Los Alamos glovebox fire sprinklers could cause criticality, safety watchdog says

Los Alamos National Laboratory is trying to prevent accidental criticalities caused when fires inside gloveboxes trigger a building’s sprinkler system, which might allow water to touch fissile material, according to a federal safety watchdog.

In a report dated Jan. 19, the National Nuclear Security Administration’s Field Office provided formal comments on a plan to limit fires inside certain gloveboxes “to avoid the scenario where an internal glovebox fire actuates the fire suppression system, and damage to the glovebox allows water ingress and potential moderation of fissile material.” 

The Defense Nuclear Facilities Safety Board (DNFSB) report said that “[m]any gloveboxes do not have criticality safety evaluations that account for flooding of the glovebox” and that “[t]hese boxes must either be analyzed to show they are safe if moderated by flooding or flooding must be incredible.” 

Accidental moderation is when a material such as water, heavy water, or graphite contacts otherwise stable fissile material such as plutonium, increasing the likelihood of fission, according to the U.S Nuclear Regulatory Commission. 

If that reaction occurs within a sealed glovebox, it could cause fissile material to reach criticality, endangering workers. The DNFSB said this issue is longstanding at Los Alamos. 

The board issued a similar report in March 2014, writing that the potential for fire safety systems to flood a glovebox, through either a burned glove or an inlet filter, could cause fissile material to go critical.  

“Criticality analysis and current inventory information further indicate about 24 locations that may not remain subcritical in a flooded condition,” the 2014 report said. 

DNFSB said in that report that Los Alamos had taken immediate actions to remedy the situation by ensuring immediate orderly exit from any facility experiencing a fire, advising responding firefighters about the situation and not allowing more than 4,500 grams of fissile material in a single location. 

“Personnel are also determining whether additional physical actions are needed to achieve a safe and stable configuration in the 24 locations,” DNFSB said.

The National Nuclear Security Administration did not immediately respond to questions Wednesday about the DNFSB’s report.