– the intergovernmental organization through which Member States act together
     on matters related to measurement science and measurement standards.
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International Reference System (SIR)

The international reference system (SIR) is characterized by its high stability and its simplicity. Since it came into existence, about 900 measurements have been made with over 60 radionuclides – giving a total of about 650 independent results – and interest in the method remains high. The results of the measurements are published in the KCDB and are used to construct the efficiency curve of the ionization chamber (IC) as a function of gamma-ray energy.

To date, the following radionuclides have been measured in the SIR:

KCDB - measurement of radionuclides
C-11   F-18   Na-22   Na-24   Sc-46   Sc-47   Cr-51   Mn-54   Mn-56   Co-56   Co-57   Co-58   Fe-59   Co-60   Cu-64   Zn-65   Ga-67   Ge-68   Se-75   Kr-85   Sr-85   Y-88   Nb-95   Mo-99   Tc-99m   Ru-103   Ru-106   Cd-109   Ag-110m   Ag-111   In-111   Sn-113   I-123   Sb-124   Sb-125   I-125   I-131   Ba-133   Xe-133   Cs-134   Cs-137   Ce-139   Ba-140   Ce-141   Ce-144   Eu-152   Gd-153   Sm-153   Eu-154   Eu-155   Ho-166m   Yb-169   Lu-177   Ta-182   Re-186   Ir-192   Au-195   Tl-201   Hg-203   Pb-203   Bi-207   Rn-222   Ra-223   Th-228   Np-237   Am-241   Am-243.

Use of a liquid scintillation techniques has allowed the SIR to be extended to include beta-ray emitters.

For the measurement of short-lived radionuclides the BIPM has developed a transportable transfer instrument (TI) that has already been taken to the NIST (USA) for the comparison of Tc-99m activity measurements. Some photographs of the TI are presented here. The protocol for the BIPM.RI(II)-K4.Tc-99m comparison using the TI is available in the KCDB.

Information for NMIs wishing to participate in the SIR is provided here.

the SIR experimental facilities in their new location ionization chambers of the international reference system

The electronics of the SIR have been updated and verification measurements are in progress.


The high stability of the SIR over more than 30 years