Fusion Engineering and Design 83 (2008) 1631–1637 Contents lists available at ScienceDirect Fusion Engineering and Design journal homepage: www.elsevier.com/locate/fusengdes Progress in neutronics for the ITER ECRH launcher Arkady Serikov ∗ , Ulrich Fischer, Roland Heidinger, Klaus Kleefeldt, Peter Spaeh, Stephanie Stickel, Haileyesus Tsige-Tamirat Forschungszentrum Karlsruhe, P.O. Box 3640, D-76021 Karlsruhe, Germany article info Article history: Available online 15 August 2008 Keywords: ITER neutronics Extended performance (EP) front steering ECRH launcher Monte Carlo method MCNP variance reduction techniques McCad interface programme abstract The paper reports the latest achievements in the neutronics modelling of the electron cyclotron resonance heating (ECRH) launcher installed in the ITER upper port. The computational neutronics analyses have been performed for the extended performance (EP) front steering launcher design, which is accepted by the ITER project as reference. The aim of the paper is to show that the considered launcher design satisfies to the nuclear criteria specified for ITER machine. Results of calculations for the essential nuclear responses such as the neutron fluxes, neutron damages, helium production, and nuclear heating are discussed. The methodology used is focused on Monte Carlo variance reduction techniques for deep-penetration neutron radiation calculations in a very heterogeneous geometry. The Monte Carlo N-particle (MCNP) code was used for the radiation transport calculations with a 3D geometry model of the launcher in ITER machine. The complexity of the launcher geometry makes inevitable to use an automated interface programme McCad for the direct conversion from CAD to MCNP. The results obtained are in compliance with the ITER nuclear regulations. The analyses reveal the necessity of detailed consideration of the most critical launcher components. © 2008 Elsevier B.V. All rights reserved. 1. Introduction This paper presents the essential results of neutronics anal- yses for the ITER electron cyclotron resonance heating (ECRH) upper port launcher. The launcher is devoted to the control of magneto-hydrodynamic (MHD) instabilities by means of injection of millimetre-wave beams into the ITER plasma. The beams are produced by 170GHz Gyrotron units, then they are coming by the tubes of the transmission line to the back side of the ECRH launcher installed in the ITER upper port, pass through the corrugated HE 11 waveguide (WG) rows, and finally they are focused of the cer- tain magnetic flux surfaces to prevent the harmful MHD activity (sawtooth instability or neoclassical tearing modes). The utmost precision of mm-beams focusing is provided by the system of focus- ing and steering mirrors. Recently the extended performance (EP) front steering launcher was selected as reference launcher design for the ITER upper port. The overview of the EP launcher is pre- sented in Ref. [1], including physics and engineering aspects. Design of the structural components and results for the associated analy- ses are described in Ref. [2]. The neutronics analyses provide the arrangement of radiation shielding in the launcher to guarantee ∗ Corresponding author. Tel.: +49 7247 82 2157; fax: +49 7247 82 3718. E-mail address: serikov@irs.fzk.de (A. Serikov). all ITER nuclear design criteria for the launcher and neighbouring reactor components. In the EP launcher the steering mirrors are located near the plasma first wall (FW). That gives possibility to reach wider plasma range with more accurate control. The main components of the EP launcher are depicted in Fig. 1. At the launcher rear part, the mm-beams enter through the tritium barrier made by the chemi- cal vapour deposition (CVD) diamond windows sealing eight WGs, which are arranged in upper and lower rows; at the mitre bend sec- tion in the launcher middle part the WGs are ending, and after the bend the mm-waves are propagated in the free space holes inside the radiation shield blocks of internal shield and blanket shield module (BSM). The BSM components are presented in Fig. 2. The opening in the FW (see Fig. 2) allows mm-beams injection to the plasma chamber, and in the same way gives possibility for excessive neutron radiation from the plasma chamber. The duty of the rota- tion mechanism of the steering mirrors must be reliable under high neutron radiation from the FW opening. The arrangement of shield blocks in the BSM is also followed by the requirement of re-welding along the vacuum vessel (VV) steel case. This requirement is met if helium production is less than 1 appm. The area of an extensive neu- tron loads also includes lateral sides of the connective flange shown in Fig. 2. The issue of nuclear heating distribution in the flange is analysed in the paper. The effect of additional shield blocks in the place of the launcher mitre bends is investigated in the neutron 0920-3796/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.fusengdes.2008.06.044