Please cite this article in press as: G. Pérez, et al., Optimized mass flow rate distribution analysis for cooling the ITER Blanket System, Fusion Eng. Des. (2014), http://dx.doi.org/10.1016/j.fusengdes.2014.03.002 ARTICLE IN PRESS G Model FUSION-7341; No. of Pages 6 Fusion Engineering and Design xxx (2014) xxx–xxx Contents lists available at ScienceDirect Fusion Engineering and Design jo ur nal home p age: www.elsevier.com/locate/fusengdes Optimized mass flow rate distribution analysis for cooling the ITER Blanket System Germán Pérez ∗ , Raphaël Mitteau, Andreas Furmanek, Alex Martin, René Raffray, Mario Merola, Flavien Sabourin ITER Organization, Route de Vinon sur Verdon, 13115 Saint Paul Lez Durance, France h i g h l i g h t s • Optimized water distribution in ITER blanket modules is presented. • All key challenging constraints are included. • The methodology and the successful result are presented. a r t i c l e i n f o Article history: Received 12 September 2013 Received in revised form 27 February 2014 Accepted 3 March 2014 Available online xxx Keywords: ITER Blanket System Mass flow rate Critical heat flux a b s t r a c t This paper presents the rationale to the optimization of water distribution in ITER blanket modules, meeting both Blanket System requirements and interface compliance requirements. The key challenging constraints include to: be compatible with the overall water allocation (3140 kg/s for 440 wall mounted BMs); meet the critical heat flux margin of 1.4 in the plasma facing units; meet a maximum temperature increase of 70 ◦ C at the outlet of each single BM; and ensure that water veloc- ity is less than 7 m/s in all manifolds, and that the pressure drops of all BMs can be equilibrated. The methodology and the successful result are presented. © 2014 Elsevier B.V. All rights reserved. 1. Introduction 1.1. Context and objective The Blanket (BLK) System is the most important ITER user of cooling water in order to remove the heat coming from the plasma. It comprises 440 water cooled wall-mounted blanket modules (BM) covering 650 m 2 , and segmented into 18 poloidal locations [1]. The BMs consist of two major components: a plasma-facing first wall (FW) panel supported by a shield block (SB) attached to the vacuum vessel (VV) (Fig. 1). One of the main constraints on the blanket cooling analysis is the plasma facing component (PFC) technology considered for the FW (also called “finger” or plasma facing unit). Two different FW concepts are utilized depending on the local heat flux require- ments (see Fig. 2): a normal heat flux (NHF) FW panel designed to accommodate up to 2 MW/m 2 (based on circular channels); and an ∗ Corresponding author. Tel.: +33 4 42 17 89 68. E-mail addresses: German.Perez@iter.org, gdp@icai.es (G. Pérez). enhanced heat flux (EHF) FW panel designed to accommodate up to 4.7 MW/m 2 (based on the hypervapotron channel). The aim of the work presented at this paper is to show the methodology that is used for optimizing the mass flow rate distribution in ITER blanket modules and the obtained results considering updated inputs and constraints. 1.2. Critical heat flux (CHF) review When an actively cooled surface is heated by a high heat flux, there is a risk of reaching critical heat flux (CHF) conditions. CHF conditions are characterized by a sharp reduction of the local heat transfer coefficient that results from the replacement of liquid by local bubbles of vapour adjacent to the heat transfer sur- face (see Fig. 3) [2,3]. Due to this event, the surface eventually melts and a water leak appears with strong consequences for the Toka- mak operation. This means that the mass flow rate analysis must consider CHF as a main constraint: following previous experiences, the CHF margin (defined as the ratio between the expected heat flux that causes a CHF event and the maximum design heat flux absorbed by the component) shall be at least 1.4 [1]. http://dx.doi.org/10.1016/j.fusengdes.2014.03.002 0920-3796/© 2014 Elsevier B.V. All rights reserved.