The employee was testing vials of plutonium samples when a radiation control officer detected radiation on a hood where the employee was working, according to a Defense Nuclear Facilities Safety Board report.
The officer examined the technician and found alpha contamination on the abdomen, lapel and right arm of her lab coat.
"When the technician was sent to the decontamination room, additional contamination was found on her personal clothing and on her skin in the vicinity of the lapel," the report said.
Lab spokeswoman Angie French said the levels were well below what could affect health but that it was investigated because the lab's goal is to avoid all such incidents.
Such contamination is measured in "disintegrations per minute." The U.S. Energy Department standard for a "reportable" incident is 5,000 dpm or more.
French said the technician's lab coat had a level of about 10,000 dpm and her personal clothing had 800 dpm. The level measured on her skin was about 400 dpm.
"It involved a very small amount of radiation," she said.
"In a year we average fewer than two reportable and four nonreportable events," French said, adding that technicians analyze hundreds of thousands of samples under the lab hoods each year.
The investigation concluded that the cause was inadequate monitoring by the employee of her gloved hands as she moved them in and out of the hood, French said.