Radiation damage accumulation and dissolution of second phase particles in Zircaloy-2 by means of ion accelerator

In order to understand the degradation behavior of LWR fuel cladding under irradiation, the correlation among the accumulation of radiation damages, dissolution behavior of second precipitate particles (SPPs), and the effect of hydrides should be clarified. For the clarification of each phenomenon, Zr self-ion irradiation examinations on Zircaloy-2 have been treated at JAEA-Takasaki Ion Accelerators for Advanced Radiation Application (TIARA) facility. Irradiated samples were observed by means of a 300 kV FE-TEM at CRIEPI. 12 MeV Zr⁺⁴ ions irradiations whose fluence are 2.8 x10¹⁵ ions/cm² (10 dpa), 5x10¹⁵ ions/cm² (18 dpa), and 1.1x10¹⁶ ions/cm² (40 dpa )at 400°C was done on Zircaloy-2, and observed in FE-TEM. At the accumulated damages of 18 and 40 dpa, the c-component dislocations are formed in the matrix whose depth from irradiation surface is around 1.5 ∼ 3.0 μm. In case of Zr(Fe, Cr)₂, some amount of Fe atoms were dissolved even at 10 dpa, and the dissolution was accelerated under higher fluence ion irradiation. This phenomenon is almost coincident with the SPP's behavior under neutron irradiation in LWR. This behavior indicates that the self ion irradiation can simulate the neutron irradiation conditions in reactors. (author)