Design and Demonstration of a Material-Plasma Exposure Target Station for Neutron Irradiated Samples PDF Download

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Languages : en
Pages : 76

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Book Description
Fusion energy is the most promising energy source for the future and one of the most important problems to be solved progressing to a commercial fusion reactor is the identification of plasma facing materials compatible with the extreme conditions in the fusion reactor environment. The development of plasma material interaction (PMI) science and the technology of plasma facing components are key elements in the development of the next step fusion device in the United States, the so-called Fusion Nuclear Science Facility (FNSF). All of these PMI issues and the uncertain impact of the 14 MeV neutron irradiation have been identified in numerous expert panel reports to the fusion community. The 2007 Greenwald report classifies reactor plasma facing materials (PFCs) and materials as the only Tier 1 issues, requiring a ". . . major extrapolation from the current state of knowledge, need for qualitative improvements and substantial development for both the short and long term." The Greenwald report goes on to list 19 gaps in understanding and performance related to the plasma-material interface for the technology facilities needed for DEMO oriented R & D and DEMO itself. Of the 15 major gaps, six (G7, G9, G10, G12, G13) can possibly be addressed with ORNL's proposal of an advanced Material Plasma Exposure eXperiment. Establishing this midscale plasma materials test facility at ORNL is a key element in ORNL's strategy to secure a leadership role for decades of fusion R & D. That is to say, our end goal is to bring the "signature facility" FNSF home to ORNL. This project is related to the pre-conceptual design of an innovative target station for a future Material-Plasma Exposure eXperiment (MPEX). The target station will be designed to expose candidate fusion reactor plasma facing materials and components (PFMs and PFCs) to conditions anticipated in fusion reactors where PFCs will be exposed to dense high temperature hydrogen plasmas providing steady state heat fluxes of 5-20 MW/m2 and ion fluxes up to 1024 m-2s-1. Since PFCs will have to withstand neutron irradiation displacement damage up to 50 dpa, the target station design must accommodate radioactive specimens (materials to be irradiated in HFIR or at SNS) to enable investigations of the impact of neutron damage on materials. Therefore, the system will have to be able to install and extract irradiated specimens using equipment and methods to avoid sample modification, control contamination, and minimize worker dose. Included in the design considerations will be an assessment of all the steps between neutron irradiation and post-exposure materials examination/characterization, as well as an evaluation of the facility hazard categorization. In particular, the factors associated with the acquisition of radioactive specimens and their preparation, transportation, experimental configuration at the plasma-specimen interface, post-plasma-exposure sample handling, and specimen preparation will be evaluated.