⁶³Ni activity measurements a bilateral intercomparison

To assess the accuracy and capabilities of BARC, for standardization of ⁶³Ni before participating in larger scale trial exercise to implement and test the methods for the extension of the SIR to β emitters, a bilateral intercomparison was organised with National Metrology Institute of Japan (NMIJ), Japan. Standardization of ⁶³Ni was carried out and the results were compared with those obtained from NMIJ to assess the accuracy and capabilities of the laboratories. The CIEMAT/NIST efficiency tracing technique based on ³H standard was used for measurement of ⁶³Ni activity concentration at BARC, India whereas Triple to Double Coincidence Ratio (TDCR) method was used at NMIJ, Japan. The procedures adopted for the standardization of ⁶³Ni by CIEMAT/NIST method at BARC and TDCR method at NMIJ are presented. The percentage deviation in activity concentration of ⁶³Ni between BARC, India and NMIJ, Japan is 0.27%. To evaluate the performance of techniques used at both the laboratories, E_n score (k = 2) and degrees of equivalence was calculated. The E_n score of -0.12 and degrees of equivalence -0.06 kBq g^-1 clearly indicates that the activity concentration of ⁶³Ni measured at BARC, India and NMIJ, Japan are in excellent agreement and comparable within uncertainty limits and demonstrates the degrees of equivalence of the standards maintained at BARC, India and NMIJ Japan.