The United States government today claimed Russia is “probably not” adhering to a global ban on nuclear weapons testing and is likely testing nuclear weapons in secret. The explosive accusation was made by the head of the Defense Intelligence Agency, Lt. Gen. Robert Ashley, but he offered no actual proof during his remarks to a DC-area think tank, and the exactmanner in which Russia is reportedly violating the ban is unclear.

In his to an audience at the Hudson Institute, Gen. Ashley gave a rundown of Russian and Chinese nuclear forces:

Russia’s development of new warhead designs and overall stockpile management efforts have been enhanced by its approach to nuclear testing. The United States believes that Russia probably is not adhering to its nuclear testing moratorium in a manner consistent with the “zero-yield” standard.

Our understanding of nuclear weapon development leads us to believe Russia’s testing activities would help it to improve its nuclear weapons capabilities. The United States, by contrast, has forgone such benefits by upholding a “zero-yield” standard.

“Zero-yield,” incidentally, is exactly what it sounds like: no nuclear explosions, period, or zero explosive yield.

The charge was repeated in the , which further stated the tests were being conducted at Russia’s remote Novaya Zemlya testing ground. North of the Arctic Circle, , including the infamous “,” which had a yield equivalent to 50,000,000 tons of TNT.

Most of the avowed nuclear powers, including the United States, Russian Federation, China, France, and the United Kingdom are signatories to the (CTBT). CTBT members agree not to conduct any nuclear weapon test explosion, or nuclear explosion. Forever. Yield, which could range from sub-kiloton (less than 1,000 tons of TNT) to multi-megaton is irrelevant.

When the avowed nuclear signatories signed it, they did it both for the good of world peace, but also because supercomputers were catching up to nuclear testing. There would be no need to test nukes, the thinking went, because a nuclear test could be just as effectively simulated in a computer without all the saber-rattling.

So what does the U.S. believe Russia is doing? It could be one of two things.

The first option is that Russia is conducting actual nuclear explosions in the sub-kiloton range. Many U.S. nuclear weapon designs are less than 1,000 tons—the new B-61-12 nuclear bomb, for example, literally has a “dial-a-yield” mechanism that allows it to explode with anywhere from the force of “just” 300 tons to 50,000 tons of TNT.

If Russia is indeed testing nuclear weapons they must be very, very small. The Comprehensive Nuclear Test Ban Treaty Organization’s International Monitoring System, or IMS, monitors the earth for underground nuclear explosions, with 170 monitoring stations spread across 76 countries worldwide. The seismic detectors at these stations can pick up the seismic tremors from a nuclear weapons test and . The CTBTO also maintains radionuclide particle monitoring stations to detect unusual nuclear radiation releases. , the CTBTO said that “The CTBTO’s International Monitoring System [IMS] is operating as normal and has not detected any unusual event.”

The international organization has not released any other statement addressing the DIA’s allegations.

The second possibility is that Russia is conducting “hydronuclear” tests. involve setting off a nuclear weapon but stopping far short of the weapon’s full potential explosive yield. Typically, hydronuclear tests involve refining existing designs, particularly safety mechanisms. The tests often substitute inert materials for plutonium or highly enriched uranium and the explosion is largely a function of the that are part of the device’s fission process. That could result in an explosive yield in the ounces or pounds, depending on the particular weapon design. Such tests, which do not result in a nuclear explosion, .

On the other hand, some hydronuclear tests do produce a teeny, tiny nuclear yield. Those tests are still banned, and according to the America’s chief negotiator for the CTBT the Russians . If such experiments are happening, they definitely ought not to be happening.

The U.S. has conducted hydronuclear tests, more commonly known as subcritical tests—or “subcrits.” Washington believes these tests are in compliance with the CTBT. Los Alamos National Labs, the home of the bomb, subcrits are useful for maintaining readiness of both the U.S. nuclear stockpile and the army of scientists and engineers that support it.

It seems very unlikely that Russia is testing actual nukes. There is no data from the International Monitoring System to support allegations of testingand it would extremely difficult to conduct any sort of testing without them finding out. It is far more likely Ashley is referring to hydronuclear tests that produce a small nuclear yield—which are also banned. The world needs to see the evidence, and hear Washington’s argument.

In the meantime, it’s important to remember that Washington has complained about Moscow violating the CTBT before—and nothing came of it. In 1997, the that Russia had probably conducted a nuclear test in violation of the treaty at Novaya Zemlaya. The report was leaked to the public but was that indicated the “nuclear test” was actually an earthquake that occurred 80 kilometers (49 miles) from the actual test site—at sea.