The United States’ thousands of nuclear warheads have the explosive equivalent of over 1 gigaton of TNT. It’s an amount of energy that could literally move mountains, reroute rivers, alter climate, and result in the deaths of hundreds of millions or even billions of people, through fire, radiation, and starvation.
Like everything else on Earth, those warheads are getting older. But unlike anything else on Earth, that mere aging may have profound consequences for the national security of the United States.
Most of the nuclear warheads in the U.S. arsenal date from the late 1970s and the 1980s, with anticipated lifetimes of 20 to 25 years; the most recent ones, the submarine-launched W88s, were added in 1988. Most of the warheads, in other words, are now past or nearing their estimated expiration dates. If nothing is done to maintain these hugely complex systems, they will in time fail, leaving the United States with no nuclear arsenal at all.
In fact, U.S. President Barack Obama has expressed an interest in eliminating all nuclear weapons—eventually. But he has also stated that the United States still needs a nuclear deterrent and that nuclear weapons should remain a key part of its security strategy for the time being.
Officials in the United States and the other seven declared nuclear powers are now grappling with a tricky and essentially unprecedented problem: What is the best way to sustain their nuclear deterrents? The question is particularly urgent in the United States, which has some 5200 functional nuclear warheads, about the same number as Russia, and several thousand more than the sum total of the world’s other nuclear arsenals combined.
Since the early 1990s, the prevailing view of nuclear weapons is that they are like other manufactured systems, such as cars and commercial jets. Their various components grow old, and eventually they will become nonfunctional. But that fate can be staved off by routine surveillance and maintenance and occasional replacement of parts or software. Such techniques have successfully extended the life spans of commercial airliners by decades.
But over the past several years, some high-placed U.S. officials, including Defense Secretary Robert Gates, have come around to a different view—that even with diligent inspection and maintenance, the current arsenal will soon become unreliable and will no longer have much deterrent value. The only solution, they say, is to design and build new warheads. These new weapons would be produced using state-of-the-art industrial methods that would vastly simplify manufacturing and maintenance and also drive down costs.
Such arguments for new warheads are compelling—but also controversial. Critics note that under the Treaty on the Non-Proliferation of Nuclear Weapons, or NPT, the United States and other nuclear nations are obligated to work toward eliminating their nuclear arsenals. Some even argue that U.S. modernization efforts, though confined so far to paper studies, have encouraged North Korea, Iran, and other countries to redouble their efforts to produce nuclear arsenals of their own. Proponents of building new warheads counter that these systems would simply be replacing antiquated weapons and that over time the total arsenal would continue to shrink.
Geopolitics is an inexact science, to put it mildly. But physics is not, and as physicists who’ve been involved in science and national security policy for many years, we believe that science and technology can, in this case at least, tell us all we need to know to decide this issue. Based on the available data, we are confident that the current program of stockpile stewardship, with some modifications, can preserve the U.S. arsenal for the foreseeable future and that it isn’t necessary—and may even be counterproductive—to pursue new warheads.
What we’re not saying is that extending the life span of the arsenal is going to be easy. To understand why, you’re going to need a quick refresher in nuclear history and technology.
The United States invented nuclear weapons during World War II and used the first ones toward the end of that war, in August 1945, when U.S. forces dropped atomic bombs on the Japanese cities of Hiroshima and Nagasaki. They remain the only nuclear weapons ever used in combat.
Not surprisingly, nuclear weapons quickly gained a central role in U.S. national security policy. A vast and secretive nuclear-weapons complex arose, with the U.S. Department of Defense dictating the military requirements that guided each new warhead design. Designing, building, testing, and stockpiling those warheads fell to the laboratories now operated by the U.S. Department of Energy (DOE)—namely, Lawrence Livermore, Sandia, and Los Alamos—and the weapons-production facilities, including Hanford, Oak Ridge, Rocky Flats, Y-12, Argonne, Savannah River, and Pantex.
Typically, the labs would produce competing designs for a new warhead, of which one would be selected. Los Alamos National Laboratory led the field: Warheads designed there now make up more than 80 percent of the active stockpile [see table, ”Warheads Produced at Los Alamos”].