Primary standardization and determination of gamma ray emission intensities of Ho-166.

The procedure followed by the Nuclear Metrology Laboratory (LMN) at the IPEN-CNEN/SP, in São Paulo, for the primary standardization of 166Ho is described. The activity of 166Ho was determined by the efficiency extrapolation technique applied to a 4πß(PC)-γ coincidence system using a gas flow proportional counter in 4π geometry coupled to a 76 × 76 mm NaI(Tl) crystal. The results for the γ-rays intensities at 80.57 and 1379.45 keV were 0.0651(11) and 0.00904(11), respectively.

Consistency test of coincidence-summing calculation methods for extended sources.

An internal consistency test of the calculation of coincidence-summing correction factors FC for volume sources is presented. The test is based on exact equations relating the values of FC calculated for three ideal measurement configurations. The test is applied to a number of 33 sets of FC 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 FC.

Data analysis software package for radionuclide standardization with a digital coincidence counting system.

The Nuclear Metrology Laboratory (LMN) - IPEN, São Paulo, Brazil - developed a Digital Coincidence System (DCS), based on the Coincidence Counting Methodology, in order to improve its capabilities in radionuclide primary-standardization. Digital process is implemented in two steps: data-acquisition (a set of measurements) and offline software data-analysis and calculation. The present work shows the basics of the data-acquisition unit (Software Coincidence System - SCS), describes the DCS' data-analysis process and the initial approaches chosen for the implementation of the software package (Coincidence Analyzing Task - CAT). 152Eu standardization, performed for DCS testing, software expansion and validation, is briefly discussed.

SUMCOR: Cascade summing correction for volumetric sources applying MCNP6.

The main features of code SUMCOR developed for cascade summing correction for volumetric sources are described. MCNP6 is used to track histories starting from individual points inside the volumetric source, for each set of cascade transitions from the radionuclide. Total and FEP efficiencies are calculated for all gamma-rays and X-rays involved in the cascade. Cascade summing correction is based on the matrix formalism developed by Semkow et al. (1990). Results are presented applying the experimental data sent to the participants of two intercomparisons organized by the ICRM-GSWG and coordinated by Dr. Marie-Cristine Lépy from the Laboratoire National Henri Becquerel (LNE-LNHB), CEA, in 2008 and 2010, respectively and compared to the other participants in the intercomparisons.

Disintegration rate and gamma-ray emission probability per decay measurement of Cu-64.

The procedure followed by the Nuclear Metrology Laboratory (LMN) at the IPEN for the standardization of activity of 64Cu is described. The measurement was carried out in a 4π (PC) ß-γ coincidence system. The activity per unit mass of the solution was determined by the extrapolation technique. The events were registered using a Time to Amplitude Converter (TAC) associated with a Multi-channel Analyzer. The gamma-ray emission probability per decay of the 1345.7keV transition of 64Cu determined with a calibrated REGe gamma-ray spectrometer was (0.472 ± 0.010) %, in agreement with the literature.

Functional analysis of iron superoxide dismutase-A in wild-type and antimony-resistant Leishmania braziliensis and Leishmania infantum lines.

In this work, we characterized the gene encoding iron superoxide dismutase-A (FeSOD-A) in wild-type (WTS) and antimony-resistant (SbR) L. (Viannia) braziliensis and L. (Leishmania) infantum lines, which were selected in vitro. FeSOD-A transcript and protein expression were similar in all tested lines; however, specific enzyme activity analysis revealed higher superoxide dismutase activity in SbIII-resistant LbSbR and LiSbR lines than in the corresponding WTS lines. These parasites were also more tolerant to oxidative stress generated by the herbicide paraquat. Functional analysis showed that in comparison to non-transfected lines, wild-type LbWTS and LiWTS clones overexpressing the FeSOD-A enzyme are 1.6- and 1.7-fold more resistant to SbIII, respectively. Our results suggest that FeSOD-A is involved in the antimony resistance phenotype in L. (V.) braziliensis and L. (L.) infantum.

A new NIST primary standardization of 18F.

A new primary standardization of (18)F by NIST is reported. The standard is based on live-timed beta-gamma anticoincidence counting with confirmatory measurements by three other methods: (i) liquid scintillation (LS) counting using CIEMAT/NIST (3)H efficiency tracing; (ii) triple-to-double coincidence ratio (TDCR) counting; and (iii) NaI integral counting and HPGe γ-ray spectrometry. The results are reported as calibration factors for NIST-maintained ionization chambers (including some "dose calibrators"). The LS-based methods reveal evidence for cocktail instability for one LS cocktail. Using an ionization chamber to link this work with previous NIST results, the new value differs from the previous reports by about 4%, but appears to be in good agreement with the key comparison reference value (KCRV) of 2005.

57Co half-life determination.

The National Laboratory for Metrology of Ionizing Radiation (LNMRI)/Brazil participated in the last (57)Co activity measurement comparison organized by IAEA, in 2008. This was made in order to realize primary standardization of this radionuclide and to reduce the measuring uncertainties in the laboratory. Additionally, one sample with 2.6g was taken from the IAEA master solution of (57)Co and was prepared to be used in the measurement of the radionuclide's half-life in an ionization chamber system. The (57)Co half-life was measured to be 271.82 (17) days.

Standardization of (166m)Ho and 243Am/239Np by live-timed anti-coincidence counting with extending dead time.

The National Laboratory for Metrology of Ionizing Radiation (LNMRI)/Brazil acquired (166m)Ho and (243)Am/(239)Np solutions from commercial suppliers in order to realize primary standardization and therefore reducing the associated uncertainties. The method used in the standardization was the live-timed 4πß(LS)-γ(ΝaI(Tl)) anticoincidence counting. The live-timed anticoincidence system is operated since 2006 in LNMRI and is composed of two MTR2 modules donated by Laboratoire National Henri Becquerel (LNE-LNHB)/France. The data acquisition system uses a homemade LabView program and an Excel file for calculus. These systems have been used for primary standardization at LNMRI for many radionuclides and recently took part in the (124)Sb and (177)Lu International Key Comparisons with good performance.

Determination of 198Au X-rays emission probabilities.

This work describes the measurements of the K X-ray and gamma-ray emission probabilities per decay of (198)Au performed at the Nuclear Metrology Laboratory (LMN) at the IPEN, São Paulo. The radioactive sample was obtained by means of (197)Au(n, gamma)(198)Au reaction irradiating an Au foil in a thermal neutron flux near the core of the IPEN 3.5 MW research reactor. The activity of samples was determined in a 4pibeta-gamma coincidence system, setting the gamma window at the 411.80 keV total energy absorption peak. The same samples were measured in two different spectrometers: a HPGe planar spectrometer with Be window, suitable for measurements in the low energy range and a coaxial REGe spectrometer. Both spectrometers were previously calibrated in a well defined geometry by means of standard sources calibrated in a 4pibeta-gamma coincidence system. MCNP4C Monte Carlo code was used for simulating the REGe spectrometer calibration curve, and a new version of code ESQUEMA was adopted for simulating the detection processes in the coincidence system, in order to predict the efficiency extrapolation curve.