Results of the application and demonstration calculations

CORTEX - Research and Innovation Action (RIA) This project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 754316.Publisher PD

Review of nuclear data improvement needs for nuclear radiation measurement techniques used at the CEA experimental reactor facilities

The constant improvement of the neutron and gamma calculation codes used in experimental nuclear reactors goes hand in hand with that of the associated nuclear data libraries. The validation of these calculation schemes always requires the confrontation with integral experiments performed in experimental reactors to be completed. Nuclear data of interest, straight as cross sections, or elaborated ones such as reactivity, are always derived from a reaction rate measurement which is the only measurable parameter in a nuclear sensor. So, in order to derive physical parameters from the electric signal of the sensor, one needs specific nuclear data libraries. This paper presents successively the main features of the measurement techniques used in the CEA experimental reactor facilities for the on-line and offline neutron/gamma flux characterizations: reactor dosimetry, neutron flux measurements with miniature fission chambers and Self Power Neutron Detector (SPND) and gamma flux measurements with chamber ionization and TLD. For each technique, the nuclear data necessary for their interpretation will be presented, the main identified needs for improvement identified and an analysis of their impact on the quality of the measurement. Finally, a synthesis of the study will be done

Investigation of ADS-Type Heterogeneities in the MUSE4 Critical Configuration

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State of the art on nuclear heating measurement methods and expected improvements in zero power research reactors

The paper focuses on the recent methodological advances suitable for nuclear heating measurements in zero power research reactors. This bibliographical work is part of an experimental approach currently in progress at CEA Cadarache, aiming at optimizing photon heating measurements in low-power research reactors. It provides an overview of the application fields of the most widely used detectors, namely thermoluminescent dosimeters (TLDs) and optically stimulated luminescent dosimeters. Starting from the methodology currently implemented at CEA, the expected improvements relate to the experimental determination of the neutron component, which is a key point conditioning the accuracy of photon heating measurements in mixed n–γ field. A recently developed methodology based on the use of 7Li and 6Li-enriched TLDs, precalibrated both in photon and neutron fields, is a promising approach to deconvolute the two components of nuclear heating. We also investigate the different methods of optical fiber dosimetry, with a view to assess the feasibility of online photon heating measurements, whose primary benefit is to overcome constraints related to the withdrawal of dosimeters from the reactor immediately after irradiation. Moreover, a fibered setup could allow measuring the instantaneous dose rate during irradiation, as well as the delayed photon dose after reactor shutdown. Some insights from potential further developments are given. Obviously, any improvement of the technique has to lead to a measurement uncertainty at least equal to that of the currently used methodology (∼5% at 1σ)

Investigation of ADS-Type heterogeneities in the MUSE4 critical configuration

The MUSE4 programme of ADS-related integral experiments has recently been completed at the MASURCA facility at Cadarache (France). Investigations have been carried out in a reference critical fast-spectrum configuration and related sub-critical core configurations driven by an accelerator. Among the various characteristics which need to be investigated are the peak power and the peak fast-neutron flux (damage in structural materials), the presence of the accelerator tube in the core creating new types of heterogeneities, the effects of which need to be modelled and quantified by appropriate calculational tools. In this context, different fission chamber traverses and various activation foil measurements in the MUSE4 programme have covered a wide range of threshold and non-threshold reaction rates. This paper presents the analyses of the corresponding experimental results from the reference critical MUSE4 configuration. Comparisons are made with calculations using both deterministic (ERANOS-2.0) and stochastic (MCNP-4C) codes in conjunction with different data libraries (JEF-2.2, ERALIB1, ENDF/B6). Significant discrepancies are observed, particularly for high-threshold reactions in the central lead diffusing region. Of the alternative calculational routes applied, the most appropriate ones for treatment of the ADS-type heterogeneities are found to be ERANOS-2.0 (with either JEF-2.2 or ERALIB1 data) and MCNP-4C in conjunction with its ENDF/B6 library