Measurements of some radionuclides using a new TDCR system and an ultra low-level conventional LSC counter in CPST,...

Beta-emitters (36)Cl and (63)Ni, and the electron capture radionuclide (55)Fe were used to calibrate a secondary standardization instrument Quantulus-1220(TM). An external standard technique was applied to assess the quenching level of samples. Nitromethane as an artificial quencher was used for sample preparation at different quenching levels. The dependence of the counting efficiency on the quenching level was determined. Samples of beta-emitters were re-measured with the triple-to-double coincidence ratio (TDCR) primary standardization instrument. The specific activities of beta-emitters were determined with the help of the software TDCRB-02 and compared with known values. It was found that for (36)Cl and (63)Ni the discrepancy was 0.9% and 2.7%, respectively, within the specified uncertainty limits. A new sample with (90)Sr was prepared and measured with the TDCR device. In this case, the divergence from the expected value was 1.7%. Results suggest the suitability of the TDCR techniques for low-level counting.