A radiation leak that exposed workers at an Idaho National Laboratory research facility in 2014 was caused by compromised equipment and air monitors that failed to detect the radioactive material, a new report says.
The 43-page internal report, completed in December and released to the Post Register last week, details what went wrong in late August 2014, when radioactive material escaped undetected from a sealed glove box over the course of several days. Former INL Director John Grossenbacher said last year the leak was the result of materials behaving in unforeseen ways.
The release of material — which occurred inside a room at the Fuel Manufacturing Facility, located at INL’s Materials and Fuels Complex west of Idaho Falls — was not discovered by employees until routine testing of air filters about a month later.
Nine workers in the room during the release were later found to have been internally exposed to the radioactive material. The report said their dose levels were well below yearly regulatory limits.
The room and glove box where the incident occurred reopened to normal operations Jan. 4, 2016.
At the high-security facility where the leak occurred, research and development work is conducted on nuclear fuels made up of materials such as plutonium, uranium and americium. Workers stand outside sealed-off “glove boxes,” sticking their arms into gloves mounted on the sides of the transparent boxes to safely work with tools and the radioactive materials located inside.
The facility includes two rooms equipped with glove boxes. According to the report, the radiation leak occurred in one of the rooms from Aug. 26 to 28, with another “minor” release Sept. 3. During the release, work had been underway heating nuclear fuel using a tool called an “arc melter,” so it could be cast into a tube for testing, INL officials told the Post Register on a tour of the facility last October.
According to the report, the radioactive material americium had managed to escape through several small holes later discovered in the glove box equipment. It was able to escape “particularly when arc melting activities” were underway, the report said.
Air monitor alarms intended to alert workers of such a dangerous event didn’t pick up on the americium.
On Sept. 24, however, officials conducted routine tests on filters taken from the air monitors, and found the americium. Workers evacuated. Air monitor data indicated the leak was limited to only a few days, the report said.
Biological assay samples were collected from 15 workers who had been working in the room over that time period, and nine were found to have received internal doses ranging from 2 millirem to 85 millirem, according to the report.
“Under federal law, (biological assay) monitoring is not required for individuals expected to receive less than 100 millirem per year on the job,” a report summary said.
Despite the leak not being discovered for nearly a month, INL officials told the Post Register they were able to estimate the worker dose levels at the time of the leak by measuring radioactivity in the workers’ urine and fecal samples, then using mathematical models from the International Commission on Radiological Protection.
The room was sealed off for months after the incident. Workers entered wearing special suits to conduct tests on the equipment to see how the leak occurred. Tests using helium pinpointed several leak points, which were fixed, according to the report.
Several steps will be taken to ensure another similar incident doesn’t occur, the report said. An annual helium leak test will take place, and certain glove box components will be replaced every three years.
Other glove boxes at INL and elsewhere under the management of INL contractor Battelle Energy Alliance are also being examined to see if similar leaks potentially could occur, according the report.
In addition, the air monitors were not set up to correctly identify americium. A software update and other changes to make the monitors more sensitive to different types and levels of contamination were made, the report said. Changes were shared with other facilities.
Details of the incident and exposure of employees were first reported by the Post Register in September, a year after the incident. The lab began releasing information on the leak and exposure of employees following inquiries from Utah resident Jack Stanton, who then alerted reporters to the event.
Jack Stanton is the brother of Ralph Stanton, a former INL employee at the center of a 2011 accident where plutonium powder spilled out of an old fuel plate, went airborne, and exposed 16 employees. That accident occurred next door to the Fuel Manufacturing Facility, at the Zero Power Physics Reactor Facility.
Some information on the incident was first posted on a DOE online incident reporting system in October 2014. The event also was briefly mentioned in a DOE Idaho operations summary distributed publicly in April 2015, however the summary did not mention several workers had received radiation doses.
Luke Ramseth can be reached at 542-6763. Twitter: @lramseth