Some solutions to on-line radiological monitoring of difficult streams

On-line monitoring for radiological contamination of dirty, but normally not radioactive, streams is considered to be difficult. Several low-fouling units are described that are intended to replace the existing sensors that monitor both beta and gamma activity. A sensor was designed, using a thin-wall Geiger-Muller tube for beta and gamma sensitivity, to monitor the influent of the sanitary sewage treatment plant. The design eliminates dead volumes inherent in the old unit by use of a double-layer, helically wound solenoid made of 5/16-in-OD thin-wall (0.02-in) Teflon tubing. A 4-L Marinelli breaker-based system that used a 3*3 NaI(Tl) scintillator was replaced with a multilayer solenoid of 5/8-in-OD Teflon. Two units for the detection of beta radiation are also described.<>