Silencing the Bomb Read online

  Picking members of the negotiating team that was sent to Moscow had to have been a major concern. It is interesting to see who was picked for the U.S. team and who was not. Seismology was the main technology used to monitor the sizes of explosions and hence the treaty’s threshold. Of the twelve members of the team, three of us were seismologists. Our delegation was unusual in that it contained two university seismologists, Eugene Herrin from Southern Methodist University in Dallas and me. Carl Romney, a chief scientist at the Advanced Research Projects Agency (ARPA) in the Pentagon, had formerly worked at the Air Force Technical Application Center (AFTAC).

  It is strange that no one from AFTAC, the agency responsible for operating the U.S. classified Atomic Energy Detecting System (AEDS), was a member of the negotiating team. Many U.S. government officials probably considered that Romney and Herrin had the greatest expertise in understanding the U.S. classified capabilities in seismology. Seismologists from the U.S. weapons labs were not part of the delegation either. Donald Springer of the Livermore Lab would have been an excellent member, but he was not chosen.

  Warren Heckrotte of Livermore, who was familiar with previous test ban negotiations, was replaced by Michael May, a high-level administrator at Livermore and an excellent physicist, about halfway through the negotiations when officials in Washington concluded that the Soviets were serious about negotiating a treaty. General Edward Rowny of the office of the U.S. Joint Chiefs of Staff, who was responsible for negotiations with the Soviet Union for the Strategic Arms Limitation Talks (SALT), also replaced one person from the Defense Department. Eric Willis of ARPA, a geochemist familiar with measuring radioactive isotopes, remained a member.

  I had worked in geophysics at the Lamont Geological Observatory since 1960. My main expertise in 1974 was studying long-period seismic surface waves, plate tectonics, and the discrimination of the signals of underground explosions from those of earthquakes.

  As it turned out, Herrin and I came to form a buffer between two warring factions within U.S. government officials at the negotiations—those who sought a verifiable treaty and hawks who opposed it, seeing it as an unadvised step toward a complete ban on nuclear testing. One member of the delegation from the Defense Department, a former professor of engineering at Columbia University, described himself to me as a “professional bastard.” Fortunately, he did not have much impact on the negotiations.

  After two weeks, some agencies in Washington wanted to replace Herrin and me with others from within the government. Ambassador Stoessel successfully resisted replacing us on the grounds that we made significant contributions to the technical discussions and to the balance of the delegation.

  About two weeks into the negotiations, the ambassador asked each of us in the delegation to state whether the allowed explosive yields of nuclear tests should be set at a threshold of 100 or 150 kilotons (a kiloton, abbreviated kt, is equivalent in explosive energy to one thousand tons of the chemical explosive TNT). Officials in Washington had sent those numbers to the ambassador. Herrin and I said that seismic waves generated by explosions of either of those yields could be detected readily all over the world, and their seismic signals could be distinguished easily from those generated by earthquakes.

  Our delegation had to be careful about classified materials. We were instructed not to leave any in our hotel rooms or on the conference room table, where they could be photographed by cameras hidden in the ornate ceiling of our meeting room in Moscow. We were not to talk about classified materials or the negotiations in Soviet cars that transported us to and from meetings. We should not talk to any of our scientific colleagues in Moscow who were not members of the Soviet delegation. I went to an opera in the Kremlin one evening where by chance I met Malcolm McKenna, a famous U.S. expert on paleontology, who held joint appointments at the American Museum of Natural History and our department at Columbia. He was en route to Mongolia to negotiate the reopening of joint scientific work between U.S. and Mongolian paleontologists at a famous dinosaur area that had not been visited by Western scientists since the 1930s. I could not tell him why I was in Moscow other than it involved earthquakes and explosions.

  A general in our delegation planned to attend the opera and asked one of the “handlers” what he should do if he got lost. The answer, in very accented English, was “Do not worry.” Obviously there was no chance of that because we were under close surveillance. One weekend our delegation traveled overnight by train to Leningrad for sightseeing. Upon our arrival at the train station, military officers saluted one of the Soviets accompanying us. Although she was not a scientist or a member of the Soviet delegation, she was obviously a high-ranking official.

  Our delegation met formally with representatives from the Soviet Union about four times a week, when members made formal presentations on specific topics followed by questions from the other delegation. I presented one on the determination of seismic magnitudes. At other times we met in the U.S. embassy, where we went over in detail the papers that were to be presented to the Soviets. Some of us walked from the embassy to our hotel for exercise and fresh air. One of our Soviet handlers later remarked that we were fast walkers.

  The Soviet delegation contained at least two members who worked on peaceful nuclear explosions (PNEs). They stated that PNEs were greatly needed for their national economy such as constructing a major canal. We met informally for dinner and drinks a few times and traveled with members of their delegation on weekends. At other times we ate with members of our delegation at our hotel. (Interestingly, we received better food after our ambassador formally announced agreements on specific topics, such as using yield as a measure of the threshold.) Roland Timerbaev of the Soviet Ministry of Foreign Affairs took two of us to the nearby historic town of Zagorsk another weekend. I was surprised that he, a Muslim, said he expected the Soviet Union to eventually accept the Russian Orthodox religion, which it did many years later.

  Kissinger and Nixon negotiated the final details of the TTBT in the first few days of July 1974. A few days later, Nixon and Soviet premier Leonid Brezhnev signed the treaty, which set the underground testing threshold at the more conservative 150-kiloton level. I flew home from Moscow to Frankfurt on a U.S. Air Force transport plane that had delivered a red convertible to Moscow, Nixon’s gift to Brezhnev, who was known to like fast cars.

  I think the Threshold Test Ban Treaty brought us another step closer to a Comprehensive Nuclear Test Ban Treaty (CTBT) by outlawing all nuclear weapons tests above the yield threshold. Nevertheless, I had no idea that twenty-two years would pass before a full test ban (a CTBT) finally would be approved by the General Assembly of the United Nations and signed by President Clinton and leaders of many other nations in 1996.

  As of mid-2017, 183 out of a total of 196 states had signed the Comprehensive Test Ban Treaty (CTBT), and 166 had both signed and ratified it. Those signing in 1996 included all states that acknowledged having nuclear weapons. The 1974 TTBT was signed about midway between the adoption of the CTBT in 1996 and the first serious calls for a Comprehensive Test Ban Treaty in 1954, soon after the United States and the Soviet Union had tested very large hydrogen (thermonuclear) weapons in the atmosphere.

  Nevertheless, although the major nuclear countries signed the CTBT in 1996, it can enter into force only after it has been signed and ratified by all forty-four countries that have either nuclear weapons or reactors. On-site inspections become possible under the treaty after its entry into force. Russia, Britain, and France have signed and ratified the treaty.

  Entry into force unfortunately remains an elusive goal. Neither the United States nor China nor Israel has ratified the treaty, even though each signed it in 1996. India, North Korea, and Pakistan, which now possess nuclear weapons, have not signed the treaty. Though not ratified, the CTBT has been very successful in that the countries that signed it have not tested nuclear weapons of military significance since 1996. India and Pakistan have not tested since 1998.

  Nuclear testing in
the atmosphere, in space, and underwater was outlawed by the Limited Test Ban Treaty (LTBT) of 1963. Nevertheless, the LTBT neither prohibited underground testing nor stopped the continued development of new nuclear weapons, as the 1996 CTBT does. While the LTBT did prevent great amounts of radioactive debris from entering the atmosphere and oceans, it was largely a public health measure.

  2

  DEVELOPMENT AND TESTING OF NUCLEAR WEAPONS

  DEVELOPMENT OF NUCLEAR WEAPONS

  During World War II, the United States government created the Manhattan District, often called the Manhattan Project, to develop the first nuclear weapons. It brought together leading scientists to work on nuclear weapons and organized facilities for producing their nuclear ingredients. Physicist J. Robert Oppenheimer, a professor at the University of California at Berkeley, was chosen as the director of the Los Alamos Laboratory, which designed the first nuclear weapons.

  The United States, fearing that Nazi Germany would get nuclear weapons first, constructed huge facilities to obtain two types of materials that can produce nuclear explosions by splitting (fissioning) the nucleus of certain atoms. The nucleus of an atom, consisting of protons and neutrons, accounts for most of the weight of an atom. The energy liberated in nuclear fission is huge. It is much greater than that in ordinary chemical reactions, which merely involve the lightweight electrons that surround the nucleus.

  One facility at Oak Ridge, Tennessee, was constructed to separate a rare form of the element uranium, abbreviated U 235, from the more abundant form of uranium, U 238. A factory at Hanford, Washington, produced plutonium in nuclear reactors. Plutonium (abbreviated Pu) is a man-made element that is not present naturally on Earth today.

  Most elements consist of different isotopes (or flavors) that differ only very slightly from one another. Consequently, they are difficult to separate. For example, all of the various isotopes of uranium consist of 92 protons and 92 electrons. The isotope U 235 of uranium contains 235 – 92 = 143 neutrons, whereas U 238 consists of 238 – 92 = 146 neutrons.

  In 1938 Otto Hahn, Fritz Strassmann, and Lise Meitner of the Kaiser Wilhelm Institute for Chemistry in Berlin, bombarded uranium atoms with neutrons and discovered that they could be fissioned, or broken into much lighter elements. Meitner, who was Jewish, fled to the Netherlands with the help of Hahn in July 1938 and went on to Sweden. In November 1938 Hahn discussed the results of his ongoing experiments with Meitner and Danish physicist Niels Bohr. Meitner and her nephew Otto Robert Frisch worked out the basic mathematics of nuclear fission in Sweden; it was Frisch who called the process nuclear fission. They realized that mass, m, was converted into a vast amount of energy, E, by Einstein’s famous equivalence of energy and mass, E = mc2 where c is the speed of light.

  In a second paper on the fissioning of uranium in February 1939, Hahn and Strassmann predicted the liberation of neutrons during the fission process. A chain reaction involving the continued fission of atoms was central to the liberation of immense amounts of energy and the development of nuclear weapons. A chain reaction occurs when a neutron causes an atom of U 235 to fission and to produce more neutrons, which go on to fission additional uranium atoms. Hahn and Strassmann, who did not leave Germany, received the Nobel Prize in 1944 for their discovery. Meitner should have been included.

  Fission involves the breakdown of either the plutonium isotope Pu 239 or uranium U 235 into lighter elements, typically ones near the middle of the periodic table of elements, and the release of huge amounts of energy as nuclear mass is converted into energy. In contrast, chemical reactions involve the release of much smaller amounts of energy per pound (or kilogram) and do not involve the change of one element into others as in nuclear reactions.

  During World War II, the United States quickly developed two types of nuclear weapons. An explosive device called the Gadget with a yield of 21 kilotons was tested in New Mexico on July 16, 1945. (A kiloton, or kt, is the equivalent energy released by 1000 tons of TNT.) Gadget consisted of 13.5 pounds (6.1 kg) of plutonium and about 5000 pounds (2270 kg) of high explosives to compress the plutonium into a denser mass. Ten seismic stations at distances of 270 to 700 miles (435 to 1130 km) recorded the explosion. An untested U 235 bomb called Little Boy was exploded over Hiroshima, Japan, on August 6, 1945. It weighed about 8000 pounds (3630 kg) and had a yield of about 13 kilotons.

  A plutonium nuclear weapon called Fat Man was detonated over Nagasaki, Japan, on August 8, 1945 with the same yield as that of the New Mexico device. The two nuclear weapons helped to bring the Pacific war to an end and ushered in the atomic age. A large bomber could carry one of the nuclear weapons of 1945 vintage, but these bombs were extremely heavy. The U 235 weapon used against Hiroshima, though not tested in a nuclear explosion beforehand, was developed by a group of some of the best scientists from many nations and to exacting tolerances. It would be difficult even today for a nonnuclear state to count on a similar device working without being fully tested, and it would be too heavy to place on a relatively crude missile.

  The United States government initiated a classified program called Long-Range Detection in 1947, under the direction of the Air Force, to monitor nuclear testing by other counties, especially the Soviet Union and later China. The classified monitoring network, called the Atomic Energy Detection System (AEDS), was, and still is, operated by the Air Force Technical Applications Center (AFTAC). Publications by AFTAC in 1997 and in 2009 by seismologist Carl Romney, who worked for them for many years, describe this early work on monitoring in more detail. In 1948 the United Kingdom and Canada were involved in monitoring nuclear tests set off by the United States on towers at Eniwetok Atoll in the western Pacific. Those explosions were detected by sampling airborne radioactivity but were not picked up by seismic stations at distances greater than 500 miles (800 km).

  The Air Weather Service of the Air Force began flying military aircraft between Alaska and Japan with special filters to try to detect radioactive debris carried by winds from possible atmospheric nuclear explosions by the USSR. Radioactive debris was captured by one such flight on September 3, 1949, and by one from Guam to Japan two days later. U.S. experts on radioactive isotopes identified collected debris as having been generated by a Soviet explosion of a plutonium device sometime between August 26 and 29, 1949. Scientists used meteorological observations to backtrack its location to somewhere in Central Asia. President Truman announced to the public on September 23 that the Soviet Union had conducted a nuclear test.

  When Premier Joseph Stalin learned about the Hiroshima explosion, he ordered the rapid development of atomic weapons by the USSR. Soon after World War II, the United States proposed the international control of fissionable materials and a halt to the arms race, but Stalin was not responsive. It was decades before it became known publicly that the Soviet explosion of 1949 was an exact copy of the U.S. Fat Man weapon of 1945.

  British scientist Klaus Fuchs, who was present at Los Alamos during the Manhattan Project, obtained its design by espionage. He had been a member of the Communist Party in Germany before fleeing to England in the early 1930s. Returning to Britain after World War II, Fuchs confessed he was a spy in 1950 and was convicted. He served nine years in prison and then immigrated to East Germany, where he died in 1988. The USSR built a reactor in the Ural Mountains to obtain plutonium for the 1949 explosion.

  The Soviet test of 1949 led Truman to order the rushed development of larger fission as well as thermonuclear weapons. The latter are often called “The Super” hydrogen or fusion weapons. The fusion of hydrogen takes place only at exceeding high temperatures, millions of degrees, like those in the sun. Stars liberate vast amounts of energy primarily by converting hydrogen by fusion into helium. Fusion weapons involve the conversion of one or two of the heavy hydrogen isotopes, deuterium and tritium, into helium. Fusion converts mass into huge amounts of liberated energy.

  The United States made several improvements in the yield-to-weight ratio of fission weapons. In a key development
called “boosting,” heavy isotopes of hydrogen—deuterium and/or tritium—were used to increase the number of neutrons bombarding the fissile material in the core of a fission device. Boosting permitted the weight of a weapon to be reduced considerably. The United States tested a boosted device named Item with a yield of about 45 kilotons in May 1951.

  In the Mike nuclear explosion of 1952 (figure 2.1), the United States tested the concept of igniting a full-scale fusion explosion with a small fission explosion, called either an initiator, a primary, or a trigger. A roomful of heavy equipment was needed to maintain its thermonuclear fuel, deuterium, at very low temperatures. Its yield of 10.4 megatons (Mt), or 10,400 kilotons, was about 800 times the yield of the Hiroshima explosion of 1945. Mike obliterated part of the Pacific island of Elugelab in the Marshall Islands. The arms race soon accelerated, and nuclear explosions of very high yield were developed and then deployed as weapons by the U.S. Air Force.

  FIGURE 2.1

  The Mike thermonuclear (hydrogen bomb) explosion.

  Photo by U.S. Atomic Energy Commission.

  The United States went on to develop fusion weapons with a solid fuel called lithium deuteride (the lightweight element lithium combined with one of the heavy isotopes of hydrogen called deuterium). That fuel is stable at room temperatures, meaning it could be used and deployed for fusion weapons. The United States tested this device first at Bikini Atoll in the Bravo explosion of March 1, 1954. Its yield of 15,000 kilotons (15 Mt) was much larger than expected, because the contribution of an isotope of lithium, Li 7, to fusion reactions was not foreseen. During the 1950s, the United States went on to develop and test a number of thermonuclear weapons in the megaton range.