Results of time-of-flight transmission measurements for natW at 25 m and 50 m stations of GELINA

Transmission measurements have been performed at the time-of-flight facility GELINA using metallic discs of natural tungsten. The measurements have been carried out at 25 m and 50 m stations using Li-glass scintillators with the accelerator operating at 800 Hz. This report describes the experimental details required to deliver the data to the EXFOR data library, which is maintained by the Nuclear Data Section of the International Atomic Energy Agency (NDS/IAEA) and the Nuclear Energy Agency of the Organisation for Economic Co-operation and Development (NEA/OECD). The experimental conditions and data reduction procedures are described. In addition, full covariance information based on the AGS concept is given such that nuclear reaction model parameters together with their covariances can be derived in a least squares adjustment to the data or the data can be used to validate resonance parameters recommended in evaluated data libraries.JRC.G.2-Standards for Nuclear Safety, Security and Safeguard

NRD Demonstration Experiments at GELINA

Neutron Resonance Densitometry (NRD), a non-destructive analysis method, was presented. The method has been developed to quantify special nuclear material (SNM) in debris of melted fuel that will be produced during the decommissioning of the Fukushima Daiichi nuclear power plants. The method is based on Neutron Resonance Transmission Analysis (NRTA) and Neutron Resonance Capture Analysis combined with Prompt Gamma–ray analysis (NRCA/PGA). The quantification of SNM relies on the NRTA results. The basic principles of NRD, which are based on well-established methodologies for neutron resonance spectroscopy, have been explained. To develop NRD for the characterization of rock- and particle like heterogeneous samples a JAEA/JRC collaboration has been established. As part of this collaboration a NRD demonstration workshop was organized at the time-of-flight facility GELINA of the JRC-IRMM in Geel (B). The potential of NRD was demonstrated by measurements on a complex mixture of different elements. It was demonstrated that the elemental composition of an unknown sample predicted by NRTA deviated on average by less than 2% from the declared value. In addition the potential to identify the presence of light elements by NRCA/PGA was shown.JRC.D.4-Standards for Nuclear Safety, Security and Safeguard

Status of evaluated data files for 238U in the resonance region

Experimental data and evaluated data libraries related to neutron induced reaction cross sections for 238U in the resonance region are reviewed. Based on this review a set of test files is produced to study systematic effects such as the impact of the upper boundary of the resolved resonance region (RRR) and the representation of the infinite diluted capture and in-elastic cross section in the unresolved resonance region (URR). A set of Benchmark experiments was selected and used to verify the test files. Based on these studies recommendations to perform a new evaluation have been defined. This report has been prepared in support to the CIELO (Collaborative International Evaluated Library Organisation) project. The objective of this project is the creation of a world-wide recognised nuclear data file with a focus on six nuclides, i.e. 1H, 16O, 56Fe, 235U, 238U and 239Pu. Within the CIELO project, the Joint Research Centre (JRC) at Geel (B) is in charge of the production of an evaluated cross section data file for neutron induced reaction of 238U in the resonance region.JRC.D.4-Standards for Nuclear Safety, Security and Safeguard

Noxious stimulation response index: a novel anesthetic state index based on hypnotic-opioid interaction

The noxious stimulation response index (NSRI) is a novel anesthetic depth index ranging between 100 and 0, computed from hypnotic and opioid effect-site concentrations using a hierarchical interaction model. The authors validated the NSRI on previously published data

Data reduction and uncertainty propagation of time-of-flight spectra with AGS

Results of neutron time-of-flight measurements are commonly used to parameterize neutron induced reaction cross sections in the resonance region based on the R-matrix reaction theory. Reaction yields or transmission as well as their covariance information are derived starting from measured counting spectra. They are then used in a least squares adjustment for obtaining model parameters. In this paper, a compact formalism is presented to propagate both the correlated and uncorrelated uncertainty components. Full information on the origin of each correlated component of the covariance matrix is maintained. This is particularly important in order to avoid a bias on the model parameters through a phenomenon known as Peelle’s Pertinent Puzzle (PPP). This compact formalism was implemented into the data reduction code AGS (Analysis of Geel Spectra).JRC.D.4-Standards for Nuclear Safety, Security and Safeguard

Characterization of nuclear material by Neutron Resonance Transmission Analysis

The use of Neutron Resonance Transmission Analysis for the characterization of nuclear materials is discussed. The method, which relies on resonance structures in neutron-induced reaction cross sections, can be applied as a non-destructive method to characterise complex nuclear materials such as melted fuel resulting from a severe nuclear accident. Results of a demonstration experiment at the GELINA facility reveal that accurate data can be obtained at a compact facility even in the case of strong overlapping resonances.JRC.G.2-Standards for Nuclear Safety, Security and Safeguar

Determination of resonance parameters and their covariances from neutron induced reaction cross section data

Cross section data in the resolved and unresolved resonance region are represented by nuclear reaction formalisms using parameters which are determined by fitting them to experimental data. Therefore, the quality of evaluated cross sections in the resonance region strongly depends on the experimental data used in the adjustment process and an assessment of the experimental covariance data is of primary importance in determining the accuracy of evaluated cross section data. In this contribution, uncertainty components of experimental observables resulting from total and reaction cross section experiments are quantified by identifying the metrological parameters involved in the measurement, data reduction and analysis process. In addition, different methods that can be applied to propagate the covariance of the experimental observables (i.e. transmission and reaction yields) to the covariance of the resonance parameters are discussed and compared. The methods being discussed are: conventional uncertainty propagation, Monte Carlo sampling and marginalization. It is demonstrated that the final covariance matrix of the resonance parameters not only strongly depends on the type of experimental observables used in the adjustment process, the experimental conditions and the characteristics of the resonance structure, but also on the method that is used to propagate the covariances. Finally, a special data reduction concept and format is presented, which offers the possibility to store the full covariance information of experimental data in the EXFOR library and provides the required information to perform a full covariance evaluation.JRC.D.4-Standards for Nuclear Safety, Security and Safeguard

Characterization of special nuclear material by neutron resonance spectroscopy

Neutrons can be used as a tool to study materials and objects. Cross sections of neutron induced reactions show characteristic resonance structures which can be used as fingerprints to determine the elemental and isotopic composition of materials and objects. They are the basis of two analytical methods which have been developed at the European Commission's Joint Research Centre in Geel (BE): Neutron Resonance Capture Analysis (NRCA) and Neutron Resonance Transmission Analysis (NRTA). The first technique is based on the detection of gamma rays emitted during a neutron capture reaction in the sample being studied; the latter determines the fraction of neutrons transmitted through a sample positioned in a neutron beam. They rely on well-established methodologies in neutron resonance spectroscopy. It has been shown that NRCA is a useful technique to determine the composition of archaeological objects. In contributions to a previous ESARDA symposium in Bruges the use of NRTA to characterize particle-like debris of melted fuel that is formed in severe nuclear accidents has been presented. However, the discussion was primarily based on theoretical studies. In this contribution the performance of NRTA as a non-destructive method to determine the amount of fissile material is discussed based on measurements carried out at the time-of-flight facility GELINA using reference materials containing uranium and plutonium. The results of these experiments demonstrate that the relative amount of special nuclear material in particle like debris can be derived absolutely without the need of calibration materials with an uncertainty less than 2%, even in the presence of strong neutron absorbing matrix materials.JRC.D.4-Standards for Nuclear Safety, Security and Safeguard

Evaluation of neutron resonance cross section data at GELINA

Over the last decade, the EC–JRC–IRMM, in collaboration with other institutes such as INRNE Sofia (BG), INFN Bologna (IT), ORNL (USA), CEA Cadarache (FR) and CEA Saclay (FR), has made an intense effort to improve the quality of neutron-induced cross section data in the resonance region. These improvements relate to both the infrastructure of the facility and the measurement setup, and the data reduction and analysis procedures. As a result total and reaction cross section data in the resonance region with uncertainties better than 0.5 % and 2 %, respectively, can be produced together with evaluated data files for both the resolved and unresolved resonance region. The methodology to produce full ENDF compatible files, including covariances, is illustrated by the production of resolved resonance parameter files for 241Am, Cd and W and an evaluation for 197Au in the unresolved resonance region.JRC.D.4-Standards for Nuclear Safety, Security and Safeguard