Nuclear Tests May Be Back on Moscow’s Agenda

Will the United States or Russia go back to explosively testing nuclear weapons underground?

Neither country has done an explosive nuclear test since 1992, stopping in the aftermath of the Soviet dissolution. Those tests were done underground: 828 in the United States at the Nevada Test Site, and 522 in the Soviet Union at the Semipalatinsk Nuclear Test Site, in what is now Kazakhstan, and on the Novaya Zemlya islands, north of the Arctic Circle. During the 1990s, Russia ratified the Comprehensive Nuclear Test Ban Treaty, and the United States signed it, promising to do no more of those tests.

That was almost 30 years ago. Both countries replaced nuclear explosive testing with a combination of smaller experiments and computer modeling. Computer modeling was part of designing nuclear weapons from the beginning, and by the early 1990s, the codes were reasonably good. They have been improved since then.

But if you’ve run a complex code for 30 years, you have a wish list of parameters to sharpen up and results that don’t fit. If the conventional experiments haven’t helped, you need nuclear explosive tests.

And then there’s the problem of existing weapons potentially wearing out. The components of nuclear weapons age, with uncertain effects. A nuclear weapon contains uranium and plutonium metals, conventional explosives, tritium gas, a variety of electrical and electronic components, and structural components. The uranium, plutonium, and tritium are radioactive, which hastens both their aging and that of the other components.

The Jasons, a high-level group of scientists who advise the U.S. government, saw no immediate problems with aging damage to plutonium pits, which provide the necessary fission part of a nuclear weapon, in 2009. But a recent letter, summarizing a longer classified report, implies more urgency in understanding the problem. Even if a pit is good for 100 years, most pits have been around for a third of that or more. The military wants to know the degree to which it can depend on nuclear weapons.

Another reason for nuclear explosive testing would be to develop a new nuclear weapon design. The United States and Russia are currently modernizing their nuclear forces, which includes upgrades to delivery vehicles, such as missiles, and the replacement of some warhead parts, but not entirely new warhead designs. In some cases, plutonium pits may be replaced. They will be rebuilt by different methods than those of 40 years ago; these differences may affect the operation of the weapons, possibly resulting in another reason for testing.

While there’s been more reporting on the U.S. side, the Russians face similar questions.

There are also political reasons for nuclear testing, both at home and the international stage. Those are particularly in play for Russia, locked in a long and costly invasion of Ukraine. The desired impression would be a show of strength, but that may not be how observers would see it. A Russian test, even as Russia is doing badly on the Ukrainian battlefield, may signal escalation, as Virginia Tech doctoral candidate Taylor Loy highlighted in a multifaceted tweet that was the impetus for this article. Or such a test may be taken to be a sign of weakness or lack of confidence in the nontesting regime. Former U.S. President Donald Trump talked about testing in a way that suggested he sees it as a show of strength.

Discussions of whether to test assume that we must continue to maintain at least the numbers of nuclear weapons that we have now, with similar capabilities. Deterrence is the easily provided justification. In a common interpretation, deterrence requires equal numbers of deployed weapons at, or currently slightly above, the limits of the New START treaty signed in 2010. Some argue that China’s apparent buildup of its nuclear arsenal requires yet more weapons.

What effect do the uncertainties of aging have on deterrence? Russia and the United States already target multiple warheads on each other to deal with the possibility of duds and shootdowns. Some increase in duds is likely to be acceptable, but those numbers are held closely. Safety in handling the warheads is an essential concern.

Rebuilding plutonium pits is expensive and potentially dangerous to workers and the environment. The United States is finding it difficult to increase pit production, and Russia’s difficulties with military equipment and its depletion in the war on Ukraine may undermine its modernization program. Perhaps the deterioration of these weapons could be an opportunity to turn toward lower numbers and, ultimately, elimination.

In 1988, a conference was held on the possibility of letting tritium, which gives a thermonuclear boost to nuclear weapons, decay without replacing it. Tritium must be produced in nuclear reactors, and it has a 12-year half-life, which means that in 12 years, half of the tritium in a weapon converts to nonradioactive helium, inert in weapons. Thus, the tritium in nuclear weapons must be replaced regularly. A tritium cutoff treaty intended to reduce or eliminate production was proposed in 1995 and again in 2020.

The United States and Russia hold the vast majority of nuclear weapons. They could agree to remove aged-out warheads from their stockpiles as those warheads reach some threshold of being unusable. The numbers to be removed yearly would be determined by information developed in the stockpile stewardship programs, but the specifics of criteria would be left up to the parties.

Plans in the United States to manufacture 30 pits a year, increasing to 80, suggest a maximum rate at which U.S. weapons designers expect pits to become unreliable. These numbers are supported by the recent Jason study. The United States and Russia now have about 1,670 deployed warheads each; the United States has 1,938 in reserve, and Russia has 2,815. If 30 were retired a year, the deployed numbers would be down to zero in 50 years; that same goal would take 20 years at 80 retirements a year.

A 50-year build-down could be gradual enough to be acceptable in domestic politics if agreed to by both sides. Verification would also be necessary. Several methods have been worked out for verifying complete warheads without divulging classified details.

The earlier proposals on tritium cutoff treaties provide ideas on how to verify tritium production. Tritium has civilian applications, so its production cannot be completely eliminated. Methods developed under the Plutonium Management and Disposition Agreement (PMDA) could allow the International Atomic Energy Agency to verify plutonium output. Agreements will also need to be made on subsequent use of plutonium, which is where the PMDA foundered. Enriched uranium can be down-blended for use in civilian power reactors, as was done in the Megatons to Megawatts program.

Other materials in the warheads—explosives and electrical equipment—have well-developed conventional methods of disposal. Some of them might be recycled into remaining warheads.

Decreasing nuclear arsenals in this way would be consistent with the promise in Article VI of the Nuclear Nonproliferation Treaty. Nonnuclear-weapons nations have long been dissatisfied with the lack of progress in that area. It might even help to avert an arms race with China.

None of this can be negotiated now, as Russia links New START to its war against Ukraine. At some point, however, the war will be over, and Russia will have to replenish its conventional armaments, which may bring on a cost crunch. Until then, negotiation strategies can be developed, along with political support in the United States and Europe, to engage with a post-war Russia.