On November 7, 1994, Nuclear Materials Control personnel at Rocky Flats performing a glovebox inspection determined that a one liter storage can containing fissile material had tipped in a heat detector tray, potentially violating criticality safety requirements related to minimum can-to-can spacing. Criticality engineering personnel analyzed the situation and concluded that a criticality violation had in fact occurred. No criticality took place, and there was no damage to facility equipment or radiation exposure to facility personnel. (ORPS Report RFO--EGGR-PUFAB-1994-0233)
Facility personnel are investigating the event and believe that the can was tipped by an accidental contact and not by movement resulting from internal oxidation. A cable was hanging near the can and may have been bumped during glovebox work, tipping the can. The investigation of this event is still ongoing.
A similar event occurred in the same building in 1993 when a one liter storage can containing plutonium metal fines and plutonium oxide was observed to be moving erratically. The can was also located on a heat detector tray in a glovebox. Facility personnel believe that can movement was caused by vibration from nearby equipment. There was no evidence of internal oxidation in the can. (ORPS Report RFO--EGGR-PUFAB-1993-0175)
A search of the ORPS data base indicates that other events involving consequences resulting from difficulties working in gloveboxes have occurred at DOE facilities in the past. In an earlier event at Rocky Flats, a vial of plutonium was not included in the (ORPS Report RFO--EGGR-ANALYTOPS-1991-1080).
Also at Rocky Flats in 1992, approximately 15 liters of nitric acid was spilled onto the floor of a glovebox, partly because the operators were unable to see that a section of tygon tubing had become disconnected (ORPS Report RFO--EGGR-771OPS-1992-0070). At Hanford in 1993, 100 gallons of nitric acid drained to a canyon floor when a worker inadvertently bumped a valve handle inside a glove box and was not aware that he had changed the position of the valve (ORPS Report RL--WHC-PFP-1993-0019).
Work inside a glovebox is by nature awkward and hampered by limited visibility. When handling and storing fissile materials in a glovebox, extra care should be taken to comply with specific criticality limitations. Facility personnel may wish to review their programs to ensure that appropriate controls are in place to maintain sufficient levels of caution when working in gloveboxes so that criticality safety limits are not exceeded.
Related guidance can be found in DOE/EH-0256T, DOE Radiological Control Manual. Article 347 discusses controls for glovebox operations. Article 312 specifies radiological planning activities that can be used to organize glovebox work. DOE 4330.4B, Maintenance Management Program, provides instructions in Part II, Section 8.3.1, that can be useful when preparing for glovebox work, by focusing on control of the work.