THE EVOLVING NUCLEAR WEAPON THREAT TO SOCIETY

Vast reductions in deployed nuclear weapons have taken place, and the international consensus against nuclear weapon proliferation is strong. However, world security is threatened by emergent nuclear powers and especially by the growing threat of non-state deliberate unauthorized use of state-owned nuclear weapons and by the threat of improvised nuclear explosives fashioned from stocks of weapon-usable fissionable materials—highly-enriched uranium or plutonium I. The nature and number of nuclear weapons. I begin by reminding you of the destructiveness of nuclear weapons, and their current numbers around the world. Then I discuss a bit what it takes to build and detonate a nuclear weapon and the change in perception of the nuclear weapon threat over the decades since the two used in war at Hiroshima and Nagasaki August, 1945. SLIDE 1 08/16/2010_ 2010 Erice Evolving Nuclear Weapon Threat to Society_e.doc 2 The Evolving Nuclear Weapon Threat To Society Richard L. Garwin Slide 1 Hiroshima, October 1945 08/16/2010_ 2010 Erice Evolving Nuclear Weapon Threat to Society_e.doc 3 The Evolving Nuclear Weapon Threat To Society Richard L. Garwin Since then, almost 1000 nuclear weapons have been exploded in tests in the atmosphere, mostly by the United States and the former Soviet Union. U.S., Soviet, and U.K. atmospheric testing was brought to an end by the Limited Test Ban Treaty of 1963. Since 1992, the United States has not tested a nuclear weapon underground, and similarly with Russia. 08/16/2010_ 2010 Erice Evolving Nuclear Weapon Threat to Society_e.doc 4 The Evolving Nuclear Weapon Threat To Society Richard L. Garwin The bombs used in 1945 are shown in SLIDE 2; Slide 2 Little Boy and Fat Man – Hiroshima and Nagasaki bombs ~13 and 20 kilotons explosive yield, ~ 4 tons weight. 08/16/2010_ 2010 Erice Evolving Nuclear Weapon Threat to Society_e.doc 5 The Evolving Nuclear Weapon Threat To Society Richard L. Garwin They weighed more than 8000 lbs and had yields of 13 and 20 kt respectively. In contrast the 3 W-78/Mk-12A warheads on the U.S. Minuteman III missile, SLIDE 3, each weighs about 700-800 lbs and has a yield of 335 kt. The warhead is 71 inches long and 21 inches in base diameter. It was placed into service in late 1979. Slide 3 Three multiple independently targeted reentry vehicles for the Minuteman III. 08/16/2010_ 2010 Erice Evolving Nuclear Weapon Threat to Society_e.doc 6 The Evolving Nuclear Weapon Threat To Society Richard L. Garwin The Comprehensive Test Ban Treaty was opened for signature in 1996, and since then there have been nuclear tests underground only by India and Pakistan in 1998 and by North Korea in 2006 and 2009. All nuclear weapons begin with the assembly of a supercritical mass of fissile material that will support an exponentially growing neutron chain reaction with a generation time of 10-20 nanoseconds. A single fission is nothing; it would kill a few cells in the body. But a microsecond’s worth of chain reaction in the case of the Nagasaki bomb fissions a kilogram of plutonium and liberates energy within the bomb equivalent to 17,000 tons of high explosive. This produces an enormous fireball, and the heated air rises to create the typical “mushroom cloud.” SLIDE 4, Slide 4 15-kiloton surface burst. Nevada Test Site, 25 May 1953 08/16/2010_ 2010 Erice Evolving Nuclear Weapon Threat to Society_e.doc 7 The Evolving Nuclear Weapon Threat To Society Richard L. Garwin Nuclear weapons are again in the news. Their control and even potential elimination is a priority with the Obama Administration and with President Obama himself. Following President Obama’s speech in Prague April 5, 2009, we have had the signature in Prague April 8, 2010, by Presidents Obama and Medvedev of the “New START” Treaty to replace the 1991 Strategic Arms Reduction Treaty—START—that expired December 5, 2009. Furthermore, on April 6, 2010 the U.S. government issued the Nuclear Posture Review report—NPR 1 , a totally unclassified document with the purpose to specify what the U.S. intends to do about its nuclear weapons over the next five to ten years, and how it views nuclear weapons in the world, On April 12-13, President Obama presided in Washington over the Nuclear Security Summit, concentrating on rendering more secure the material that might be used to make nuclear weapons, transforming the administration goal of securing all weaponusable material within four years to a global goal to do the same thing. By “weapon usable material” is meant highly enriched uranium (by IAEA definition >20% U-235 in U-238, but in reality probably >80% U-235). The other major material for building nuclear weapons is plutonium, of which the Pu-239 isotope is most useful. However, even the plutonium separated from power reactor fuel in some countries for recycle into power reactors as Mixed OXide fuel (MOX) can be used by knowledgeable weapon builders to make a nuclear weapon without yield penalty or, by relative novices, with no less than a 1-2 kiloton yield (i.e., the content of 1000 trucks loaded with 2 tons of HE). Even a 1 kiloton nuclear explosion could kill many tens of thousands of people in a city within days by exposure to radiation fallout. For an excellent account, see “The Making of the Atomic Bomb” by Richard Rhodes. The wartime Manhattan Project to develop and produce the nuclear weapons cost the United States some $2 billion, and for many years that cost of “a billion dollars per bomb” and a feeling of American superiority persuaded many that only America could possess the superweapon. By 1949, though, the Soviet Union detonated its first nuclear weapon—a copy of the plutonium design tested July 16, 1945 near Alamogordo, New Mexico. The plutonium was created in production reactors fueled by natural uranium; the necessary 6 kg of Pu required 6000 megawatt-days of reactor power—in the case of the 200 MW(thermal) Hanford reactor, this was 30 fullpower days. For a modern power reactor of one-million kWe (3000 MWt) 2 days of operation would suffice. The Hiroshima gun-type weapon used about 60 kg of HEU, produced by a particularly inefficient “gaseous diffusion” isotopic separation process from the 0.71% U-235 content in natural uranium. Now most of the world uses the gas centrifuge in an extremely clever design that consumes only about 2% of the energy needed by gaseous diffusion for the same product. The common “light water” power reactor, of which the United States operates 104 at present, each produces about a million kWe of 1 http://www.defense.gov/npr/docs/2010%20nuclear%20posture%20review%20report.pdf 08/16/2010_ 2010 Erice Evolving Nuclear Weapon Threat to Society_e.doc 8 The Evolving Nuclear Weapon Threat To Society Richard L. Garwin electrical power and consumes annually about 25 tons of low-enriched uranium fuel, fissioning a ton per year of U-235. The 25 tons of spent fuel downloaded annually contains about 150 kg of Pu-239 and almost 100 kg of Pu-240 and heavier Pu isotopes. Most of the “separative work” required to produce a ton of HEU is already invested in the ton of LEU (4% U-235) fed annually to each power reactor. Each “unit of separative work” (SWU) costs on the world market about $100; 151 SWU are invested in each kg of U-235 in 4.4% fuel, so the SWU content of 1 kg of U-235 content costs about $15,100 and the SWUs in the ton of U-235 annual feed represents about $15.1 million in enrichment cost. At 60 kg of HEU per gun-type weapon and a SWU content of 232 SWU/kg, the SWU cost per kg is $23,200 and the enrichment cost of a weapon is $1.39 million. Naturally, a centrifuge plant that is built to make a few weapons will have higher cost than one that is amortized over 10 years of commercial fuel production, but the cost is negligible for a state of any size. And unfortunately, with the passage of time and the availability of the internet, the original “secrets” of the atomic bomb have become relatively common knowledge. Among useful books to help understand both nuclear weapons and nuclear power is “Megawatts and Megatons,” by Richard L. Garwin and Georges Charpak (2001). On January 4, 2007 four U.S. leaders in the security field—George P. Shultz, Sam Nunn, Henry A. Kissinger, and William J. Perry, following a well-prepared meeting at Stanford University, published an Op-Ed in the Wall Street Journal to proclaim their goal of the elimination of nuclear weapons and, in the nearer term, massive reductions in nuclear weaponry. President Obama has adopted this goal, and the April, 2010, NPR details some of the early conditions that must be met in order that a world without nuclear weapons might come about. Although the Department of Defense was responsible for the NPR, the Department of Energy, the State Department and the National Security Council (NSC) all contributed heavily, and it the NPR is a policy document that guides the entire government. Fortunately the NPR is entirely unclassified, although, naturally, some of the implementation directives will inevitably be secret. The Department of Energy’s National Nuclear Security Administration (NNSA), responsible for designing and creating U.S. nuclear weapons, receives its guidance consistent with the NPR, as do the military departments responsible for raising, equipping, and training the military personnel. 08/16/2010_ 2010 Erice Evolving Nuclear Weapon Threat to Society_e.doc 9 The Evolving Nuclear Weapon Threat To Society Richard L. Garwin It is clear to all, even those who believe that the elimination of nuclear weapons is infeasible or undesirable, that the 35,000 nuclear warheads the United States had at its peak in 1967 and the 45,000 Soviet nuclear warheads in 1982 are far in excess of a potential need for nuclear weaponry in the 21 st century. These were built and maintained, together with their delivery means and the command and control system to make it absolutely clear that an attempt the Soviet Union to destroy the United States (or vice versa) would l