There are no problems with the data from a recent subcritical plutonium experiment in Nevada, despite the unprecedented breach of the protective steel container in which the explosive test took place, the National Nuclear Security Administration (NNSA) said.
The breach also has not set back the schedule for other planned subcritical tests, despite personnel at the Nevada National Security Site (NNSS) needing about a month to decontaminate the room used for the experiment, an NNSA spokesperson said last week by email.
The agency fired its last subcritical plutonium experiment, dubbed Ediza, on Feb. 13 at the Nevada National Security Site some 100 miles northwest of Las Vegas. After the test, however, radiological control technicians discovered some contamination near the welded steel confinement vessel used to contain the experiment’s explosive blast, according to a Defense Nuclear Safety Facilities Board (DNFSB) report from March.
The Nevada site’s Honeywell-led operations contractor, Mission Support and Test Services, later “identified cracks in [the Ediza vessel’s] fastener washers but found no evidence that the cover plates on the vessel were fractured,” according to a subsequent DNFSB report. The contractor inspected the vessel visually but did not do any further tests “to avoid the risk of releasing more radioactive material,” the DNFSB said.
Mission Support and Test Services later “entombed” the Ediza vessel in the Nevada site’s U1a Complex, the DNFSB reported. The NNSA performs all its subcritical plutonium tests at the underground U1a Complex.
The room in which the Ediza test took place was decomtaminated by March 12, the NNSA said.
“No personnel were exposed to contamination,” the spokesperson wrote. “The vessel is situated in a zero-room which is the containment barrier that protects NNSA workers and the public.”
In subcritical plutonium tests, the NNSA explosively compresses plutonium without causing a large nuclear explosion. The experiments help the agency determine whether aging plutonium can still provide the explosive yield specified by nuclear weapons designed during the Cold War.
