ITER Equatorial Port Research Articles

Thermal and hydraulic analysis of the cooling system for the ITER equatorial port plugs

Thermo-hydraulic analysis of the equatorial port plug (EPP) is currently being performed by CIEMAT within the framework of the engineering activities related to the ITER port plug diagnostic integration launched by EFDA. This study is focussed on calculating the main hydraulic parameters for the reference cooling circuit, and analyzing different piping configurations, in order to achieve a balanced circuit, this being a key point for obtaining an homogeneous refrigeration of the port plug. It also analyzes the cooling requirements for the Diagnostic Shield Modules (DSM), considering not only the reference circuit design, where the piping cooling circuits run through those parts that need to be cooled, but also a new design proposal which entails a port plug cooling system based on the thermal contact between the DSM and the port plug itself. The overall study represents not only an improvement in the equatorial port plug cooling system design, but also a better understanding of the whole system so as to foresee the weak points that will need to be taken into account in the subsequent detailed design.

Thermo-hydraulical and thermo-mechanical analysis of the HCLL-TBM breeding unit

This paper concerns the latest design of the Helium Cooled Lithium-Lead (HCLL)-Test Blanket Module (TBM) according to the new dimensions of the space available for the module in the ITER equatorial ports. The performances of the proposed design are evaluated by means of new FE models of one breeding unit and the corresponding box structure. Detailed temperature and stress field distributions in each part of the structure have been obtained for nominal and accidental load conditions. The results of the FE calculations are analyzed with respect to thermal-hydraulics and thermo-mechanical stresses in order to verify the compliance with the established design criteria (maximum temperature in the structural material and SDC-IC rules). Also, the operating parameters are discussed in view of the DEMO-relevance of the proposed TBM design. Finally, possible improvements and modifications of the current design are proposed.

A study of the potential influence of frame coolant distribution on the radiation-induced damage of HCLL-TBM structural material

Within the European Fusion Technology Programme, the Helium-Cooled Lithium Lead (HCLL) breeding blanket concept is one of the two EU lines to be developed for a Long Term fusion reactor, in particular with the aim of manufacturing a Test Blanket Module (TBM) to be implemented in ITER. The HCLL-TBM is foreseen to be located in an ITER equatorial port, being housed inside a steel-supporting frame, actively cooled by pressurized water. That supporting frame has been designed to house two different TBMs, providing two cavities separated by a dividing Plate 20 cm thick. As the nuclear response of HCLL-TBM might vary accordingly to the supporting frame configuration and composition, at the Department of Nuclear Engineering of the University of Palermo, a parametric study has been launched to investigate such an influence. Previous works dealt with the dependence of the nuclear response of HCLL-TBM on the configuration of a homogeneous frame, the present one has been focused on the investigation of the potential influence of coolant distribution within the frame on the radiation-induced damage of the HCLL-TBM structural material. To this purpose, a detailed parametric study of the HCLL-TBM nuclear response has been performed by means of 3D-Monte Carlo neutronic analyses to asses both the rates of displacements per atom and helium and hydrogen production within the structural material. A semi-heterogeneous model of the supporting frame, assuming a realistic coolant distribution, and a 3D heterogeneous model of the HCLL-TBM, taking into account EUROFER as structural material, has been set-up. Therefore, the models of the TBM and of its frame have been inserted into the existing 3D ITER one, simulating realistically the reactor lay-out up to the cryostat and providing for a proper D-T neutron source. The analyses have been performed by means of the MCNP-4C code, and the results obtained are reported and critically discussed.

D-T neutron streaming experiment simulating narrow gaps in ITER equatorial port

Under the ITER/ITA task, we have conducted the neutron streaming experiment simulating narrow and deep gaps at boundaries between ITER vacuum vessel and equatorial port plugs. Micro-fission chambers and some activation foils were used to measure fission rates and reaction rates to evaluate the relative fast and slow neutron fluences along the gap in the experimental assembly. The MCNP4C, TORT and Attila codes were used for the experimental analysis. From comparing our measurements and calculations, the following facts were found: (1) in case of a such narrow and deep gap structure, the calculation with MCNP, TORT and Attila codes and FENDL-2.1 is sufficient to predict fast neutron field inside the gap; (2) by scattering neutrons in the experimental room, experimental error considerably increased at the deeper region than 100 cm; (3) angular quadrature set of upward biased U315 and last collided source calculation on TORT and Attila were very important technique for accurate estimation of neutron transport.

Application of importances or weight windows in MCNP4C to a geometry similar to an ITER equatorial port

Neutron streaming through the gap between a port plug and the port walls will be a major contributor to the shutdown dose rate in ITER, and calculating this streaming requires very effective variance reduction. The article describes a way of estimating importances for a calculation of the fast neutron flux, which will then generate weight windows. If necessary, these can be refined iteratively. Once the fast neutron calculation works well, the weight windows can be extended to lower energies and to photons using appropriate factors for which some values are suggested here. Again, these weight windows can be improved iteratively. Test runs in a simplified geometry performed fairly well, though optimizing performance simultaneously for the gamma flux at the end of the port and above it is difficult.

A study of the potential influence of frame coolant on HCLL-TBM nuclear response

Within the European Fusion Technology Programme, the Helium-Cooled Lithium Lead (HCLL) breeding blanket concept is one of the two EU lines to be developed for a long term fusion reactor, in particular with the aim of manufacturing a test blanket module (TBM) to be implemented in ITER. The HCLL-TBM is foreseen to be located in an ITER equatorial port, being housed inside a steel-supporting frame, actively cooled by pressurized water. This supporting frame has been designed to house two different TBMs providing two cavities separated by a dividing plate 20 cm thick. As the nuclear response of HCLL-TBM could vary with the supporting frame configuration and composition, a parametric study has been launched to investigate such an influence. Previous works dealt with the dependence of the nuclear response of HCLL-TBM on the configuration of an homogeneous frame while the present one has been focussed on the investigation of the influence of coolant distribution within the frame. A detailed parametric study of HCLL-TBM nuclear response has been performed by means of 3D-Monte Carlo neutronic and photonic analyses, simulating the frame in a semi-heterogeneous way. Three-dimensional heterogeneous models of HCLL-TBM and of the supporting frame have been set-up considering both the usual poloidal lay-out and a toroidal one and taking into account 9% Cr martensitic steel (EUROFER) as structural material. The models have been inserted into an existing 3D semi-heterogeneous ITER-FEAT one, simulating realistically the reactor lay-out up to the cryostat and providing for a proper D-T neutron source. The analyses have been performed by means of the MCNP-4C code, running a large number of histories (2·10 8) in such a way that results obtained are affected by statistical uncertainties lower than 1%. The results obtained are reported and critically discussed.

On the effects of the supporting frame on the radiation-induced damage of HCLL-TBM structural material

Within the European Fusion Technology Programme, research activities have been conducted on the Helium-Cooled Lithium Lead (HCLL) breeding blanket concept with the aim of manufacturing a Test Blanket Module (TBM) to be irradiated in ITER. HCLL-TBM is planned to be located in an ITER equatorial port, housed inside an AISI 316 stainless steel-supporting frame. Since that frame has been designed to provide two positions separated by a dividing plate and the HCLL-TBM is expected to fill one of them, its nuclear response could vary depending on the filling status of the other position and on the plate thickness. A parametric study has been carried out to investigate the potential effects on the radiation-induced damage of the HCLL-TBM structural material, due to the dividing plate thickness and to the presence of either a void, a water-cooled steel plug, or a Helium-Cooled Pebble Bed TBM in the adjacent frame position.

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.

ITER radiation shielding and neutronics analysis

Two dimensional radiation transport calculations have been carried out to determine radiation streaming through the ITER equatorial ports. The NBI port has been identified as the most critical. Shielding requirements were estimated to minimize the nuclear heating rates in the toroidal field (TF) coils and the activation of the cryostat, where hands-on maintenance is anticipated. The shielding efficiency of steel/water port walls was investigated as a function of port and wall dimensions and steel volume fraction. For open ports, i.e. the neutral beam injector ducts, 40–50 cm thick port walls composed of 40% SS-60% H 2O–75% SS-25% H 2O will reduce the TF coil heating to acceptable levels, while 60–65 cm thick walls are necessary for reducing the dose rates at ∼2 weeks after shutdown to levels of 750 μSv h −1 at the cryostat.

Status of ITER RF systems design

ITER will require ∼100 MW of auxiliary power for plasma heating, current drive and plasma kinetic control functions. As in most of the present-day tokamaks, these functions will be shared among different heating methods. A (negative-ion) neutral beam injection (NBI) and three RF heating and current drive (H&CD) systems - ion cyclotron (ICRF), electron cyclotron (ECRF) and lower hybrid (LBW) - are under conceptual development, the latter being developed by the European Home Team. The three RF H&CD Systems, described in this paper, offer together a range of features and services capable of satisfying all ITER requirements. A standardized design approach is adopted for the systems: all launchers are integrated in ITER equatorial ports, feature an all-metal construction, have a very limited impact on the torus layout, and do not significantly modify vacuum and tritium boundaries. They are removable through the port with similar manual and remote handling operations. A discussion of the RF systems design and of the associated R&D programmes is presented.