The U.S. Nuclear Regulatory Commission (USNRC) contracted with the Packaging Review Group (PRG) at Lawrence Livermore National Laboratory (LLNL) to conduct a single, 30-ft shallow-angle drop test on the Combustion Engineering ABB-2901 drum-type shipping package. The purpose of the test was to determine if bolted-ring drum closures could fail during shallow-angle drops. The PRG at LLNL planned the test, and Defense Technologies Engineering Division (DTED) personnel from LLNL’s Site-300 Test Group executed the plan. The test was conducted in November 2001 using the drop-tower facility at LLNL’s Site 300. Two representatives from Westinghouse Electric Company in Columbia, South Carolina (WEC-SC); two USNRC staff members; and three PRG members from LLNL witnessed the preliminary test runs and the final test. The single test clearly demonstrated the vulnerability of the bolted-ring drum closure to shallow-angle drops—the test package’s drum closure was easily and totally separated from the drum package. The results of the preliminary test runs and the 30-ft shallow-angle drop test offer valuable qualitative understandings of the shallow-angle impact. • A drum package with a bolted-ring closure may be vulnerable to closure failure by the shallow-angle drop, even if results of the steep-angle drop demonstrate that the package is resistant to similar damage. • Although there exist other mechanisms, the shallow-angle drop produces closure failure mainly by buckling the drum lid and separating the drum lid and body, which the bolted ring cannot prevent. • Since the closure failure by the shallow-angle drop is generated mainly by structural instabilities of a highly discontinuous joint, the phenomenon can be rather unpredictable. Thus, a larger-than-normal margin of safety is recommended for the design of such packages. • The structural integrity of the bolted-ring drum closure design depends on a number of factors. To ensure that the drum closure survives the shallow-angle drop, the following general qualitative rules should be observed: – The drum closure components should be quality products made of ductile materials, and the torque value for tightening the bolted ring should be included in the SAR and operating procedures to ensure quality. – The package should not be too heavy. – The package internal structure should be impact-absorbent and resistant to disintegration and collapse under high compressive load. However, a strong internal structure may defeat the purpose of protecting the containment vessel from damage during a free drop. • If not previously tested, drum packages with bolted-ring drum closures should be drop-tested at shallow angles. Due to the unpredictable nature of the behavior, the demonstration should be completed by test and on a case-by-case basis. The test plan should take into account the behavior’s sensitivity to the details of the package design and the impact condition. • Because the shallow-angle drop can open the drum closure, organizations using these types of drum packages should assess the consequences of exposing the radioactive contents in the containment vessel to unconsidered external elements or conditions. This work was supported by the United States Nuclear Regulatory Commission under a Memorandum of Understanding with the United States Department of Energy, and performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract W-7405-Eng-48.
Drop Test Results for the Combustion Engineering Model No. ABB-2901 Fuel Pellet Shipping Package
