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

Beta-emitters 36Cl and 63Ni, and the electron capture radionuclide 55Fe were used to calibrate a secondary standardization instrument Quantulus-1220TM. 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 36Cl and 63Ni the discrepancy was 0.9% and 2.7%, respectively, within the specified uncertainty limits. A new sample with 90Sr 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. - Highlights: ► Relatively low-level beta-emitters were measured with the TDCR equipment. ► Specific activities were determined with the help of the software TDCRB-02. ► Discrepancies from known values were 1–3% for 36Cl, 63Ni and 90Sr. ► Results suggest the suitability of the TDCR techniques for low-level counting. ► A conventional LSC counter Quantulus-1220 was calibrated at different quenching levels.