapons—weapons they knew worked and would work for a long time. He suggested that what each of the weapons labs needed most was “a chief engineer” whose only mission would be assessing “the health of the stockpile.” Peurifoy said he had nothing against putting expensive bomb simulators and supercomputers at each of the nuclear weapons labs, if taxpayers were willing to pay for them, but commented that lab directors were misleading Congress and the public about the need for them.

A continuing fear is that funding of current programs to inspect existing weapons and to manufacture and replace aging parts will suffer as greater amounts of funding are devoted to the National Ignition Facility at Livermore and other very expensive long-term facilities at the weapons labs.

On May 31, 2000, Terry Wallace of the University of Arizona, Gregory van der Vink, and I convened a special session “The Comprehensive Test Ban Treaty: Issues of Verification and Monitoring” at the meeting of the American Geophysical Union in Washington, DC. Acting Assistant Secretary of State O. J. Sheaks opened the session with a broad overview of the CTBT, focusing on its role in promoting global arms control and nonproliferation objectives. Several of us described how poorly the Senate had examined the CTBT, especially verification and monitoring. I described the negative role of Larry Turnbull as cited by senators Lott and Helms in 1999.

On June 12, 2000, the Washington Post reported that new nuclear weapons were on the minds of a small but powerful cadre in the United States. It said that Senate Republicans had put a provision in the FY 2001 defense authorization bill that specifically required the secretaries of defense and energy to undertake a study to develop a new “low-yield” nuclear weapon that could destroy deeply buried targets and to permit the nuclear weapons labs to conduct limited research and development that might be necessary to complete the study. If it had become law, which it did not, it could have provided a rationale for resuming nuclear testing to confirm the new warhead design.

By April 2000 it was clear that Bush and Gore would be their parties’ presidential candidates in the November election. Gore was in favor of the CTBT. Bush was against it and remained so during his two terms in office. Bush, however, advocated and continued a moratorium on nuclear testing. One member of his administration publically advocated a resumption of nuclear testing before it got bogged down in Iraq. Here are the replies of the two presidential candidates in September 2000 to questions in Arms Control Today, the publication of the Arms Control Association:

ACT: What is your position on the ratification of the Comprehensive Test Ban Treaty (CTBT)? If the treaty is not ratified, should the United States continue the current testing moratorium?

Bush: Our nation should continue its moratorium on testing. But in the hard work of halting proliferation, the Comprehensive Test Ban Treaty is not the answer. The CTBT does not stop proliferation, especially to renegade regimes. It is not verifiable. It is not enforceable. And it would stop us from ensuring the safety and reliability of our nation’s deterrent, should the need arise. On these crucial matters, it offers only words and false hopes and high intentions with no guarantees whatever. We can fight the spread of nuclear weapons, but we cannot wish them away with unwise treaties.

Gore: I believe the Senate rejection of the Comprehensive Test Ban Treaty last year was an act of massive irresponsibility damaging to the security interests of the United States, and if elected president, I will immediately revive the ratification process and seek to rally the full force of American public opinion behind it.

Bush, of course, became president in January 2001 after a decision in his favor by the U.S. Supreme Court about the counting of votes in Florida.

U.S. NATIONAL ACADEMIES CTBT REPORT OF 2012

Interest in the Comprehensive Nuclear Test Ban Treaty (CTBT) resumed when Barak Obama became president in January 2009. John Holdren, a Harvard professor and director of the Woods Hole Research Center, became Obama’s science adviser and head of the White House Office of Science and Technology Policy. Later in 2009, Holdren’s office and the office of the U.S. Vice President requested that the National Academies conduct a follow-up CTBT study. Its report, published in 2012, was released in both unclassified and classified forms. While CTBT critics continued to find fault with findings in the 2002 report, several critics were generally more complimentary about the 2012 report.

As in the 2002 study, the 2012 report addressed the nuclear weapons stockpile, nuclear monitoring, and potential technical advances to nuclear weapons capabilities that might be gained by other countries from testing that might escape detection. Administration officials also requested views on the utility of on-site inspections as a verification tool and possible effects of undetectable cheating.

Ellen Williams chaired the 2009–2012 CTBT study. Her move from the University of Maryland to BP in London in early 2011 presented some communication complications. Except for two of us, the selected committee members had expertise in nuclear weapons but not nuclear monitoring. In addition to me, the other exception was Theodore Bowyer of Northwest Pacific Laboratories, an expert on the detection of bomb-produced xenon and other radioactive materials.

At first I was the only seismologist on the parent committee, but it would have been too difficult for me to evaluate seismic and other monitoring by myself. Hence, after our first meeting, the main committee established a Subcommittee on Seismology, which I was asked to chair. It was to provide input on detecting, locating, and identifying underground nuclear explosions and determining their yields. All nuclear tests since 1980 had been conducted underground. The Limited Test Ban Treaty of 1963 had banned tests in the atmosphere, space, and underwater but not those underground.

MAJOR CONCLUSIONS OF THE 2012 REPORT

The major conclusions of the 2012 report were:

1. The United States has the technical capability to maintain a safe, secure, and reliable stockpile of nuclear weapons into the foreseeable future without nuclear explosion testing, provided that sufficient resources for stockpile stewardship are in place. The Stockpile Stewardship Program (which was set up to increase understanding of nuclear device performance and the aging of weapons materials and components) has been more successful than was anticipated in 1999.

2. Seismic and radionuclide monitoring improved substantially during the decade after the 2002 report. Most of the seismic stations of the IMS are now operating and certified, determining data quality, calibration, and integrity as to tampering. U.S. National Technical Means provide additional monitoring capability.

3. Russia and China are unlikely to be able to deploy new types of strategic nuclear weapons that fall outside the design range of their nuclear explosion test experience without several multi-kiloton tests to be confident of their performance. Such multi-kiloton tests would be detectable even with evasive measures. Other countries intent on acquiring and deploying modern, two-stage thermonuclear weapons would not be able to be confident in their performance without multi-kiloton testing as well. Such tests likely would be detectable (even with evasion measures) by appropriately resourced U.S. National Technical Means and a completed IMS network.

STOCKPILE SECURITY

Many people had argued that corrosion, aging, and the phase stability of plutonium would result in short lifetimes for the plutonium pits, which constitute the first stage of thermonuclear weapons. Those pits consist of a hollow shell of plutonium clad in a corrosion-resistant metal, which is surrounded by chemical explosives. When a weapon is detonated, the explosives compress the pit into a supercritical mass and a fission chain reaction occurs. Plutonium pits are a main nuclear component of modern lightweight fission weapons. The behavior of plutonium at or near design yields is critical to the functioning of modern weapons. Work done by the weapons laboratories and reviewed by the JASON group in 2007 indicated long pit lifetimes of eighty-five to a hundred years, much longer than had been assessed earlier. Thus, ascertaining longer pit lifetimes has been a major advance in stockpile reliability.

Life extension programs (LEPs) to repair or replace components and to ascertain the aging of materials were completed as of 2014 for two of the weapons in the U.S. arsenal without the need for nuclear explosion tests. Another LEP is underway as of mid-2017 for the remaining versions of the B61 bomb.

MONITORING

The number of certified stations of the International Monitoring System grew from three in October 2000 to 283 as of mid-2017. The CTBT Organization provides data from areas that the United States previously had difficulty accessing. It also furnishes a common baseline of data to the world’s scientific community.

The yield of the North Korean test of 2006 was somewhat smaller than one kiloton, one of many indications that seismic monitoring techniques have improved significantly since the 2002 report.

The classified version of the 2012 report contains a separate section on U.S. verification capabilities, including those of the Air Force Technical Applications Center (AFTAC), which operates the U.S. classified program. While the IMS focuses on global monitoring, the United States also pays great attention to countries of special concern to it.

As discussed earlier, the most significant improvement in radionuclide monitoring since 2002 was the development of very sensitive detectors for radioactive bomb-produced gases such as xenon and argon. They are two of the six inert noble gases, which are difficult to contain following a nuclear explosion. The IMS radionuclide network has gone from being essentially nonexistent in 2002 to a nearly fully functional and robust network with new technology that has surpassed most expectations. The 2012 report states that in at least 50 percent of underground nuclear explosions near one kiloton or larger, even those carried out by experienced testers, xenon may be detectable offsite.

Xenon gases were detected for two of the North Korean underground nuclear tests, including the smallest in 2006. Many past underground Soviet explosions at Novaya Zemlya are known to have leaked radioactive noble gases. Of course, a nuclear explosion in the atmosphere would produce a greater variety of radioactive products and in larger amounts than an underground test.

WHAT OTHER COUNTRIES MIGHT ACCOMPLISH IN WEAPONS DESIGN BY TESTING AT VARIOUS YIELDS

Table 16.1, from the 2012 report, distinguishes technical achievements that might be accomplished for six different ranges of yields (left column) by countries with no or little prior nuclear test experience (center column) and those with greater experience, such as Russia, China, and the United States (right column). Those with greater experience obviously can accomplish more by testing at a given yield. Nevertheless, they have less to learn because they already have tested many devices and weapons with a variety of yields. It is clear that less can be accomplished as yields become smaller.

TABLE 16.1 Purposes and Plausible Technical Achievements for Underground Testing at Various Yields

YIELD (TONS OF TNT EQUIVALENT)	COUNTRIES OF LESSER PRIOR NUCLEAR EXPLOSION TEST EXPERIENCE AND/OR DESIGN SOPHISTICATION (ADVANCES ACHIEVABLE IN THE SPECIFIED YIELD RANGES ALSO INCLUDE ALL OF THOSE ACHIEVABLE AT LOWER YIELDS)	COUNTRIES OF GREATER PRIOR NUCLEAR EXPLOSION TEST EXPERIENCE AND/OR DESIGN SOPHISTICATION (ITEMS IN COLUMN TO LEFT, PLUS)
Subcritical experiments (permissible under the CTBT)	• Equation-of-state studies	• Limited insights relevant to designs for boosted fission weapons
	• High-explosive lens tests for implosion weapons
	• Development and certification of simple, bulky, relatively inefficient unboosted fission weapons (e.g., gun-type weapon)
< 1 ton (likely to remain undetected)	• Building experience and confidence with weapons physics experiments	• One-point safety tests
		• Validation of some unboosted fission weapon designs
		• Address some stockpile and design code issues
1–100 tons (may not be detectable, but strongly location dependent without evasion)	• One-point safety tests	• Develop low-yield weapons (validation of some unboosted fission weapon designs with yield well below a kiloton)
	• Pursue unboosted designs	• Possible overrun range for one-point safety tests
100 tons–1 kiloton (likely to be detected without evasion; reduced probability of detection with evasion, but strong location dependence)	• Pursue improved implosion weapon designs	• Proof tests of compact weapons with yield up to 1 kiloton
	• Gain confidence in certain small nuclear designs	• Validate some untested implosion weapon designs
		• Assess stockpile issues and validate some design codes
1–10 kilotons (unlikely to be concealable)	• Begin development of low-yield boosted fission weapons	• Development of low-yield boosted fission weapons
	• Eventual development and full testing of some implosion weapons and low-yield thermonuclear weapons	• Development and full testing of some implosion weapons and low-yield thermonuclear weapons
	• Eventual proof tests of fission weapons with yield up to 10 kilotons	• Proof tests of fission weapons with yield up to 10 kilotons
> 10 kilotons (not concealable)	• Eventual development and full testing of boosted fission weapons and thermonuclear weapons or higher-yield unboosted fission weapons	• Development and full testing of new configurations of boosted fission weapons and thermonuclear weapons
		• Pursue advanced strategic weapons concepts (e.g., EMP)

Source: National Academies Report of 2012, Table 4-3.

The conclusion of the 2012 report indicates that while much can be accomplished by various nations testing at yields greater than 10 kilotons (bottom row), these explosions can be readily detected. Smaller explosions between 1 and 10 kilotons are also unlikely to be concealed. Countries intent on acquiring and deploying modern, two-stage thermonuclear weapons would not be able to have confidence in their performance without multi-kiloton testing.

Note in Table 16.1 that the development of low-yield lightweight boosted fission weapons is possible only for yields of 1 to 10 kilotons for countries with little or no testing experience.

Table 16.1 indicates that proof tests of compact weapons with yields up to 1 kiloton are possible with tests of 0.1 to 1 kiloton by the three most experienced nuclear states. That yield range is likely to be detected in the absence of evasion. Evasive testing via the decoupling scenario is strongly dependent upon the location of an explosion. The Russian and Chinese test sites are well monitored down to very small levels, and neither country contains enough salt at those sites for a significant decoupled test in a large underground cavity.

Subcritical experiments called hydrodynamic tests, which involve no nuclear yield, are permitted under the CTBT (first row of Table 16.1). They can be used to test the properties of plutonium at very high shock pressures. The United States and Russia each stated that experiments conducted after 1996 were of zero yield and hence permitted under the terms of the CTBT. Each country observed the preparation and conduct of those experiments by the other in Nevada and Novaya Zemlya, probably by satellite imagery and other national technical means. No seismic waves were detected close to those times from the announced experiments at Novaya Zemlya.

Tests that involve a very tiny nuclear release equivalent to a few pounds (1 kg) of chemical explosive—called hydronuclear—are not permitted under the treaty. During the moratorium on testing in the early 1960s, the United States detonated hydrodynamic explosions in Nevada. It wanted to make sure that its weapons were “one-point safe” —that an accidental blow would generate at most a tiny nuclear yield. Those tests demonstrated that they were one-point safe. Presumably the other major nuclear powers ascertained before they signed the CTBT that their weapons were one-point safe as well. It is unclear if India, Pakistan, and North Korea, which did not sign the CTBT, have weapons that are one-point safe.

In 1994 Kathleen Bailey, a defense analyst, wrote an open technical report titled “Hydronuclear Experiments: Why They Are Not a Proliferation Danger.” I have included quotes from her paper here because they indicate that neither hydronuclear nor hydrodynamic experiments can be used to develop advanced nuclear weapons. (In 2014 Bailey and her husband Robert Barker, a former weapons scientist, who have long opposed limitations on nuclear testing, stated that the United States should unsign and renounce its participation in the CTBT.)

Bailey’s report was part of the debate in the United States about what yields should be banned under the CTBT as it was being negotiated. She stated, “If a country pursues boosted fission weapons or thermonuclear secondaries [in which the energy from a primary fission reaction compresses and ignites a secondary nuclear fusion reaction], HNEs [hydronuclear explosions] will be an ineffective tool.” She went on to say, “Also, HNEs cannot be used to optimize the advanced designs used by existing nuclear weapons states; they are far too low in energy to confirm that boosting will occur in boosted designs, much less provide useful information for staged thermonuclear weapons. They cannot accurately project the neutron multiplication rate at the time a device explodes.”

Some CTBT critics claim that Russia continues to perform hydronuclear tests and, if so, that gives them a large advantage. Bailey’s 1994 article indicates, however, how little can be learned from those very low yield tests. Can any country develop advanced, lightweight nuclear weapons by such tiny tests and be confident that they will work at yields of say 10 or 100 kilotons? The answer is no.

COMMENTS AT A FORUM HELD BY THE HERITAGE FOUNDATION

Soon after the 2012 NAS report was published, the Heritage Foundation, a conservative research think tank based in Washington, DC, released a transcript of an open forum “Comprehensive Test Ban Treaty: Questions and Challenges.” Paul Robinson, a former director of the Sandia weapons lab; John Foster, a former head of Livermore; and Thomas Scheber, a former director of strategic policy in the Department of Defense each spoke and took questions. The quotes that follow are from that transcript.

Robinson said, “Now, whereas one could not accuse that first [2002] report of being an intellectually deep or well-balanced study, I believe you can say that about this report [2012]. It is very much improved, they cover a much larger set of issues, and on some of them they do a very good job. I still have some I find fault with, as you will see. But, it does make far more interesting reading in its thoroughness, and, indeed, I’m proud to say that this group took up the primary issue of this treaty as being foremost about the defense of the country and our national security, and it tried to keep that uppermost…. I believe they [the 2012 NAS committee] have done an honest job.”

Each of the three, however, had specific criticisms of the 2012 report. It should be remembered that most experts are familiar either with weapons or with verification. The expertise of Robinson, Foster, and Scheber relate to weapons, not verification. They make a number of comments about verification that are decades behind current capabilities.

Robinson said, “One curious weakness in judgment that I’ll point out here is the extensive discussions in the report, based on the assumption that if a nation wanted to clandestinely carry out evasive tests, it would choose to do so within its nuclear test site. Now, this is exactly the opposite of what our intelligence community believes; an evader would never attempt to go to the area that we’re most heavily monitoring to carry out such an explosion, but certainly countries with large territorial masses would likely find very remote areas in which to conduct their tests, not only because of the ability of great secrecy there, but because they’re the farthest from any U.S. monitoring systems.”

The 2012 report, in fact, did not state that any country would conduct nuclear explosions only at an existing test site. What is different today from 2002 is that data are now available in near real time from numerous seismic stations in Russia, China, Mongolia, and the now independent countries of Central Asia. For sixty years the United States had sought greater monitoring capabilities in those areas. Their use greatly improves verification throughout various countries of concern to the United States. If stations in one country were unplugged at the time of a suspect event, it would be even more suspect. From his statements, Robinson clearly is not familiar with the present capabilities and how much verification has improved for countries of concern to the United States.

Foster stated, “If we look at the National Research Council report, we see that it talks a lot about detection. Detection is quite different from verification.” That statement is no longer correct. Previously, many people thought that to identify an event it needed to be about three times larger than that needed for detection. That criterion was correct when data were only available at large (teleseismic) distances. Once regional seismic data became available, it was no longer correct.

A previous standard rule was that data from at least four seismic stations were needed for detection and the determination of a good location. Today, good data from one or two regional stations can be used. An example of this is an earthquake of magnitude 2.8 that occurred near the Russian test site at Novaya Zemlya on June 26, 2007. High-frequency P and S waves at the seismic arrays in northern Norway and Spitsbergen were sufficient to identify the event as an earthquake. To obtain a better location, recordings of the 2007 event were cross-correlated with those of previous larger nuclear explosions. Had it been a fully coupled nuclear explosion, its yield would have been about 0.04 kilotons, or 40 tons.

Robinson said, “[W]e in the U.S. labs requested that the permitted test level [under a CTBT] should be set to a level which is in fact lower than a one-kiloton limit, which would have allowed us to carry out some very important experiments, in our view, to determine whether the first stage of multiple stage devices was indeed operating successfully…. [T]oday others may be carrying out such experiments without detection, while the U.S. is forbidden to do so.”

Debate raged in the United States for nearly twenty years about the determination of Soviet yields near the 150-kiloton limit of the Threshold Treaty. Setting a threshold under the CTBT near the lower limit of detection would be a mistake. Picking a zero nuclear yield was a better choice because debate likely would have gone on for decades about the yields near the lower limit of a very low threshold treaty.