Design status and procurement activities of the High Voltage Deck 1 and Bushing for the ITER Neutral Beam Injector

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Abstract

The ITER Neutral Beam Injector (NBI) power supply system includes several non-standard components, whose ratings go beyond the present industrial practice. Two of these items, to be procured by Fusion for Energy, are:

  • 1.

    A −1 MVdc air-insulated Faraday cage, called High Voltage Deck 1 (HVD1), hosting the Ion Source and Extractor Power Supplies (ISEPS) and the associated diagnostics.

  • 2.

    A −1 MVdc feedthrough, called HVD1-TL Bushing, aimed at connecting the HVD1 to the gas (SF6) insulated Transmission Line (TL), containing inside its High Voltage (HV) conductor all ISEPS power and control cables coming from the HVD1 to be connected to the NBI Ion Source services.

The paper deals with the status of the design of the HVD1 and HVD1-TL Bushing, focusing on insulation, mechanical and thermal issues as well as on their integration with the other components of the power supply system. In particular, the insulation issue of the integrated system has been addressed by means of an electrostatic Finite Element (FE) analysis whilst a FE thermal simulation has been carried out to assess the impact of the dissipation of the proposed design of the inner conductors (ISEPS conductors) not actively cooled. Finally, the paper describes the status of procurement strategy and execution.

Highlights

► ITER Neutral Beam Injector includes several non-standard components. ► The design status of the −1 MVdc HVD1 and Bushing is described. ► The paper reports also on the integrated layout of the two components. ► Preliminary electrostatic and thermal analyses are presented. ► Procurement activities are outlined.

Introduction

In ITER the plasma burning conditions will be obtained and controlled by means of two Neutral Beam Injectors (NBIs) – belonging to the additional Heating and Current Drive systems – designed to deliver up to 16.5 MW power of neutral particles (H or D) to the plasma at 1 MeV of energy and with a pulse length up to 3600 s [1]. To optimize the NBI design and operation, a dedicated Test Facility (PRIMA – Padua Research on Injectors with Megavolt Acceleration) is under construction in Padua, Italy, at the Consorzio RFX premises. PRIMA will host a full scale prototype of the ITER NBI (MITICA – Megavolt ITER Injector & Concept Advancement) [2].

The ITER NBI and MITICA experiment include a complex power supply system, represented by the simplified scheme of Fig. 1. The whole Ion Source is polarized to ground at acceleration voltage (−1012 kVdc); all the Ion Source services, i.e. the power supplies, indicated as Ion Source and Extractor Power Supplies (ISEPS [3]), and the cubicles for control and diagnostics shall be therefore hosted inside an air insulated platform – named High Voltage Deck 1 (HVD1) – and fed by an insulating transformer [4]. The HVD1-TL Bushing (hereinafter called the Bushing) connects the HVD1 to the central conductor of the SF6 Insulated Transmission Line (TL). The TL is a multipolar line connecting both the Ion Source services and the Acceleration Grid Power Supply (AGPS) to the NB Injector.

This paper reports on:

  • The design status of the HVD1 and Bushing, on the basis of the integrated layout chosen between the two originally envisaged [5].

  • The results of analysis made by an electrostatic Finite Element (FE) model of the HVD1 and Bushing assembly with respect to the High Voltage Hall (HVH) to verify the insulation level.

  • The results of analysis made by a FE thermal model of the Bushing carried out to assess the impact of the heat dissipation of the inner conductors relevant to the latest Bushing configuration.

  • The status of procurement activities for the HVD1 and Bushing carried out by the European Domestic Agency, Fusion for Energy (F4E).

Section snippets

HVD1 design elements

The HVD1 is an air insulated cage, polarized at −1 MVdc electric potential with respect to ground, which contains all devices forming the ISEPS (such as transformers, power and control cubicles), the Ion Source diagnostics and other auxiliary equipment; the overall components will be arranged over two floors. During normal operation the equipment inside the HVD1 is fed by an external 5 MVA insulating transformer providing main AC power at 6.6 kV. The HVD1, whose external reference dimensions are 12

Finite Element simulations

Electrostatic and thermal Finite Element (FE) simulations have been carried out to obtain a first assessment of the electric field distribution expected for HVD1 and Bushing assembly installed inside the HVH and to evaluate preliminarily the Bushing thermal regime.

Procurement activities

The procurement of the three HVD1 and Bushing units required for the MITICA experiment and for the two ITER injectors is the object of a Competitive Dialogue, one of the procurement procedures of F4E, in which an exchange – so-called Dialogue – on all aspects of the Supply, either technical or contractual, takes place between F4E and the potential Suppliers, after their selection upon a Call for Expressions of Interest. This procedure was elected in view of the technical challenges that the

Conclusions

The design status of the HVD1 and Bushing as well as of their integrated layout has been described in previous sections. Preliminary FE electrostatic and thermal analyses, supporting the design choices, have shown the validity of the design. Finally, the paper reported on the procurement activities carried out by Fusion For Energy, including information on procurement strategy and execution progress.

Acknowledgment

This work was set up in collaboration and financial support of Fusion for Energy.

References (5)

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Cited by (5)

  • 1 MV power supplies integration issues in MITICA experiment, the ITER Heating Neutral Beam Injector prototype

    2021, Fusion Engineering and Design
    Citation Excerpt :

    the Acceleration Grid Power Supply (AGPS, see detail 1 in Fig. 1) [3], composed of five DC Generators (DCG) rated for -200 kVdc each, connected in series to produce -1 MVdc acceleration voltage; each DCG consists of a three phase step up oil insulated transformer (detail A) which high voltage terminals are connected to a three phase diodes bridge, contained inside a pressurized rectifier tank (detail B) insulated with SF6 at 0.6 MPa abs; DCG output conductors are connected to a RC filter unit (DCF, detail 2); the Ion Source and Extraction Power Supply system (ISEPS [4]) includes all the devices providing the electrical power required by the Ion Source and the cubicles for control and diagnostics; this equipment is installed inside a large (12.5 m (L) x 8.4 m (W) x 9.6 m (H)) -1 MVdc air insulated Faraday cage (High Voltage Deck1, HVD1, detail 3) [5–7] and is fed by an insulating transformer (detail 4) [8]; HVD1 is connected to the Transmission Line (TL) through an air-to-SF6 Bushing (High Voltage Bushing Assembly, HVBA, detail 5); a 100 m SF6 (at 0.6 MPa abs) insulated TL (detail 6), connecting AGPS and ISEPS to the beam source installed inside MITICA Vessel (detail 8) through

  • The High Voltage Deck 1 and Bushing for the ITER Neutral Beam Injector: Integrated design and installation in MITICA experiment

    2019, Fusion Engineering and Design
    Citation Excerpt :

    Underneath the HVD1 there is a pit where the HVBA is installed and interfaced with the TL (see Fig. 2). This configuration, described and analysed in [5,6], has been taken as reference for the procurement technical specification [7] mainly for its electrostatic reasons (HVBA installed in the uniform electric field produced underneath the HVD1). As a consequence, more free space for a functional layout of the equipment inside the HVH is made available.

  • Final design of the High Voltage Deck 1 and Bushing for MITICA: The ITER Heating Neutral Beam Injector prototype

    2017, Fusion Engineering and Design
    Citation Excerpt :

    The chosen layout foresees the installation of the HVBA in a pit underneath the HVD1, with the HVBA base (Interface Box) aside of the TL (Fig. 2). This integrated layout allows simplifying the overall design [5,6], because the HVBA takes advantage of the HVD1 shielding effect, avoiding the installation of additional screens; all the electrical connections at the interfaces are flexible, so the HVBA is mechanically decoupled from the HVD1 and the TL. As a result of previous analyses of different technological solutions [6], ungraded SF6 fully insulated technology was finally selected, as the most reliable insulating structure able to withstand the very frequent voltage stresses due to grid breakdowns.

Disclaimer: The views and opinions expressed herein do not necessarily reflect those of the ITER Organization.

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