E. Günther

Standardization of 59Fe and 131I by liquid scintillation counting

Abstract The CIEMAT/NIST liquid scintillation efficiency tracing method is frequently used to determine the activity of pure beta-particle emitters. With the programme EBEGA it can be extended to beta-particle emitters with no more than one coincident gamma ray per decay path. In this work it is shown that the method can also be applied to 59 Fe and 131 I, which are beta-gamma emitters with gamma cascades.

STANDARDIZATION AND DECAY DATA OF 153SM

Abstract The activity concentration of a 153 Sm solution was determined by 4 πβ – γ coincidence measurements and by liquid scintillation counting (LSC). Both methods yielded results which differ by only 0.1%, the relative standard uncertainty being 0.1 and 0.2%, respectively. X-ray and gamma-ray emission probabilities of several transitions were measured; they were used to calculate beta transition probabilities. The emission probabilities of the 69.7 and the 103.2 keV gamma rays were found to be 0.0465±0.0005 and 0.2923±0.0018, respectively; and the half-life was found to be (46.274±0.007) h.

Standardization and decay data of 68Ge/68Ga

Abstract A gamma and an x-ray spectrometer, 4πβ—γ-coincidence equipment, liquid-scintillation counting (LSC) equipment and a calibrated ionization chamber (IC) have been used to determine the decay scheme parameters of 68Ga and the specific activity of a 68Ge/68Ga solution. The transition probability of the positron branch and the EC branch to the ground state of 68Zn, b1 and e1, the corresponding branches to the 1077 keV level of 68Zn, b2 and e2, the total emission probability of annihilation radiation from the 68Ga decay, pann, and the gamma-ray emission probabilities of the quanta corresponding to the 1077 keV transition (p1077) and to some weak transitions were redetermined. The results are b1 = 0.8785 ± 0.0012, e1 = 0.0892 ± 0.0012, b2 = 0.0129 ± 0.004, e2 = 0.0193 ± 0.0004, pann = 1.7829 ± 0.0022, p1077 = 0.0322 ± 0.0003. The specific activity of a 68Ge/68Ga solution was determined with a relative uncertainty of 1% (1σ) using 4πβ—γ coincidence, LSC and IC measurements. A half-life of T 1 2 = (270.99 ± 0.19) d for 68Ge was obtained by measurements with an ionization chamber.

Standardization of the EC nuclides55Fe and 65Zn with theCIEMAT/NIST LSC tracer method

Abstract A study is made of the standardization of 55 Fe and 65 Zn under different experimental and theoretical conditions. Sample composition, tracer nuclide, ionization quench approximations, k B values and approximations for the average L Auger electron energy, were varied to find out the optimum conditions. A standardization of 55 Fe and 65 Zn is possible with a relative standard uncertainty of about 0.5% using 54 Mn as a tracer. However, the experiments with 3 H as a tracer show that the EC decay model and the LSC theory which are included in the CIEMAT/NIST programs are not fully satisfactory for these two EC radionuclides.

Activity determination of 93mNb

Abstract A 93mNb solution has been standardized by liquid scintillation efficiency tracing and Si(Li) measurements, which were carried out as part of an international intercomparison.

The photoionization-reduced energy in LSC

The atomic rearrangement cascade that follows the electron-capture decay process in low-Z radionuclides involves X-rays which have high photoelectric interaction probabilities. When the K-shell binding energy of the ionized atom (e.g., hydrogen) is significantly lower than the energy of the X-ray photon, the detector response to a photon-equivalent energy electron and the whole photoionization process are very similar. This is not the case when the scintillator cocktail contains larger atoms (e.g., oxygen and phosphorus in Ultima Gold). For larger Z atoms, the reduced energy of the whole photoionization process is less than the reduced energy of the interacting photon due to the nonlinear effects of ionization quenching. This paper shows the convenience of including a more detailed simulation of the photoionization process in the atomic rearrangement detection model for electron-capture nuclides such as (55)Fe, (51)Cr and (54)Mn. The need for more elaborate atomic rearrangement models is a consequence of the analysis of (125)I data.

Determination of the 32P activity in angioplastic balloons by LSC

The determination of the 32P activity in angioplastic balloons involves two problems: the extraction of 32P, which is covered with plastic foils, and the determination of the 33P impurity. At PTB the active balloons are destroyed by combustion in an oxygen stream. The active phosphorus is extracted quantitatively from the tube. The activities of 32P and 33P are determined by measurements performed over a period of one month or more by a subsequent data fit.

Standardization of 237Np by the CIEMAT/NIST LSC tracer method

The standardization of 237Np presents some difficulties: several groups of alpha, beta and gamma radiation, chemical problems with the daughter nuclide 233Pa, an incomplete radioactive equilibrium after sample preparation, high conversion of some gamma transitions. To solve the chemical problems, a sample composition involving the Ultima Gold AB scintillator and a high concentration of HCl is used. Standardization by the CIEMAT/NIST method and by pulse shape discrimination is described. The results agree within 0.1% with those obtained by two other methods.

Standardization and decay data of 186Re

Abstract The specific activity of a 186 Re solution was measured using 4πβ—γ-coincidence and liquid scintillation counting techniques to within a relative uncertainty of 0.4% (1σ). Efficiency-calibrated semiconductor spectrometers were used to measure the emission probabilities of the X- and gamma rays. A half-life of 186 Re of (3.7183±0.0011) d was measured using an ionization chamber and a 4π proportional counter, and the transition probabilities for the beta and EC transitions were deduced from the measured data.

Radionuclide analyses of urine samples: results of an intercomparison

Abstract The measurement of radioactivity concentrations in urine samples is an important tool for monitoring possible radionuclide intakes by occupationally exposed workers, especially for radionuclides emitting alpha or beta radiation. Quality assurance requires systematic intercomparisons involving all laboratories responsible for these measurements. Such analyses were performed by the German—Swiss Radiation Protection Association. The main purpose of these measurements was the specification of criteria for the acceptance of laboratories by radiation protection authorities. This contribution presents some measurement results of Th-nat, 90 Sr, and 241 Am in urine and discusses the implications for internal dosimetry.