S. Sharafat US ITER TBM Meeting. April 23 24, 2007

Transcription

1 Advanced Copper Alloys for FW S. Sharafat US ITER TBM Meeting UCLA April 23 24, 2007

2 Irradiation Effects on Advanced Copper Alloys Effects of Neutron Irradiation The literatureon neutron irradiation effects on copper and its alloys is extensive. High temperature (415 o C) irradiation data of up to 150 dpa have been reported. Effects on physical and mechanical properties have been well documented and have been the subject of several recent reviews. In summary, the fine distribution of precipitate or oxide particles plus a relatively stable dislocation network in copper alloys provide high sink densities and recombination sites for radiation produced defects. Consequently, neutron generated vacancies and interstitial atoms can be removed from the lattice at a rate high enough to show saturation of many defect induced property changes after about 0.1 dpa. The radiation damage resistance of ODS copper alloys is because the Al particles are thermodynamically stable, resist overaging, and have been shown to resist cascade induced dissolution after high dose neutron radiation.

3 Irradiation Effects on Advanced Copper Alloys Irradiation Temperature Low temperature (<100 C) irradiation experiments show a sharp increase in electrical resistivity due to the defect clusters formation alone. However, high annealing temperatures (>200 C) result in a recovery of up to 92% of the electrical conductivity. The increases in embrittlement and loss of strength, associated with low irradiation temperatures are sharply py reduced in high temperature (>200 C) experiments following solution annealing. Swelling Copper and its alloys generally exhibit a bell-shaped swelling curve between 180 o Cand550 o C, with the maximum occuring around 300 o C Depending on the amount of cold work, the Cu-AI alloys have shown remarkably low swelling levels after 150 dpa at 415 o C, with a maximum of less than 0.5% at 100 dpa. Frost et al. [22] determined the change in electrical resistivity due to swelling to be negligible for the PH and ODS alloys [Dρ e <0.01xl0-8 W-m; DV/V<0.5%]. Helium And Hydrogen Hydrogenandheliumproductionareestimatedtobearound40H-appm/dpaand7He-appm/dpain copper per 1 MW/m 2, based on fusion neutron spectrum. The data base on the effects of H and He content on the mechanical properties of copper alloys is limited. Fabritsiev has reported that MAGT-0.2 (ODS) has a Heembrittlement threshold temperature of about 900oC (60 He-appm), while that for pure copper would be at about 350 o C Solid Transmutations Natural copper consists of the two isotopes 63 Cu and 65 Cu, with relative abundances of 69.1% and 30.9% [21]. Thepredominant nuclear reaction is (n,2n) for both isotopes, which results primarily in the production of 62 Ni, 64 Ni, 64 Zn and 66 Zn. Other principal transmutation elements are Co and Fe. All of these transmutation products are soluble in copper, with Ni being completely soluble and Zn up to 37 at.% at 350 o C. Table 1 lists the transmutation rates of the principal elements and their specific electrical resistivity and thermal conductivities, per 1MW-y/m 2 of neutron fluence ).

4 Time temperature Diagram of RT UTS and YS G.M. Kalinin, JNM 2007

5 RT Tensile Strength G.M. Kalinin, JNM 2007

6 D.J. Edwards, B.N. Singh, S. Tähtinen, JNM 2007

7 Fracture Map FW Example (next slide) M. Li, S.J. Zinkle / Journal of Nuclear Materials 361 (2007)

8 Thermal + Pressure Stresses are VERY LOW CuCrZr: q = 1 MW/m 2 h(fw) = 9000 W/m 2 K h (back) = 3500 W/m 2 K P(He) = 6 MPa σ max = 74 MPa T in (He) = 100 Oc T max = 217 o C

9 Concluding Remarks Advanced Copper Alloys are really advanced: Radiaiton damage effects saturate 0.1 to 0.3 dpa (T> 200 o C) Neutron effects on properties are well documented (hardening, but manageable, depends on various treatments and initial conditions) Swelling, transmuations, ations He & H, have been investigated Simple example of a FW exposed to 1 MW/m2 heat load seems to put the minimum operating time near 1.5 years (more detailed analysis required)