Living with Nuclear Weapons: Sixty Years and Counting

IN HIS MEMORABLE PRESENTATION of 16 November 1945, J. Robert Oppenheimer began with the theme of unaccustomed secrecy and then proceeded to his main point, which was that nuclear weapons, during our lifetime, "could be either a great or a small trouble. They cannot be a small hope. They can be a great one." Oppenheimer judged that if nuclear weapons were used again, it could well be by the thousands or tens of thousands, and that the use of many nuclear weapons could lead to the destruction of civilization. He noted also that "wherever reactors are in operation there is a potential source, not necessarily a convenient one, of materials for weapons." Oppenheimer also commented that the much-observed $2 billion cost of the Manhattan Project to obtain the two bombs used to destroy Hiroshima and Nagasaki was highly misleading if used to calculate the cost of a bomb at $1 billion, and that any reasonable assessment should lead to a number even a thousand times smaller. He could not say even a few words about the construction of nuclear weapons, because President Truman had formally banned publication of such information beyond the highly informative but qualitative Smyth Report of August 1945.3 Oppenheimer spoke with the authority associated with his having directed the Los Alamos Scientific Laboratory from its inception in March 1943 through the assembly and delivery of the two nuclear weapons over Hiroshima and Nagasaki and the prior 16 July 1945 detonation of the implosion weapon at Alamogordo, New Mexico. Los Alamos was created to assemble the weapon-usable material to arrive from Oak Ridge in the form of highly enriched (at least 90% U-235, compared with the 0.711% U-235 in natural uranium), and the artificial fissionable isotope plutonium-239 that would arrive from the 200-megawatt (thermal) reactor at Hanford, at the rate of about 0.2 kg per day. Oppenheimer led the Los Alamos effort with inspiration and excellence. His choice for that role was itself an inspired one by the managing genius of the Manhattan Project, Brigadier General Leslie R. Groves. By all reports, Oppenheimer had a deep understanding of everything that passed at Los Alamos, both theoretical and experimental, and guided with a sure hand both substance and process. Oppenheimer was thus seized with the problem of the proliferation of nuclear weapons-one that is currently at the top of the talk, but not of the action, in the United States and in other leading countries. Where do we stand now on the beneficial uses of nuclear energy, on the number of nuclear weapons and the readiness to use them, and on the effort to obtain security by limiting proliferation? First I present the facts and then my own views. THE "PEACEFUL USE" OF NUCLEAR ENERGY More than a million intense radioactive sources are in use worldwide4 for industrial radiography, cross-linking of plastics, and food sterilization. Powerful sources are also used in radiation therapy for cancer, and weak sources in the ever-present nuclear scans for heart disease, and for other medical diagnostic purposes. By far the greatest investment and perhaps most visible aspect of things nuclear is the more than four hundred nuclear reactors worldwide, equivalent to about three hundred million-kilowatt power generators. A bewildering variety of practical fission reactors for extracting energy from the uranium nucleus is represented in a mere three types: * Light-water reactors * Heavy-water reactors * Graphite-water reactors Enrico Fermi and his group in Rome clearly saw the products of fission in their experiments with slow neutrons on uranium, beginning in 1934, but it was not established until late 1938 that this was the "fission" or breakup of the uranium nucleus into two very large fragments, despite work in many laboratories in the intervening four years. By 1939, Fermi and others had realized that the 0. …