Cascade Complex Inventory Difference Study Committee: Mass Measurement Subcommittee: RMS (Replicate Mass Standards) Weighing

摘要

The subcommittee's purpose was to discuss present mass measurement methods and to propose a program for mass assurance. The goal was to provide information needed to evaluate shipper-receiver (S-R) differences between the gaseous diffusion plants. As part of the work to meet this goal a stainless steel replicate of a model 48Y cylinder was circulated among the diffusion plants for test weighings. This report describes the weighing test and the results of this test. The stainless steel cylinder weighed was one of the Replicate Mass Standards (RMS) as described in ANSI Standard N15.18-1975 titled Mass Calibration Techniques for Nuclear Material Control. This cylinder, number RMS-5, had its mass established by the National Bureau of Standards (NBS) in 1977. The cylinder, RMS-5 was shipped to each gaseous diffusion plant (GDP) and weighed on each scale used for interplant cylinder flows and other scales as desired. The test weighings were to be made twice a day for five days. This exercise allowed estimates of the parameters, scale bias, and scale process standard deviation to be madw which is the type of information needed to evaluate shipper-receiver differences. The main problem was the quantity (i.e. number of weighings) of information used for these estimates. Because of the small sample size the parameters estimated should be considered rough estimates. These estimates should also be estimated from check weight data available at each GDP. Using this data would allow more information for the bias and standard deviation estimates. In addition actual S-R differences can be used as a verification that the scale parameters are as stated and remain constant. (ERA citation 12:009014)