Application of the sum-peak method to activity standardizations of Eu sources in LNMRI (BR).

The sum-peak method, an absolute measurement technique that uses coincidence counting and γ-ray spectrometry, was applied to activity standardization of Eu sources. The decay branch used was that of Sm, as it is almost entirely electron capture and exhibits X-rays with a high probability of coincidence with the 121.8keVgamma rays, as evidenced by the matrix technique used for complex decay schemes, a method for deriving counting rate equations describing coincidence summing of gamma and X-rays. The result was compared with the calibration performed by ionization chamber traceable to BIPM. The results presented uncertainty values of 0.50% (k = 1).