EVALUATION OF COPPER-ALLOYS FOR FUSION-REACTOR DIVERTOR AND FIRST WALL COMPONENTS

This paper presents a critical analysis of the main factors of radiati on damage limiting the possibility to use copper alloys in the ITER di vertor and first wall structure. In copper alloys the most significant types of radiation damage in the proposed temperature-dose operation range are swelling, creep, and low-temperature radiation embrittlement . Low-temperature radiation embrittlement at T-irr < 150 degrees C pre sents considerable problems for dispersion strengthened (DS) and preci pitation-hardened (PH) copper alloys, as their uniform elongation at T -test - T-irr - 100 degrees C drops to similar to 0.1% after irradiati on doses of 0.01 to 0.1 dpa. At irradiation temperatures above 300 deg rees C, pronounced softening occurs in PH copper alloys due to radiati on-enhanced precipitate coarsening and dislocation recovery and recrys tallization processes. The DS copper alloys are relatively resistant t o radiation-enhanced softening up to temperatures of similar to 400 de grees C, The analysis of all available data indicates that copper allo ys are suitable for structural applications in ITER components within a relatively narrow temperature range of 180 degrees C to 280 degrees C for PH alloys such as Cu-Cr-Zr and 180 degrees C to 350 degrees C fo r DS alloys such as oxide dispersion strengthened copper (e.g., GlidCo p). Operation at lower temperatures is possible if uniform elongations < 1% can be tolerated in the design. Based on the available unirradia ted and irradiated data, oxide dispersion strengthened copper (Cu-Al2O 3) is considered to be the best candidate for high heat flux structura l applications, followed by CuNiBe and CuCrZr.