BY MAIRE O’NEILL
An investigation team has made several recommendations related to implementation of procedures in a causal analysis report for a glovebox glove breach incident June 8 at the Los Alamos National Laboratory Plutonium Facility (PF-4) that resulted in 15 employees being exposed to Plutonium-238.
The report says the role and responsibility that glovebox operators have in preventing harm to themselves or others should be reinforced by addressing all glovebox safety procedure elements to maintain the integrity of the glovebox confinement system. (A glovebox is a controlled environment enclosure. Operations inside gloveboxes are performed through sealed glove openings for the protection of workers, the environment, and/or the process.)
The current failure rate of glovebox gloves is noted at 2-3 failures a month with 33 failures a year over the last two years. There are more than 7,000 gloves at PF-4.
The causal analysis team concluded that the failed glove in the June incident showed some degradation which was indication by some discoloration of the glove, but noted that efforts to puncture the glove at the fingertips and pull on the existing tear did not result in punctures or propagation of the existing tear. They concluded that something else happened to the glove after it was inspected the morning of the event.
“Pu-238 was then released into the room; gradually at first, then more significantly when (the operator) removed his hands from the gloves while reversing the failed glove into the room,” the report states.
A contributing cause of the incident is the failure to self-monitor for contamination after each removal of hands from the glovebox gloves, a practice the report says is accepted by management. The report recommends that management oversight failure be addresses through ensuring expectations, training and requirements are aligned to address any gap between work as imagined and work as performed.
The report also suggests more effective capture of glovebox glove failure information, replacement information and routine radiological monitoring data as well as the assignment of responsibility for gathering all glove replacement data and more frequent glove inspections. It also suggested that alternatives to reduce hands on work be evaluated.
Issues with the continuous air monitoring (CAM) system alarms in the room were also noted. The report said there was a nine minute interval between the generation of airborne radioactivity outside the glovebox and the first CAM alarm. Some employees in the room were unable to hear the alarms and were alerted by radiological control technicians to exit. The report indicates that there have been multiple incidents of alarming CAMs not being audible with some portable CAMs not as loud as other CAMs.
Internal dosimetry review and bioassay results indicated that at least six of the 15 persons who were in the room during the event had 100 percent probability of some internal uptake of radiation, with a ~79 to 90 percent probability for three of them, ~50 to 65 percent for four, and ~37 to 49 percent for two. The operator received two doses of chelation and all 15 of employees were reportedly off work for more than three weeks.