ENEA Brasimone Research Centre

The paper describes the application of a coupled methodology between Fluent CFD code and RELAP5 System Thermal-Hydraulic code developed at the DICI (Dipartimento di Ingegneria Civile e Industriale) of the University of Pisa. The methodology was applied specifically to the LBE-water heat exchanger HERO located inside the S100 vessel of the CIRCE facility, built at ENEA Brasimone Research Centre, to investigate the capabilities of this component. In the proposed methodology, the primary side of the HX-HERO, containing LBE, is simulated by the CFD code, while the secondary side, containing a two phase mixture of water and vapour, is reproduced by the System Thermal-Hydraulic code. During the calculation the two codes exchange, at the coupled boundaries: the bulk temperature and heat transfer coefficient of the ascending water (RELAP5 to Fluent) and the wall temperature at the water side surface of the pipes (Fluent to RELAP5). The coupling technique was tested by comparing the numerical results with the experimental data recently obtained by ENEA; the numerical results predicted well the qualitative trend of the temperature and provided an overall good prediction of the temperature also from a quantitative point of view. It is worth noticing that this good performance remained reliable for all the cases simulated, proving the general applicability of the methodology.

Abstract The current studies on the development of the EU DEMO breeding blanket include among the options the use of liquid Lithium-Lead (17Li-83Pb) as tritium breeder (and multiplier), with different coolants. As the tritium is steadily produced in the blanket during the reactor operation, suitably efficient strategies for the Tritium Extraction System (TES) from the breeder must be developed, allowing a closed fuel cycle in situ and avoiding tritium accumulation in the machine. The Permeator Against Vacuum (PAV) appears to be one of the most promising solutions to achieve this goal. In this paper, the performance of a PAV system is studied by means of different models describing the transport of tritium in the liquid PbLi and in the metallic membrane separating it from the vacuum. The comparison of the results for different membrane materials and size of the device, for a given target efficiency, allows to optimize the PAV design, also taking into account corrosion issues. The approximations and limitations of the adopted models are also addressed.

Abstract This paper presents the work ongoing at the DICI (Dipartimento di Ingegneria Civile e Industriale) of the University of Pisa on the application of coupled methodology between Fluent CFD code and RELAP5/Mod3.3 system code. In particular, this methodology was applied to the LBE-water heat exchanger HERO, with the aim to analyse the performances of this component. The test section object of this study is installed inside the vessel S100 of the CIRCE facility, built at ENEA Brasimone Research Centre. In the proposed methodology the CFD code is adopted to simulate the LBE side of the HERO heat exchanger, whereas the secondary side (two-phase flow, water-vapour) is simulated by the STH code. In this procedure, the variables exchanged between the boundaries of the two codes are: the bulk temperature and heat transfer coefficient of the ascending water (in two-phase flow) obtained from RELAP5 and transferred to Fluent code; the wall temperature at the water side surface of the pipes is calculated by Fluent and passed to RELAP5 code. The coupling procedure was verified by comparing the obtained results with the analogous ones achieved with the RELAP5 stand-alone calculation, proving that the developed coupling methodology is reliable. Further, the coupled simulation allows to obtain more accurate information on the LBE side.

Composite materials for strengthening existing structural members represent a valid alternative to the traditional strengthening techniques. In particular, Fabric Reinforced Cementitious Matrix (FRCM) composites have been successfully employed to strengthen existing reinforced concrete and masonry structures. Among the different FRCM composites available on the market, the attention of the authors was recently focalized on systems composed of high tensile strength steel cords embedded in a cementitious matrix (systems also well known as Steel Reinforced Grout, SRG). The main failure mechanism of FRCM is represented by the debonding at the matrix-fiber interface. Therefore, the study of the bond behavior of FRCM composites is a key topic to develop reliable design procedures. In this paper, the applicability of different existing bond-slip interface models for FRP-concrete interface to SRG system is studied. The different parameters characterizing the models are calibrated by using an experimental database available by the authors and including results of direct single-lap shear tests on concrete prisms bonded to SRG strips. All the models are calibrated using a classical technique which minimizes the difference between the measured and computed interfacial shear stress values at different slip levels. The results indicate that all the models predict relatively well the slope of the ascending branch of the shear stress-slip curve, but they give substantially different descending branch profiles. The calibrated models are, then, compared with some other laws proposed in the literature for PBO and basalt FRCM systems; some of them are also implemented within a numerical procedure developed by the authors for the estimation of both the maximum axial stress at debonding and the corresponding effective bonded length of the SRG strip. The comparison with the experimental data has allowed for verifying the accuracy of the calibrated bond-slip models.

A new design of a hydrogen sensor for Pb-16Li, based on the previous experience and testing results, is performed. The new permeation sensor is made of pure iron. The intention of this optimized design is to improve the response time and to minimize the number of welds to be made. Some simulations were conducted to estimate the time taken for the sensor to reach equilibrium with the partial pressure of hydrogen in the lead-lithium. With respect to the old sensor design, the diameter of the steel connection pipe has been reduced, while its length has been increased. In this way, it was possible to reduce the dead volume within the sensor and increase the permeation area, giving the sensor a faster time response.

Adhesive bonding is an excellent candidate for realising connections for secondary structures in structural applications such as offshore wind turbines and installations, avoiding the risk and associated welding problems. The strength of the adhesive layer is an important parameter to consider in the design process it being lower than the strength capacity of the bonding material. The presence of defects in the adhesive materials undoubtedly influences the mechanical behaviour of bonded composite structures. More specifically, the reduction in strength is more pronounced as the presence of defects (voids) increases. For this reason, a correct evaluation of the presence of defects, which can be translated into damage parameters, has become essential in predicting the actual behaviour of the bonded joints under different external loading conditions. In this paper, an extensive experimental programme has been carried out on adhesively bonded connections subjected to Mode I and Mode II loading conditions in order to characterise the mechanical properties of a commercial epoxy resin and to define the damage parameters. The initial damage parameters of the adhesive layer have been identified according to the Kachanov-Sevostianov material definition, which is able to take into account the presence of diffuse initial cracking.

Understanding and predicting the behaviour of bonded joints under different loading conditions is certainly an aspect of primary importance. Although numerous experimental studies have been carried out over the last few decades, the shear behaviour of bonded joints under cyclic loading has not been investigated in detail. To fill this gap, an extensive experimental and numerical program of double lap shear bonded joints has been carried out. The double lap shear joints were tested under static and cyclic loading to evaluate and compare the influence of external forces on the adhesive performance. The results are discussed in terms of the force-displacement relationship, shear stress, stiffness, residual displacement, and initial damage. Finally, a method is presented for predicting the actual behaviour of double lap shear bonded joints under different loading conditions using an imperfect interface model with damage evolution. The numerical results are in good agreement with the experimental results for all loading conditions. This work has provided and validated an interesting design tool for adhesive structures.

In offshore structures, the need to replace or strengthen existing metal components arises over time. One possible solution is the use of bonded connections. Nevertheless, the durability of the adhesive connections is highly compromised by the prolonged contact with water. In this paper, an experimental and numerical evaluation of hydro-thermal ageing's effects on polyurethane adhesive connections has been analysed. An efficient semi-analytical procedure is developed for the design or verification of existing structures reinforced by bonded steel elements. The model can evaluate the interfacial shear stress at all loading stages up to the failure of bonded joints exposed to the marine environment. The model is based on Bernoulli beam theory and satisfies the requirements of equilibrium and strain compatibility, allowing for interfacial deformations. Furthermore, the mechanical behaviour of bonded connections subject to accelerated ageing has been experimentally investigated. More in detail, an experimental program including double lap shear and end-notch flexure tests was performed to evaluate the cohesive behaviour in Mode II of a polyurethane structural adhesive under the combined effects of water and temperature during 150 days of exposure. The experimental and numerical investigation shows how the performance of the adhesive joints is influenced by the ageing conditions.

Abstract In the framework of the activities coordinated by the EUROfusion consortium, the Water thermal-HYDRAulic (W-HYDRA) experimental platform is being built at the ENEA Brasimone Research Centre in order to support the development of the Water-Cooled Lead Lithium (WCLL) Breeding Blanket (BB). In particular, this infrastructure will make possible the installation and testing of prototypical mock-ups under relevant working conditions, such as the First Wall (FW), the manifold and the Steam Generator (SG). Moreover, it will represent an integral test facility for the investigation of phenomena characteristic of WCLL BB concept, such as the PbLi/water interaction. Finally, the collection of data coming from the different planned experimental campaigns will allow to qualify and validate numerical models and codes currently adopted for the design of components, as well as for the modelling of complex phenomena typical of the WCLL BB. In order to come to a definitive design of the different facilities constituting the experimental platform, several design analyses assessing the thermal, hydraulic and structural performances of the different facilities and components are necessary. The paper reports a highlight of the W-HYDRA platform with a general description of the facilities. Some of the most relevant design studies carried out so far are reported as well, highlighting their impact on the evolution of the design.

Knowledge of the long-term performance of adhesive connections is undoubtedly of paramount importance to enable their deployment in civil, mechanical, and other engineering applications. Over time, adverse environmental conditions can strongly influence the performance of adhesive joints leading to a progressive deterioration of their initial mechanical properties. The use of adhesive connections for secondary structures in offshore applications is a technology that allows for the rapid creation of structural members that, however, cannot ignore the influence of hydrothermal effects on mechanical performance due to environmental conditions. In this context, the investigation of the hygrothermal durability of adhesive connections was undertaken through an extensive experimental programme. More specifically, 130 cylindrical steel joints bonded with a commercially epoxy resin for structural applications were tested in Mode I using an Arcan-modified device. Prior to test, the specimens were placed in climatic ovens capable of combining the effects of temperature and humidity for approximately 320 days. In addition, the glass transition temperature, T g , was assessed by employing the differential scanning calorimeter (DSC) technique to correctly define the experimental ageing conditions. The experimental results show how ageing conditions influence the mechanical properties of the epoxy resin investigated. Finally, some predictive formulations are proposed to calculate the loss of strength of adhesive joints over time.

A detailed study of lithium-related topics in the IFMIF-DONES facility is currently being promoted and supported within the EUROfusion action, paying attention to different pivotal aspects including lithium flow stability and the monitoring and extraction of impurities. The resistivity meter is a device able to monitor online non-metallic impurities (mainly nitrogen) in flowing lithium. It relies on the variation of the electric resistivity produced by dissolved anions: the higher the concentration of impurities in lithium, the higher the resistivity measured. The current configuration of the resistivity meter has shown different measuring issues during its operation. All these issues reduce the accuracy of the measurements performed with this instrument and introduce relevant noise affecting the resistance value. This paper proposes different upgrades, supported by CFD simulations, to optimize lithium flow conditions and to reduce measurement problems. Owing to these upgrades, a new design of the resistivity meter has been achieved, which is simpler and easier to manufacture.

One of the crucial steps toward the commercial exploitation of fusion energy is the availability of a high-intensity neutron source able to test and qualify structural materials to be used in future fusion power reactors. The International Fusion Materials Irradiation Facility-DEMO Oriented NEutron Source (IFMIF-DONES) facility, which is currently being designed within the framework of the EUROfusion Consortium, represents the European effort to develop such a neutron source. It employs a liquid lithium target struck by an accelerated deuteron (D+) beam to produce fusion-like neutrons used to irradiate materials samples. So far, a detailed investigation of the thermomechanical behavior of the IFMIF-DONES target system has been accomplished for the case of steady-state operation, considering the D+ beam steadily running at full nominal power (5 MW). However, the study of the effects generated in the lithium and in the surrounding steel structure backplate (BP) during the unavoidable beam trips needs to be carried out as well to exclude the possibility of system failure by fatigue phenomena. To this aim, a numerical assessment of the fatigue damage produced on the BP by repeated thermally induced shock waves propagating in the lithium as a consequence of accelerator fast beam trip events has been carried out following the methodology outlined in the RCC-MRx nuclear design code. In this article, the details of the calculations and the results obtained from such analysis are presented showing the capability of the system to survive for its whole expected lifetime.

A new facility, known as Pyrel III, has been installed at ENEA laboratories for pyrochemical process studies under inactive conditions. It is a pilot plant which allows electrorening and electroreduction experiments to be conducted on simulated fuel. The main component of the plant is a zirconia crucible. The crucible is heated by a furnace which is supported in an externally water-cooled well under the oor of a steel glove-box, where an argon atmosphere is maintained by a continual purge of about 10 L·min-1. The vessel is loaded with LiCl-KCl eutectic salt (59-41 mol%) and is currently operated at 460 °C. Several improvements on Pyrel II (the previous operating plant) have been introduced into Pyrel III. They are described in detail, together with the results from the rst experimental campaign which used lanthanum metal.Moreover, studies about the treatment of chloride salt wastes from pyroprocesses have been conducted in parallel. They follow two main routes: on one hand, a matrix termed sodalite, a naturally occurring mineral containing chlorine, has been synthesized from a mix of nepheline, simulated exhausted salts and glass frit; on the other hand, a novel method proposed by Korea Atomic Energy Research Institute (KAERI) is under assessment. The nal waste forms have been fully characterized with the support of the Politechnique of Milan, by means of density measurements, thermal analysis, and stereomicroscopy observations, FTIR, XRD, and RAMAN spectra, as well as leach tests under static conditions

A fundamental step in the best preservation of heritage materials is investigating their chemical and physical characteristics, and understanding how they interact with the surrounding environment. For this reason, the stone masonry of the monumental UNESCO site of Panamá Viejo was subjected to a thorough study to characterize the materials and evaluate their state of conservation. Additionally, potential outcrops were explored in order to identify sites for the supply of raw materials. The methodological approach encompassed mineralogical-petrographic investigations using stereomicroscopy, polarized light microscopy (PLM), X-ray powder diffraction (XRPD), scanning electron microscopy and energy dispersive X-ray spectrometry (ESEM-EDS) and X-ray fluorescence (XRF). The results revealed that the masonries primarily consists of polygenic breccia, basaltic andesite, rhyodacite, tuffite, and rhyolite. In addition, at the potential quarries, breccia and basaltic andesite were identified. The porous structure was studied using mercury intrusion porosimetry (MIP). Possible issues due to salt dissolution/crystallization cycles were considered. Consequently, ion chromatography (IC) was conducted on samples exhibiting alteration patinas to study the presence of soluble salts. In assessing the state of conservation, prevalent forms of deterioration included biological colonization, detachments, material loss, potential salt weathering, and chromatic alteration. In conclusion, the outcomes of this work provide a valuable resource for the current and future preservation of this site.

The large plasma focus facility (PF‐1000) which has been operated at the Institute of Plasma Physics and laser Microfusion for about five years, was recently modernised and optimised. At present the PF‐1000 facility is equipped with electrodes of considerably larger dimensions then those used previously for starting experiments. The both electrodes are now about 600 mm in length. The outer one (cathode), formed of 24 stainless steel rods is 400 mm in diameter. The inner electrode (anode), made of copper in a tubular form and embraced at the base with an alumina insulator, is 230 mm in diameter. The PF‐1000 device can operate up to 1 MJ stored energy in the condenser bank.

New facilities have been installed at ENEA laboratories for pyrochemical process studies under inactive conditions. In particular, PYREL III is a pilot plant which allows to make experiments of electrorefining and electroreduction of simulated fuel. The main component is a zirconia crucible heated by a furnace supported in an externally water-cooled well under the floor of a steel glove-box, where an argon atmosphere is maintained by a continual purge of about 10 L'min-1. The vessel is loaded with LiCl-KCl eutectic salt (59-41 mol%) and is currently operated at 460°C for electrorefining experiments, while electroreduction is made in a bath of LiCl with 1 wt.% of Li2O at 650°C. Treatment of chloride salt wastes coming from pyroprocesses is made inside another argon-atmosphere glove-box, where a matrix termed sodalite is synthesized from a mix of nepheline, simulated exhausted salts and glass frit, through a Pressureless Consolidation (PC) process. The product obtained by heating at 925°C is then fully characterized by means of density measurements, thermal analysis, stereomicroscopy observations, FTIR and XRD spectra, as well as leach tests under static conditions. A novel method proposed by Korea Atomic Energy Research Institute (KAERI) is also applied to the treatment of such wastes. It is based on a matrix, SAP (SiO2-Al 2O3-P2O5), synthesized by a conventional sol-gel process, able to stabilize the volatile salt wastes owing to the formation of metalaluminosilicates, metalaluminophosphates and metalphosphates. The addition of a borosilicate glass as a chemical binder and a treatment at around 1000°C gives the final waste form. With this method a higher disposal efficiency and a lower waste volume can be obtained. A melt crystallization plant (MECRYP) is used for the regeneration of LiCl salts from electroreduction experiments. Alkaline and alkaline-earth metals contained in the waste salt are separated by means of a melt crystallization process, based on the solubility difference of solutes (e.g. CsCl and SrCl2) between molten salt and solid states. In this process, the group I/II radionuclides are concentrated in the melt phase, while the other solid phase contains relatively purified LiCl salt. This crystal phase contains a very small amount of group I/II fission products and is recycled to the electrolytic reduction process for reuse. Another facility, termed off-gas treatment apparatus (OGATA), has been set-up for studies about capture of volatile and semi-volatile fission products, such as cesium, iodine, and ruthenium. It consists of a little furnace which can operate up to 1200°C for the generation of volatile compounds, which then pass through a specific trap able to retain them by virtue of chemical or physico-chemical mechanisms. For example, silver coated mordenite is used for iodine, and zeolite 4A for volatile cesium.

To analyze the impact of the magnetohydrodynamics (MHD) effect on the fast draining of a LiPb channel (lithium-lead eutectic, 15.7 at. % Li) for a liquid metal fusion blanket such as the water-cooled lithium-lead test blanket system of ITER or DEMO, an experimental campaign was carried out with the support of the Integrated European Lead Lithium LOop experimental facility (IELLLO), installed at the ENEA Brasimone research center, Italy. The experiments were carried out by measuring the drainage time of the internal permanent magnet pump channel, normally used to circulate the LiPb in the loop, with and without the magnetic field. Moreover, this paper proposes a new numerical methodology to study the time delay induced by the MHD by using the commercial software COMSOL Multiphysics. In this way, it was possible to evaluate the LiPb fraction present at each time step in the computational domain and to estimate the time necessary for the complete drainage of the channel. The level set method was used to describe the transient behavior of the MHD flow under low-Rm approximation. The developed code was compared with the experimental results and showed good agreement, and it constitutes the first step in model validation as a possible application to ITER and DEMO. The experimental and numerical analyses performed in this work can be used as a benchmark case for MHD code development.

A major safety concern addressed during the design of the water-cooled lead-lithium (PbLi) breeding blanket (BB) is represented by an in-box loss-of-coolant accident, where high-pressure water is supposed to interact with PbLi inside the BB. Code development activities are being carried out to create the needed tools for the safety analysis of these systems in the case of incidental scenarios, which are supported by extensive experimental campaigns that aim at providing data for SIMMER code verification and validation (V&V). In this regard, the present work aims at presenting the dataset generated during the Series D experimental campaign performed at the LIFUS5/Mod3 facility operated at the ENEA Brasimone Research Centre. This is a separate effect facility able to simulate the mixing of water and PbLi alloy in conditions of temperature and pressure similar to the ones encountered by the system during nominal operation and to acquire significant data on all the relevant thermochemical parameters. Moreover, a preliminary analysis of the data has been performed to critically determine the quality of the data and to identify possible issues in the experimental process. In the end, the foreseen extension of the experimental work is described, as well as the foreseen application of the acquired data in the code V&V activities.

This study introduces numerical advancements in an alternative design for the Super Proton Synchrotron (SPS) Beam Dump Facility (BDF) at the European Laboratory for Particle Physics (CERN). The design envisions a high-power operation target made of flowing liquid lead. The proposed BDF is a versatile facility for both beam-dump-like and fixed-target experiments. The target behavior is studied, assuming a proton beam with a momentum of 400 GeV/c, a pulse frequency of 1/7.2 Hz, and an average beam power of 355 kW. Using various Computational Fluid Dynamics (CFD) codes, we evaluate the behavior of liquid lead and predict the thermal stress on the target vessel induced by the pulsed heat source generated by the charged particle beam. The comparison increases the reliability of the results, investigating the dependencies on the CFD modeling approach. The beam is a volumetric heat source with data from the beam-lead interaction simulations provided by the European Laboratory for Particle Physics and obtained with a Monte Carlo code. Velocity field and stress profiles can enhance the design of the lead loop and verify its viability and safety when operated with a liquid metal target.

This study introduces numerical advancements in an alternative design for the SPS Beam Dump Facility (BDF) at CERN. The design envisions a high-power operation target made of flowing liquid lead. The BDF is a proposed versatile facility at CERN, intended for both beam-dump-like and fixed-target experiments. The target behavior is assessed, assuming a proton beam with a momentum of 400 GeV/c, a pulse frequency of 1/7.2 Hz, and an average beam power of 355 kW. An evaluation is conducted using various Computational Fluid Dynamics (CFD) codes to analyze the behavior of liquid lead and to predict the thermal stress on the target vessel induced by the pulsed heat source generated by the charged particle beam. The comparison increases the reliability of the results, investigating the dependencies on the CFD modeling approach. The beam is modeled as a volumetric heat source with data coming from beam-lead interaction simulations provided by CERN and obtained with the Monte-Carlo code FLUKA. The velocity field and stress profiles are utilized to enhance the design of the lead loop and verify its viability and safety when operated with a liquid metal target.