Followup Activity
In OE Weekly Summary 94-08, ONS described an event that occurred on February 9, 1994, at the Savannah River Site where an operator discovered a bulging lid on a sealed forty- ounce plutonium-oxide storage can in a storage vault. By February 18, facility personnel discovered six other slightly deformed cans containing stabilized plutonium oxide blended with other stable oxides. (ORPS Report SR--WSRC-FBLINE-1994-0010)
On November 29, 1993, plutonium oxide was released from a vessel containing plutonium metal at Los Alamos National Laboratory (ORPS Report ALO-LA-LANL-TA55-1993-0039; DP Safety Information Letter 93-05). The incident resulted from the rupture of an inner storage vessel caused by mechanical forces from expansion due to plutonium oxidation. After contamination was released from a plutonium storage container during handling, workers transferred the package to a reduced-oxygen glove box. When the outer container was opened, the bagging material inside was found to be severely embrittled and deteriorated, and one end of the inner welded tube was ripped open as a result of massive oxide formation in the tube. After approximately 2 hours in the reduced-oxygen atmosphere, the inner tube swelled by approximately 50 percent in diameter and was noticeably warm to the touch. Reaction and swelling ceased after the tube was transferred to an argon-atmosphere glovebox.
A similar event in December 1992 resulted in release of plutonium oxide at a facility in the United Kingdom (DP Safety Information Letter 93-05). A slip-lid inner aluminum can containing a 2.2 kg plutonium ingot was bagged in polyvinylchloride and contained in a rim- seal outer can. Facility personnel measured the container mass periodically following storage in 1985. A constant mass was observed until 1990, when a three-to-four gram increase was noted. Oxidation and expansion occurred between 1990 and December 1992, which converted the entire ingot to oxide, ruptured both the inner and outer vessels, and released oxide into the storage environment.
Because of the potential for additional occurrences at DOE facilities, the Office of Defense Programs (DP) issued Safety Information Letter (SIL) 93-05, Potential Worker Contamination from Failed Plutonium Storage Containers, in December 1993 to notify DP facility managers and contractor personnel of safety problems associated with plutonium storage containers. The SIL included descriptions of the Los Alamos and United Kingdom events, a detailed discussion of the processes that can lead to plutonium oxidation and subsequent failure of storage vessels, and recommended remedial actions for certain plutonium storage configurations.
Also, in September 1993, DP issued DOE DP-60 Draft Report, Assessment of Plutonium Storage Safety Issues at Department of Energy Facilities. Personnel at DOE facilities where plutonium is stored should consider reviewing these documents and their recommendations for applicability to their facilities.