The National Nuclear Security Administration plans to perform two subcritical explosive experiments at the Nevada National Security Site in the fiscal year that ends Oct. 1, 2024, according to Deputy Administrator for Defense Nonproliferation Corey Hinderstein.
Since the Comprehensive Test Ban Treaty (CBTB) took effect in 1992, NNSA has performed 33 subcritical experiments at the Nevada site, Hinderstein told the CTBT: Science and Technology Conference 2023 in Vienna, Austria, recently.
Subcritical tests are designed so that no self-sustaining nuclear fission chain reaction occurs. Performed deep underground at Nevada’s U1a complex, the experiments apply conventional high explosives to nuclear materials to determine their explosive properties without a full-yield nuclear explosion.
Two more tests are scheduled for the fiscal year that runs from Oct. 1, 2023 to Sept. 30, 2024, Hinderstein said. The next high-explosive experiment is planned to take place late in fiscal 2023.
In February, a senior official from the Lawrence Livermore National Laboratory said the first of the two experiments, called Nob Hill, should fire in August. The next, called Twin Peaks, would fire a few months after that. The tests are part of a three-shot series the lab calls Nimble.
The Nevada site is the primary U.S. location where experiments with radioactive and other high-hazard materials are conducted, and the only location where high-explosive driven plutonium experiments can be conducted.
“We are open with the public and the international community about our plans for subcritical experiments,” Hinderstein said. “These experiments, permitted by the CTBT, help us to maintain the U.S. stockpile without nuclear explosive testing.”
The NNSA notifies treaty officials in advance of high explosive experiments so international monitoring stations are aware of and can detect the resultant seismic signals. That was most recently done in September 2020 for a series of explosive tests designed to validate the main high-explosive charge for future experiments, Hinderstein said.
The NNSA also publishes data after conducting subcritical experiments. The most recent data set was published in 2021 for experiments that took place in 2018 and 2019 in Nevada.
Hinderstein also reiterated the U.S. commitment to the test ban treaty, saying the U.S. nuclear weapon stockpile can be maintained without resorting to the explosive testing on which it relied until 1992.
“We do not need, and do not plan, to conduct nuclear explosive tests,” Hinderstein said. “The United States continues to observe its nuclear explosive testing moratorium as part of our commitment to the letter and the spirit of the CTBT, and calls on all states possessing nuclear weapons to declare or maintain a moratorium on nuclear explosive testing.”
Still, the NNSA has a presidential directive to be ready to return to explosive testing at any time if necessary, Hinderstein said. That requirement has been in place for several administrations and does not mean the U.S. has plans for actually testing a nuke, only that it could if needed, Hinderstein said.
