Temperature-tuned Maxwell-Boltzmann neutron spectra for kT ranging from 30 up to 50keV for nuclear astrophysics studies

The need of neutron capture cross section measurements for astrophysics motivates present work, where calculations to generate stellar neutron spectra at different temperatures are performed. The accelerator-based 7Li(p,n)7Be reaction is used. Shaping the proton beam energy and the sample covering a specific solid angle, neutron activation for measuring stellar-averaged capture cross section can be done. High-quality Maxwell–Boltzmann neutron spectra are predicted. Assuming a general behavior of the neutron capture cross section a weighted fit of the spectrum to Maxwell–Boltzmann distributions is successfully introduced.G. Martín-Hernández acknowledges support from Laboratori Nazionali di Legnaro, Instituto Nazionale di Fisica Nucleare and M. Pignatari from Ambizione grant of the SNSF, NSF grants PHY 02-16783 and PHY 09-22648 (Joint Institute for Nuclear Astro physics, JINA), EU MIRG-CT-2006-046520, and Eurogenesis (MASCHE).Peer reviewe

Zirconium Evaluations for ENDF/B-VII.2 for the Fast Region

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Measurement and modelling of the cross sections for the reaction 230Th(3He,3n)230U

230U and its daughter nuclide 226Th are promising therapeutic nuclides for application in targeted alpha therapy of cancer. We investigated the feasibility of producing 230U/226Th via irradiation of 230Th with 3He particles according to the reaction 230Th(3He,3n)230U. The experimental excitation function for this reaction is reported for the first time. Cross sections were measured using thin targets of 230Th prepared by electrodeposition and 230U yields were analysed using alpha spectrometry. Beam intensities were obtained via monitor reactions on aluminium foils using high resolution gamma spectrometry and IAEA recommended cross sections. Incident particle energies were calculated using the SRIM 2003 code. The experimental cross sections for the reaction 230Th(3He,3n)230U are in good agreement with model calculations by the EMPIRE-3 code, once breakup and transfer reactions are properly considered in the incident channel. The obtained cross sections are too low to allow the production of 230U/226Th in clinically relevant levels.JRC.E.5-Nuclear chemistr

Unrecognized Sources of Uncertainties (USU) in Experimental Nuclear Data

Evaluated nuclear data uncertainties reported in the literature or archived in data libraries are often perceived as unrealistic, most often because they are thought to be too small. The impact of this issue in applied nuclear science has been discussed widely in recent years. Commonly suggested causes are: poor estimates of specific error components, neglect of uncertainty correlations, and overlooked known error sources. However, instances have been reported where very careful, objective assessments of all known error sources have been made with realistic error magnitudes and correlations provided, yet the resulting evaluated uncertainties still appear to be inconsistent with observed scatter of predicted mean values. These discrepancies might be attributed to significant unrecognized sources of uncertainty (USU) that limit the accuracy to which these physical quantities can be determined. The objective of our work has been to develop qualitative and quantitative procedures for revealing and including USU estimates in nuclear data evaluations involving experimental input data. This paper identifies several specific clues that can be explored by evaluators in identifying the existence of USU. It then describes numerical procedures we have introduced to generate quantitative estimates of USU magnitudes. Key requirements for these procedures to be viable are that sufficient numbers of data points be available, for statistical reasons, and that additional supporting information about the measurements be provided by the experimenters. Several realistic examples are described here to illustrate these procedures and demonstrate their outcomes and limitations. Our work strongly supports the view that USU is an important issue in nuclear data evaluation, with significant consequences for applications, and that this topic warrants further investigation by the nuclear science community.JRC.G.2-Standards for Nuclear Safety, Security and Safeguard

Results of the Collaborative International Evaluated Library Organisation (CIELO) Project

Simulation of nuclear systems requires complete data that represents the relevant nuclear physics. This requires many types of experimental measurements, theoretical physics, semi-empirical models and software systems, as well as experts to integrate and guide the process. This discipline is collectively known as nuclear data, and separate programmes within various European countries, the USA, Japan, Russia, and other OECD Nuclear Energy Agency (NEA) member countries have been operating for many decades. The NEA Working Party on International Nuclear Data Evaluation Co-operation (WPEC) exists to improve the quality and completeness of nuclear data by bringing together representatives of the major nuclear data evaluation projects of NEA member countries and selected Invitees. The Sub- and Expert Groups of the WPEC typically focus on specific technical topics, while the Collaborative International Evaluated Library Organisation Pilot Project (CIELO) was established to generate complete evaluations for a selection of the most important isotopes for criticality in nuclear technologies: 235,238U, 239Pu, 56Fe, 16O and 1H. This project stimulated numerous activities, resulting in, directly or indirectly, an entire Special Issue of the Nuclear Data Sheets journal (issue 148, 2018) and the production of a suite of new nuclear data evaluations that have been incorporated in major nuclear data libraries ENDF and JEFF. The outcomes of these evaluations include significant harmonisation of discrepancies between the independent programmes, improvement in the performance for international standard nuclear criticality and neutron transmission benchmarks, complete uncertainties for nearly all parameters and the utilisation of modern data storage technologies. This work has leveraged the considerable, parallel experimental work in collecting improved experimental measurements to support nuclear data and highlighted high-priority areas for further study. A productive and durable framework for international evaluation has been established which will build upon the lessons learned. These will continue through new WPEC groups and a new IAEA evaluation network, which has been initiated in response to the success of the CIELO project. This article summarizes some performance feedback on the CIELO evaluations, including recent results, and will describe ongoing and future, planned CIELO-related collaborations to further advance our understanding.JRC.G.2-Standards for Nuclear Safety, Security and Safeguard

TANGRA – an experimental setup for basic and applied nuclear research by means of 14.1 MeV neutrons

For investigation of the basic characteristics of 14.1 MeV neutron induced nuclear reactions on a number of important isotopes for nuclear science and engineering, a new experimental setup TANGRA has been constructed at the Frank Laboratory of Neutron Physics of the Joint Institute for Nuclear Research in Dubna. For testing its performance, the angular distribution of gamma-rays (and neutrons) from the inelastic scattering of 14.1 MeV neutrons on high-purity carbon was measured and the angular anisotropy of gamma-rays from the reaction 12C(n, n'g)12C was determined. This reaction is important from fundamental (differential cross-sections) and practical (non-destructive elemental analysis of materials containing carbon) point of view. The preliminary results for the anisotropy of the gamma-ray emission from the inelastic scattering of 14.1-MeV neutrons on carbon are compared with already published literature data. A detailed data analysis for determining the correlations between inelastic scattered neutron and gamma-ray emission will be published elsewhere.JRC.G.2-Standards for Nuclear Safety, Security and Safeguard