PHOTONEUTRON CROSS SECTIONS MEASUREMENTS IN 9Be, 13C e 17O WITH THERMAL NEUTRON CAPTURE GAMMA-RAYS

Medidas das secções de choque de fotonêutrons do 9Be, 13C e 17O foram obtidas no intervalo de energia entre 1,6 e 10,8 MeV, utilizando radiação gama de alta resolução em energia (3 a 21 eV) produzida na captura de nêutrons térmicos por 21 materiais alvo, quando posicionados no interior de um canal tangencial, junto ao núcleo do reator de pesquisa IEAR1 (5 MW) do IPEN/CNEN-SP. As amostras foram irradiadas no interior de um sistema detector de nêutrons Long Counter", de geometria 4π, a 520,5 cm de distância do alvo de captura. O fluxo de raios gama foi determinado por meio da análise do espectro gama obtido fazendo uso de um detector de estado sólido do tipo Ge(Li) (EG&G ORTEC, 25 cm3, 5%), previamente calibrado com raios gama de captura produzidos por uma amostra padrão de nitrogênio (Melamina). A secção de choque de fotonêutron foi medida para o espectro de raios gama de captura de cada alvo (secção de choque composta). Uma metodologia de inversão de matrizes para a resolução de problemas inverso discretos foi utilizada para a deconvolução do conjunto de valores experimentais da secção de choque composta, com a finalidade de obter a secção de choque em valores específicos de energia de excitação (energia das linhas gama principais dos alvos de captura). As secções de choque obtidas, nas energias das linhas gama principais de todos os alvos, foram comparadas com as medidas realizadas por outros autores utilizando diferentes fontes de radiação gama. Uma boa concordância foi observada entre os resultados experimentais deste trabalho com as relatados na literatura.Photoneutron cross sections measurements of 9Be, 13C e 17O have been obtained in the energy interval between 1,6 and 10,8 MeV, using neutron capture gamma-rays with high resolution in energy (3 a 21 eV), produced by 21 target materials, placed inside a tangential beam port, near the core of the IPEN/CNEN-SP IEA-R1 (5 MW) research reactor. The samples have been irradiated inside a 4π geometry neutron detector system Long Counter", 520,5 cm away from the capture target. The capture gamma-ray flux was determined by means of the analysis of the gamma spectrum obtained by using a Ge(Li) solid-state detector(EG&G ORTEC, 25 cm3, 5%), previously calibrated with capture gamma-rays from a standard target of Nitrogen (Melamine). The neutron photoproduction cross section has been measured for each target capture gamma-ray spectrum (compound cross section). A inversion matrix methodology to solve inversion problems for unfolding the set of experimental compound cross sections, was used in order to obtain the cross sections at specific excitation energy values (principal gamma line energies of the capture targets). The cross sections obtained at the energy values of the principal gamma lines were compared with experimental data reported by other authors, with have employed different gamma-ray sources. A good agreement was observed among the experimental data in this work with reported in the literature

Triton angular distributions from the /sup 7/Li([gama],t)[gama] reaction near threshold

Angular distributions of tritons emitted in the reaction ⁷Li(y,t)α have been measured for two photon energy intervals (6.4–6.7 and 8.5–9.0 MeV), and θt between 30° and 150°. Monochromatic photons from neutron capture reactions of the IPEN/CNEN-SP IEA-R1 research reactor were used. The measured data were analyzed in the framework of an α-cluster model for the ⁷Li structure. Results are in good agreement with a recent measurement of the azimuthal cross section asymmetry

Triton angular distributions from the /sup 7/Li([gama],t)[gama] reaction near threshold

Angular distributions of tritons emitted in the reaction ⁷Li(y,t)α have been measured for two photon energy intervals (6.4–6.7 and 8.5–9.0 MeV), and θt between 30° and 150°. Monochromatic photons from neutron capture reactions of the IPEN/CNEN-SP IEA-R1 research reactor were used. The measured data were analyzed in the framework of an α-cluster model for the ⁷Li structure. Results are in good agreement with a recent measurement of the azimuthal cross section asymmetry

The 2021 IAEA software intercomparison for k₀-INAA

In order to establish the variation between results in mass fractions due to software implementation, as measured by the k0-method for INAA, the IAEA has organized a software intercomparison. A complete set of test spectra and associated information was assembled. Efficiency curves, neutron spectrum parameters, correction factors and mass fractions were calculated with the participating programs (k0-IPEN, k0-INRIM, k0-DALAT, k0-IAEA and KayWin) using identical peak areas. In this paper, we report on the observed discrepancies, causes, remedies and future software developments. The test data, as well as intermediate results and observed mass fractions of the certified reference material BCR-320R “channel sediment” are available through the IAEA on request. The variations in concentrations attributed to differences between the programs were initially found to be 5.6 and 7.9%, for certified and uncertified concentrations, respectively. After the certified concentrations had been made available to the participants and they had been allowed to improve their programs, the variations found were 2.7 and 3.4%, respectively. The main identified remaining causes of variation are differences in the procedures used for detector efficiency characterisation and neutron spectrum parameter determination.RID/KEWO/Kwaliteitszorg-IM

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. © 2019 Elsevier Lt