Reaction has been widespread to a memorandum issued Sept. 1 by the Defense Nuclear Facilities Safety Board regarding what it calls a criticality safety event that occurred Aug. 18 at the Los Alamos National Laboratory Plutonium Facility.
National Nuclear Security Administration (NNSA) officials are now saying that the amount of material involved was well within parameters known to be safe and that there was no risk of an inadvertent criticality at any time.
The DNFSB memorandum indicates that the event occurred in the casting room where the casting crew did not utilize a “required use-every-time attachment” to the material move procedure. It states that as a result, the crew moved a shell into a location that already contained plutonium metal, violating the posted limit set, which allows for wither metal or shells.
“The crew discovered this violation on Aug. 21 while moving the shell to another location. Following discovery, the crew conducted two additional nuclear material movements that they felt were necessary for product quality and security, rather than declare a potential process deviation as required by procedure and training. They then contacted programmatic operations management for a post-job review,” the memorandum states. “Notably, this casting operation had recently completed a federal readiness review and is one of the few operations where the crew that underwent readiness has not experienced personnel turnover.”
It adds that this was the first shell cast in the facility in about four years and the second time that a restarted operation encountered conduct of operations issues related to the criticality safety of material movements shortly after resuming nuclear work.
The memorandum states that Plutonium Facility management briefed the NNSA Field Office Aug. 29 on immediate actions taken, which included:
- conducting a formal causal analysis;
- pausing all casting operations;
- disqualifying the involved workers;
- requiring group leader authorization for all future moves in the casting room;
- mandating all group leaders observe at least three material movements;
- temporarily requiring a hard copy of the material move checklists for all moves; and
- studying longer-term improvements to the material movement process.
Also in the memorandum it was reported that on the afternoon of Aug. 30, the Plutonium Facility operations center restricted access to and suspended movement of all personnel within the facility for about two hours after radiological control technicians (RCT) found contamination on the personal protective clothing of several workers.
In total, RCTs identified contamination on 11 workers associated with a job removing a limited volume chilled water supply—one worker with 1.3 k dpm alpha contamination on his knuckle and the rest with contamination on their protective clothing, mainly booties, at levels ranging from 2–10 k dpm alpha.
Although surveys in the affected rooms found no indications of airborne contamination, the memorandum says they revealed multiple contaminated locations, including two discarded booties found with 100 k dpm alpha. Attendees at the subsequent fact-finding identified issues with the congested and space constrained location of the job, which was adjacent to the main room exit and the hand and foot monitors. The memorandum says they surmised that small drops of liquid from the system, which had been previously sampled and found to be below detection levels were actually contaminated (or became contaminated during the course of the job) and the liquid spread beyond the room as a result of the job.
The memorandum concludes that management identified corrective actions associated with evaluating:
- the methodology for sampling liquid systems to be breached;
- the approach for relaxing radiological controls when breaching systems; and
- the design of hot job exclusion area boundaries.
A spokesperson for the NNSA said Tuesday that the Lab reported Aug. 22 that it did not follow its operating procedures during a movement of materials within the facility.
“The amount of material involved was well within parameters known to be safe. At no time was there any risk of an inadvertent criticality. There was also no risk of injury or exposure to the workforce or public,” she said. “The Lab has since taken steps to prevent a similar event in the future and the qualifications of the workers involved were suspended pending rigorous retraining.”
She went on to say that NNSA requires its contractors to meet the highest standards of safety while working with hazardous and nuclear materials.
“At each of our laboratories, sites and production plants there are multiple layers of defense to prevent accidents involving these materials. These multiple layers of defense account for the fact that people will occasionally make mistakes and that equipment will occasionally malfunction,” she said.
All violations of operating procedures and equipment failures, however, are examined closely to minimize recurrence even when those incidents have no impact on the safety of the workers, facility, or the public, she added.
“NNSA’s safety record is a direct reflection of a committed workforce that ensures that the U.S. nuclear deterrent is safe and secure. With this focus on conservative operating parameters and multiple layers of defense, there has not been a nuclear criticality accident at a Department of Energy nuclear facility in nearly 40 years,” she concluded.
Jack Jekowski of Innovative Technology Partnerships, a consultant to the Regional Coalition of LANL Communities, told the Los Alamos Daily Post Tuesday that the event was one more thing to add to the long series of events going back to 2014 that have to be looked at and worked out.