Author :
Chotoo, Susan D. ; DeVol, T.A. ; Fjeld, R.A.
Author_Institution :
US Nuclear Regulatory Comm., Washington, DC, USA
Abstract :
A pulse shape discriminating flow-cell radiation detection system constructed with polymer-coated CsI:Tl was evaluated for simultaneous gross alpha/gross beta quantification. The CsI:Tl scintillator was crushed and sieved to 63-90-μm particle size and encapsulated with Parylene C to slow its dissolution rate. Averaged over the first hour of use, the pulse shape discrimination figure of merit was 1.4, and the detection efficiencies (±1σ) were 64.9±5.7%, 52.5±4.5%, and 4.5±0.2% for 233U, 90Sr/90Y, and 14C, respectively. The typical background count rates in the alpha and beta pulse shape window were 0.004 and 0.17 cps, respectively. The resultant minimum detectable activities (±1σ) for a 30-s count time were calculated to be 0.19±0.01 Bq, 0.9±0.1 Bq, and 11.4±0.6 Bq for 233U, 90Sr/90Y, and 14C, respectively. Although the 3-μm-thick encapsulation slowed CsI:Tl dissolution, the detection efficiency declined by a factor of two after 4.8 h, while the pulse shape resolution degraded slightly. With an appropriate coating, CsI:Tl is a good candidate for a heterogeneous pulse shape discriminating flow-cell
Keywords :
alpha-particle detection; beta-ray detection; solid scintillation detectors; 0.18 to 0.2 becquerel; 0.8 to 1.0 becquerel; 10.8 to 12 becquerel; 3 mum; 30 s; 4.8 h; 63 to 90 mum; CsI:Tl; Parylene C; alpha/beta pulse shape discriminating flow cell; background count rates; detection efficiencies; detection efficiency; dissolution rate; flow-cell radiation detection system; polymer-coated CsI:Tl; simultaneous gross alpha/gross beta quantification; Educational institutions; Encapsulation; Isotopes; Polymers; Protection; Pulse shaping methods; Radiation detectors; Shape; Solid scintillation detectors; Strontium;
