The US has revealed new details of an alleged Chinese nuclear test

By Jonathan Lande

WASHINGTON, Feb 17 (Reuters) – A senior U.S. official on Tuesday revealed what he said were new details of an underground nuclear test explosion that China allegedly carried out in June 2020.

Assistant Secretary of State Christopher Yew told an event at the Hudson Institute think tank in Washington that a remote seismic station in Kazakhstan measured a 2.75-magnitude “explosion” on June 22, 220, 450 miles (720 km) from the Lop Nor test site in western China.

“I’ve looked at more data since then. There’s very little chance that I could say it was anything other than an explosion, a single explosion,” Yeaw said, adding that the data was not consistent with mine explosions.

“It’s completely inconsistent with earthquakes,” said Yew, a former intelligence analyst and defense official with a doctorate in nuclear engineering. “It’s what you would expect from a nuclear explosive test.”

The Comprehensive Test Ban Treaty Organization, which is charged with detecting nuclear test explosions, said there was not enough data to confidently confirm Yaw’s allegations.

The Chinese embassy in Washington did not immediately respond to a request for comment.

U.S. President Donald Trump is pressing China, the U.S., and Russia to join the New Start deal, a replacement for the last U.S.-Russia strategic nuclear arms limitation agreement that expired on February 5.

The expiration of the treaty has raised concerns that the world is on the brink of an accelerated nuclear arms race.

China has denied nuclear tests

China, which has signed but not ratified the 1996 International Treaty Banning Nuclear Tests, has denied setting up an underground nuclear test site since the US first accused it at an international conference earlier this month. China’s last official underground test was in 1996.

The PS23 seismic station in Kazakhstan is part of a globe-spanning monitoring system operated by the Comprehensive Test Ban Treaty Organization (CTBTO).

The organization’s executive secretary, Robert Floyd, said in a statement that the PS23 station recorded “two small seismic events” 12 seconds apart on June 22, 2020.

The CTBTO’s monitoring system can detect “events” consistent with a nuclear test explosion that produced 551 tons (500 metric tons) of TNT or more, he said.

“These two incidents were well below that level. As a result, it is not possible to confidently assess the cause of these incidents, with this data alone,” Floyd said.

Yew said China tried to cover up the test by using a method known as decoupling, in which the device is detonated inside a large underground chamber to reduce the magnitude of the shock waves it sends through the surrounding rock.

Like China, the US has signed but not ratified the test ban. Under international law, both countries are bound to uphold the agreement.

The U.S. conducted its last underground nuclear test in 1992 and relies on a multibillion-dollar program that uses advanced instrumentation and supercomputer simulations to ensure its nuclear warheads function properly.

China has rejected Trump’s call to negotiate a three-way treaty to replace New START, claiming its strategic nuclear arsenal has been undermined by Washington and Moscow, the world’s biggest nuclear powers.

The Pentagon says China now has more than 600 operational warheads and is vastly expanding its strategic nuclear force. By the year 2030, China has projected to produce more than 1,000 weapons.

(Reporting by Jonathan Lande; Editing by Don Durfee and Jonathan Otis)