DEFENSE NUCLEAR FACILITIES SAFETY BOARD

February 23, 2024

TO: Katherine R. Herrera, Acting Technical Director

FROM: A. Holloway and C. Stott, Resident Inspectors

SUBJECT: Pantex Plant Activity Report for Week Ending February 23, 2024

Facility Appurtenances: Last week, during a preoperational check of the overhead hoist in a 

nuclear explosive bay, CNS production technicians noted that a plastic chain coupler had broken

into several pieces that fell to the facility floor. This coupler, which does not support the load 

during hoisting activities, connects the bridge motor gearbox to the final drive assembly for 

maneuvering the overhead hoist. Per the Pantex Technical Safety Requirements, appurtenances 

within nuclear explosive facilities are required to remain in place during design basis seismic 

events to prevent impacting a nuclear explosive. Consequently, CNS safety analysis engineering

declared a potential inadequacy of the safety analysis. Also, CNS implemented an operational 

restriction prohibiting hoist operations in facilities with this same chain coupler arrangement 

unless a barrier is installed around the coupler that would prevent broken pieces from falling.

Previously, CNS implemented a coupler replacement frequency of two years after three failures 

of this coupler design in other facilities within a six-year period. Last month, during an 

inspection of the most recently failed coupler, CNS did not identify degradation or excessive 

wear. CNS facility engineering has created work orders for installation of clamshell-type 

barriers in the affected facilities to permit resumption of hoisting activities. The resident 

inspectors note that CNS corrective actions do not prevent coupler failure resulting in a 

movement limitation for the facility crane assembly. For the facility with the broken coupler, 

CNS is assessing options to manually position the hoist to a desired location. 

Emergency Exercise: Last week, Pantex conducted a functional emergency exercise involving

a microburst—a localized column of sinking air within a thunderstorm—affecting the 

transportation of tritium reservoirs via a forklift. Strong winds from the microburst resulted in 

the deformation of a security roll-up door along the transportation route, which struck the forklift 

and caused it to topple onto its side. The scenario consequences included the forklift catching 

fire, the tritium being released, and the forklift driver sustaining minor injury. In this exercise, 

CNS added realism by requiring response actions to use actual weather conditions (e.g., wind 

speed and direction) after the simulated microburst. Specific topics evaluated by Pantex during 

the emergency exercise include (1) appropriate categorization and classification of the 

operational emergency by the plant shift superintendent, as well as implementation of correct site 

protective actions; (2) development of plume models for consequence assessment; (3) activation 

and standup of the emergency operations center; (4) response by the fire department and 

radiation safety department; and (5) development of a preliminary recovery plan.

Fire Protection: This week, CNS emergency services dispatch center reported a water flow 

alarm concurrent with a diesel fire pump start. These occurrences may indicate the presence of a 

leak that exceeds the ability of jockey pumps to maintain system pressure in the safety-class high 

pressure fire loop (HPFL). After entering the appropriate limiting condition for operation (LCO) 

for an unexplained diesel fire pump start, CNS identified and isolated a leak in the HPFL lead-in

piping for a non-nuclear facility and subsequently exited the LCO.