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• Investigation of the steady-state thermal-hydraulic behaviour of the DEMO divertor PFCs cooling circuit. • Analysis of a realistic model adopting a Computational Fluid-Dynamic approach basedon Finite Volume Method. • Assessment of the PFCs cooling circuit thermal-hydraulic performances under both nominal and alternative operative conditions. • Evaluation of the major thermal-hydraulic parameters. Within the framework of the Work Package DIV 1 – "Divertor Cassette Design and Integration" of the EUROfusion action, a research campaign has been jointly carried out by University of Palermo and ENEA to investigate the steady state thermal-hydraulic behaviour of the DEMO divertor cassette cooling circuit, focussing the attention on its Plasma Facing Components (PFCs). The research campaign has been carried out following a theoretical-computational approach based on the Finite Volume Method and adopting the commercial Computational Fluid-Dynamic code ANSYS-CFX. A realistic model of the PFCs cooling circuit has been analysed, specifically embedding each Plasma Facing Unit (PFU) cooling channel with the foreseen swirl tape turbulence promoter, hence resulting in a finite volume model much more detailed than those assessed in previous analyses. Its thermal-hydraulic performances have been numerically evaluated under nominal steady state conditions, also comparing the obtained results with the corresponding outcomes of analogous analyses carried out for a simplified PFCs configuration, without swirl tapes. Moreover, the main thermal-hydraulic parameters have been evaluated in order to check whether the considered PFCs cooling circuit might fulfil the total pressure drop requirement (Δp <1.4 MPa), providing a uniform cooling of the Vertical Target PFU channels with a viable CHF margin (>1.4). The PFCs cooling circuit thermal-hydraulic behaviour has been additionally assessed at alternative operative conditions, issued to check the viability of a coolant velocity reduction, in order to minimize corrosion and vibrations inside the PFU channels. Models, loads and boundary conditions assumed for the analyses are herewith reported and critically discussed, together with the main results obtained. [ABSTRACT FROM AUTHOR]

• Estimation of major criticalities in the CB thermal-hydraulic performances. • Adoption of a theoretical approach based on a lumped parameter 1D model. • Assessment of several CB configurations thermal-hydraulic performances. • Identification of the most promising CB layout configuration to be further improved. Within the framework of the Work Package DIV 1 - "Divertor Cassette Design and Integration" of the EUROfusion action, a research campaign has been jointly carried out by University of Palermo and ENEA to investigate the thermal-hydraulic performances of the DEMO divertor cassette cooling system. The research activity has been focused onto the most recent design of the Cassette Body (CB) cooling circuit equipped with a Liner, whose main function is to protect the underlying vacuum pump hole from the radiation arising from the plasma. The research campaign has been carried out following a theoretical-computational approach based on the Finite Volume Method and adopting the commercial Computational Fluid-Dynamic code ANSYS-CFX. The CB thermal-hydraulic performances have been assessed in terms of coolant and structure temperature, coolant overall pressure drop, flow velocity distribution and mass flow rate fed to the Liner cooling circuit, mainly in order to check coolant aptitude to provide a uniform and effective cooling to both CB and Liner structures. The outcomes of the study have shown some major criticalities, mainly in terms of water coolant vaporization as well as non-symmetric coolant distribution between the two Liner inlets. As a consequence, the following potential solutions have been successfully explored in order to allow the CB to safely operate while complying with its design constraints: • revising the CB design layout in order to increase the coolant mass flow rate fed to Liner; • increasing coolant inlet pressure to rise water saturation temperature and, hence, its margin against vaporization; • increasing coolant mass flow rate to reduce its overall thermal rise. The main results and the achieved optimized model are herewith described and critically discussed. [ABSTRACT FROM AUTHOR]

Highlights • The thermal-hydraulic performances of the DEMO divertor Cassette Body cooling circuit have been investigated. • A numerical approach based on the Finite Volume Method has been followed, adopting the ANSYS-CFX code. • Cooling circuit is generally able to provide a uniform cooling to steel structure with a total pressure drop of 0.1 MPa. • Limited hot spots have been found in the steel structure to be further investigated. Abstract Within the framework of the Work Package Divertor, Subproject: Cassette Design and Integration (WPDIV-Cassette) of the EUROfusion action, a research campaign has been jointly carried out by ENEA and University of Palermo to investigate the thermal-hydraulic performances of the DEMO divertor cassette cooling system. The research activity has been carried out following a theoretical-computational approach based on the finite volume method and adopting a qualified Computational Fluid-Dynamic (CFD) code. Fully-coupled fluid-structure CFD analyses have been carried out for the recently-revised cassette body cooling circuit under nominal steady state conditions, imposing a non-uniform spatial distribution of nuclear-deposited heat power volumetric density drawn from the most recent neutron transport analysis. The pertaining thermal-hydraulic performances have been assessed in terms of coolant flow velocity and total pressure distributions as well as of coolant and structure temperature distributions to check whether they comply with the corresponding prescribed limits. Results obtained are reported and critically discussed. [ABSTRACT FROM AUTHOR]

Highlights • The thermal-hydraulic performances of the DEMO divertor Plasma Facing Components (PFCs) cooling circuit have been optimized. • The effects of increasing inlet/outlet manifolds diameters and placing a diffuser at the inlet of each Vertical Target have been assessed. • A numerical approach based on the Finite Volume Method has been followed, adopting the ANSYS-CFX code. • The "optimized" configuration foresees a total pressure drop of 1.098 MPa and a minimum margin against CHF occurrence of 1.462. Abstract Within the framework of the Work Package Divertor, Subproject: Cassette Design and Integration (WPDIV-Cassette) of the EUROfusion action, a research campaign has been jointly carried out by ENEA and University of Palermo to investigate the thermal-hydraulic performances of the DEMO divertor cassette cooling system. Attention has been focussed on the divertor Plasma Facing Components (PFCs) cooling circuit and a parametric analysis has been carried out in order to assess the potential impact of proper layout changes on its thermal-hydraulic performances, mainly in terms of coolant total pressure drop, flow velocity distribution and margin against critical heat flux occurrence. The research activity has been carried out following a theoretical-computational approach based on the finite volume method and adopting a qualified Computational Fluid-Dynamic (CFD) code. Results obtained have allowed to select a revised PFCs cooling circuit configuration, suitable to comply with the prescribed thermal-hydraulic limits assumed for the DEMO divertor design. They are reported and critically discussed. [ABSTRACT FROM AUTHOR]

Within the framework of the Work Package DIV 1 – “Divertor Cassette Design and Integration” of the EUROfusion action, a research campaign has been jointly carried out by ENEA and University of Palermo to investigate the thermal-hydraulic performances of the DEMO divertor cassette cooling system. A comparative evaluation study has been performed considering the two different options under consideration for the divertor cassette body coolant, namely subcooled pressurized water and helium. The research activity has been carried out following a theoretical-computational approach based on the finite volume method and adopting a qualified Computational Fluid-Dynamic (CFD) code. CFD analyses have been carried out for the considered options of cassette body cooling circuit under nominal steady state conditions and the pertaining thermal-hydraulic performances have been assessed in terms of overall coolant thermal rise, coolant total pressure drop, flow velocity and pumping power, to check whether they comply with the corresponding limits. Results obtained are reported and critically discussed. [ABSTRACT FROM AUTHOR]

Within the framework of the research and development activities supported by the ITER Organization on the blanket system issues, an intense analysis campaign has been performed at the University of Palermo with the aim to investigate the thermal-hydraulic behaviour of the cooling system of a standard 20° sector of ITER blanket during the draining transient operational procedure. The analysis has been carried out following a theoretical-computational approach based on the finite volume method and adopting the RELAP5 system code. In a first phase, attention has been focused on the development and validation of the finite volume models of the cooling circuits of the most demanding modules belonging to the standard blanket sector. In later phase, attention has been put to the numerical simulation of the thermal-hydraulic transient behaviour of each cooling circuit during the draining operational procedure. The draining procedure efficiency has been assessed in terms of both transient duration and residual amount of coolant inside the circuit, observing that the former ranges typically between 40 and 120 s and the latter reaches at most ∼8 kg, in the case of the cooling circuit of twinned modules #6–7. Potential variations to operational parameters and/or to circuit lay-out have been proposed and investigated to optimize the circuit draining performances. In this paper, the set-up of the finite volume models is briefly described and the key results are summarized and critically discussed. [ABSTRACT FROM AUTHOR]