The room is among the work areas in the plutonium facility being “decontaminated and decommissioned.”

In this case, crews are removing the support systems of the sealed compartments known as glove boxes, used to handle radioactive materials, to prepare for new equipment. The old components have some degree of radioactive contamination.

It’s part of the lab’s effort to ready the facility for a yearly production of 30 nuclear bomb cores, or pits, to modernize the arsenal and equip two new warheads being developed.

The affected employee was wearing a lab coat and booties for protection while escorting carpenters into the room, because guidelines only require someone to don full protective gear when a crew is doing work that could release contaminants, the Defense Nuclear Facilities Safety Board said in a December report.

The report noted a room is supposed to be decontaminated to enable a person to enter in a lab coat. But a radioactive substance — described as a particle — was missed.

An alarm sounded as the employee’s hands and feet were scanned at the exit, the report said. Personnel found one hand was affected and decontaminated it.

The room had several “contamination spreads” and instances of personnel having their protective gear contaminated in the previous several weeks, the most likely sources of the lingering radioactivity, the report said.

In an email, lab spokesman Steven Horak wrote contamination spreading in a room is not normal, because engineered controls — such as air filtering and containment systems — as well as permit guidelines are designed to quell it at the source.

“But PPE [personal protective equipment] and the immediate work area may become contaminated below the radiological work permit’s suspension limits,” Horak wrote.

Neither the safety board’s report nor Horak’s email indicated whether the room’s previous contamination remained within the permit’s allowable limits.

The worker’s skin being contaminated triggered the safety board’s report, Horak wrote, adding workers’ protective equipment getting contaminated during this type of project is tracked but not reported.

The report described two other incidents the day before in the facility’s basement, suggesting airborne radioactive contamination.

A worker’s protective gear was contaminated. The next day a crew, accompanied by a radiological technician, inspected waste bags as the possible cause but found no leak or damage.

Contamination was detected on three of the workers’ gear during body scans, with air-monitor alarms sounding as they left the basement.

Nuclear safety advocates said the larger concern is the increased frequency that employees are being contaminated through mishaps or even normal workdays as the lab pushes to make pits that can detonate warheads.

“This is not a one-off. This is a pattern,” said Dan Hirsch, retired director of environment and nuclear policy programs at the University of California, Santa Cruz. “This suggests the lab does not have sufficient controls to undertake the extraordinarily hazardous, new operations of pit production. They are having repeated contamination events, which shouldn’t be occurring.”

The lab had a string of glove box mishaps in 2023 that well surpassed the number logged in previous one-year periods.

In a recent incident, a sealed compartment caught on fire while workers were pulverizing 40-year-old legacy materials. No workers were contaminated or breathed in radioactive toxins, but a section of the facility was shut down for 10 days.

A week later, a worker lost control of a container inside a glove box, causing it to slam against the window. It shattered the outer leaded glass used as radiation shielding. Nasal swabs indicated the worker might have inhaled airborne contaminants, so the employee was given an examination known as a bioassay.

Earlier in the year, the lab recorded five glove box breaches in four weeks.

Horak has said worker safety remains the highest priority regardless of the pace of the work. With all abnormal events, including the latest ones, managers meet with personnel to discuss what went wrong and how controls can be improved to be more effective, he wrote in an email.

But one anti-nuclear activist contends more lapses are likely to happen with the lab being pressed to pursue pit manufacturing while doing daily operations in a facility growing busier and more crowded.

“They’re under pressure — that’s a big part of this,” said Greg Mello, executive director of the Los Alamos Study Group. “There’s too much going on in this facility.”

Decontaminating a room is a painstaking process that is more likely to be rushed with the push to get the decommissioning work done, Mello said, which means radioactive particles can be missed, as was the case here.

The lab should not try to normalize events that potentially imperil workers just because they’re happening more often, Mello said. “Personal contamination and airborne contamination should never be accepted or normalized.”

Horak insisted the plutonium facility is one of the safest places in the country because of the redundant safety measures in place to protect the work force and the community.

“We have ongoing programs to ensure the safe handling of materials,” Horak wrote.

But Hirsch argued the plain truth is a worker with almost no protective gear was let inside a room that was presumed to be decontaminated and wasn’t — resulting in a risk to the person’s health.

And this is just the latest incident in a short period, he said.

“I could see one of these events every few months,” Hirsch said. “You had multiple ones in a week.”