Optoelectronic reader for CET dosimeter, a radiation accident chemical dosimetry system

The use of chlorobenzene-ethanol-trimethylpentane solution (CET) in radiation dosimetry is based on radiolytic formation of hydrochloric acid which protonates a pH indicator, thymolsulphonphthalein. The high molar absorptivity of its red form at 552 nm is responsible for a high sensitivity of the system: doses in the range 0.2-15 Gy can be measured. Together with a visual colour comparator it has formed a personnel dosimetry system suitable for accident and civil defense use. A newly constructed optoelectronic reader with two two-colour light emitting diodes (550 and 690 nm) as light sources and a silicone photocell as a detector uses the differential absorbance at these two wavelengths as the response. The response is a direct function of dose and can be recorded and processed electronically