That Alleged Chinese Nuclear Test

You may have seen the uproar about a possible Chinese nuclear test in 2020. It’s being publicized mainly because the Trump administration wants 1) to beat on China and 2) to have an excuse to start up nuclear testing again.

Earlier this week, Christopher Yeaw, Assistant Secretary of State for Arms Control and Nonproliferation presented a statement to the Council on Disarmament in Vienna that included a seismic trace of what the administration claims to be a Chinese test on June 22, 2020. Although formal complaints about a test go back to the Biden administration, this is the first time that evidence has been presented for it.

Why is this important? Let’s back up to the Comprehensive Nuclear Test Ban Treaty (CTBT) and the 1990s.

The Soviet Union cratered, but Russia inherited its stock of nuclear weapons. The Cold War was over. Arms control was a concern. President George H. W. Bush had removed some thousands of nuclear weapons from the US stockpile in a gesture of good will to Russia, to extend confidence that the US would not take advantage of its weakened state. The CTBT needed the nuclear states to sign in order to come into effect. Bush also ended nuclear testing, in line with the CTBT, so quickly that a device was downhole at the Nevada Test Site.

President Bill Clinton later signed the CTBT, but the Republicans in the Senate refused to ratify it as they had earlier arms control treaties. No treat of any kind has been signed since then.

So the CTBT could not come into effect. China has said they’ll ratify when the US ratifies.

The US and Russia have stuck with their testing moratoriums. But there has always been a faction that sees nuclear tests not as a way to obtain parameters for the design of nuclear weapons, but rather as a way to show the world how powerful the US is. So they are complaining about a possible Chinese breach of a treaty that their own warlike party won’t ratify.

They seem to have only one instance, June 22, 2020, almost six years ago, to complain about. The administration claims 100 tons of TNT yield if directly coupled to the rock, more if it’s in a thick metal container in a giant hole. That last is called decoupling and seems more trouble than it’s worth.

One hundred tons of TNT is both pretty big and pretty small. It’s small relative to most nuclear weapons, which yield the equivalent of thousands or millions of tons of TNT. But it’s large compared to smaller underground experiments that might have been done.

The squiggles from the seismographs are hard to interpret for this small a yield. Yeaw gives no information about the interpretation, and I am looking for interpretations by others. Fortunately, there is at least one seismologist who is willing to do this publicly. Here he is. This thread is the beginning of his work. He hasn’t published a conclusion yet.

The argument about Chinese violation of the test moratorium is based on one test. I would expect the US to come up with more if they have detected them. It’s possible that the sleuths who so badly want to find Chinese violations have simply missed other tests.

Why would the Chinese do only one test?

The primary purpose of nuclear weapons tests is to improve weapons designs. The number of tests depends on the goals and the findings of the tests. It’s possible that there were other, smaller, tests in this series. They would be much harder to detect. The US has done 1,054 tests. China has done 45. The fact that they are increasing their nuclear arsenal suggests that they are satisfied with their designs.

Dexter Eveleth suggests a reason for a single nuclear test, and there is a historical US precedent.

The most important quality of bombs – any type of bombs, but particularly nuclear bombs – is that they explode when they are supposed to and not at other times. Because conventional explosives crush the fissile material into criticality, there are two stages to this caution for nuclear bombs. If the conventional explosives go off by accident, will the nuclear explosion take place? This is known as one-point safety because nuclear bombs have more than one detonator.

Back in the late 1950s, the US and the Soviet Union observed a testing moratorium. The US found reason to believe that one of the nuclear designs in its stockpile was not one-point safe. The design needed to be tested and changed. It was a big deal because of the moratorium, and President Eisenhower had to approve a series of tests.

The tests were conducted underground, near Los Alamos. In a way, it was a forerunner of the underground testing that would become standard a few more years later. Being underground would contain the spread of radionuclides into the atmosphere, which was the primary way of detecting nuclear tests back then.

The tests were a few hundred feet underground and designed to give much lower yields than is alleged for the Chinese test. Both hydronuclear (yield-producing) and smaller tests were done. The problem was found and corrected. The Soviets found out about the tests and raised a stink, but that’s another story.

One Chinese test producing a low yield could have been to check out a one-point safety problem. Perhaps they simulated the condition that they feared could occur. An accident producing even 100 tons yield would be immediately damaging and would raise alarms in other countries.

If that was the purpose, the test would have been a good thing. It is to nobody’s advantage to have unsafe nulear weapons in the stockpiles. Perhaps a safety exception should be incorporated in the CTBT.

Cross-posted to Nuclear Diner