A long-running disagreement between the Defense Nuclear Facilities Safety Board and the Department of Energy resurfaced last week when DNFSB Chairman Joyce Connery forwarded a staff issue report with a transmittal letter warning National Nuclear Security Administration chief Frank Klotz of unresolved safety problems at the Los Alamos National Laboratory’s Plutonium Facility. The issues concern component deficiencies, structural vulnerabilities, and operational risks in the event of a worst-case earthquake and fire that could breach the integrity of the structure and release plutonium and other hazardous materials into the environment.
The Plutonium Facility’s fire suppression system (FSS) “cannot be credited as a seismically qualified safety class control for postseismic fires without further analysis, significant system modifications, or potential replacement,” Connery stated in her May 12 letter. ”Taking our report under consideration, we request your written assessment of the FSS vulnerabilities and their impact on the facility’s current and planned safety posture, within 90 days of receipt of this letter.”
The report advises DOE and lab management and operations contractor Los Alamos National Security to keep in mind a growing set of interrelated problems as they make plans for future upgrades in the facility. The review team took the opportunity to remind decision-makers that DNFSB has since its 2009 recommendation encouraged a seismic retrofit for the building’s active confinement ventilation system as an alternative to their cost-saving priorities of that time. “This strategy would allow the confinement ventilation system to reduce reliably the consequences of a seismically induced event by many orders of magnitude to acceptably low values,” DNFSB recommended at the time.
When it is operational, the 235,000-square-foot complex known as PF-4 is the only fully capable plutonium facility in the nation, central to nuclear stockpile maintenance and plutonium research and processing. However, since June 2013 it has been mostly on pause during a period of structural and safety improvements related to addressing criticality issues, including earthquake and fire risks.
On Feb. 12, a DNFSB weekly site report for LANL noted that Plutonium Facility management declared a potential inadequacy of the safety analysis (PISA), requiring review of the quality of the iron fittings in the fire suppression system and interim compensatory measures if necessary, one of the problems identified in the staff review report, now tagged for further evaluation. An inadequate safety analysis was based on the assumption that the pipe connections were all steel fittings rather than cast or malleable iron. When the Plutonium Facility was built 40 years ago, the use of cast iron was more common, and upon further review construction documents for PF-4 indicated that both cast and malleable iron were used rather than steel. The matter is further complicated by the fact that the malleable iron can be used in low seismic stress areas, which means that each instance of iron material used in fittings would have to be tested to see if it is malleable or the more brittle cast iron. This question first came up in 2012 and was identified again during a 2015 DNFSB review.
A summary of multiple concerns about the safety quality of the building in the Jan. 29 report. included seismic interaction hazards between structures, as well as systems and components that are qualified for the earthquake risk that depend on components that are less than qualified. The report also highlighted a problem with incomplete in-service inspections caused by the need to obtain special permits for confined space inspections and led to a decision not to perform the inspections.
The Jan. 29 review noted that DOE’s upgrades in response to previous DNFSB concerns included seismic analysis and retrofits not only for the fire suppression system but also for the laboratory ceilings, which have to maintain their integrity in an earthquake in order for the fire suppression system to work properly.
In a statement, a Los Alamos National Laboratory representative said “The Laboratory looks forward to working closely with the NNSA in responding to the DNFSB letter on the PF-4 fire suppression system.”
