STANDARDIZATION OF 123-I
A comparison of activity concentration measurements was carried out by laboratories in Belgium, U.K., France. The nucleus 123-I decays to excited states of 123-Te by electron capture and thence to the ground state of the daughter by the simultaneous emission of several gamma rays. The principal decay mode (98%) is by electron capture to the 159 keV excited state of 123-Te followed by a de-excitation to the ground state by the emission of a 159 keV gamma ray (83%), or by internal conversion (15%). The participants agreed to use a common set of decay scheme data. The 123-I was produced in the cyclotron at Louvain- la-Neuve, Belgium, using the 127-I(p,5n)123-Xe reaction. Four different standarization procedures were used by the participants namely, 4pi(PC)A,X-gamma coincidence counting (CBNM), 4pi gamma(NaI(Tl)) integral counting (SCK-CEN) calibrated, high resolution gamma ray spectrometry (LMRI, CBNM, IRE) and calibrated ionization chamber assay (NPL, LMRI). Each participant also determined the level of the 125-I impurity in the 123-I samples and appropriate corrections were made. The results are summarized in the form of tables. The uncertainties were calculated according to the recommendations of the BIPM. The weighted mean of the results is 499.8+- 1.3 Bq/mg, with the uncertainty corresponding to one standard deviation of the mean. As weights the inverse squared uncertainties of the different results were used.
Bibliographic Reference: INT. J. APPL. RADIAT. ISOT., VOL. 35 (1984) NO. 10, PP. 923-926
Record Number: 1989123106200 / Last updated on: 1987-01-01
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