[en] Measurements of neutron-induced cross sections to generate nuclear data are a core activity of the JRC-Directorate G Standards for Nuclear Safety, Security and Safeguards unit in Geel. Thin ¹⁰B layers are of great importance in this activity as they are used to measure the absolute neutron flux in the beam using the standard ¹⁰B(n,α)⁷Li reaction cross-section as a reference. After a period of reduced activity and in line with a renewed interest for nuclear data, the demand for high quality ¹⁰B targets increased. In this paper we describe the design and features of a new e-beam evaporator specifically customized for the preparation of boron targets as replacement of the old dysfunctional equipment. Several ¹⁰B targets of varying thicknesses were prepared and characterized as part of the factory acceptance tests and implementation in the JRC-Geel target preparation laboratory. Differential substitution weighing was applied for mass determination and in order to calibrate the thickness monitor. Comparative time-of-flight measurements relative to ¹⁰B and ²³⁵U standard targets were conducted at the GELINA neutron time-of-flight facility at the JRC-Geel site as second methodology for the determination of ¹⁰B areal density. The morphology of the layers was assessed by means of Scanning Electron Microscopy (SEM). The determination of impurities was realized by means of Energy Dispersive X-ray (EDX). Finally, two boron targets were prepared in the frame of the measurement of the neutron induced fission cross-section of ²³⁰Th at the n_TOF neutron time-of-flight facility at CERN.

[en] A global sensitivity analysis of effective neutron multiplication factor k_eff to the change of nuclear data library revealed that JEFF-3.2T2 neutron-induced evaluated data library produces closer results to ENDF/B-VII.1 than does JEFF-3.1.2. The analysis of contributions of individual evaluations into k_eff sensitivity allowed establishing the priority list of nuclides for which uncertainties on nuclear data must be improved. Detailed sensitivity analysis has been performed for two nuclides from this list, ⁵⁶Fe and ²³⁸Pu. The analysis was based on a detailed survey of the evaluations and experimental data. To track the origin of the differences in the evaluations and their impact on k_eff, the reaction cross-sections and multiplicities in one evaluation have been substituted by the corresponding data from other evaluations. (authors)

[en] From 2012 to 2014, Neutron Resonance Densitometry (NRD) is being developed as a non-destructive assay to quantify U and Pu isotopes. NRD is composed of neutron resonance transmission analysis (NRTA) and neutron resonance capture analysis (NRCA)/prompt gamma-ray analysis (PGA). NRTA in NRD plays a role of quantifying the amounts of the isotopes of a nuclear fuel material (U,Pu) in molten fuel debris. Therefore, the neutron absorption measurement using Time-of-Flight (TOF) method is carried out. A demonstration NRTA experiment was performed at a neutron time of flight facility GELINA (Belgium). Consequently, we succeeded in quantifying the randomly selected sample from B, Mn, Co, Cu, Nb, Rh, W, Au contained in a black box. In this presentation, we describe the principle of measurement of the developed NRTA and explain details of the demonstration experiment. (author)

[en] Neutron Resonance Densitometry (NRD) was developed as a non-destructive assay to quantify U and Pu isotopes in particle-like debris. NRD is composed of neutron resonance transmission analysis (NRTA) and neutron resonance capture analysis (NRCA) or prompt gamma-ray analysis (PGA). NRCA/PGA in NRD plays a role of identifying impurities in debris under the high-radiation field primarily caused by ¹³⁷Cs. For this purpose, a novel LaBr₃ gamma-ray detector employing specific shields has been newly developed. With the developed gamma-ray detector, a demonstration NRCA experiment was performed at a neutron time of flight facility GELINA (Belgium). As a result, all samples placed in a black box that is completely sealed by third party were successfully identified by the experiment. (author)

[en] MetroFission project has been looking at solving metrological problems related to a new generation of NPPs. The proposed Gen. IV NPPs are designed to run safely, make efficient use of natural resources, minimize the waste and maintain proliferation resistance. In order to reach these goals, the reactor operation involves higher temperatures, high-energy neutron fluence, different types of fuel where the minor actinides are included etc. The work has focused on improved temperature measurements, investigation of thermal properties of advanced materials, determination of new and relevant nuclear data and development of measurement techniques for radionuclides suitable for Gen. IV NPPs. The improved temperature measurement for nuclear power plant applications includes the development of a new Fe-C fixed point. Robust, repeatable and versatile cells have been constructed and compared with success among the project participants and their melting temperatures have been determined. Methodology of self-validating thermocouples has proven efficient at several fixed point temperatures using different designs. A practical acoustic thermometer has been tested at 1000 deg. C with success thanks to the use of innovative signal processing methods. Mo/Nb thermocouples have been obtained with different sheath materials and tested with the aim to achieve for the first time a reference function determined with the best possible uncertainties. Following reviews of designs and technology proposed for fourth generation nuclear plants effort within this project, with regards to thermal properties of advanced materials for nuclear design, has concentrated on provision of thermodynamic data to support the development of the sodium cooled fast reactor. Data has been critically assessed to represent the potential interaction between the Na coolant and the nuclear fuel taken to be based on (U, Pu)O₂ but incorporating minor actinides such as Np and Am. Data for the fission products and containment materials have also been reviewed and new data assessed to represent the interaction between them and the Na coolant, in order to permit calculation of phase and chemical equilibria for severe accident scenarios. Reference metrological facilities and methods have been developed or improved for the measurements of normal spectral emissivity and specific heat up to 1500 deg. C, and thermal diffusivity up to 2000 deg. C. The following actions were notably performed: - Development of two complementary facilities based on different metrological approaches by PTB and LNE for the measurement of emissivity of solid materials at high temperature. - Modification of the LNE diffusivimeter with the development and integration of a specific inductive furnace, and the adaptation of the associated IR detection systems. These facilities have now been used for the measurement of thermophysical properties of some materials. Advantage has been taken of National Measurement Institutes experience in neutron fluence measurements to improve high-energy cross-section measurements. A secondary fluence standard has been established and used to determine the cross sections of actual interest improving nuclear data standards in the form of reduced measurement uncertainties. The heavier actinides and their decay products have a role in the future development and adoption of nuclear power plants in whose fuels they will be present in controlled amounts. An objective of the MetroFission project was to measure the alpha particle emission probabilities of ²³⁸U with certified isotopic composition. The nuclear data from alpha spectrometry of ²³⁸U sources has been successful, obtaining data that will be provided to the international community and that further lower the uncertainties of the nuclear data. The quality of the alpha spectrum measurement, in terms of energy resolution and peak tailing of the ²³⁸U alpha spectra, was significantly better than in any previous measurement. Fission fragments containing more beta-decay isotopes will result from proposed fast reactors. Cry ogenic detectors have been developed aimed at improving the measurement of beta spectra and verifying theoretical models. A beta spectrum shape of ⁶³Ni has successfully been obtained. Improvements have been made in the source components and in the source production method in order to lower uncertainties. The exchange effect has been implemented in the calculation of theoretical beta spectra. The measurement of the beta spectrum of ⁶³Ni has for the first time confirmed the exchange effect at very low energy. The energy threshold of the metallic magnetic calorimeter is 180 eV. At this energy, the enhancement of the beta emission due to the exchange effect is larger than 20 %. Nuclear power plants would benefit from on-site activity measurements of radionuclides including low-energy beta emitters that are abundant but can prove difficult to assay. A primary liquid scintillation coincidence counting method called Triple to Double Coincidence Ratio (TDCR) has been modified for this purpose. Five partners have built miniature TDCR systems, using newer, smaller, more efficient photomultiplier tubes. The system also includes replacing the analogue electronic modules with digital acquisition systems and signal processing in order to significantly improve digital coincidence counting (DCC)

[en] The MetroFission project, a Joint Research Project within the European Metrology Research Program, aims at addressing a number of metrological problems involved in the design of proposed Generation IV nuclear reactors. One of the objectives of this multidisciplinary project is the improvement of neutron cross section measurement techniques in order to arrive at uncertainties as required for the design and safety assessment of new generation power plants and fuel cycles. This objective is in line with the 'Uncertainty and target accuracy assessment for innovative systems using recent covariance data evaluations' published by a working party of the OECD Nuclear Energy Agency in 2008. These requests are often very challenging, being at or beyond the state-of-the-art in neutron measurements, which is set by self-normalizing methods and the neutron data standards used at laboratories where the data are measured. A secondary neutron fluence standard has been developed and calibrated at the neutron time-of-flight facility GELINA of the JRC's Institute for Reference Materials and Measurements (IRMM). It consists of a flux monitor, a reference ionization chamber containing a ¹⁰B layer and a ²³⁵U layer, and a parallel plate ionization chamber with 8 well characterized ²³⁵U deposits. These devices are used to determine the neutron fluence, based on the well-known neutron induced fission reaction on ²³⁵U. All deposits have been prepared and characterized at the IRMM target preparation lab. The secondary fluence standard at the GELINA facility can be used for reliable determination of the efficiency of fluence measurement devices used in neutron data measurements at IRMM and elsewhere. It is an essential tool to reliably calibrate fluence normalization devices used in neutron time-of-flight cross section measurements. (authors)

[en] A characterization of cylindrical samples by neutron resonance transmission analysis (NRTA) at the GELINA facility of JRC Geel (Belgium) is presented. The samples were designed and produced for reactivity worth measurements in the MINERVE reactor of CEA Cadarache (France). NRTA was applied to determine the nuclide composition of UO₂, Al₂O₃ and liquid samples that were doped with silver. The volume number densities of ²³⁸U, ¹⁰⁷Ag and ¹⁰⁹Ag obtained by NRTA are within 2% fully consistent with the values that are quoted by the manufacturer. In addition, the NRTA data reveal a tungsten contamination which is not reported by the provider. It is shown that such a contamination contributes by up to 5.7% to the reactivity worth. (author)

[en] A characterization of cylindrical samples by neutron resonance transmission analysis (NRTA) at the GELINA facility of JRC Geel (Belgium) is presented. The samples were designed and produced for reactivity worth measurements in the MINERVE reactor of CEA Cadarache (France). NRTA was applied to determine the nuclide composition of UO₂, Al₂O₃ and liquid samples that were doped with silver. The volume number densities of ²³⁸U, ¹⁰⁷Ag and ¹⁰⁹Ag obtained by NRTA are within 2% fully consistent with the values that are quoted by the manufacturer. In addition, the NRTA data reveal a tungsten contamination which is not reported by the provider. It is shown that such a contamination contributes by up to 5.7% to the reactivity worth.

[en] The use of neutron resonance transmission analysis to characterise samples with a complex geometry is discussed. Analytical expressions for such samples have been derived and implemented in the resonance shape analysis code REFIT. They were validated by experiments at the time-of-flight facility GELINA using a set of metallic natural copper samples and pellets made of silver mixed with uranium-oxide powder. The expressions were used to derive sample characteristics by a least squares adjustment to experimental transmission data. In addition, the resonance parameters of ⁶³Cu and ⁶⁵Cu for energies below 6.5 keV, which are reported in the literature and recommended in evaluated data libraries, were verified. (authors)

[en] The windowless target electron beam experimental irradiation (WEBEXPIR) program was set-up as part of the MYRRHA/XT-ADS R and D effort on the spallation target design to investigate the interaction of a proton beam with a liquid lead-bismuth eutectic (LBE) free surface. In particular, possible free surface distortion or shockwave effects in nominal conditions and during sudden beam on/off transient situations, as well as possible enhanced evaporation were assessed. An experiment was conceived at the IBA TT-1000 Rhodotron, where a 7 MeV electron beam was used to simulate the high power deposition at the MYRRHA/XT-ADS LBE free surface. The geometry and the LBE flow characteristics in the WEBEXPIR set-up were made as representative as possible of the actual situation in the MYRRHA/XT-ADS spallation target. Irradiation experiments were carried out at beam currents of up to 10 mA, corresponding to 40 times the nominal beam current necessary to reproduce the MYRRHA/XT-ADS conditions. Preliminary analyses show that the WEBEXPIR free surface flow was not disturbed by the interaction with the electron beam and that vacuum conditions stayed well within the design specifications