Fusion Engineering and Design 89 (2014) 1341–1345 Contents lists available at ScienceDirect Fusion Engineering and Design jo ur nal home p age: www.elsevier.com/locate/fusengdes Requirements for helium cooled pebble bed blanket and R&D activities D. Carloni ∗ , L.V. Boccaccini, F. Franza, S. Kecskes Institute of Neutron Physics and Reactor Technology, Karlsruhe Institute of Technology (KIT), Germany a r t i c l e i n f o Article history: Received 15 September 2013 Received in revised form 14 January 2014 Accepted 7 February 2014 Available online 11 March 2014 Keywords: HCPB Blanket DEMO a b s t r a c t This work aims to give an outline of the design requirements of the helium cooled pebble bed (HCPB) blanket and its associated R&D activities. In DEMO fusion reactor the plasma facing components have to fulfill several requirements dictated by safety and process sustainability criteria. In particular the blanket of a fusion reactor shall transfer the heat load coming from the plasma to the cooling system and also provide tritium breeding for the fuel cycle of the machine. KIT has been investigating and developed a helium-cooled blanket for more than three decades: the concept is based on the adoption of separated small lithium orthosilicate (tritium breeder) and beryllium (neutron multiplier) pebble beds, i.e. the HCPB blanket. One of the test blanket modules of ITER will be a HCPB type, aiming to demonstrate the soundness of the concept for the exploitation in future fusion power plants. A discussion is reported also on the development of the design criteria for the blanket to meet the requirements, such as tritium environmental release, also with reference to the TBM. The selection of materials and components to be used in a unique environment as the Tokamak of a fusion reactor requires dedicated several R&D activities. For instance, the performance of the coolant and the tritium self-sufficiency are key elements for the realization of the HCPB concept. Experimental campaigns have been conducted to select the materials to be used inside the solid breeder blanket and R&D activities have been carried out to support the design. The paper discusses also the program of future developments for the realization of the HCPB concept, also focusing to the specific campaigns necessary to qualify the TBM for its implementation in the ITER machine. © 2014 Elsevier B.V. All rights reserved. 1. Introduction The HCPB blanket concept is considered in EU a near term solu- tions for a first DEMO reactor since 1995 and it is considered in the EU TBM Programme for testing in ITER [1]. In KIT (formerly KfK and FZK) helium concepts have been studied for more than three decades with the selection of a solid breeder and beryllium as neu- tron multiplier; in early 1990s Dalle Donne proposed a Breeder Out of Tube (BOT) concept for NET. This concept became some years later (1995 during a selection exercise in EU) a reference concept in the EU Breeding Blanket Programme with the name of helium cooled pebble bed (HCPB) concept for DEMONET and TBM [2]. In 2000 this blanket concept was selected as part of the PPCS as ref- erence component for PPCS Model B [3]. The main features of the HCPB concept are the employment of lithiated ceramic breeders (CB) and beryllium as neutron multiplier in form of a flat pebble ∗ Corresponding author. Tel.: +49 176 47 28 97 34. E-mail address: dario.carloni@kit.edu (D. Carloni). beds. The coolant is helium at a pressure of 8 MPa with temper- atures in the range of 300–500 ◦ C. The velocities of helium up to 80 m/s in the FW are required to obtain the right heat transfer coef- ficient. An independent helium loop at relatively low pressure, in the range of few bar, provides the purging of the tritium from the pebble beds. Since the purge flow velocity is very low practically no heat removal is provided by the helium circulating in the loop. 2. Design requirements 2.1. Geometry The blanket system shall be adapted on a reactor design subdivided toroidally on 16 sectors (16 TF coils). The Vertical Maintenance System (VMS) is based on a reactor design char- acterized by large vertical ports for extraction of large blanket portions (segments). In fact each of the blanket sectors is made by 5 segments: three for the Outboard (OB) and two for the Inboard (IB). The primary option for the design of the segment is the multi module segment (MMS) concept; a common back supporting http://dx.doi.org/10.1016/j.fusengdes.2014.02.036 0920-3796/© 2014 Elsevier B.V. All rights reserved.