Silencing the Bomb Page 24

  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 d
estroy 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.

  I suggested the names of four other experts in seismic monitoring. The parent committee approved these four as members of the subcommittee: Hans Hartse of Los Alamos; Paul Richards of Columbia University; William Walter of Livermore; and Gregory van der Vink, who had headed the OTA studies on Seismic Verification in 1988 and Containment of Underground Nuclear Explosions in 1989. Our subcommittee analyzed the monitoring of a large number of countries and the main remaining method of possible evasion, decoupling, and wrote extensive sections of the 2012 report on them.

  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 signi
ficant 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