Cf-252-source-correlated transmission measurements for uranyl fluoride deposit in a 24-in-OD process pipe

Characterization of a hydrated uranyl fluoride (UO2F2 . bH(2)O) deposit in a 17 ft long, 24 in OD process pipe at the former Oak Ridge Gaseous Diffusi on Plant was successfully performed using Cf-252-source-correlated time-of- flight (TOF) transmission measurements. These measurements of neutrons and gamma rays through the pipe from an external Cf-252 fission source were use d to measure the deposit profile and its distribution along the pipe, the h ydration (or H/U), and the total uranium mass. The measurements were perfor med with a source in an ionization chamber on one side of the pipe and dete ctors on the other. Scanning the pipe vertically and horizontally produced a spatial and time-dependent radiograph of the deposit in which transmitted gamma rays and neutrons were separated in time. The cross-correlation func tion between the source and the detector was measured with the Nuclear Weap ons Identification System. After correcting for pipe effects, the deposit t hickness was determined from the transmitted neutrons and H/U from the gamm a rays. Results were consistent with a later intrusive observation of the s hape and the color of the deposit; i.e., the deposit was annular and was on the top of the Fire at some locations, demonstrating the usefulness of thi s method for deposit characterization. (C) 1999 Elsevier Science B.V. All r ights reserved.