Standardization and decay data of 153Sm

Standardization of Sm-153 solution by absolute methods

Standardization of (153)Sm by 4π(LS)-γ coincidence and anticoincidence counting and the CIEMAT/NIST method in three LS-counters is presented. This short half-life radionuclide is applied in tumor therapy and bone pain palliation. A simplified disintegration scheme of (153)Sm was applied in the calculation of the counting efficiency. Standard uncertainties of 0.4% for the (153)Sm measurements by the 4π(LS)-γ coincidence and anticoincidence techniques and 0.7% by the C/N method were evaluated, respectively. An agreement of the standardization results by both methods within the respective uncertainties was obtained. The half-life of (153)Sm of (1.92895±0.00024) days was determined during one month of measurements and correction for europium isotope impurities by the C/N method in the TriCarb 2910 LS-counter.

Standardization of radionuclide by β(LS)-γ coincidence counting using the geometry-efficiency variation method

A liquid scintillation counting method consisting of three photomultiplier tubes for beta counters and a NaI(Tl) gamma counter has been developed for the standardization of radionuclides with the beta-gamma coincidence technique. The beta detection efficiency functions are obtained by means of a geometry-variation method developed in the present work; an array of beta detectors is moved uniformly at the same time from a centrally located counting vial to 50 mm. The method has been applied in the standardization of 60Co and 134Cs. Unquenched liquid scintillation samples with nominal count rates from 1000 to 6000 s-1 were prepared. The observed beta detection efficiencies with this method are from 90 to 45% in the case of 60Co, and from 84 to 50% for 134Cs. The output of each beta channel is summed together and compared with gamma data by the coincidence analyzer. The dead time of each counting channel is adjusted to be 20 micros, sufficiently long to suppress the afterpulses in the beta counting channel. The activity of each sample is determined by using the Cox and Isham formula. The obtained results are in good agreement with KRISS certified values.

Determination of the intensity of X- and gamma-ray emissions in the decay of 153Sm

The activity of a 153Sm solution was determined by means of liquid scintillation counting and an ionization chamber. Several accurately calibrated X- and gamma-ray spectrometers were used to measure point sources. The use of different detectors results in improvements to the accuracy of the data around 100 keV where the efficiency curve changes significantly. Photon emission intensities have been derived for the main X- and gamma-rays, and the 103-keV emission has a measured intensity of (29.07 (20)) per 100 disintegrations.

Half-life measurements with ionization chambers—A study of systematic effects and results

Accurate half-lives have been determined at the Physikalisch-Technische Bundesanstalt (PTB) using ionization-chamber measuring systems to assure the quality of radioactivity standards over the period of their use as detector calibrants or other purposes such as nuclear medicine and environmental monitoring. Some long-lived radionuclides have been measured for up to 28 years: 85Kr, 90Sr, 108Agm, 133Ba, 152Eu, 154Eu, and more recently 65Zn, 106Ru, 109Cd and 137Cs; short-lived radionuclides have also been studied such as: 18F, 67Ga, 81Rb, 99Mo, 99Tcm, 103Pd, 111In, 123I, 131I, 153Sm, 169Er, 177Lu, 186Re, 188Re, 201Tl, 222Rn and 224Ra. Relative uncertainties of half-life values of the order of 5 x 10(-4) were obtained. These values are compared to the results of other measurements and evaluations, and the limiting systematic effects are discussed.