EXPERIENCE USING A SPENT-FUEL MEASUREMENT SYSTEM

Year
1983
Author(s)
P.M. Rinard - Los Alamos National Laboratory
J. K. Halbig - Los Alamos National Laboratory
J.R. Phillips - Los Alamos National Laboratory
H.O. Menlove - Los Alamos National Laboratory
G. E. Hosier - Los Alamos National Laboratory
S. F. Klosterbuer - Los Alamos National Laboratory
Abstract
A portable nondestructive measurement system has been developed and used to measure neutron and gross gamma-ray emission from irradiated BWR and PWR fuel assemblies. The system has two principal components: a water-tight polyethylene detector head containing two sets of ion chambers and fission chambers for measuring opposite sides of the fuel assembly simultaneously, and a battery- powered electronics unit with a microprocessor for performing internal diagnostics and for assisting the operator in collection and analysis of the data. An average of 5-7 min is required to (1) position the fuel-handling bridge, (2) vertically raise the fuel assembly partially out of the storage rack, (3) perform the measurements, and (4) replace the fuel assembly in the storage rack. The neutron results with proper calibration are used to determine the exposures of individual fuel assemblies with an average accuracy of about 5%. Consistency of operator-declared values for cooling time and exposure can be verified using the gross gammaray measurements with an average accuracy of about 10%. Fuel assemblies with unusual irradiation histories or reconstituted fuel pins are easily identified.