CALIBRATION OF MARINELLI VESSELS FOR MEASUREMENT OF RADIOACTIVE ENVIRONMENTAL-SAMPLES

In order to measure low-activity radioactive environmental samples, bo th in liquid and solid phases, the use of Marinelli (reentrant) beaker s is recommended. Standards were prepared by mixing of standardized ra dioactive solutions with CaCO3 of density 1.1 to 1.3 g cm(-3), similar to densities of environmental samples. Measurements of calibrated Mar inelli comparator standards on detector surface showed that the depend ence of log Eff vs. log E is almost linear in the 120 keV to 1500 keV range. The data can be fitted more accurately by assuming a parabolic correlation (log Eff vs. log E). The validity of these standards was c hecked by determining the concentration of radio-europium, radio-cesiu m and Ra-226 in three certified reference standard materials. The resu lts obtained agreed well with the published certified data. The limit of detection for the determination of radio-cesium by gamma-ray spectr ometry under the prevailing experimental conditions is 0.1 Bq (2.7 pCi ), for 0.5 kg of environmental samples.