Statistical Analyses of AY-101 Ultrasonic Measurements of Wall Thickness

[摘要] Tank AY-101 wall thicknesses have been measured using ultrasonic (UT) images. Interest is in using the available data to estimate a worst-case minimum wall thickness for regions of the tank that remain unexamined with the UT approach. Each UT image can provide the wall thickness at a very large number of pixels, but only the minimum value for each image is used in this work. Since the data arise in this manner, one of several candidate statistical extreme value distributions should successfully fit these reported minimum values. Given a set of multiple UT images and the resulting minimum measured wall thicknesses, extreme value distributions are fit to the data with subsequent extrapolations made to estimate the minimum measured wall thickness expected for the entire tank. Such a minimum estimate incorporates both the variability in wall thicknesses and the uncertainty associated with the measurement method. Uncertainties of the estimated parameters are also derived and used in propagation of variance methods to obtain confidence bounds on the estimated minimum measured wall thickness as well.

[发布日期] 2002-10-31 [发布机构] Pacific Northwest National Laboratory (U.S.)

[关键词] Statistics;Radioactive Waste Storage;Storage Facilities;Thickness;Walls