Helium Cooled Lithium Lead Test Research Articles

Numerical Simulations with RELAP5-3D and RELAP5/mod3.3 of the Second Experimental Campaign on In-Box LOCA Transients for HCLL TBS

In-box LOCA was identified as one of the worst accidental scenarios for the HCLL TBS (Helium Cooled Lithium-Lead Test Blanket System). Aiming to experimentally analyze the consequences of this transient, ENEA designed and built THALLIUM (Test HAmmer in Lead LIthiUM), a facility that reproduces the LiPb loop of the HCLL TBS. Two experimental campaigns were carried out by simulating the rupture of a stiffening plate and the related helium injection in the LiPb loop. The obtained experimental data were used to check the capabilities of RELAP5 system code to reproduce the pressure wave propagation that follows this accident. The first simulations were made with RELAP5-3D using LBE (Lead–Bismuth Eutectic) as a system fluid, as the thermophysical properties of LiPb are tabulated only up to a maximum value of 40 bar in this version of the code. Then, LiPb properties were implemented in RELAP5/mod3.3, after selecting the proper correlations from a literature review. This work summarizes the numerical simulations of the second experimental campaign, which was simulated with both versions of the code. The simulations highlight that the code is able to accurately reproduce the experimental results and that RELAP5-3D is slightly more precise than RELAP5/mod3.3 in predicting the pressure trends.

Numerical simulations with RELAP5-3D of the first experimental campaign on In-box LOCA transient for HCLL TBS

• Results of RELAP5-3D simulations of an experimental campaign in a mock-up of the HCLL TBS LiPb loop. • RELAP5-3D is able to accurately reproduce the pressure wave propagation in the facility. • Two main general differences between numerical and experimental results have been highlighted. • Average discrepancy of about 3.5 bar between experimental data and numerical results on 5 tests. • The code accurately predicts the first pressure peak, the most relevant input for the designers. In this work the capabilities of RELAP5-3D are tested against the experimental data gathered in the first experimental campaign on THALLIUM (Test HAmmer in Lead LIthiUM). THALLIUM, a LiPb facility, was built in 2015 at ENEA R.C. Brasimone with the aim to study the In-box LOCA by reproducing the LiPb loop of the HCLL TBS and the pipe forest at 1:1 scale. HCLL TBS (Helium Cooled Lithium-Lead Test Blanket System) was one of the Breeding Blanket concepts selected for ITER. The ITER classification system identified the In-box LOCA as a critical accidental transient for this type of TBS. For this reason, codes able to reproduce the consequences of this transient are needed to support the design of the LiPb loop. The simulations with RELAP5-3D used LBE (Lead-Bismuth Eutectic) as system fluid, as the thermophysical properties of LiPb are tabulated only up to a maximum value of 40 bar. The results of the simulations suggest that RELAP5-3D is able to reproduce the pressure wave propagation in the facility, with an average discrepancy of about 3.5 bar (i.e. an average percentage discrepancy of about 9.7 %), but also highlight two general discrepancies between computations and experiments.

Assessment of HCLL-TBM optimum welding sequence scenario to minimize welding distortions

The ITER HCLL-TBM (Helium Cooled Lithium Lead Test Blanket Module) box assembly development implies the welding development of the following components: the Box and the Stiffening Grid (SG) made of vertical and horizontal Stiffening Plates (noted respectively v-SP and h-SP). This multi-chamber box structure in EUROFER97 steel is made of plates cooled by multiple meandering channels where circulates pressurized helium. For the assembly of these components, characterized by numerous multipass welds, Gas Tungsten Arc Welding (GTAW) is envisaged as reference process. Moreover, the TBM has large dimensions and thin plates which makes it very sensitive to welding distortions and is problematic regarding the assembly feasibility and compliance with geometric tolerances. This paper presents the numerical simulation and experimental work performed to optimize the v-SP to box assembly sequence, which is the most critical assembly regarding distortions, in order to minimize welding distortions.One of the technical lock of this study is high calculation times needed for this large component which implies to set up a simplified welding simulation method. The study is composed of three main phases: an experimental-numerical study of a T-joint fillet mock-up GTAW used to develop the preliminary welding procedure and to validate a simplified simulation method, a numerical optimization of the v-SP to box welding sequence via the simplified method, and the experimental application of the optimized v-SP to Box welding sequence on the TBM mock-up. The calculation and comparison of four different v-SP to box welding sequences allowed to identify the best sequence regarding welding distortions and to apply it experimentally.

THALLIUM: An experimental facility for simulation of HCLL In-box LOCA and validation of RELAP5-3D system code

The experimental facility THALLIUM (Test HAmmer in Lead LithIUM) was designed to reproduce the hydraulic transient in the HCLL TBS (Helium Cooled Lithium Lead Test Blanket System) breeder loop following the rupture of a Cooling or a Stiffening Plate, i.e. In-box LOCA (Loss Of Coolant Accident). In addition, the facility will be used to validate the simulations of the pressure wave propagation with RELAP5-3D system code. THALLIUM reproduces the geometry of the LLE (Lead Lithium Eutectic) loop of the HCLL TBS and it was installed at the ENEA Brasimone Research Centre. In this paper, the facility is presented in detail, emphasizing the similarities and the differences with the reference HCLL TBS design. Particular attention has been paid to the TBM mock-up and to the TBS Storage/Recirculation Tank, which are the components that required the biggest simplifications among the key components of the facility. An analytical study of the pressure wave was carried out, with the aim to highlight a possible source of inaccuracy that might be displayed in the future simulations with the code. The results of the analytical study show that the fluid-structure interactions will decrease the speed of sound in the LLE. Instead, RELAP5-3D does not consider the fluid-structure interactions and, therefore, a difference between the experimental and the simulation data could arise from the different wave speed. Finally, the RELAP5-3D nodalization and the results of a pre-test simulation are presented. These results proved to be useful for the design of the facility

Experimental and RELAP5-3D results on IELLLO (Integrated European Lead Lithium LOop) operation

The experimental facility IELLLO (Integrated European Lead Lithium LOop) was designed and installed at the ENEA Brasimone Research Centre to support the design of the HCLL TBM (Helium Cooled Lithium Lead Test Blanket Module).This work presents the results of the experimental campaign carried out within the framework of F4E-FPA-372 and which had three main objectives. First, to produce new experimental data for flowing LLE (Lead-Lithium Eutectic) for an analysis of the loop and the characterization of its main components. Then, to evaluate performances of commercial instrumentation as available instrumentation is not designed for use in LLE. Lastly, to use the data for validation of the model developed with the system code RELAP5-3D. The data collected could prove helpful to analyze the behavior of the LLE loop of ITER and DEMO in accidental conditions.The results show that the regenerative countercurrent heat exchanger has an efficiency ranging from 70 to 85%, mainly depending on the LLE mass flow rate. It was verified that the air cooler has the capability to keep the cold part of the loop at 623K, even in the most demanding situation (700rpm and maximum temperature of the hot part). The instrumentation tested showed good accuracy, with the exception of the turbine flow meter. Nevertheless, specific limitations in the upper operative temperatures were found for the LLE direct contact pressure transducer. RELAP5-3D simulations fit very well the associated experimental results achieved.

HCLL TBM design status and development

The Helium Cooled Lithium Lead Test Blanket Module (HCLL-TBM) is one of the two European TBMs, representative of DEMO blanket technology, that shall be ready for installation in ITER starting from the first day of operation. It is developed by the CEA in the framework of the activities of the Test Blanket Module Consortium of Associates and under contract with the European Joint Undertaking Fusion For Energy (F4E). A series of 4 different HCLL-TBMs will be installed into one of the ITER equatorial ports during the experimental campaign. This paper aims at presenting the development process and design status of HCLL-TBM, with particular focus on the so-called “integral-TBM (IN-TBM)”, which will include all the main features of the corresponding DEMO blanket module. The design of such a complex component already poses considerable issues and is complicated by the peculiarities of the ITER environment (high temperature, radiation damage, pulsed plasma operation), which are not always addressed in present nuclear design codes. After recalling the main features of the HCLL IN-TBM, supporting design analyses are presented and manufacturing techniques are discussed.

Measurement and analysis of neutron flux spectra in a neutronics mock-up of the HCLL test blanket module

Fast neutron and gamma-ray flux spectra and time-of-arrival spectra of slow neutrons have been measured in a neutronics mock-up of the European Helium-Cooled Lithium–Lead Test Blanket Module with the aim to validate nuclear cross-section data. The mock-up was irradiated with fusion peak neutrons from the DT neutron generator of the Technical University of Dresden. A well characterized cylindrical NE-213 scintillator was inserted into two positions in the LiPb/EUROFER assembly. Pulse height spectra from neutrons and gamma-rays were recorded from the NE-213 output. The spectra were then unfolded with experimentally obtained response matrices of the NE-213 detector. Time-of-arrival spectra of slow neutrons were measured with a 3He counter placed in the mock-up, and the neutron generator was operated in pulsed mode. Monte Carlo calculations using the MCNP code and nuclear cross-section data from the JEFF-3.1.1 and FENDL-2.1 libraries were performed and the results are compared with the experimental results. A good agreement of measurement and calculation was found with some deviations in certain energy intervals.

Sensitivity and uncertainty analyses of the HCLL mock-up experiment

Within the European Fusion Technology Programme dedicated computational methods, tools and data have been developed and validated for sensitivity and uncertainty analyses of fusion neutronics experiments. The present paper is devoted to this kind of analyses on the recent neutronics experiment on a mock-up of the Helium-Cooled Lithium Lead Test Blanket Module for ITER at the Frascati neutron generator. They comprise both probabilistic and deterministic methodologies for the assessment of uncertainties of nuclear responses due to nuclear data uncertainties and their sensitivities to the involved reaction cross-section data. We have used MCNP and MCSEN codes in the Monte Carlo approach and DORT and SUSD3D in the deterministic approach for transport and sensitivity calculations, respectively. In both cases JEFF-3.1 and FENDL-2.1 libraries for the transport data and mainly ENDF/B-VI.8 and SCALE6.0 libraries for the relevant covariance data have been used. With a few exceptions, the two different methodological approaches were shown to provide consistent results. A total nuclear data related uncertainty in the range of 1–2% (1σ confidence level) was assessed for the tritium production in the HCLL mock-up experiment.

Thermal–mechanical and thermal–hydraulic integrated study of the Helium-Cooled Lithium Lead Test Blanket Module

The Helium-Cooled Lithium Lead Test Blanket Module (HCLL-TBM) is one of the two TBM to be installed in an ITER equatorial port since day 1 of operation, with the specific aim to investigate the main concept functionalities and issues such as high efficiency helium cooling, resistance to thermo-mechanical stresses, manufacturing techniques, as well as tritium transport, magneto-hydrodynamics effects and corrosion. In particular, in order to show a DEMO-relevant thermo-mechanical and thermal–hydraulic behavior, the HCLL-TBM has to meet several requirements especially as far as its coolant thermofluid-dynamic conditions and its thermal–mechanical field are concerned. The present paper is focused on the assessment of the HCLL-TBM thermal–mechanical performances under both nominal and accidental load conditions, by adopting a computational approach based on the Finite Element Method. A realistic 3D finite element model of the whole HCLL-TBM, in the horizontal first wall design has been set up, consisting of about 597,000 elements and 767,000 nodes. In particular, since the thermal fields of both the module and the coolant are strictly coupled, the helium flow domain has been modeled too and a thermal contact model has been set up to properly simulate the convective heat transfer between the structure wall and the coolant. Pure conductive heat transfer has been assumed within the Pb–Li eutectic alloy of the breeder units. The volumetric density of the nuclear deposited power, recently calculated at Department of Nuclear Engineering of the University of Palermo by the MCNP 4C code, has been applied as distributed thermal load in order to assess the potential influence on the module thermo-mechanical performances of the markedly non-uniform poloidal and toroidal distributions that have been predicted within the Segment Box. Different loading scenarios have been considered as to the heat flux onto the module First Wall. Steady state and transient thermal–mechanical analyses have been carried out and the detailed spatial distributions of the thermal and mechanical fields obtained as to the considered loading scenarios are reported, together with a critical analysis intended to verify their compliance with the agreed design criteria and the DEMO relevance requirements.

Study of the helium-cooled lithium lead test blanket module nuclear behaviour under irradiation in ITER

Abstract The present paper deals with the detailed investigation of the helium-cooled lithium lead test blanket module (HCLL-TBM) nuclear behaviour under irradiation in ITER, carried out at the Department of Nuclear Engineering of the University of Palermo adopting a numerical approach based on the Monte Carlo method. A realistic 3D heterogeneous model of the HCLL-TBM was set-up and inserted into an ITER 3D semi-heterogeneous model that realistically simulates the reactor lay-out up to the cryostat. A Gaussian-shaped neutron source was adopted for the calculations. The main features of the HCLL-TBM nuclear response were assessed, paying a particular attention to the neutronic and photonic deposited power, the tritium production rate and the spatial distribution of their volumetric densities. Structural material irradiation damage was also investigated through the evaluation of displacement per atom and helium and hydrogen production rates.

The HCLL Test Blanket Module system: Present reference design, system integration in ITER and R&D needs

This paper gives an overview of the most recent developments for the Helium-Cooled Lithium Lead Test Blanket Modules (HCLL-TBM) in terms of TBM design, related analyses, fabrication developments and safety features. It also addresses the issues concerning the interfaces of the HCLL-TBM system with ITER and the corresponding proposals of its integration in the ITER machine and buildings. Beside the overview of the progresses realized in several domains of this project, the paper finally outlines the remaining R&D necessary for the main unsolved issues to cope with an installation of the HCLL-TBM system for day one of ITER operation.

On the influence of the supporting frame on the nuclear response of the Helium-Cooled Lithium Lead Test Blanket Module for ITER

Within the European Fusion Technology Programme, very intense research activities have been promoted on the Helium-Cooled Lithium Lead (HCLL) breeding blanket concept with the specific aim of manufacturing a Test Blanket Module (TBM) to be irradiated in ITER. HCLL-TBM is foreseen to be located in an ITER equatorial port, being housed inside a proper steel-supporting frame. In particular, since that frame has been designed to provide two cavities separated by a dividing plate and HCLL-TBM is foreseen to fill just one of them, its nuclear response could vary accordingly to the filling status of the other one, unless the dividing plate is thick enough to isolate the components housed in the two cavities, avoiding any significant nuclear interaction among them. At the Department of Nuclear Engineering of the University of Palermo a research campaign has been launched to investigate the potential impact on the HCLL-TBM nuclear response of either the dividing plate thickness or the filling status of the frame cavities. A computational approach based on the Monte Carlo method has been followed and a detailed parametric study has been carried out considering thicknesses of the dividing plate ranging from 0 to the reference value (20 cm) and assuming, for each case, the presence of either void, or a water-cooled steel plug, or a HCLL-TBM or a Helium-Cooled Pebble Bed (HCPB) TBM in the other frame cavity. The analyses have been carried out by means of the MCNP-4C code, running a large number of histories (2 × 10 7) so that the results obtained are affected by statistical uncertainties lower than 1%. The results obtained are herewith reported and critically discussed.

On the nuclear response of the helium-cooled lithium lead test blanket module in ITER

The helium-cooled lithium lead (HCLL) concept has been recently selected as one of the two European reference designs foreseen for the breeding blanket of a demonstration fusion reactor. In particular, within the framework of the research and development activities on this blanket line, an HCLL test blanket module (TBM) has to be designed and manufactured to be implemented in ITER. At the Department of Nuclear Engineering (DIN) of the University of Palermo, a research campaign has been carried out to investigate the nuclear response of HCLL-TBM inside ITER by a numerical approach based on the Monte Carlo method. A realistic 3D heterogeneous model of HCLL-TBM has been set-up and inserted into an ITER 3D semi-heterogeneous one that simulates realistically the reactor lay-out up to the cryostat. A Gaussian-shaped neutron source has been adopted for the calculations. The main features of the HCLL-TBM nuclear response have been determined, paying particular attention to the deposited power and the tritium production rate together with the spatial distribution of their volumetric densities. The radiation damage of the structural material has also been investigated through the evaluation of displacement per atom and helium and hydrogen production rate.