Safety issues arose again at Los Alamos National Laboratory's plutonium facility last month, the latest in a series of radiation releases and operational mistakes as the site ramps up its work with nuclear material.
On May 16, a crew of pipe fitters was stripped and decontaminated after radioactive contamination was found on a worker's hands, on the crew's protective clothing and in the work area. The contamination wasn't discovered until after the job was finished. All pipe-fitting work was paused.
A week later, members of a separate work crew placed plutonium salts in a prohibited area, resulting in the temporary loss of their "fissile material handler" certifications.
The incidents were reported in weekly dispatches from the Defense Nuclear Facilities Safety Board, an independent advisory panel to the U.S. Secretary of Energy.
A lab spokesman said all workers were "thoroughly decontaminated" and did not receive a measurable dose of radiation.
He referred to the improper placement of plutonium salts as a "process deviation," and said it "did not create a criticality safety risk and posed no significant safety risks to workers or the public."
Criticality refers to a nuclear chain reaction.
The National Nuclear Security Administration announced this spring that Los Alamos would be tasked with building at least 30 plutonium pits each year. Crafting the grapefruit-sized plutonium metal spheres - used to trigger nuclear weapons-- is dangerous work and meticulous safety rules are intended to prevent a runaway chain reaction.
But numerous problems complying with these rules have been reported over the last few years, including a shutdown of the facility for more than a year in 2013. These issues come less than two months after managers at the plutonium facility called for pausing all work with nuclear materials for several days to improve safety practices and worker comprehension.
The pause was the result of recurrent problems related to criticality safety. In March, workers placed a plutonium pit in an unauthorized glove box and placed fissile material in a plutonium metal shell, causing a brief evacuation.
The safety board noted that the May 16 event was also similar to a contamination event last September. In both instances, a pipe-fitting crew was installing piping on a glove box - a contained box with attached gloves used to manipulate nuclear elements - and both jobs, which involved "high-hazard work," were unplanned.
It is at least the sixth time since January that the safety board has reported a contamination event at Los Alamos.