The joint evaluated fission and fusion nuclear data library, JEFF-3.3

The joint evaluated fission and fusion nuclear data library 3.3 is described. New evaluations for neutron-induced interactions with the major actinides $^{235}$U, $^{238}$U and $^{239}$Pu, on $^{241}$Am and $^{23}$Na, $^{59}$Ni, Cr, Cu, Zr, Cd, Hf, W, Au, Pb and Bi are presented. It includes new fission yields, prompt fission neutron spectra and average number of neutrons per fission. In addition, new data for radioactive decay, thermal neutron scattering, gamma-ray emission, neutron activation, delayed neutrons and displacement damage are presented. JEFF-3.3 was complemented by files from the TENDL project. The libraries for photon, proton, deuteron, triton, helion and alpha-particle induced reactions are from TENDL-2017. The demands for uncertainty quantification in modeling led to many new covariance data for the evaluations. A comparison between results from model calculations using the JEFF-3.3 library and those from benchmark experiments for criticality, delayed neutron yields, shielding and decay heat, reveals that JEFF-3.3 performes very well for a wide range of nuclear technology applications, in particular nuclear energy

Preliminary scattering kernels for ethane and triphenylmethane at cryogenic temperatures

Two potential cold moderator materials were studied: ethane and triphenylmethane. The first one, ethane (C2H6), is an organic compound which is very interesting from the neutronic point of view, in some respects better than liquid methane to produce subthermal neutrons, not only because it remains in liquid phase through a wider temperature range (Tf = 90.4 K, Tb = 184.6 K), but also because of its high protonic density together with its frequency spectrum with a low rotational energy band. Another material, Triphenylmethane is an hydrocarbon with formula C19H16 which has already been proposed as a good candidate for a cold moderator. Following one of the main research topics of the Neutron Physics Department of Centro Atómico Bariloche, we present here two ways to estimate the frequency spectrum which is needed to feed the NJOY nuclear data processing system in order to generate the scattering law of each desired material. For ethane, computer simulations of molecular dynamics were done, while for triphenylmethane existing experimental and calculated data were used to produce a new scattering kernel. With these models, cross section libraries were generated, and applied to neutron spectra calculation

Effect and uncertainties of H in Ice thermal scattering laws on the neutron multiplication factor for PWR fuel criticality applications

International audienceIn the context of the IAEA recommendation to ensure the transportation of fuel assemblies between 233 K and 311 K, thermal scattering laws of hydrogen in iced water have been produced with the LEAPR module of the NJOY code and included in the JEFF-3.3 nuclear data evaluation. Following this work, a benchmark was launched by the OECD/NEA Working Party on Nuclear Criticality-Safety subgroup-3 to evaluate the effect of the temperature on a PWR assembly criticality. This paper first focuses on the results obtained on this benchmark by CEA with the TRIPOLI-4 ® Monte-Carlo code. They show that, in terms of criticality-safety, computations made at 293 K are conservative and that the impact of density on the k eff is much stronger than the nature of the hydrogen bound or the adjustment of nuclear data to temperature. To go further, the uncertainties associated with the thermal scattering laws of hydrogen in iced water have been evaluated and propagated on one of the benchmark cases. The reference method to do so consists in a direct propagation of the LEAPR model parameters uncertainties. Another method, based on covariance matrix of the hydrogen in iced water scattering cross section, was also used in order to evaluate its relevance. The direct propagation leads to an uncertainty of 111 pcm. The uncertainty evaluated with the second method is lower by around 50 pcm. Whatever the method considered, those uncertainties remain acceptable in the criticality-safety context especially as the effect of the temperature on the k eff and the impact of the hydrogen bound nature are both low regarding density effects

Diagnosis of the conservation status in archaeological objects from Museo de la Patagonia by using imaging complementary techniques

We present the application of imaging complementary techniques to the interdisciplinary study of a selection of archaeological metal objects belonging to funerary assets from Patagonean Indigenous. This selection belongs to the archaeological collection Andres Giai which is under the care of the Museum of Patagonia, Bariloche, Argentina. It was regrettably left with no contextual data and most of the objects were kept in uncontrolled storage conditions over many years. Its general conservation status motivated the design and implementation of an interdisciplinary methodology to address a Conservation Plan considering the application of analytical techniques for materials in its approach. This work intends to achieve the first stage on this Plan, which consists in a suitable diagnosis of the conservation status to specific and representative pieces of the Andr s Giai metal collection. We highlight the Diagnosis stage as the most important to determine accurate treatments for each object during any conservation plan. The diagnosis was carried out by implementing neutron and X Ray tomography at the Helmholtz Zenturm Berlin, Germany. The results obtained allowed us to study the distribution of corrosion products and other degradation products such as crusts; verify the presence of a metal core under these product, study the homogeneity of the thicknesses, and show characteristics of the internal surfaces. This information is vital for the proposal of tailored conservation treatments that allow guaranteeing sustainable intervention

Validated scattering kernels for triphenylmethane at cryogenic temperatures

Cold neutrons are widely used in different fields of research such as the study of the structure and dynamics of solids and liquids, the investigation of magnetic materials, biological systems, polymer science, and a rapidly growing area of industrial applications. In a pulsed neutron source where the pulse width is an important parameter to be considered, hydrogenated materials are often used because of their high energy transfer in each collision. The preliminary scattering kernel for triphenylmethane, a material of great potential interest for cold neutron production, had been presented at the ND2016 conference. Here, a new model for the generation of the scattering kernels for this material, together with experimental results on its total cross section measured at the VESUVIO instrument (ISIS Neutron and Muon Source, United Kingdom) is presented. The thermal scattering kernel was generated by means of the NJOY Nuclear Data Processing system, using as input the vibrational modes obtained by density functional theory techniques (DFT). The agreement between measurements and our model validates the scattering kernel construction and the cross section library generated in ENDF and ACE formats

Experimental validation of the temperature behavior of the ENDF/B-VIII.0 thermal scattering kernel for light water

The Neutron Physics Department at Centro Atómico Bariloche developed new models for the interaction of thermal neutrons with water which have been validated against experimental data, including new thermal scattering experiments, and were adopted for the release of ENDF/B-VIII.0. Although the older models are, in general, good for most applications, some discrepancies had appeared in the case of heavy water, and this motivated new measurements that validated the new model. In the case of light water, the new model predicts a reduction of the total cross section around 0.025 eV when the temperature is increased from room temperature. This reduction, that is not predicted by the existing models, and potentially affects the calculation of temperature reactivity coefficients in nuclear reactors, has been traced to a shift in the vibrational frequency spectrum of liquid water. The only experimental data previously available is from an experiment performed at the Demokritos reactor in the ’60s at 293 K and 473 K, which validates the new model when the cross section ratios are computed. In order to verify this effect at a lower temperature range, a transmission experiment was carried out at the VESUVIO spectrometer in the ISIS facility in the UK in June 2018, measuring the total neutron cross section in the range from 283 K to 353 K. Here, we present this new experimental data and its comparison with the models

The sciences and applications of the Electron LINAC-driven neutron source in Argentina

The Neutron Physics group at Centro Atómico Bariloche (CNEA, Argentina) has evolved for more than forty five years around a small 25MeV linear electron accelerator. It constitutes our compact accelerator-driven neutron source (CANS), which is dedicated to the use and development of neutronic methods to tackle problems of basic sciences and technological applications. Its historical first commitment has been the determination of the total cross sections of materials as a function of neutron energy by means of transmission experiments for thermal and sub-thermal neutrons. This also allowed testing theoretical models for the generation of scattering kernels and cross sections. Through the years, our interests moved from classic pulsed neutron diffraction, which included the development of high-precision methods for the determination of very low hydrogen content in metals, towards deep inelastic neutron scattering (DINS), a powerful tool for the determination of atomic momentum distribution in condensed matter. More recently non-intrusive techniques aimed at the scanning of large cargo containers have started to be developed with our CANS, testing the capacity and limitations to detect special nuclear material and dangerous substances. Also, the ever-present “bremsstrahlung” radiation has been recognized and tested as a useful complement to instrumental neutron activation, as it permits to detect other nuclear species through high-energy photon activation. The facility is also used for graduate and undergraduate students’ experimental work within the frame of Instituto Balseiro Physics and Nuclear Engineering courses of study, and also MSc and PhD theses work.Fil: Granada, Jose Rolando. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro; Argentina. Comisión Nacional de Energía Atómica; ArgentinaFil: Mayer, R. E.. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro; Argentina. Comisión Nacional de Energía Atómica; ArgentinaFil: Dawidowski, Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Comisión Nacional de Energía Atómica; ArgentinaFil: Santisteban, Javier Roberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Comisión Nacional de Energía Atómica; ArgentinaFil: Cantargi, F.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Comisión Nacional de Energía Atómica; ArgentinaFil: Blostein, Juan Jeronimo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Comisión Nacional de Energía Atómica; ArgentinaFil: Rodriguez Palomino, Luis Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Comisión Nacional de Energía Atómica; ArgentinaFil: Tartaglione, Aureliano. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Comisión Nacional de Energía Atómica; Argentin