Induced activity of several candidate superconductor materials in a tokamak-type fusion reactor

The induced activity and compositional change of several superconducting materials such as Nb-based alloys, V-based alloys and MgB2 have been evaluated with a numerical calculation. We assume that the materials are irradiated for 10 MW a/m(2) at the magnet of the inboard position of a tokamak-type fusion reactor with a neutron wall loading of 1 MW/m(2). The materials are Nb3Sn, Nb3Al, NbTi, NbZr, V2Zr, V-2(Zr,Ht), V3Ga, V3Si and MgB2. Most of the induced activity of V-based alloys and MgB2 after the shutdown of the reactor is controlled by the Co-60 formed from Cu. After the irradiation, the dose rate decreases to a safe level of 10 muSv/h within 30 years. However, Nb-based alloys are predicted to emit gamma rays for tens of thousands years. The compositional changes and irradiation damage of Vbased alloys and MgB2 are minimal. (C) 2004 Elsevier B.V. All rights reserved.