WASHINGTON — Personnel at the Nevada National Security Site have fired the second in a series of three planned subcritical plutonium tests called Nightshade, the acting head of the National Nuclear Security Administration said Wednesday.
Charles Verdon, the agency’s acting administrator, confirmed the test firing to Weapons Complex Morning Briefing after he testified before the Senate Appropriations energy and water development subcommittee.
The Los Alamos National Laboratory was overseeing the test at the Nevada National Security Site’s U1 underground complex. Nightshade B, the test that just fired, was scheduled for “spring 2021,” the lab had previously told the Monitor. It was not clear at deadline exactly when the second of three planned Nightshade shots went off; meteorological spring ended Sunday.
Nightshade A, the first subcritical test in more than a year, fired on Nov. 3. Nightshade C, the series finale, was scheduled to fire by September 2021, Los Alamos National Laboratory has said.
Subcritical tests explosively compress plutonium to the brink of a self-sustaining chain reaction so that scientists can judge how the metal is aging and whether it retains its designed destructive potential.
Combined with supercomputer parsing of Cold War era explosive testing and other data, subcritical tests allow the U.S. to be sure, without resorting to full-yield explosive tests, that its nuclear weapons are as potent as the military requires them to be.
The start of the Nightshade series of tests was delayed almost a year after difficulties with the final experiment in the previous subcritical series, the Lawrence Livermore National Laboratory-led Ediza, effectively closed U1a to subcritical tests. The last Ediza shot breached a diagnostic port in its steel confinement vessel, contaminating the room that hosts the contained explosions.
