The Superpowers
In 1988, before the collapse of the Soviet Union began, the two superpowers had approximately 40,000 nuclear warheads altogether. The U.S. had about 12,000 strategic warheads (those capable of being delivered directly to the territory of the other side), and the USSR had about the same. The remaining warheads were tactical, that is, designed for use at shorter range. These were mostly deployed in Europe, across the line between East and West Germany, or on ships (although the navies were beginning to conclude that nuclear explosives were not useful to them). The START Treaty, aimed at 30% reductions, was under negotiation.

The End of the Cold War
As a consequence of the collapse of the Communist system in eastern Europe and the end of tensions between the two powers, all tactical nuclear weapons have been removed from Europe; the START Treaty (now called "START I") was ratified and all reductions have been completed. Further agreements, negotiated under the first President Bush and Russian Presidents Gorbachev and Yeltsin, were signed (START II) and ratified (by the U.S. in 1996, by Russia in 2000). Presidents Putin and George W. Bush agreed in 2002 to further reductions (called the "Moscow Treaty"), down to about 2000 strategic warheads on each side.
New START
The New START agreement between Russia and the U.S. was signed in April 2010, and was ratified by Congress in the last month of 2010, with largely bipartisan support and the support of the military. It further reduces the number of deployed nuclear warheads, to 1550 for each state. As in earlier treaties, there is no limitation on non-deployed warheads; that is, warheads taken out of deployment can be stored for future use. The agreement also places limitations on delivery vehicles (missiles and bombers): The maximum for deployed vehicles is 700, and the maximum for total deployed plus non-deployed is 800. Strict verification measures were in place in the earlier START I and START II agreements but not in the Bush-Putin agreements of 2002. The new treaty returns to a verification regime, in fact one more precise than in the earlier treaties: In previous treaties each side could verify the number of delivery vehicles on the other side, but not the number of warheads; in the new treaty verification also applies to warheads.

Verification
Verification of nuclear treaties includes a number of complementary measures:
  1. National technical means: This refers to steps that one side can take without necessarily any cooperation by the other side. The most important of these is satellite photography, with which one can pinpoint motions of even small objects on the earth's surface, and also detect any effort at operations to build new underground facilities. National technical means also includes detection of electronic signals for communication among weapons and command centers.
  2. Data exchanges, in which each side provides the other with information about its capabilities.
  3. Exhibitions: Each side invites the other to observe its nuclear facilities at regular intervals.
  4. On-site inspections: Each side is permitted to inspect facilities of the other side, and to demand on short notice to inspect facilities where questionable activities have occurred.
Of course there is nothing to prevent one side from refusing to allow verification measures to proceed. But the point of verification is not that you can guarantee that you will not be attacked by the other side. The point is to know when there is a risk, and to feel confident, when verification measures are going on normally, that there is no risk.

Remaining concerns
  • There is no plan for disposing of fissile material.
  • There is no plan for limiting production of new fissile material.
  • Strict accounting of deployed and dismantled weapons, and of fissile material, is not entirely reliable in Russia, because the nuclear establishment (scientists and engineers) is not well-supported. This means there is concern that weapons or fissile material may be deliberately or inadvertently transferred to other nations or non-governmental groups.
  • Perhaps most important, the warheads that remain deployed by the U.S. and Russia are still kept on alert status; they are poised to be launched rapidly in the event of a signal -- possibly faulty -- indicating an enemy attack.

Nunn-Luger
The Nunn-Luger program (named after the senators who originated it in the early 1990s) provides U.S. money to the Russians, to pay for deactivation of nuclear warheads, for tightened security surrounding nuclear facilities, and even for employment of some Russian nuclear scientists. The Bush administration, after initial opposition, supported continuing this program, and it continues today. These efforts reduce the chance of nuclear materials falling into the hands of terrorist groups, or nations that sanction terrorism.

Diluting uranium
What can be done with hundreds of tons of enriched uranium and plutonium, to prevent them from being made into weapons again? In the case of enriched uranium, the easiest first step is to mix it with ordinary uranium (which is 99.3% 238U), and so reduce the concentration of 235U to a level far below 90%. One could reduce the concentration to 3 or 5%, and then use that uranium as fuel in existing civilian nuclear reactors. The U.S., in fact, has recently agreed to purchase some such "diluted" uranium from Russia. Diluted uranium is much safer to have around than enriched uranium or plutonium, because any group wanting to make an explosive would have to again go through the expensive and technically complex enrichment process, to obtain weapons-grade uranium.


Using plutonium
As for plutonium, one could plan to fission it in civilian reactors. If one wanted to use plutonium metal (which is the form used in weapons) directly, the reactor would have to be one of a new type, which currently exists only in a design stage. Another possibility is to fabricate "mixed oxide fuel", a mixture of plutonium oxide and uranium, which can be used in existing reactors. Making this fuel involves some environmental cost, and there are hazards in its use in a reactor.

In general, many people feel it would be best to dispose of plutonium entirely and quickly, rather than keep it around for years as part of the civilian energy system. One proposal is to oxidize plutonium, then mix it with radioactive waste from existing reactors, solidify the combination into ceramic or glass blocks, and bury it deep underground. It would then be very difficult (and require complex technical equipment) for anyone intent on rebuilding weapons to reconstitute the plutonium metal from this mixture.


The Nuclear Posture Review
Under the administration of George W. Bush, with the U.S. the dominant power in the world, new nuclear issues, perhaps more urgent than those discussed above, came into view. The Bush Nuclear Posture Review, government's official statement of policy for use of nuclear weapons, suggested that the gradual phasing out of nuclear weapons as an element in national policy, was being reversed. Whereas during earlier decades, nuclear weapons existed only to deter the Soviet Union from nuclear attack against us, with the end of the Cold War, concern shifted to what were called "rogue states" which, though much weaker than the U.S., might threaten the use of biological or chemical weapons. The Nuclear Posture Review of the Obama administration (fall 2010) points to stricter limits on possible use of nuclear weapons by the U.S., but still allows for use in response to a non-nuclear attack by a nuclear-armed state. This seems clearly pointed at Iran and North Korea. Although left-leaning analysts might criticize the Bush Posture, and right-leaning analysts might criticize the Obama Posture, it can be argued that an official statement of nuclear policy is not really real-world-relevant; the important fact just being possession of nuclear weapons, which acts as a deterrent.

Earth-penetrators
During the Cold War the two super-powers built command and control centers deep under the ground, so that control of nuclear operations would survive during a nuclear attack. Hence there was interest in systems that could penetrate the earth, burrow underground, and detonate deep below the surface to destroy these command centers. Under the Bush II administration, plans were being developed for such earth-penetrators. In the fall 2005 Congress voted to end funding for this program.

KEY CONCEPTS

  • Tens of thousands of hydrogen weapons at peak of the arms race
  • Reductions under START I and II, Moscow, and New START
  • Verification measures
  • Continuing alert status
  • The Nunn-Luger program
  • Disposal problem for fissile material from weapons
    • Dilute uranium with 238U.
    • Fission plutonium in reactors.
    • Mix plutonium with waste and bury it.
  • The Nuclear Posture Reviews
  • Earth-penetrators