On December 13, 1994, two workers at the Hanford Plutonium Finishing Plant (PFP) inhaled airborne plutonium after removing a double-bagged contaminated plastic bottle from a seismic overpack. Nasal smears from the two workers tested positive for plutonium inhalation. Whole body counts were unable to detect ingestion of plutonium. During the critique, facility investigators identified an infraction of criticality prevention specifications. (ORPS Reports RL--WHC-PFP-1994-0056 and RL--WHC-PFP-1994-0057)
On December 12, operators removed and double-bagged four one-half liter plastic bottles, called polyjars, from a glovebox in room A of the PFP. The exterior surfaces of the polyjars were known to be contaminated with plutonium which is why each bottle was double-bagged. The operators moved the bagged polyjars to a second room for processing, but found that the glovebox in that room was filled with other items. They decided to store the polyjars in four seismic overpacks and leave them in the second room overnight. Seismic overpacks are seismically-qualified storage containers. However, they must be used in a glovebox or, if used outside a glovebox, they must be continuously monitored. The polyjars are typically inserted into the lid portion of the overpack and then the overpack is closed.
Two of the seismic overpacks in the second room were small and the operators had difficulty fitting the polyjars into the lids. They stopped work and requested guidance from their manager. The manager directed the workers to leave the polyjars partially installed in the overpack lids until they could be moved into the glovebox the next day.
On December 13, an operator attempted to remove one of the bagged polyjars stored in a small overpack to place it in the glovebox. When he could not remove it, he carried the lid to an adjoining room to get assistance from other workers. With the help of a second operator, he removed the polyjar. Two minutes later, a room continuous air monitor alarmed. Five workers left the area and submitted nasal smears to radiological control technicians (RCT).
Two workers had positive indications of plutonium inhalation. As a precaution, the RCTs administered chelating drugs to the two operators to aid in removal of plutonium from their bodies. RCTs took whole body counts of each worker, but were unable to detect plutonium. The RCTs surveyed and found contamination in four rooms presumably spread by the operators or by air movement between rooms.
During the critique, facility investigators determined that between December 12, and 13, the workers had stored the plutonium-bearing material in an unattended room in violation of criticality prevention specifications. At PFP, storage of fissile material in seismic overpacks outside a glovebox is acceptable provided that they are not left unattended. To correct the violation, operators moved the seismic overpacks into the glovebox.
PFP personnel are continuing their investigation to determine causes and to develop corrective actions and lessons learned.
Personnel should review criticality safety requirements before moving or storing fissile material to ensure that proper storage requirements are maintained. At a minimum, good work planning practice requires that approved, properly sized containers be readily available before they are needed.
Personnel at DOE facilities may wish to review work planning procedures to ensure that sufficient materials are staged before contaminated materials are packaged and moved.