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• Deterministic Accident Analysis for DONES licensing are performed with MELCOR fusion version. • Lithium Loop and Accelerator models are developed for relevant scenarios. • Candidate safety systems, requirements and metrics under control are identified. • First scenario: beam shutdown and margin to lithium disappearance are addressed. • Second scenario: fast isolation valve and water reaching the target are addressed. Safety assessment is a key issue for the licensing of DONES facility, the DEMO-Oriented Neutron Source. A first phase of the safety assessment includes Failure Mode Analyses of systems to identify postulated initiating events (PIEs), while deterministic accident analyses are lately performed to estimate source terms in radiological hazards. In addition, the deterministic analyses are also the basis to identify safety class structures, systems and components, and to establish the operational range of system parameters as well as the actuation of the protection system. In this paper two accident scenarios, previously identified as PIEs, are explored with the fusion version of the MELCOR 1.8.6 code. A loss of flow (LOFA) in the lithium loop due to the trip of the electromagnetic pump and a loss of vacuum (LOVA) in the accelerator beam duct due to containment rupture have been studied to provide a preliminary estimation of the available actuation time for detection and mitigation systems with a particular focus on the beam shutdown system and isolation of the vacuum duct. [ABSTRACT FROM AUTHOR]

IFMIF-DONES will be an experimental facility designed to irradiate material samples under conditions similar to those expected in future fusion power reactors. As a radiological facility, it requires the precise design of specific safety subsystems to ensure the protection of the public, the plant personnel and the environment. This is the case of the Argon Purification Subsystem (ArPS), which is responsible for ensuring the inertization of those rooms where liquid Li may be present, involving a risk of fire and hazardous releases. In this context, it is important to set Ar purity requirements as design input for the ArPS to ensure this inertization while being technically sound due to the large amounts of volumes involved. To support this design process, a MELCOR simulation model of the IFMIF-DONES ArPS has been developed. Using this model, we perform a parametric study to analyse the performance of this subsystem under different configurations. The goal is to keep the impurity concentrations of the inert rooms stable during a year of operation in order to minimize the risk of Li reactions, while ensuring dynamic confinement and reducing Ar consumption. In addition, the transition between maintenance and operation modes is considered, analysing the effect of different transition periods and injected Ar inventory. • The MELCOR modelling of the IFMIF-DONES argon purification system is described. • Different parameters are analysed from simulations of inert rooms of the building. • We study how to keep impurities stable in inert rooms over a year of operation. • We analyse how different parameters affect the maintenance-operation transition. [ABSTRACT FROM AUTHOR]

• Summary of IFMIF-DONES Preliminary Engineering Design for a generic site is presented. • Design solutions for Test Cell (TC) penetrations and confinement are proposed. • Integrated neutronic analyses in the target area are performed. • Radiation maps and shielding configuration in the TC and surrounding rooms are discussed. • Integration of RH systems and maintenance procedures in the TC are developed. The need of a high-intensity, 14 MeV neutron source for the qualification of materials under fusion-relevant conditions has been recognized in the European fusion programme as an essential step towards the design and licensing of DEMO and future commercial fusion power plants. This need has pushed the EU to support the development of a Li(d,nx) neutron source called IFMIF-DONES (International Fusion Materials Irradiation Facility-DEMO Oriented NEutron Source) based on and taking advantage of the results obtained in the IFMIF/EVEDA (IFMIF Engineering Validation and Engineering Design Activities) project conducted in the framework of the bilateral EU-Japan Broader Approach Agreement. The design activities and the supporting R&D work of the IFMIF-DONES facility are presently being carried out in the framework of the Work Package Early Neutron Source (WPENS) of the EUROfusion Consortium in direct collaboration with F4E Agency, with the main goal of consolidating the underlying technology and developing a sound design basis in order to be ready for IFMIF-DONES construction at the early beginning of the next decade. In this paper, some important aspects of the IFMIF-DONES Preliminary Engineering Design concerning in particular the main design integration issues in the target area are presented and briefly discussed. [ABSTRACT FROM AUTHOR]

MELCOR is an integral code developed by Sandia National Laboratories (SNL) for the US Nuclear Regulatory Commission (USNRC) to perform severe accident analyses of Light Water Reactors (LWR). More recently, MELCOR capabilities are being extended also to analyze non-LWR fission technologies. Within the European MELCOR User Group (EMUG), organized in the framework of USNRC Cooperative Severe Accident Research Program (CSARP), an activity on the evaluation of the applicability of MELCOR 2.2 for fusion safety analyses has been launched and it has been coordinated by ENEA. The aim of the activity was to identify the physical models to be possibly implemented in MELCOR 2.2 necessary for fusion safety analyses, and to check if those models are already available in MELCOR 1.8.6 for fusion version, developed by Idaho National Laboratory (INL). From this activity, a list of modeling needs emerged from the safety analyses of fusion-related installations have been identified and described. Then, the importance of the various needs, intended as the priority for model implementation in the MELCOR 2.2 code, has been evaluated according to the technical expert judgement of the authors. In the present paper, the identified modeling needs are discussed. The ultimate goal would be to propose to have a single integrated MELCOR 2.2 code release capable to cover both fission and fusion applications. [ABSTRACT FROM AUTHOR]

Abstract: The IFMIF-EVEDA accelerator will be a 9MeV, 125mA cw deuteron accelerator prototype for verifying the validity of the accelerator design for IFMIF. A beam stop will be used for the RFQ and DTL commissioning as well as for the EVEDA accelerator tests. Therefore, this component must be designed to stop 5MeV and 9MeV deuteron beams with a maximum power of 1.13MW. The first step of the design is the beam-facing material selection. The criteria used for this selection are low neutron production, low activation and good thermomechanical behavior. In this paper, the mechanical analysis and radioprotection calculations that have led to the choice of the main beam dump parameters will be described. The present design is based on a conical beam stop (2.5m length, 30cm diameter, and 3.5mm thickness) made of copper plus a cylindrical 0.5m long beam scraper. The cooling system is based on an axial high velocity flow of water. This design is compliant with the mechanical design rules during full power stationary operation of the accelerator. The radioprotection calculations performed demonstrate that, with an adequate local shielding, doses during beam on/off phases are below the limits. [Copyright &y& Elsevier]