Plasma facing components, PFC

The data in Fig. 3.20 and similar observations in JET [39,40] imply that a non-negligible amount of the main plasma ELM energy loss may reach plasma facing components (PFCs) in the main chamber of the device and not the divertor target. While this can enlarge the range for ITER oper-... 

In the fusion devices (tokamaks) using carbonaceous plasma facing components (PFC), erosion as well as re-deposition of carbon atoms have been observed. In the current configuration of Tore Supra (TS), the tokamak located in Cadarache, France, the largest part of PFCs is the toroidal pumped limiter, which is in close interaction with the plasma. It is composed of actively cooled (120°C) carbon fiber composites (CFC) tiles. Analysis of long plasma discharges has pointed out an abnormal deuterium retention which can be due to redeposited layers, as observed on several places on the PFCs [1]. These carbon layers (up to 800 micrometers thick) have been collected and their chemical analysis performed using nuclear reaction analysis shows a D/C deuterium concentration less than 10 % [2]. This low co-deposition rate makes difficult explanation of the particle retention and it is possible that porosity and structural properties of deposits play an important role in deuterimn retention. 

The potential applications of SiC SiC composites currently considered are core components, especially the control rod sheath and cladding of the VHTR, GFR, SFR, MSR, and LFR. Because the scope of this chapter is restricted to the Generation IV system, only part of the nuclear applications of SiCf/SiC was described. However, SiC SiC composites are also considered as the in-vessel components of magnetic confinement fusion devices including blanket structures, flow channel inserts (FCI) for the liquid metal (LM) blankets, and plasma-facing components (PFCs) [88—91]. In addition, they are candidates for an advanced fuel cladding for LWRs as an ATF (accident tolerance fuel) concept [72,92—97] and a channel box for the BWRs (boiling water-cooled reactors) [96,98,99]. 

Safe management and accounting of tritium will be crucial for the acceptance of fusion as an environmentally benign power source. ITER will be routinely fuelled with mixtures of D and T, and tritium retention in plasma facing materials with CFC PFCs has emerged as a primary concern with strong implications for in-vessel component design, material selection, operational schedule and safety. 

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