The paper presents some recent results of the Radionuclide Metrology Laboratory (RML) from IFIN-HH, concerning the assurance of the international traceability for the measurement of 131 I solution aimed to continue the national chain for nuclear medicine applications in Romania. The following sequences of the traceability are presented: the absolute standardization of solution by the 4πβ-γ coincidence, efficiency extrapolation method and participation in the BIPM.RI(II)-K1.I-131 key comparison; and recalibration of the CENTRONIC IG12/20A ionization chamber secondary standard. The participation in the IAEA/SSDL (SSRL) 131 I comparison is also presented.