High Flux Test Module Research Articles

Validation activities at ENEA Brasimone in support of the IFMIF-DONES design

IFMIF-DONES is a powerful neutron source which is being designed with the main purpose of qualifying structural materials (EUROFER being the first candidate) to be used in DEMO and fusion power plants envisaged after it. This source relies on one high current (125 mA) deuterons beam accelerated to 40 MeV which impacts on a liquid lithium target to produce an intense neutron flux through Li(d,n) stripping reactions able to simulate the nuclear responses expected on the first wall of the reactor. The engineering design of IFMIF-DONES is presently being carried out mainly in the framework of the EUROfusion Work Package Early Neutron Source (WPENS). Since 2021, a new phase has started with the launch of the FP9 WPENS workplan whose objective is to continue advancing the engineering design of the facility, putting special effort on the experimental validation of those aspects which still need to be qualified to demonstrate the fulfillment of functional and safety requirements. The ENEA Brasimone Research Centre has been and still is strongly committed in several validation tasks concerned in particular with the lithium systems design and the Remote Handling (RH) maintenance.In this paper, an overview of the most relevant validation activities carried out in recent years or still in progress or planned at the ENEA Brasimone Research Centre in both of the aforementioned areas is presented, including the erosion/corrosion tests in the Lifus 6 loop; the nitrogen-gettering materials qualification in the ANGEL facility; and the RH and prototypes testing in the DRP laboratory for the validation of the High Flux Test Module electric connectors and the pre-heating of the Target Assembly.

Thermal and structural analysis of the DONES target system under steady state and transient loading conditions

One of the crucial steps in the European Roadmap to the realisation of fusion energy is the design and construction of the Demo-orientated NEutron Source (DONES) facility. DONES is a fusion-like neutron source, based on the International Fusion Materials Irradiation Facility (IFMIF) concept, aimed at qualifying and testing the materials to be used in fusion reactors. The Target System (TSY) is a crucial system as it is the component where the interactions between deuterons and a liquid lithium target, flowing on a solid surface (i.e. the Back Plate), take place to produce neutrons for irradiating the testing materials. In this regard, an investigation campaign has been performed to evaluate the thermo-mechanical behaviour of the DONES TSY under selected steady state and transient loading conditions, in light of the most recent design updates (new bellows and connection systems). The first part of the assessment concerned the analysis of the TSY under the normal operation steady state loading scenario. A detailed 3D FEM model has been set up, considering the newest updates of the TSY geometry and of the operational parameters, and a thermo-mechanical analysis has been launched. Results have been mainly checked in terms of TSY global deformation, focusing on the Back Plate and on the connecting bellows displacements, in order to exclude overlapping with the High Flux Test Module and misalignments with the beam footprint. Afterwards, since the lithium inlet temperature has been increased from 250 °C to 300 °C, a transient thermo-mechanical analysis of the TSY under the start-up loading conditions has been performed to check if it is able to withstand the hotter lithium flow according to the RCC-MRx criteria. Therefore, the reference pre-heating strategy has been adopted, assessing the thermal and mechanical behaviour of the TSY, focusing on the Back Plate. The obtained results are presented and critically discussed, suggesting important recommendations for the follow-up of the design.

Preliminary Remote Handling Analysis and Validation of the Electrical Connectors Bridge for the IFMIF-DONES High Flux Test Module

Preliminary Remote Handling Analysis and Validation of the Electrical Connectors Bridge for the IFMIF-DONES High Flux Test Module

Object-oriented modeling, simulation and control of a 6-DoF parallel kinematic manipulator for remote handling in DONES facility

This paper describes the modeling and simulation activities performed, within the EUROfusion framework, to support the engineering design and the development of the control system of the DONES Parallel Kinematic Manipulator (PKM), a 6-DoF parallel robot part of the Remote Handling System of the DONES facility. The main tasks of the PKM are the planned annual replacement of the Target Assembly and the High Flux Test Module, two of the crucial and most activated components of DONES. The PKM model, developed using the Modelica object-oriented language, is able to simulate the dynamics of the entire robots, including the main non-linear effects due to backlashes and static friction. The simulator is employed to support the preliminary design of the control system, based on an independent-joint approach with dual-loop cascade-PID logic. Simulations are then conducted to assess robot performances in terms of resolution, accuracy, repeatability and generated forces.

Hydraulic analysis of the start-up monitoring module (STUMM) for IFMIF-DONES

The International Fusion Materials Irradiation Facility – Demo Oriented Neutron Source (IFMIF-DONES) will allow accelerated material testing in fusion-like conditions, up to the doses above the expected lifetime. To successfully irradiate the samples in the High Flux Test Module (HFTM) an extensive start-up phase is needed to confirm the irradiation parameters as well as the conditions inside HFTM. STUMM (Start-Up Monitoring Module) is designed exactly for that purpose and will be operated during the commissioning phase of IFMIF-DONES. The outer part of STUMM resembles HFTM, but inside is equipped with measuring systems: active detectors and Rabbit Systems tightly arranged in the Container. The flow of helium gas used for cooling was analyzed in Ansys Fluent. A pressure drop of 2.9 kPa and 3.4 kPa was found for the two possible flow directions. 8 turbulence models were tested: Spalart-Allmaras, Standard k-ε, RNG k-ε, Realizable k-ε, Standard k-ω, Baseline k-ω, SST k-ω and the Reynolds Stress Model. Out of them, only the Standard k-ε mode did not converge and all the other models gave a correct result. The solution time was analyzed for both the Single Precision and Dual Precision solvers. The Single Precision solver was 3.6-5.5 faster. Analysis of the solution residuals, outlet velocity, and pressure drop showed that both solvers gave almost identical results, therefore the Single Precision solver is sufficient to obtain a correct solution and only 100 iterations are required.

Validation study of turbulence models for thermal-hydraulic simulation of helium cooled DONES high flux test module

Abstract Helium flow at low pressure (0.3 MPa) is used to cool the specimen capsules and the structure of the neutron irradiated High Flux Test Module (HFTM) of the IFMIF-DONES (International Fusion Materials Irradiation Facility- DEMO Oriented NEutron Source). The flow path includes mini-channels with gap-widths less than 1 mm where a high velocity low Reynolds number helium flow is used as cooling medium. The large span of Reynolds numbers from laminar to fully turbulent is a significant challenge for the simulation of the complete HFTM. Four turbulence models, the Reynolds Stress transport (RSM); the k-e (KE) model; the k-ω Shear-Stress-Transport (SST) model and the V2F model were tested using experiments conducted in Karlsruhe Institute of Technology (KIT). Numerical simulations have been performed for low Reynolds number (Re = 4000–10000) helium flows in a heated mini-channels. The RSM model provides the best heat transfer prediction for the full range of Reynolds numbers. KE and V2F models are not suitable for the simulation of the transitional flows. The accuracy of the SST model can be increased by variation of the time scale limiter coefficient. RSM and SST turbulence models can be considered as appropriate numerical tools for the heat transfer analysis of HFTM.

Shut-Down Dose Rate Distribution Calculation in the Access Cell With Activated HFTM in the IFMIF-DONES Facility

International Fusion Materials Irradiation Facility–DEMOnstration Power Station (DEMO)-Oriented Neutron Source (IFMIF-DONES) is an accelerator-based d-Li neutron source that is aimed at the qualification of materials at the irradiation conditions of a DEMO fusion power reactor. It is being developed in the frame of EUROfusion’s Power Plant Physics and Technology (PPPT) work program. The intense neutron radiation produced in the liquid lithium target results in a strong activation of the test cell (TC) and its high flux test module (HFTM). This article presents the analyses performed within the Early Neutron Source (ENS) project of EUROfusion/PPPT directed to provide up-to-date estimates of the activity inventories and the decay heat production in the DONES TC facility. To this end, a series of coupled Monte Carlo N-Particle code (MCNP)+ McDelicious transport and FISPACT inventory calculations were performed using the 2017 DONES TC model and nuclear cross section data from the Joint Evaluated Fission and Fusion (JEFF)–3.1.2 data library. The article presents the shut-down dose rate maps generated by HFTM that was irradiated at the TC and later relocated to the access cell. Performed calculations used to addresses the issue of the radiation dose loads that are to be expected due to the activated components/systems including the HFTM. In addition to that, activation calculations of HFTM materials are also provided.

Activation of high flux test module sample holder after IFMIF-DONES operation

Nuclear safety assessment in nuclear fusion devices relies on the Monte Carlo method based neutron transport calculations. This paper presents information about the calculation results of the activities and dose rates caused by neuron irradiation for the structural materials of the high flux test module sample holder of IFMIF-DONES. The neutron induced activities and dose rates at shutdown were calculated by means of the FISPACT-2010 code with data from the EAF-2010 nuclear data library. Neutron fluxes and spectra were obtained with MCNP neutron transport calculations. The activities and dose rates were calculated at the end of irradiation of the assumed device operation scenario for cooling times of 0 s – 1000 year. In addition, radionuclides with contribution of at least 0.5% to the total value of activation characteristics at the previously mentioned cooling times were identified. After the operation, the most active radionuclide is 55Fe, with an activity share ranging from 30% (M200) to 63% (M8), and at the end of the prediction it accounts for 86% of the total activity. The highest dose rates at the end of irradiation are attributed to 56Mn radionuclide. 54Mn and 60Co are the most dominant radionuclides during intermediate and long cool-down periods.

Using sodium as filling and heat-conducting material in the irradiation capsules of the fusion materials irradiation facility IFMIF-DONES

The capsules of the IFMIF-DONES High Flux Test Module (HFTM) are packed densely with Eurofer specimens. A filling material (previously NaK-78 and currently sodium) is needed to fill any empty volume to improve the heat conduction and obtain uniform temperature distribution. NaK-78 is replaced by sodium because potassium, in NaK-78, generates argon isotopes leading to a pressure increase and formation of bubbles which counteract the purpose of introducing NaK-78 as a heat conductor. In this experimental study, two setups are used to investigate sodium as the new filling material. The first setup is dedicated to test the wettability of various specimens of Eurofer and stainless steel 316L by sodium within the range of 100 °C–430 °C. The second setup consists of: (i) a full scale prototype of the HFTM capsule, (ii) a stainless steel container for melting the sodium, and (iii) heaters, thermocouples and supporting parts. The objective is to perform a successful sodium filling of the prototype capsule and to determine how well the specimens are wetted and the empty volumes are filled with sodium. All experiments are performed inside a glovebox filled with dry argon to maintain an oxygen- and moisture-free atmosphere. The results of these experiments, which are relevant to IFMIF-DONES HFTM capsules and other sodium applications, are presented. For example, the results showed that efficient wettability of Eurofer and stainless steel 316L specimens by sodium may be assured when the steel-sodium system is at 430 °C or higher.

Measurement of neutron fluence in the High-Flux Test Module of the Early Neutron Source by neutron activation

The High Flux Test Module (HFTM) carries the specimens to be irradiated with the Early Neutron Source. The knowledge of the total neutron fluence on the specimen will be necessary for analysis. Neutron activation is a widely used method for neutron fluence measurement. We have tested a set of activation materials which seem to be suitable for application in the HFTM considering half-lives of the induced activities, the environmental conditions and the deployment time in the HFTM. Test foils were irradiated for 9.5 h with a cyclotron of NPI Řež in a white neutron field with energies up to 32 MeV. The induced activities were determined 61 days after the irradiation. We present the resulting saturation activities with estimated uncertainties and draw conclusions on the application of the selected activation materials in the HFTM.

Key conception of the remote maintenance for the target assembly of Advanced Fusion Neutron Source (A-FNS)

A key conception of the remote maintenance (RM) method is presented of the target assembly (TA) of Advanced Fusion Neutron Source (A-FNS), that is an accelerator-driven fusion neutron source utilizing the Li(d,xn) nuclear reactions. The RM method, newly proposed here, is aimed at (i) enhancing the modularity of the TA RM and (ii) keeping the compatibility with the materials irradiation tests, compared to the preceding TA RM design of International Fusion Material Irradiation Facility (IFMIF). A 3-dimensional kinematics simulation indicates that the large clearance of 52 mm between the TA and high flux test module (HFTM) brings the independent removal from and the installation in the test cell, regardless of the presence of the test modules in the test cell. A neutronics performance of the HFTM with the enlarged clearance is also studied. The gradient of the calculated neutron irradiation damage is found to be decreased and satisfies a users’ requirement of the irradiation environment when the clearance is enlarged from 2 to 52 mm. (The former value was the IFMIF engineering design value.) These simulation results suggest that the proposed TA RM method will enhance not only the modularity of the TA, but also will improve the materials irradiation test environment.

Numerical study of conjugated heat transfer for DONES high flux test module

Helium flows at low pressure (3 bar) are used to cool the specimen capsules and the structure of the neutron irradiated High Flux Test Module (HFTM) of the DEMO-Oriented Neutron Source (DONES). The flow path includes inlet and outlet ducts with large cross sections, but also mini-channels with gap widths less than 1 mm, where a high velocity low Reynolds number flow influences the temperature of the irradiated specimens. The aim of the study was the achievement of thermal requirements to the HFTM. The large span of Reynolds numbers from laminar to fully turbulent is a significant challenge for the simulation of the complete HFTM. Several turbulence models were tested using experimental results obtained in the ITHEX (IFMIF Thermal-Hydraulic Experiment) experimental facility. Reynolds Stress (RSM) and k-ω Shear Stress Transport (SST) models are able to reproduce the heat transfer within the Reynolds number range between 4500 and 10,000.Simulations show that in case of 100% nuclear heating conditions the prescribed temperature of specimen can be achieved by justification of electrical power and variation of helium mass flow rate for each HFTM compartment.

Global Flux Calculation for IFMIF-DONES Test Cell Using Advanced Variance Reduction Technique

Global neutron flux and dose maps for the test cell (TC) of the IFMIF-DONES (International Fusion Materials Irradiation Facility–DEMO Oriented NEutron Source) have been calculated applying the advanced variance reduction tool ADVANTG. The neutronics model of the TC has been updated to the current IFMIF-DONES design of the target assembly, the high flux test module, and the lithium quench tank as well as the TC surrounding rooms. A weight-window (WW) mesh has been produced using ADVANTG with the well-configured setups for IFMIF-DONES conditions. This WW mesh has been adjusted to achieve reasonably good statistics for the global flux mesh tally. It is concluded that the thickness of the beam upstream and lateral wall can be reduced by 0.5 m without strongly affecting the shielding performance. The neutron streaming through the gaps of the shielding plugs to the access cell above the TC requires local shielding to allow frequent access during operation.

Planned material irradiation capabilities of IFMIF-DONES

IFMIF-DONES (International Fusion Materials Irradiation Facility - DEMO-oriented Neutron Source) is currently being developed in the frame of the EUROfusion Early Neutron Source work package (WPENS), based on the results achieved in the ongoing IFMIF/EVEDA (Engineering Validation and Engineering Design Activities) project by Japan and Europe in the frame of the Braoder Approach (BA) agreement. The neutron source's limited product of “irradiation volume × neutron fluence” on one hand and the large potential test matrix (defined by number of material grades, test types, irradiation- and test temperature levels and damage dose levels) on the other hand, require a careful selection of test conditions by collaborative effort of the communities of DEMO designers, fusion materials science and the irradiation facility designers. This paper describes achievable irradiation conditions in the High Flux Test Module (HFTM) of IFMIF-DONES, characterized by levels and gradients of irradiation temperatures and nuclear responses (dpa, H and He production). The HFTM development focuses on 9%-Cr Reduced Activation Ferritic Martensitic steel irradiations, but also the possibilities of tungsten and copper alloy irradiations are explored. Possible specimen arrangements and issues of the Small Specimens Test Technique are also discussed.

Thermomechanical analysis supporting the preliminary engineering design of DONES target assembly

The design of the Demo Oriented NEutron Source (DONES) is the main objective of the Work Package Early Neutron Source (WPENS) of EUROfusion Power Plant Physics and Technology (PPPT) programme. DONES is an IFMIF-based neutron source with the goal of testing and qualifying candidate materials to be used in DEMO and future fusion power plants.In the framework of these activities, a research campaign has been carried out at the University of Palermo, in close cooperation with ENEA labs, in order to assess the thermomechanical performances of the DONES target system, endowed with an integrated Target Assembly (TA) when it undergoes the thermomechanical loads typical of its nominal operating scenario. The effects on TA behaviour of two possible different configurations for the accelerator beam foot-print have been investigated, considering an entire (20 × 5 cm2) or a halved (10 × 5 cm2) beam foot-print area with respect to that of IFMIF.The study has been carried out following a theoretical-numerical approach, based on the Finite Element Method (FEM), and adopting the qualified ABAQUS v. 6.14 commercial FEM code.The obtained thermomechanical results have been assessed in order to check whether the BP deformation field is such to prevent the contact of the BP itself with the High Flux Test Module, as well as to verify their compliance with the design criteria foreseen for the structural material. To this purpose, a stress linearization procedure has been performed along the most critical paths located within the BP, in order to check the fulfilment of the rules prescribed by the ITER structural design code SDC-IC. The obtained results are herewith presented and critically discussed.

Investigation of Mo-99 radioisotope production by d-Li neutron source

A plan of an advanced fusion neutron source (A-FNS) by using d-Li reaction is in progress at Rokkasho in Japan. We investigate multipurpose usages of the A-FNS in addition to fusion material irradiation test. Production of medical isotope 99Mo is considered as one of the usages. We conducted a conceptual study on a module for radioisotope production which was composed of a neutron spectrum shifter and a neutron reflector. We examined impacts of materials of the shifter and reflector on amounts of the 99Mo production, and their thicknesses. It was concluded that beryllium is the most suitable material both for the shifter and the reflector from the viewpoint of the 99Mo production. It was shown that we produced an enough amount of the 99Mo for the demand in Japan. We can apply natural molybdenum for this purpose. It was also shown that we could use a part of irradiation capsules in high flux test module, which was for the fusion material irradiation test originally, by using isotopically enriched 100Mo to meet that.

IFMIF-DONES HFTM neutronics modeling and nuclear response analyses

IFMIF-DONES (International Fusion Materials Irradiation Facility- DEMO Oriented NEutron Source) is a neutron irradiation facility aiming at providing material irradiation data for the construction of DEMOnstration fusion power plants. This work presents nuclear analyses and associated neutronics modeling conducted on an updated design of the High Flux Test Module (HFTM) of IFMIF-DONES. Neutron fluxes, damage dose rates and gradients, gas production and nuclear heating have been calculated for the standard profile in 20 × 5 cm2 and a reduced size in 10 × 5 cm2 of the deuteron beam with 40 MeV energy and 125 mA current. The results indicate that the reduced beam can provide higher damage dose rates fulfilling the DONES requirement. On the other hand, the reduced beam size results in less irradiation uniformity, higher gas production to damage dose ratios, as well as stronger peak nuclear heating.

The accomplishments of lithium target and test facility validation activities in the IFMIF/EVEDA phase

As part of the engineering validation and engineering design activities (EVEDA) phase for the international fusion materials irradiation facility IFMIF, major elements of a lithium target facility and the test facility were designed, prototyped and validated. For the lithium target facility, the EVEDA lithium test loop was built at JAEA and used to test the stability (waves and long term) of the lithium flow in the target, work out the startup procedures, and test lithium purification and analysis. It was confirmed by experiments in the Lifus 6 plant at ENEA that lithium corrosion on ferritic martensitic steels is acceptably low. Furthermore, complex remote handling procedures for the remote maintenance of the target in the test cell environment were successfully practiced. For the test facility, two variants of a high flux test module were prototyped and tested in helium loops, demonstrating their good capabilities of maintaining the material specimens at the desired temperature with a low temperature spread. Irradiation tests were performed for heated specimen capsules and irradiation instrumentation in the BR2 reactor at SCK-CEN. The small specimen test technique, essential for obtaining material test results with limited irradiation volume, was advanced by evaluating specimen shape and test technique influences.

Potential irradiation of Cu alloys and tungsten samples in DONES

Tungsten and Cu alloys are currently proposed as reference candidate material for ITER and DEMO first wall and divertor. Tungsten is proposed for its high fusion temperature and CuCrZr alloys for their high thermal conductivity together with good mechanical properties. However its behaviour under the extreme irradiation conditions as expected in ITER or DEMO fusion reactors is still unknown. Due to the determinant role of H and He played in the material behaviour any irradiation experiment must take into account the amount of these gases produced during the irradiation in Fusion reactors with high-energy neutrons.DONES (DEMO oriented neutron source) has been conceived as a simplified IFMIF (International Fusion Material Irradiation Facility) like plant to provide in a reduced time scale and with a reduced budget—both compared to IFMIF—the basic information on materials damage. The objective of DONES-IFMIF in its first stage will be to test structural materials under similar neutron irradiation nuclear fusion conditions as expected in fusion reactors. These tests will be carried out with specimens irradiated in the so called high flux test module (HFTM).The objective of this paper is to assess on the potential use of DONES to irradiate copper (Cu) alloys and tungsten (W) in the HFTM together with reduced activation ferritic martensitic steel like for example EUROFER (9%-Cr-steel). The presence of Cu alloys or W specimens may have an effect in the irradiation parameters of the EUROFER samples placed also in the HFTM and in the samples of the creep fatigue test module (CFTM).McDeLicious code is used for neutron transport calculations. Damage dose rate and H and He production are analysed in the different locations and compared with the irradiation conditions in first wall and divertor in fusion machines.

Overview of the IFMIF/EVEDA projectaaIn Memoriam Yoshikazu Okumura who passed away on 6 March 2017.

IFMIF, the International Fusion Materials Irradiation Facility, is presently in its engineering validation and engineering design activities (EVEDA) phase under the Broader Approach Agreement.The engineering design activity (EDA) phase was successfully accomplished within the allocated time.The engineering validation activity (EVA) phase has focused on validating the Accelerator Facility (AF), the Target Facility and the Test Facility (TF) by constructing prototypes. The ELTL at JAEA, Oarai successfully demonstrated the long-term stability of a Li flow under the IFMIF’s nominal operational conditions keeping the specified free-surface fluctuations below ±1 mm in a continuous manner for 25 d. A full-scale prototype of the high flux test module (HFTM) was successfully tested in the HELOKA loop (KIT, Karlsruhe), where it was demonstrated that the irradiation temperature can be set individually and kept uniform. LIPAc, designed and constructed in European labs under the coordination of F4E, presently under installation and commissioning in the Rokkasho Fusion Institute, aims at validating the concept of IFMIF accelerators with a D+ beam of 125 mA continuous wave (CW) and 9 MeV. The commissioning phases of the H+/D+ beams at 100 keV are progressing and should be concluded in 2017; in turn, the commissioning of the 5 MeV beam is due to start during 2017. The D+ beam through the superconducting cavities is expected to be achieved within the Broader Approach Agreement time frame with the superconducting cryomodule being assembled in Rokkasho.The realisation of a fusion-relevant neutron source is a necessary step for the successful development of fusion. The ongoing success of the IFMIF/EVEDA involves ruling out concerns about potential technical showstoppers which were raised in the past. Thus, a situation has emerged where soon steps towards constructing a Li(d,xn) fusion-relevant neutron source could be taken, which is also justified in the light of costs which are marginal to those of a fusion plant.