In OE Weekly Summary 94-32, NFS reported on an event at Los Alamos National Laboratory Plutonium Processing Facility (PPF) where a Continuous Air Monitor (CAM) alarmed as a result of airborne plutonium-238 which was traced to defective window gaskets on a glove-box in an adjacent room. On March 17, 1995, the facility manager issued the final report on the event. Following is a summary of the findings and lessons learned from the report. (ORPS Final Report ALO-LA-LANL-TA55-1994-0021)
In the early morning hours of July 21, 1994, operations center personnel received a CAM alarm for room 206 in the PPF and notified the Radiological Control Technician (RCT) assigned to the room. The room was closed down for backshift and no personnel were present. A week before the alarm, health physics operations personnel noticed elevated airborne activity on the fixed head air samples in room 207 and began an investigation to identify the source. They did not inform the operations group of the elevated readings. The samples were below 10 percent of a Derived Air Concentration (DAC), which would require posting as an airborne radioactivity area, but were higher than normal for about one-third of the sample filters. They set up a portable air sample unit in an attempt to locate the source of the elevated airborne activity. The RCT, responding to the alarm, red-lighted both rooms to prevent personnel from entering the rooms for normal work activities until the source of airborne radioactivity was located and corrected. During the day, operations personnel replaced a pair of defective glove-box gloves, contaminated to a level of 60,000 disintegrations per minute/100 cm2, in the trolley system in room 207. Facility personnel also corrected a flow inbalance between rooms 206 and 207, which they determined had caused the CAM in room 206 to alarm. Health physics personnel surveyed room 207 and recommended opening the rooms for normal operations.
On the morning of July 22, 1994, an RCT noticed elevated readings on the CAMs in room 207 and on the fixed head air sample filters. After changing the fixed head air sample filters, he informed the room supervisor of the elevated readings and took the filters to the health physics laboratory for immediate analysis. While the RCT was in the laboratory, a CAM alarmed in room 207 and three employees, working in the room without respiratory protection, red-lighted the room and evacuated to the adjacent corridor. They were not contaminated and their nasal smears were negative. The room remained red-lighted during the day while health physics and operations personnel, wearing full anti-contamination clothing and respiratory protection, attempted to locate the source of the airborne activity. The CAMs alarmed several times during these activities but the personnel in the room were not contaminated and their nasal smears were negative. On Monday July 25, 1994, facility personnel identified the source of the airborne activity to be defective window gaskets in a glove-box in room 207.
Facility managers investigating the event determined that the direct cause of this event was the defective window gasket material. A contributing cause was a work planning and organization deficiency. The defective gaskets were identified during a January 1994 inspection, but they were not replaced because of procurement lead time requirements for local containment devices. Management determined that the root cause of the event was inadequate administrative control because the window gasket inspection procedure did not provide a time limit for replacement of gaskets in poor condition, the health physics operations group did not notify operations of the elevated airborne radioactivity, the operations supervisor did not require precautionary respirator protection when he was informed of elevated radioactivity in room 207, and there were no formal written controls for adjustments to the ventilation line-up.
Facility managers instituted extensive corrective actions including temporary sealing of window gaskets, suspension of work activities in two glove-boxes, and replacement of the defective window gaskets. They also changed facility procedures to provide for timely replacement of gaskets in poor condition, to require notification of the operations group of abnormal radiological conditions, and to cover temporary changes in critical systems. Facility managers developed extensive lessons learned in the areas of procedure effectiveness, communications between work groups, reaction to abnormal conditions, configuration management of temporary changes, and procurement.
NFS personnel reviewed the ORPS database for similar events involving glove-box failures and spread of contamination and determined that the root cause in 30 percent of the events was attributed to management problems.
Although no personnel were contaminated, this event is significant because it resulted in a one month delay in the programs conducted in the room. The event could have been prevented by advance planning of procurement and replacement of the window gaskets when the periodic inspections indicated the need for it. This event also illustrates the need for attention to detail in investigating indications of elevated radioactivity to ensure that all sources are identified and appropriate mitigating actions are taken. Thorough management actions in analyzing the causes and developing corrective actions and lessons learned are noteworthy in this event.
DOE 4330.4B, Maintenance Management Program, Chapter II, Section 7 provides guidance for planning, scheduling, and coordinating maintenance activities. DOE facility personnel responsible for the conduct of maintenance activities should consider reviewing their maintenance program to ensure that it provides for the timely procurement and replacement of materials and components when periodic surveillance indicates the need for it.