PHENIX U.S.-Japan Collaboration Investigation of Thermal and Mechanical Properties of Thermal Neutron–Shielded Irradiated Tungsten

Abstract

The United States and Japan have collaborated on fusion materials research in a series of agreements reaching back to 1981. The PHENIX collaboration is the latest U.S.-Japan project which spans 2013 to 2019 and has the goal of assessing technical feasibility of tungsten-based, helium-cooled plasma-facing component concepts for a demonstration fusion power reactor (DEMO). Task 2 within the PHENIX project is focused on evaluating the neutron irradiation effects in tungsten. For tungsten, the transmutation to Re and Os is at least as important to determining its properties after irradiation as the displacement damage, and the transmutation rate depends on the energy spectrum of the reactor. A large-scale, instrumented irradiation capsule with thermal neutron shielding to better mimic fusion conditions was irradiated in the High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory. The tungsten specimens were irradiated in different temperature zones between 500°C and 1200°C to doses of ~0.2 to 0.7 displacements per atom. More than 20 varieties of pure tungsten and tungsten alloys were included in the irradiation, and they were evaluated in the 3025E hot-cell facility and at the Low Activation Materials Development and Analysis Laboratory. The elevated temperature tensile, fracture toughness, hardness, thermal conductivity, electrical resistivity, density, elemental composition, and microstructure properties of the irradiated materials are being collected. This paper overviews the experimental design, specimen matrix, and the initial results of postirradiation examinations.

Keywords:

• Neutron irradiation
• tungsten
• divertor
• mechanical properties
• fusion materials

Acknowledgments

The work was performed as part of the U.S.-Japan PHENIX Cooperation Project on Technological Assessment of Plasma Facing Components for DEMO Reactors, supported by the U.S. Department of Energy (DOE), Office of Science, Fusion Energy Sciences and the Ministry of Education, Culture, Sports, Science and Technology, Japan. This manuscript has been authored by UT-Battelle, LLC, under contract number DE-AC05-00OR22725 with the DOE. This research used resources at the HFIR, a DOE Office of Science User Facility operated by ORNL. This manuscript has been authored by UT-Battelle, LLC, under contract DE-AC05-00OR22725 with DOE. The U.S. government retains and the publisher, by accepting the article for publication, acknowledges that the U.S. government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for U.S. government purposes. DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (http://energy.gov/downloads/doe-public-access-plan).