In situ long-term monitoring system for radioactive contaminants.
A long-term in situ subsurface instrument for monitoring radioactive contaminant plumes, as an alternative to soil analysis, is described. A portable, laser-based reader optically stimulates luminescence from sensors, each containing an Al2O3:C dosemeter. The sensors, designed for placement at various subsurface locations around a waste site, are allowed to accumulate dose for a predetermined time that is based on the instrument's minimum detectable dose (MDD). The reader is then attached to the sensor by fibre optic cable to read the accumulated dose; an increase above natural background levels indicating the presence of leaked radioactivity. Based on an MDD of 5 microGy, it is shown that the sensor can measure soil concentrations of 1.85 Bq cm(-3) after an exposure time of 50 h for 137Cs and 67 h for 90Sr/90Y. Discrimination between beta and gamma radiation is possible using an end cap placed over one of the two paired sensors, allowing simultaneous measurement of 137Cs and 90Sr/90Y in a mixed field. The monitor system represents a substantial improvement over quarterly soil sampling because of a greatly increased measurement frequency and the ability to perform measurements reproducibly.
Klein
D M
DM
Department of Physics, Oklahoma State University, Stillwater OK 74078, USA. kleinf@okstate.edu
Yukihara
E G
EG
McKeever
S W S
SW
Durham
J S
JS
Akselrod
M S
MS
D004307:Dose-Response Relationship, Radiation; D004784:Environmental Monitoring / Q000379:methods; D004867:Equipment Design; D019544:Equipment Failure Analysis; D005336:Fiber Optic Technology / Q000295:instrumentation* / Q000379:methods; D008422:Materials Testing; D011829:Radiation Dosage; D011835:Radiation Protection / Q000295:instrumentation* / Q000379:methods; D011850:Radioactive Waste / Q000032:analysis*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013819:Thermoluminescent Dosimetry / Q000295:instrumentation* / Q000379:methods
D011850:Radioactive Waste