Leak rate tests on PC-1 plutonium product cans sealed by welding. Final report, September 1978--January 1979

The feasibility of sealing the PC-1 product can, the inner container in the plutonium air transportable (PAT) package, by welding the lid to the product can is discussed. We filled four PC-1 product cans with helium and sealed the cans by welding. A vacuum was drawn around each product can, and the leak rate of helium out of the can was measured with a mass spectrometer helium leak detector. To ensure that helium was trapped in the can after sealing, we analyzed the contents of each can with a mass spectrometer. We found that all four cans met the PC-1 equivalent air leak rate criterion specified by the Safety Analysis Report for the PAT package (leak rate less than 1 x 10-3 atm cm3 s-1). In addition, we found that three of the four cans met the leaktight criterion (equivalent air leak rate less than 1 x 10-7 atm cm3 s-1). We conclude that (1) sealing of the existing PC-1 product can by welding requires an apparatus for holding the lid on the can during welding, (2) welding of the PC-1 product can consistently results in a leak rate less than 1.0 x 10-3 atm cm3 s-1 (air), (3) by welding the PC-1 product can, it is possible to obtain a leak rate of less than 1.0 x 10-7 atm cm3 s-1 (air); however, the welding procedure used in these tests is not reliable for obtaining seals of this quality, and (4) it is not possible to identify leak rates of the order of 1.0 x 10-4 atm cm3 s-1 (air) or smaller by standard x-ray weld inspection