By Dan Parsons
Engineers at the Los Alamos National Laboratory continue to upgrade the ventilation system at the plutonium pit production facility after two separate incidents where the system failed to blow contaminated air away from clean rooms where employees were working.
The most recent failure occurred on Aug. 22, when ventilation in the Plutonium Facility, called PF-4, experienced a loss of differential pressure between dirtier areas where radioactive material is allowed to be and cleaner areas where people work.
All personnel were evacuated from the affected areas in Technical Area 55 in Building 4. The plant was shut down for a day while engineers diagnosed the problem and found a solution. Normal pressures were restored to the south half of the facility several hours later through manual control, allowing regular access to that portion of the building. The northern wings remained restricted as personnel continued troubleshooting efforts until the evening of Aug. 31.
“There was never any risk to the workers, the community, or the environment,” a LANL spokesperson told the Exchange Monitor. “As with any mechanical system, components sometimes fail. We strive to minimize component failure through planned maintenance which is designed to improve system operability, reliability, availability, and maintainability.”
NNSA has spent “tens of millions of dollars” over the past decade to repair and upgrade the ventilation systems at PF-4, the LANL spokesperson said. They declined to provide a specific cost or timeline for the remaining work.
“We have been upgrading the ventilation system and other safety systems to replace aging or obsolete components,” the spokesperson said. “System engineers are assigned to all nuclear safety systems in PF-4. They track system performance through system health reports, identify necessary spare parts, and oversee maintenance on their systems.”
As with all federal facilities where radioactive materials are handled, PF-4’s ventilation system is configured to blow radioactive particles away from areas where it is unsafe for them to be suspended in the air. It is rare for the systems to fail, but a similar event occurred in March, according to LANL and a Defense Nuclear Facilities Safety Board (DNFSB) memo published in September.
In both cases, the failures were attributed to dampers that control the flow of air through the system, the DNFSB found. The March incident occurred when the actuators that control the dampers failed. In August, water accumulated in the air system, causing a similar failure of the positioners that control the damper actuators. Those components were replaced with parts found elsewhere in the plant but are no longer in use, according to the DNFSB.
A subsequent inspection of the ventilation system found several components that were either shut down or inoperable, including systems designed to condense moisture and remove it from the system to avoid water accumulation issues. One moisture analyzer was out of service for several months for lack of spare parts but was repaired and reactivated just two days before the August incident.
That inspection also found that ductwork and other components of the safety-significant system did not meet standards for performance in an earthquake or other seismic event. Those portions of the system were not previously upgraded because of “high cost and low safety benefit,” the DNFSB found. That specific ductwork is designed to protect workers inside the facility. It is not part of the boundary that keeps radioactive particles from leaving the facility and harming the public during seismic events.
