Supplemental Report: Technetium-99 On-Line Monitoring by Beta Counting for Hanford Supernate Waste Solutions

摘要

SRTC is investigating approaches for near-real-time monitoring of 99Tc at selected points in the proposed pretreatment process for Hanford supernate waste solutions. The desired monitoring points include both the feed to and decontaminated product from a technetium-removal column. A Cs-removal column precedes technetium decontamination in the proposed process. Our earlier report (Ref. 1) showed that a simple flow-through beta counting system can easily meet 99Tc detection limit goals for solutions that do not contain interfering radionuclides; however, concentrations of residual interferences were too high in process solutions at the desired monitoring points. That is, technetium can not be measured without additional purification. In this supplement, ADS evaluated ion exchange cartridges to remove radionuclides that interfere with 99Tc beta measurements. Tests on radioactive standard solutions and on Hanford Envelope B (AZ-102) pretreated process solutions show that 99Tc passes through the cation removal cartridge to an on-line beta counter, and that interfering radionuclides were nearly totally removed. Envelope B solutions included both the process's Cs-removed feed to the Tc-removal column and product from the column. Analyses of these solutions before and after the cation exchange cartridge show that the concentration of the primary interference, 137Cs, was reduced to about 1/250th of the feed concentration.