We present the experimental campaigns - namely, three per facility - carried out between 2018 and 2021 in the AKR-2 and CROCUS zero power reactors within the framework of the Horizon 2020 European project CORTEX. Their purpose was to produce high-quality and noise-specific experimental data for the validation of the neutron noise computational models developed in CORTEX. In both reactors, perturbations were induced by two devices, separately and altogether. In AKR-2, they consisted of a rotating absorber, i.e. an absorber of variable strength, and a linear oscillator, i.e. a vibrating absorber, both sets in horizontal channels close to the core. In CROCUS, the project benefited from the COLIBRI experimental program and its fuel rods oscillator set in the outer lattice; an additional vibrating absorber called POLLEN was set in a vertical air-channel at core center. The campaigns at both facilities consisted of neutron measurements with numerous detectors at reference static states, and with the addition of the mechanical perturbations to induce neutron reactivity modulation. The present article documents the experimental setups and measurements for each facility and perturbation type. A focus is set on the experimental designs and their evolution along the project, as well as motivations and learned lessons. Results are presented and discussed in details in associated papers.

The work presented in this paper was performed within the Euratom Horizon 2020 GEMINI+ project. The GEMINI+ reactor is a prismatic block-type High -Temperature Gas-Cooled Reactor (HTGR). Within tasks devoted to safety, an analysis of air ingress scenario was performed by NRG with the thermal-hydraulic system code SPECTRA, while UJV and NCBJ worked with the integral system code MELCOR. Two air ingress scenarios were analyzed: Design Basis Accident (DBA) scenario. The air ingress scenario selected as DBA is a 65 mm break of a Helium purification line on top of the Steam Generator, Large air ingress scenario. The air ingress scenario selected is guillotine break of the coaxial gas duct. The DBA scenario is characterized by a very long period with practically stagnant gas in the primary system after the initial depressurization. However, very small gas flows through the break due to counter flow and diffusion in the break region (gas velocities of 10-2 m/s) are difficult to model with system codes. Therefore the break models in the system code were calibrated by performing CFD simulations. Furthermore, a model of gas mixing by diffusion was introduced in the NRG analysis for the practically stationary gas in the primary system (gas velocities of 10-4 m/s). The large air ingress scenario, with relatively large flow through the break, easier to model from this standpoint. The NRG SPECTRA results showed that the amount of air that can reach the core is extremely small in the DBA accident (0.5 kg of graphite consumed after 100 h). The maximum depth of oxidation was 2 mu m. In the large air ingress scenario the air ingress is significantly larger. At 100 h, approximately 105 kg of graphite was consumed. Even then, the maximum depth of oxidation was very small, approximately 0.2 mm. MELCOR results, performed at NCBJ and UJV, basically confirmed that the amount of air ingress is very small. The numbers were somewhat higher, mainly due to heavy flow oscillations in the break that could not be mitigated in MELCOR calculations.

The Horizon2020 European project CORTEX aims at developing an innovative core monitoring technique that allows detecting anomalies in nuclear reactors, such as excessive vibrations of core internals, flow blockage, or coolant inlet perturbations. The technique will be mainly based on using the fluctuations in neutron flux recorded by in-core and ex-core instrumentation, from which the anomalies will be differentiated depending on their type, location and characteristics. The project will result in a deepened understanding of the physical processes involved, allowing utilities to detect operational problems at a very early stage. In this framework, neutron noise computational methods and models are developed. In parallel, mechanical noise experimental campaigns are carried out in two zero-power reactors: AKR-2 and CROCUS. The aim is to produce high quality neutron noise-specific experimental data for the validation of the models. In CROCUS, the COLIBRI experimental program was developed to investigate experimentally the radiation noise induced by fuel rods vibrations. In this way, the 2018 first CORTEX campaign in CROCUS consisted in experiments with a perturbation induced by a fuel rods oscillator. Eighteen fuel rods located at the periphery of the core fuel lattice were oscillated between ±0.5 mm and ±2.0 mm around their central position at a frequency ranging from 0.1 Hz to 2 Hz. Signals from 11 neutron detectors which were set at positions in-core and ex-core in the water reflector, were recorded. The present article documents the results in noise level of the experimental campaign. Neutron noise levels are compared for several oscillation frequencies and amplitudes, and at the various detector locations concluding to the observation of a spatial dependency of the noise in amplitude.

Concrete exposure to high temperatures induces thermo-hygral phenomena, causing water phase changes, buildup of pore pressure and vulnerability to spalling. In order to predict these phenomena under various conditions, a three-phase transport model is proposed. The model is validated on X-ray CT data up to 320 °C, showing good agreement of the temperature profiles and moisture changes. A dehydration description, traditionally derived from thermogravimetric analysis, was replaced by a formulation based on data from neutron radiography. In addition, treating porosity and dehydration evolution as independent processes, previous approaches do not fulfil the solid mass balance. As a consequence, a new formulation is proposed that introduces the porosity as an independent variable, ensuring the latter condition.

The present article gives an overview of the first experimental campaigns carried out in the AKR-2 and CROCUS reactors within the framework of the Horizon 2020 European project CORTEX. CORTEX aims at developing innovative core monitoring techniques that allow detecting anomalies in nuclear reactors, e.g. excessive vibrations of core internals. The technique will be mainly based on using the fluctuations in neutron flux, i.e. noise analysis. The project will result in a deepened understanding of the physical processes involved. This will allow utilities to detect operational problems at a very early stage, and to take proper actions before such problems have any adverse effect on plant safety and reliability. The purpose of the experimental campaigns in the AKR-2 and CROCUS reactors is to produce noise-specific experimental data for the validation of the neutron noise computational models developed within this framework. The first campaigns at both facilities consisted in measurements at reference static states, and with the addition of mechanical perturbations. In the AKR-2 reactor, perturbations were induced by two devices: a rotating absorber and a vibrating absorber, both sets in experimental channels close to the core. In CROCUS, the project benefited from the COLIBRI experimental program: 18 periphery fuel rods were oscillated at a maximum of ±2 mm around their central position in the Hz range. The present article documents the experimental setups and measurements for each facility and perturbation type.

The Horizon2020 European project CORTEX aims at developing an innovative core monitoring technique that allows detecting anomalies in nuclear reactors, such as excessive vibrations of core internals, flow blockage, or coolant inlet perturbations. The technique will be mainly based on using the fluctuations in neutron flux recorded by in-core and ex-core instrumentation, from which the anomalies will be differentiated depending on their type, location and characteristics. The project will result in a deepened understanding of the physical processes involved, allowing utilities to detect operational problems at a very early stage. In this framework, neutron noise computational methods and models are developed. In parallel, mechanical noise experimental campaigns are carried out in two zero-power reactors: AKR-2 and CROCUS. The aim is to produce high quality neutron noise-specific experimental data for the validation of the models. In CROCUS, the COLIBRI experimental program was developed to investigate experimentally the radiation noise induced by fuel rods vibrations. In this way, the 2018 first CORTEX campaign in CROCUS consisted in experiments with a perturbation induced by a fuel rods oscillator. Eighteen fuel rods located at the periphery of the core fuel lattice were oscillated between ±0.5 mm and ±2.0 mm around their central position at a frequency ranging from 0.1 Hz to 2 Hz. Signals from 11 neutron detectors which were set at positions in-core and ex-core in the water reflector, were recorded. The present article documents the results in noise level of the experimental campaign. Neutron noise levels are compared for several oscillation frequencies and amplitudes, and at the various detector locations concluding to the observation of a spatial dependency of the noise in amplitude.

This paper deals with the processes involved in the generation of reliable experimental data for the validation of computer simulations. In the field of neutron noise, the analysis of results is based on spectral features of the detector signals in the frequency domain. Neutron noise simulators also produce estimates that are subjected to studies in the same domain. The validation process of such simulations begins with the generation of reliable experimental data. In this work, we analyze results from two neutron noise experimental campaigns. The focus is placed upon de comparison of results obtained by different data acquisition systems (DAQs) that were used to record the data in parallel. The goal is to verify whether results obtained by the different DAQs are consistent, and thus reliable. The neutron noise-dedicated experiments were carried out in the AKR-2 reactor at the Technische Universitat Dresden and in the CROCUS reactor at the Ecole polytechnique federale de Lausanne. The experiments consisted in introducing different types of periodic reactivity perturbations: a rotating neutron absorber with a varying absorption crosssection with respect to the rotation angle; a linearly vibrating absorber that is moved back and forth inside the reactor core; and a fuel rods oscillator that allows to vibrate a set of fuel rods.

CuCrZr alloy is candidate heat sink material for the ITER blanket, first wall, and divertor. During ITER operation it will be exposed to a combination of elevated temperatures, heat flux, and intense fast neutron radiation. This environment will challenge the performance of components and joints based on CuCrZr. To address this issue, mechanical tests were performed with irradiated and reference specimens of CuCrZr and its joints with 316 L(N)-IG (ITER Grade) stainless steel made by hot isostatic pressing. The reactor exposure up to similar to 0.7 dpa was performed in the BR2 reactor at SCK center dot CEN, in water at a temperature of 257 degrees C A special design was used to allow irradiation of specimens axially pre-stressed at different strain levels. The post-irradiation examination included: (i) tensile test, (ii) measurements of plastic deformation of samples axially loaded during irradiation (in situ creep test); (iii) thermal creep tests on irradiated samples. The fracture surfaces were examined in a hot cell using a Scanning Electron Microscope (SEM). The results were compared with data obtained from mechanical tests and SEM/EDX fracture surface analysis on non-irradiated reference samples. The level of a possible creep under irradiation is below the experimental uncertainty.

The generation of nuclear energy by means of the existing nuclear reactor systems is based mainly on the fission of U-235. But this comes along with the capture of neutrons by the U-238 faction and results in a build-up of plutonium isotopes and minor actinides as neptunium, americium and curium. These actinides are dominant for the long time assessment of the radiological risk of a final disposal therefore a minimization of the long living isotopes is aspired. Burning the actinides in a high temperature helium cooled graphite moderated reactor (HTR) is one of these options. The use of plutonium isotopes to sustain the criticality of the system is intended to avoid on the one hand highly enriched uranium because of international regulations and on the other hand low enriched uranium because of the build up of new actinides from neutron capture in the U-238 fraction. Because initial minor actinide isotopes are typically not fissionable by thermal neutrons the idea is to fission instead the intermediate isotopes generated by the first neutron capture. This paper comprises calculations for plutonium/minor actinides/thorium fuel compositions and their correlated final burn-up for a generic pebble bed HTR based on the reference design of the 400 MW PBMR. In particular the cross sections and the neutron balance of the different minor actinide isotopes in the higher thermal energy spectrum of a HTR will be discussed. For a fuel mixture of plutonium and minor actinides a significant burn-up of these actinides up to 20% can be achieved but at the expense of a higher residual fraction of plutonium in the burned fuel. Combining thorium with a significant fraction of minor actinides and burned LWR plutonium results in a nearly unchanged amount of minor actinides while the isotope composition significantly changes. This behaviour with respect to the initial heavy metal load will also be discussed. (C) 2012 Elsevier B.V. All rights reserved.

The production of nuclear energy with existing nuclear reactors is equivalent to the use of low enriched uranium. But the neutron capture of the large corresponding U-238 fuel fraction also generates a build-up of plutonium isotopes and minor actinides as Neptunium, Americium and Curium. These actinides are dominant for the long time assessment of final disposal therefore a minimization of the long living isotopes is aspired. Burning the actinides in a high temperature helium cooled graphite moderated reactor (HTR) is one of these options. Using plutonium isotopes to sustain the criticality of the system is intended to avoid highly enriched uranium because of international regulations and low enriched uranium because of the build up of new actinides from neutron capture in U-238. Also fractions of plutonium isotopes are build up to minor actinides but for this absorption the overall number of actinides keeps constant. Nevertheless for the final assessment the activity and toxicity of all important actinides have to be taken into account. This paper comprises calculations for plutonium/minor actinides/thorium fuel compositions, their correlated final burn-up and the long term activity and toxicity for a generic pebble bed HTR based on the reference design of the 400MW PBMR. In particular the behaviour of the different minor actinide isotopes in the higher thermal energy spectrum of a HTR will be discussed. Thorium based fuel – as a promising alternative to uranium based fuel – offers several advantages as a minimized build up of new Pu and MA, a higher thermal conductivity and melting point. Combining the thorium fuel with a significant fraction of minor actinides and an isotope fraction consistent with burned LWR fuel the total amount of the minor actinides stays nearly unchanged while the isotope composition significantly changes. This behaviour with respect to the initial heavy metal load and the influence on the long term activity and toxicity will be discussed.

Domain analysis involves not only looking at standard requirements documents (e.g., use case specifications) but also at customer information packs, market analyses, etc. Looking across all these documents and deriving, in a practical and scalable way, a feature model that is comprised of coherent abstractions is a fundamental and non-trivial challenge. We conduct an exploratory study to investigate the suitability of information retrieval (IR) techniques for scalable identification of commonalities and variabilities in requirement specifications for software product lines. Accordingly, based on observations derived from industrial experience and on state-of-the-art research and practice, we also propose an initial framework, leveraging IR to systematically abstract requirements from existing specifications of a given domain into a feature model. We evaluate this framework, present a roadmap for its further extension, and formulate hypotheses to guide future work in exploring IR techniques for domain analysis.

SAP is the world’s largest vendor of enterprise software. SAP Research is interested in understanding, evaluating, and applying aspect-oriented techniques in the context of large enterprise systems. This interest is also reected by our involvement several European and national research projects on Aspect-Oriented Software Development (AOSD). We report on existing aspect-oriented concepts at SAP and present a case study that illustrates several non-obvious crosscutting concerns in business software. We also discuss the benets and challenges that arise when applying AOSD to large scale industrial projects and present a road map to adopting AOSD at SAP for productive use. 1. MOTIVATION

In real world business applications traditional software product line engineering and modeldriven software development (MDSD) [6] often cannot properly reflect the decomposition of system features. For instance, Governance, Risk and Compliance (GRC) checks or late introduction of security properties often crosscut the architectural design of a system. To overcome these issues Aspect-Oriented Software Development (AOSD) [1] modularizes such crosscutting concerns in independent aspects. Although aspects can already be captured at requirements stage [2, 7], there is no clear mapping to later development stages. MDSD can address this by model transformation. However, AOSD still increases the complexity of traceability (and hence, maintainability) because it adds yet another dimension of variability [3]. This issue is one of the most important arguments against applying AOSD techniques in an industrial context. Future research has to take care of this issue in order to lay the basis for industry acceptance of AOSD. According to an internal audit of customers of SAP, missing traceability during the whole development cycle is the top-rated weakness. In addition missing traceability information was explicitly mentioned as weakness in 2005 in an external ISO certification audit. The current state of trace support imple-

This paper gives an overview of the support for traceability in an industrial context. The state of best practices are described and shortcomings are identi ed. Furthermore the AMPLE project is introduced, encompassing an overview on our approach towards traceability in the context of Model-Driven Development (MDD) and Software Product Lines (SPL) in conjuction with Aspect-Oriented Software Development (AOSD). AMPLE can be considered as a joint e ort to tackle the shortcomings of current industrial practice. The paper is of positional nature and outlines our work currently in progress.