In July, the complete TCAPTA instrument was shipped to METC. In early August, setup and preliminary test of the TCAPTA for the METC 1-foot fluidized bed unit was conducted by METC and UIUC personnel. Following the same procedure as described in the report for the period January 1--March 31, 1990, the detector was found to saturated when the tracer was located 90 mm away from the center of the crystal at 0.5 mCi source strength and 1300 V detector power supply. The detectors were then located 264 mm from the center line of the bed, which is equivalent to a clearance of 76 mm between the detector front surface and the outside surface of the bed. The discriminator threshold was set at 28.4 mV for an apparent detector signal height of 50 mV. Two calibrations were performed. Data were collected for a continuous four hour run with a sampling interval of 20 ms. The data were brought to UIUC for processing. In UIUC, the accuracy of the calibrations were analyzed first. It was found that the standard deviation for the empty bed calibration was about 20 mm, whereas the deviation was more than doubled for the second calibration, when the radiation was attenuated by both the wall and the particles. Using these calibration data, the calculated solids mean velocity and bulk density distributions had very low accuracy. It was then decided that a study of the nature of the gamma radiation attenuation through materials should be made in order to make corrections in processing the experimental data. Actual attenuation in experimental measurement depends not only on material property and geometry, but also on the discriminator setting which affects the contributions of the small angle scattered radiation. Critical experimental studies of the attenuation process is now planned in order to optimize the detection process and provide data for a corrosion scheme to be incorporated in the data processing software. 1 ref., 4 figs.