Measurement of the activity and determination of the half-life of 225Ac at POLATOM

A method for absolute measurements of the 225Ac activity in equilibrium with its progeny was developed. Measurements were performed using the triple-to-double coincidence ratio (TDCR) method in two different TDCR counters. The activity concentration of an 225Ac solution was determined and the solution was sent to the SIR system for a comparison. The half-life of 225Ac was determined by one of the TDCR counters and found to be 9.9150(63) days.

The international reference system for beta-particle emitting radionuclides: Validation through the pilot study CCRI(II)-P1.Co-60

The Bureau International des Poids et Mesures (BIPM) is developing a new transfer instrument to extend its centralized services for assessing the international equivalence of radioactive standards to new radionuclides. A liquid scintillation counter using the triple/double coincidence ratio method is being studied and tested in the CCRI(II)-P1.Co-60 pilot study. The pilot study, involving 13 participating laboratories with primary calibration capabilities, validated the approach against the original international reference system based on ionization chambers, which has been in operation since 1976. The results are in agreement and an accuracy suitable for purpose, below 5×10-4, is achieved. The pilot study also reveals an issue when impurities emitting low-energy electrons are present in the standard solution, which have a different impact on liquid scintillation counting compared to other primary measurement methods.

Activity standardization and half-life measurement of 177Lu

The activity of the ¹⁷⁷Lu solution has been measured by means of the CIEMAT/NIST efficiency tracing method. This result has been compared to the previous obtained results received from 4πβ(LS)-γ coincidence and anticoincidence counting. The activities determined with various methods have been found to be consistent. The decay curve of the ¹⁷⁷Lu solution has been followed in the TDCR counter to determine the half-life of this isotope. The half-life has been separately determined for double and triple coincidence events. The arithmetic mean value of these two results has been found to be T_1/2 = 6.6489(52) d.

Consistency test of coincidence-summing calculation methods for extended sources

An internal consistency test of the calculation of coincidence-summing correction factors F_C for volume sources is presented. The test is based on exact equations relating the values of F_C calculated for three ideal measurement configurations. The test is applied to a number of 33 sets of F_C values sent by 21 teams. Most sets passed the test, but not the results obtained using the quasi-point source approximation; in the latter case the test qualitatively indicated the magnitude of the bias of F_C.

Impurities in Tc-99m radiopharmaceutical solution obtained from Mo-100 in cyclotron

The gamma emitting impurities in ^99mTc solution obtained from enriched molybdenum ¹⁰⁰Mo metallic target after its irradiation in a cyclotron were measured using a high-purity germanium (HPGe) detector. The radioactivity range of tested samples of ^99mTc was rather low, in the range from 0.34 to 2.39 MBq, thus creating a challenge to investigate the standard measurement HPGe system for impurity detection and quantification. In the process of ^99mTc separation from irradiated target the AnaLig® Tc-02 resin, Dionex H⁺ and Alumina A columns were used. Fractions of eluates from various steps of separation process were taken and measured for radionuclidic purity. The overall measurement sensitivity of gamma emitters in terms of minimum detectable activity (MDA) was found at the level of 14-70Bq with emission lines in range of 36 - 1836keV resulting in impurity content range of 6.7 × 10^-4 to 3.4 × 10^-3 % for ⁹³Tc, ^93mTc, ⁹⁴Tc, ^94mTc, ⁹⁵Tc, ^95mTc, ⁹⁶Tc ⁹⁶Nb, ⁹⁷Nb, ⁹⁹Mo contaminants and 9.4 × 10^-3 % for ^97mTc. The usefulness of the chosen measurement conditions and the method applied to testing the potential contaminators was proved by reaching satisfactory results of MDAs less than the criteria of impurity concentration of all nuclides specified in the European Pharmacopoeia.

Preparation method and quality control of multigamma volume sources with different matrices

The aim of the work was to develop new radioactive standard sources based on epoxy resins. The optimal proportions of the components and the homogeneity of the matrices were determined. The activity of multigamma sources prepared in Marinelli beakers was determined with reference to the National Standard of Radionuclides Activity in Poland. The difference of radionuclides activity values determined using calibrated gamma spectrometer and the activity of standard solutions used are in most cases significantly lower than measurement uncertainty limits. Sources production method and quality control procedure have been developed.